Changes v4 => v5:
1. Do not use atomic64 for bpf_jit_current. (Alexei)
Changes v3 => v4:
1. Rename text_poke_jit() => text_poke_copy(). (Peter)
2. Change comment style. (Peter)
Changes v2 => v3:
1. Fix tailcall.
Changes v1 => v2:
1. Use text_poke instead of writing through linear mapping. (Peter)
2. Avoid making changes to non-x86_64 code.
Most BPF programs are small, but they consume a page each. For systems
with busy traffic and many BPF programs, this could also add significant
pressure to instruction TLB.
This set tries to solve this problem with customized allocator that pack
multiple programs into a huge page.
Patches 1-5 prepare the work. Patch 6 contains key logic of the allocator.
Patch 7 uses this allocator in x86_64 jit compiler.
Song Liu (7):
x86/Kconfig: select HAVE_ARCH_HUGE_VMALLOC with HAVE_ARCH_HUGE_VMAP
bpf: use bytes instead of pages for bpf_jit_[charge|uncharge]_modmem
bpf: use size instead of pages in bpf_binary_header
bpf: add a pointer of bpf_binary_header to bpf_prog
x86/alternative: introduce text_poke_copy
bpf: introduce bpf_prog_pack allocator
bpf, x86_64: use bpf_prog_pack allocator
arch/x86/Kconfig | 1 +
arch/x86/include/asm/text-patching.h | 1 +
arch/x86/kernel/alternative.c | 32 ++++
arch/x86/net/bpf_jit_comp.c | 136 +++++++++++++----
include/linux/bpf.h | 4 +-
include/linux/filter.h | 23 ++-
kernel/bpf/core.c | 211 ++++++++++++++++++++++++---
kernel/bpf/trampoline.c | 6 +-
8 files changed, 356 insertions(+), 58 deletions(-)
--
2.30.2
From: Song Liu <[email protected]>
This enables sub-page memory charge and allocation.
Signed-off-by: Song Liu <[email protected]>
---
include/linux/bpf.h | 4 ++--
kernel/bpf/core.c | 17 ++++++++---------
kernel/bpf/trampoline.c | 6 +++---
3 files changed, 13 insertions(+), 14 deletions(-)
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index dce54eb0aae8..9232db5014a3 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -827,8 +827,8 @@ void bpf_image_ksym_add(void *data, struct bpf_ksym *ksym);
void bpf_image_ksym_del(struct bpf_ksym *ksym);
void bpf_ksym_add(struct bpf_ksym *ksym);
void bpf_ksym_del(struct bpf_ksym *ksym);
-int bpf_jit_charge_modmem(u32 pages);
-void bpf_jit_uncharge_modmem(u32 pages);
+int bpf_jit_charge_modmem(u32 size);
+void bpf_jit_uncharge_modmem(u32 size);
bool bpf_prog_has_trampoline(const struct bpf_prog *prog);
#else
static inline int bpf_trampoline_link_prog(struct bpf_prog *prog,
diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index de3e5bc6781f..b9c6a426a7dd 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -833,12 +833,11 @@ static int __init bpf_jit_charge_init(void)
}
pure_initcall(bpf_jit_charge_init);
-int bpf_jit_charge_modmem(u32 pages)
+int bpf_jit_charge_modmem(u32 size)
{
- if (atomic_long_add_return(pages, &bpf_jit_current) >
- (bpf_jit_limit >> PAGE_SHIFT)) {
+ if (atomic_long_add_return(size, &bpf_jit_current) > bpf_jit_limit) {
if (!bpf_capable()) {
- atomic_long_sub(pages, &bpf_jit_current);
+ atomic_long_sub(size, &bpf_jit_current);
return -EPERM;
}
}
@@ -846,9 +845,9 @@ int bpf_jit_charge_modmem(u32 pages)
return 0;
}
-void bpf_jit_uncharge_modmem(u32 pages)
+void bpf_jit_uncharge_modmem(u32 size)
{
- atomic_long_sub(pages, &bpf_jit_current);
+ atomic_long_sub(size, &bpf_jit_current);
}
void *__weak bpf_jit_alloc_exec(unsigned long size)
@@ -879,11 +878,11 @@ bpf_jit_binary_alloc(unsigned int proglen, u8 **image_ptr,
size = round_up(proglen + sizeof(*hdr) + 128, PAGE_SIZE);
pages = size / PAGE_SIZE;
- if (bpf_jit_charge_modmem(pages))
+ if (bpf_jit_charge_modmem(size))
return NULL;
hdr = bpf_jit_alloc_exec(size);
if (!hdr) {
- bpf_jit_uncharge_modmem(pages);
+ bpf_jit_uncharge_modmem(size);
return NULL;
}
@@ -906,7 +905,7 @@ void bpf_jit_binary_free(struct bpf_binary_header *hdr)
u32 pages = hdr->pages;
bpf_jit_free_exec(hdr);
- bpf_jit_uncharge_modmem(pages);
+ bpf_jit_uncharge_modmem(pages << PAGE_SHIFT);
}
/* This symbol is only overridden by archs that have different
diff --git a/kernel/bpf/trampoline.c b/kernel/bpf/trampoline.c
index 4b6974a195c1..e76a488c09c3 100644
--- a/kernel/bpf/trampoline.c
+++ b/kernel/bpf/trampoline.c
@@ -213,7 +213,7 @@ static void __bpf_tramp_image_put_deferred(struct work_struct *work)
im = container_of(work, struct bpf_tramp_image, work);
bpf_image_ksym_del(&im->ksym);
bpf_jit_free_exec(im->image);
- bpf_jit_uncharge_modmem(1);
+ bpf_jit_uncharge_modmem(PAGE_SIZE);
percpu_ref_exit(&im->pcref);
kfree_rcu(im, rcu);
}
@@ -310,7 +310,7 @@ static struct bpf_tramp_image *bpf_tramp_image_alloc(u64 key, u32 idx)
if (!im)
goto out;
- err = bpf_jit_charge_modmem(1);
+ err = bpf_jit_charge_modmem(PAGE_SIZE);
if (err)
goto out_free_im;
@@ -332,7 +332,7 @@ static struct bpf_tramp_image *bpf_tramp_image_alloc(u64 key, u32 idx)
out_free_image:
bpf_jit_free_exec(im->image);
out_uncharge:
- bpf_jit_uncharge_modmem(1);
+ bpf_jit_uncharge_modmem(PAGE_SIZE);
out_free_im:
kfree(im);
out:
--
2.30.2
From: Song Liu <[email protected]>
Most BPF programs are small, but they consume a page each. For systems
with busy traffic and many BPF programs, this could add significant
pressure to instruction TLB.
Introduce bpf_prog_pack allocator to pack multiple BPF programs in a huge
page. The memory is then allocated in 64 byte chunks.
Memory allocated by bpf_prog_pack allocator is RO protected after initial
allocation. To write to it, the user (jit engine) need to use text poke
API.
Signed-off-by: Song Liu <[email protected]>
---
include/linux/filter.h | 7 ++
kernel/bpf/core.c | 187 ++++++++++++++++++++++++++++++++++++++++-
2 files changed, 190 insertions(+), 4 deletions(-)
diff --git a/include/linux/filter.h b/include/linux/filter.h
index 27ea68604c22..a58658442d2e 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -1074,6 +1074,13 @@ void *bpf_jit_alloc_exec(unsigned long size);
void bpf_jit_free_exec(void *addr);
void bpf_jit_free(struct bpf_prog *fp);
+struct bpf_binary_header *
+bpf_jit_binary_alloc_pack(unsigned int proglen, u8 **image_r_ptr,
+ unsigned int alignment,
+ bpf_jit_fill_hole_t bpf_fill_ill_insns);
+void bpf_jit_binary_free_pack(struct bpf_binary_header *hdr);
+int bpf_prog_pack_max_size(void);
+
int bpf_jit_add_poke_descriptor(struct bpf_prog *prog,
struct bpf_jit_poke_descriptor *poke);
diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index f252d8529b0b..f1bc89047173 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -808,6 +808,116 @@ int bpf_jit_add_poke_descriptor(struct bpf_prog *prog,
return slot;
}
+/*
+ * BPF program pack allocator.
+ *
+ * Most BPF programs are pretty small. Allocating a hole page for each
+ * program is sometime a waste. Many small bpf program also adds pressure
+ * to instruction TLB. To solve this issue, we introduce a BPF program pack
+ * allocator. The prog_pack allocator uses HPAGE_PMD_SIZE page (2MB on x86)
+ * to host BPF programs.
+ */
+#define BPF_PROG_PACK_SIZE HPAGE_PMD_SIZE
+#define BPF_PROG_CHUNK_SHIFT 6
+#define BPF_PROG_CHUNK_SIZE (1 << BPF_PROG_CHUNK_SHIFT)
+#define BPF_PROG_CHUNK_COUNT (BPF_PROG_PACK_SIZE / BPF_PROG_CHUNK_SIZE)
+
+struct bpf_prog_pack {
+ struct list_head list;
+ void *ptr;
+ unsigned long bitmap[BITS_TO_LONGS(BPF_PROG_CHUNK_COUNT)];
+};
+
+#define BPF_PROG_MAX_PACK_PROG_SIZE HPAGE_PMD_SIZE
+#define BPF_PROG_SIZE_TO_NBITS(size) (round_up(size, BPF_PROG_CHUNK_SIZE) / BPF_PROG_CHUNK_SIZE)
+
+static DEFINE_MUTEX(pack_mutex);
+static LIST_HEAD(pack_list);
+
+static struct bpf_prog_pack *alloc_new_pack(void)
+{
+ struct bpf_prog_pack *pack;
+
+ pack = kzalloc(sizeof(*pack), GFP_KERNEL);
+ if (!pack)
+ return NULL;
+ pack->ptr = module_alloc(BPF_PROG_PACK_SIZE);
+ if (!pack->ptr) {
+ kfree(pack);
+ return NULL;
+ }
+ bitmap_zero(pack->bitmap, BPF_PROG_PACK_SIZE / BPF_PROG_CHUNK_SIZE);
+ list_add_tail(&pack->list, &pack_list);
+
+ set_vm_flush_reset_perms(pack);
+ set_memory_ro((unsigned long)pack->ptr, BPF_PROG_PACK_SIZE / PAGE_SIZE);
+ set_memory_x((unsigned long)pack->ptr, BPF_PROG_PACK_SIZE / PAGE_SIZE);
+ return pack;
+}
+
+static void *bpf_prog_pack_alloc(u32 size)
+{
+ unsigned int nbits = BPF_PROG_SIZE_TO_NBITS(size);
+ struct bpf_prog_pack *pack;
+ unsigned long pos;
+ void *ptr = NULL;
+
+ mutex_lock(&pack_mutex);
+ list_for_each_entry(pack, &pack_list, list) {
+ pos = bitmap_find_next_zero_area(pack->bitmap, BPF_PROG_CHUNK_COUNT, 0,
+ nbits, 0);
+ if (pos < BPF_PROG_CHUNK_COUNT)
+ goto found_free_area;
+ }
+
+ pack = alloc_new_pack();
+ if (!pack)
+ goto out;
+
+ pos = 0;
+
+found_free_area:
+ bitmap_set(pack->bitmap, pos, nbits);
+ ptr = (void *)(pack->ptr) + (pos << BPF_PROG_CHUNK_SHIFT);
+
+out:
+ mutex_unlock(&pack_mutex);
+ return ptr;
+}
+
+static void bpf_prog_pack_free(struct bpf_binary_header *hdr)
+{
+ void *pack_ptr = (void *)((unsigned long)hdr & ~(BPF_PROG_PACK_SIZE - 1));
+ struct bpf_prog_pack *pack = NULL, *tmp;
+ unsigned int nbits;
+ unsigned long pos;
+
+ mutex_lock(&pack_mutex);
+
+ list_for_each_entry(tmp, &pack_list, list) {
+ if (tmp->ptr == pack_ptr) {
+ pack = tmp;
+ break;
+ }
+ }
+
+ if (WARN_ONCE(!pack, "bpf_prog_pack bug\n"))
+ goto out;
+
+ nbits = BPF_PROG_SIZE_TO_NBITS(hdr->size);
+ pos = ((unsigned long)hdr - (unsigned long)pack_ptr) >> BPF_PROG_CHUNK_SHIFT;
+
+ bitmap_clear(pack->bitmap, pos, nbits);
+ if (bitmap_find_next_zero_area(pack->bitmap, BPF_PROG_CHUNK_COUNT, 0,
+ BPF_PROG_CHUNK_COUNT, 0) == 0) {
+ list_del(&pack->list);
+ module_memfree(pack->ptr);
+ kfree(pack);
+ }
+out:
+ mutex_unlock(&pack_mutex);
+}
+
static atomic_long_t bpf_jit_current;
/* Can be overridden by an arch's JIT compiler if it has a custom,
@@ -860,10 +970,59 @@ void __weak bpf_jit_free_exec(void *addr)
module_memfree(addr);
}
+static struct bpf_binary_header *
+__bpf_jit_binary_alloc(unsigned int proglen, u8 **image_ptr,
+ unsigned int alignment,
+ bpf_jit_fill_hole_t bpf_fill_ill_insns,
+ u32 round_up_to)
+{
+ struct bpf_binary_header *hdr;
+ u32 size, hole, start;
+
+ WARN_ON_ONCE(!is_power_of_2(alignment) ||
+ alignment > BPF_IMAGE_ALIGNMENT);
+
+ /* Most of BPF filters are really small, but if some of them
+ * fill a page, allow at least 128 extra bytes to insert a
+ * random section of illegal instructions.
+ */
+ size = round_up(proglen + sizeof(*hdr) + 128, round_up_to);
+
+ if (bpf_jit_charge_modmem(size))
+ return NULL;
+ hdr = bpf_jit_alloc_exec(size);
+ if (!hdr) {
+ bpf_jit_uncharge_modmem(size);
+ return NULL;
+ }
+
+ /* Fill space with illegal/arch-dep instructions. */
+ bpf_fill_ill_insns(hdr, size);
+
+ hdr->size = size;
+ hole = min_t(unsigned int, size - (proglen + sizeof(*hdr)),
+ PAGE_SIZE - sizeof(*hdr));
+ start = (get_random_int() % hole) & ~(alignment - 1);
+
+ /* Leave a random number of instructions before BPF code. */
+ *image_ptr = &hdr->image[start];
+
+ return hdr;
+}
+
struct bpf_binary_header *
bpf_jit_binary_alloc(unsigned int proglen, u8 **image_ptr,
unsigned int alignment,
bpf_jit_fill_hole_t bpf_fill_ill_insns)
+{
+ return __bpf_jit_binary_alloc(proglen, image_ptr, alignment,
+ bpf_fill_ill_insns, PAGE_SIZE);
+}
+
+struct bpf_binary_header *
+bpf_jit_binary_alloc_pack(unsigned int proglen, u8 **image_ptr,
+ unsigned int alignment,
+ bpf_jit_fill_hole_t bpf_fill_ill_insns)
{
struct bpf_binary_header *hdr;
u32 size, hole, start;
@@ -875,11 +1034,19 @@ bpf_jit_binary_alloc(unsigned int proglen, u8 **image_ptr,
* fill a page, allow at least 128 extra bytes to insert a
* random section of illegal instructions.
*/
- size = round_up(proglen + sizeof(*hdr) + 128, PAGE_SIZE);
+ size = round_up(proglen + sizeof(*hdr) + 128, BPF_PROG_CHUNK_SIZE);
+
+ /* for too big program, use __bpf_jit_binary_alloc with round_up_to
+ * of BPF_PROG_MAX_PACK_PROG_SIZE.
+ */
+ if (size > BPF_PROG_MAX_PACK_PROG_SIZE)
+ return __bpf_jit_binary_alloc(proglen, image_ptr,
+ alignment, bpf_fill_ill_insns,
+ BPF_PROG_MAX_PACK_PROG_SIZE);
if (bpf_jit_charge_modmem(size))
return NULL;
- hdr = bpf_jit_alloc_exec(size);
+ hdr = bpf_prog_pack_alloc(size);
if (!hdr) {
bpf_jit_uncharge_modmem(size);
return NULL;
@@ -888,9 +1055,8 @@ bpf_jit_binary_alloc(unsigned int proglen, u8 **image_ptr,
/* Fill space with illegal/arch-dep instructions. */
bpf_fill_ill_insns(hdr, size);
- hdr->size = size;
hole = min_t(unsigned int, size - (proglen + sizeof(*hdr)),
- PAGE_SIZE - sizeof(*hdr));
+ BPF_PROG_CHUNK_SIZE - sizeof(*hdr));
start = (get_random_int() % hole) & ~(alignment - 1);
/* Leave a random number of instructions before BPF code. */
@@ -907,6 +1073,19 @@ void bpf_jit_binary_free(struct bpf_binary_header *hdr)
bpf_jit_uncharge_modmem(size);
}
+void bpf_jit_binary_free_pack(struct bpf_binary_header *hdr)
+{
+ u32 size = hdr->size;
+
+ bpf_prog_pack_free(hdr);
+ bpf_jit_uncharge_modmem(size);
+}
+
+int bpf_prog_pack_max_size(void)
+{
+ return BPF_PROG_MAX_PACK_PROG_SIZE;
+}
+
/* This symbol is only overridden by archs that have different
* requirements than the usual eBPF JITs, f.e. when they only
* implement cBPF JIT, do not set images read-only, etc.
--
2.30.2
From: Song Liu <[email protected]>
This enables module_alloc() to allocate huge page for 2MB+ requests.
To check the difference of this change, we need enable config
CONFIG_PTDUMP_DEBUGFS, and call module_alloc(2MB). Before the change,
/sys/kernel/debug/page_tables/kernel shows pte for this map. With the
change, /sys/kernel/debug/page_tables/ show pmd for thie map.
Signed-off-by: Song Liu <[email protected]>
---
arch/x86/Kconfig | 1 +
1 file changed, 1 insertion(+)
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 8910b09b5601..b5d1582ea848 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -158,6 +158,7 @@ config X86
select HAVE_ALIGNED_STRUCT_PAGE if SLUB
select HAVE_ARCH_AUDITSYSCALL
select HAVE_ARCH_HUGE_VMAP if X86_64 || X86_PAE
+ select HAVE_ARCH_HUGE_VMALLOC if HAVE_ARCH_HUGE_VMAP
select HAVE_ARCH_JUMP_LABEL
select HAVE_ARCH_JUMP_LABEL_RELATIVE
select HAVE_ARCH_KASAN if X86_64
--
2.30.2
With sub page allocation, we cannot simply use bpf_func & PAGE_MASK to
find the bpf_binary_header. Add a pointer to struct bpf_prog to avoid
this logic.
Use this point for x86_64. If the pointer is not set by the jit engine,
fall back to original logic.
Signed-off-by: Song Liu <[email protected]>
---
arch/x86/net/bpf_jit_comp.c | 2 ++
include/linux/filter.h | 10 ++++++++--
2 files changed, 10 insertions(+), 2 deletions(-)
diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c
index ce1f86f245c9..fe4f08e25a1d 100644
--- a/arch/x86/net/bpf_jit_comp.c
+++ b/arch/x86/net/bpf_jit_comp.c
@@ -2339,6 +2339,7 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog)
if (header)
bpf_jit_binary_free(header);
prog = orig_prog;
+ header = NULL;
goto out_addrs;
}
if (image) {
@@ -2406,6 +2407,7 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog)
if (tmp_blinded)
bpf_jit_prog_release_other(prog, prog == orig_prog ?
tmp : orig_prog);
+ prog->hdr = header;
return prog;
}
diff --git a/include/linux/filter.h b/include/linux/filter.h
index 5855eb474c62..27ea68604c22 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -584,6 +584,7 @@ struct bpf_prog {
const struct bpf_insn *insn);
struct bpf_prog_aux *aux; /* Auxiliary fields */
struct sock_fprog_kern *orig_prog; /* Original BPF program */
+ struct bpf_binary_header *hdr;
/* Instructions for interpreter */
union {
DECLARE_FLEX_ARRAY(struct sock_filter, insns);
@@ -893,9 +894,14 @@ static inline void bpf_jit_binary_lock_ro(struct bpf_binary_header *hdr)
static inline struct bpf_binary_header *
bpf_jit_binary_hdr(const struct bpf_prog *fp)
{
- unsigned long real_start = (unsigned long)fp->bpf_func;
- unsigned long addr = real_start & PAGE_MASK;
+ unsigned long real_start;
+ unsigned long addr;
+ if (fp->hdr)
+ return fp->hdr;
+
+ real_start = (unsigned long)fp->bpf_func;
+ addr = real_start & PAGE_MASK;
return (void *)addr;
}
--
2.30.2
From: Song Liu <[email protected]>
Use bpf_prog_pack allocator in x86_64 jit.
The program header from bpf_prog_pack is read only during the jit process.
Therefore, the binary is first written to a temporary buffer, and later
copied to final location with text_poke_copy().
Similarly, jit_fill_hole() is updated to fill the hole with 0xcc using
text_poke_copy().
Signed-off-by: Song Liu <[email protected]>
---
arch/x86/net/bpf_jit_comp.c | 134 +++++++++++++++++++++++++++---------
1 file changed, 103 insertions(+), 31 deletions(-)
diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c
index fe4f08e25a1d..6d97f7c24df2 100644
--- a/arch/x86/net/bpf_jit_comp.c
+++ b/arch/x86/net/bpf_jit_comp.c
@@ -216,11 +216,34 @@ static u8 simple_alu_opcodes[] = {
[BPF_ARSH] = 0xF8,
};
+static char jit_hole_buffer[PAGE_SIZE] = {};
+
static void jit_fill_hole(void *area, unsigned int size)
+{
+ struct bpf_binary_header *hdr = area;
+ int i;
+
+ for (i = 0; i < roundup(size, PAGE_SIZE); i += PAGE_SIZE) {
+ int s;
+
+ s = min_t(int, PAGE_SIZE, size - i);
+ text_poke_copy(area + i, jit_hole_buffer, s);
+ }
+
+ /*
+ * bpf_jit_binary_alloc_pack cannot write size directly to the ro
+ * mapping. Write it here with text_poke_copy().
+ */
+ text_poke_copy(&hdr->size, &size, sizeof(size));
+}
+
+static int __init x86_jit_fill_hole_init(void)
{
/* Fill whole space with INT3 instructions */
- memset(area, 0xcc, size);
+ memset(jit_hole_buffer, 0xcc, PAGE_SIZE);
+ return 0;
}
+pure_initcall(x86_jit_fill_hole_init);
struct jit_context {
int cleanup_addr; /* Epilogue code offset */
@@ -361,14 +384,11 @@ static int __bpf_arch_text_poke(void *ip, enum bpf_text_poke_type t,
ret = -EBUSY;
mutex_lock(&text_mutex);
- if (memcmp(ip, old_insn, X86_PATCH_SIZE))
+ if (text_live && memcmp(ip, old_insn, X86_PATCH_SIZE))
goto out;
ret = 1;
if (memcmp(ip, new_insn, X86_PATCH_SIZE)) {
- if (text_live)
- text_poke_bp(ip, new_insn, X86_PATCH_SIZE, NULL);
- else
- memcpy(ip, new_insn, X86_PATCH_SIZE);
+ text_poke_bp(ip, new_insn, X86_PATCH_SIZE, NULL);
ret = 0;
}
out:
@@ -537,7 +557,7 @@ static void emit_bpf_tail_call_direct(struct bpf_jit_poke_descriptor *poke,
*pprog = prog;
}
-static void bpf_tail_call_direct_fixup(struct bpf_prog *prog)
+static void bpf_tail_call_direct_fixup(struct bpf_prog *prog, bool text_live)
{
struct bpf_jit_poke_descriptor *poke;
struct bpf_array *array;
@@ -558,24 +578,15 @@ static void bpf_tail_call_direct_fixup(struct bpf_prog *prog)
mutex_lock(&array->aux->poke_mutex);
target = array->ptrs[poke->tail_call.key];
if (target) {
- /* Plain memcpy is used when image is not live yet
- * and still not locked as read-only. Once poke
- * location is active (poke->tailcall_target_stable),
- * any parallel bpf_arch_text_poke() might occur
- * still on the read-write image until we finally
- * locked it as read-only. Both modifications on
- * the given image are under text_mutex to avoid
- * interference.
- */
ret = __bpf_arch_text_poke(poke->tailcall_target,
BPF_MOD_JUMP, NULL,
(u8 *)target->bpf_func +
- poke->adj_off, false);
+ poke->adj_off, text_live);
BUG_ON(ret < 0);
ret = __bpf_arch_text_poke(poke->tailcall_bypass,
BPF_MOD_JUMP,
(u8 *)poke->tailcall_target +
- X86_PATCH_SIZE, NULL, false);
+ X86_PATCH_SIZE, NULL, text_live);
BUG_ON(ret < 0);
}
WRITE_ONCE(poke->tailcall_target_stable, true);
@@ -867,7 +878,7 @@ static void emit_nops(u8 **pprog, int len)
#define INSN_SZ_DIFF (((addrs[i] - addrs[i - 1]) - (prog - temp)))
-static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image,
+static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image, u8 *tmp_image,
int oldproglen, struct jit_context *ctx, bool jmp_padding)
{
bool tail_call_reachable = bpf_prog->aux->tail_call_reachable;
@@ -894,8 +905,8 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image,
push_callee_regs(&prog, callee_regs_used);
ilen = prog - temp;
- if (image)
- memcpy(image + proglen, temp, ilen);
+ if (tmp_image)
+ memcpy(tmp_image + proglen, temp, ilen);
proglen += ilen;
addrs[0] = proglen;
prog = temp;
@@ -1324,8 +1335,10 @@ st: if (is_imm8(insn->off))
pr_err("extable->insn doesn't fit into 32-bit\n");
return -EFAULT;
}
- ex->insn = delta;
+ /* switch ex to temporary buffer for writes */
+ ex = (void *)tmp_image + ((void *)ex - (void *)image);
+ ex->insn = delta;
ex->type = EX_TYPE_BPF;
if (dst_reg > BPF_REG_9) {
@@ -1706,7 +1719,7 @@ st: if (is_imm8(insn->off))
pr_err("bpf_jit: fatal error\n");
return -EFAULT;
}
- memcpy(image + proglen, temp, ilen);
+ memcpy(tmp_image + proglen, temp, ilen);
}
proglen += ilen;
addrs[i] = proglen;
@@ -2248,8 +2261,10 @@ int arch_prepare_bpf_dispatcher(void *image, s64 *funcs, int num_funcs)
struct x64_jit_data {
struct bpf_binary_header *header;
+ struct bpf_binary_header *tmp_header;
int *addrs;
u8 *image;
+ u8 *tmp_image;
int proglen;
struct jit_context ctx;
};
@@ -2259,6 +2274,7 @@ struct x64_jit_data {
struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog)
{
+ struct bpf_binary_header *tmp_header = NULL;
struct bpf_binary_header *header = NULL;
struct bpf_prog *tmp, *orig_prog = prog;
struct x64_jit_data *jit_data;
@@ -2267,6 +2283,7 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog)
bool tmp_blinded = false;
bool extra_pass = false;
bool padding = false;
+ u8 *tmp_image = NULL;
u8 *image = NULL;
int *addrs;
int pass;
@@ -2301,7 +2318,9 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog)
ctx = jit_data->ctx;
oldproglen = jit_data->proglen;
image = jit_data->image;
+ tmp_image = jit_data->tmp_image;
header = jit_data->header;
+ tmp_header = jit_data->tmp_header;
extra_pass = true;
padding = true;
goto skip_init_addrs;
@@ -2332,14 +2351,18 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog)
for (pass = 0; pass < MAX_PASSES || image; pass++) {
if (!padding && pass >= PADDING_PASSES)
padding = true;
- proglen = do_jit(prog, addrs, image, oldproglen, &ctx, padding);
+ proglen = do_jit(prog, addrs, image, tmp_image, oldproglen, &ctx, padding);
if (proglen <= 0) {
out_image:
image = NULL;
- if (header)
- bpf_jit_binary_free(header);
+ tmp_image = NULL;
+ if (header) {
+ bpf_jit_binary_free_pack(header);
+ kfree(tmp_header);
+ }
prog = orig_prog;
header = NULL;
+ tmp_header = NULL;
goto out_addrs;
}
if (image) {
@@ -2362,13 +2385,27 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog)
sizeof(struct exception_table_entry);
/* allocate module memory for x86 insns and extable */
- header = bpf_jit_binary_alloc(roundup(proglen, align) + extable_size,
- &image, align, jit_fill_hole);
+ header = bpf_jit_binary_alloc_pack(roundup(proglen, align) + extable_size,
+ &image, align, jit_fill_hole);
if (!header) {
prog = orig_prog;
goto out_addrs;
}
- prog->aux->extable = (void *) image + roundup(proglen, align);
+ if (header->size > bpf_prog_pack_max_size()) {
+ tmp_header = header;
+ tmp_image = image;
+ } else {
+ tmp_header = kzalloc(header->size, GFP_KERNEL);
+ if (!tmp_header) {
+ bpf_jit_binary_free_pack(header);
+ header = NULL;
+ prog = orig_prog;
+ goto out_addrs;
+ }
+ tmp_header->size = header->size;
+ tmp_image = (void *)tmp_header + ((void *)image - (void *)header);
+ }
+ prog->aux->extable = (void *)image + roundup(proglen, align);
}
oldproglen = proglen;
cond_resched();
@@ -2379,14 +2416,24 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog)
if (image) {
if (!prog->is_func || extra_pass) {
- bpf_tail_call_direct_fixup(prog);
- bpf_jit_binary_lock_ro(header);
+ if (header->size > bpf_prog_pack_max_size()) {
+ /*
+ * bpf_prog_pack cannot handle too big
+ * program (> ~2MB). Fall back to regular
+ * module_alloc(), and do the fixup and
+ * lock_ro here.
+ */
+ bpf_tail_call_direct_fixup(prog, false);
+ bpf_jit_binary_lock_ro(header);
+ }
} else {
jit_data->addrs = addrs;
jit_data->ctx = ctx;
jit_data->proglen = proglen;
jit_data->image = image;
+ jit_data->tmp_image = tmp_image;
jit_data->header = header;
+ jit_data->tmp_header = tmp_header;
}
prog->bpf_func = (void *)image;
prog->jited = 1;
@@ -2402,6 +2449,17 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog)
kvfree(addrs);
kfree(jit_data);
prog->aux->jit_data = NULL;
+ jit_data = NULL;
+ if (tmp_header != header) {
+ text_poke_copy(header, tmp_header, header->size);
+ kfree(tmp_header);
+ /*
+ * Do the fixup after final text_poke_copy().
+ * Otherwise, the fix up will be overwritten by
+ * text_poke_copy().
+ */
+ bpf_tail_call_direct_fixup(prog, true);
+ }
}
out:
if (tmp_blinded)
@@ -2415,3 +2473,17 @@ bool bpf_jit_supports_kfunc_call(void)
{
return true;
}
+
+void bpf_jit_free(struct bpf_prog *fp)
+{
+ if (fp->jited) {
+ struct bpf_binary_header *hdr = bpf_jit_binary_hdr(fp);
+
+ if (hdr->size > bpf_prog_pack_max_size())
+ bpf_jit_binary_free(hdr);
+ else
+ bpf_jit_binary_free_pack(hdr);
+ }
+
+ bpf_prog_unlock_free(fp);
+}
--
2.30.2
From: Song Liu <[email protected]>
This is necessary to charge sub page memory for the BPF program.
Signed-off-by: Song Liu <[email protected]>
---
include/linux/filter.h | 6 +++---
kernel/bpf/core.c | 11 +++++------
2 files changed, 8 insertions(+), 9 deletions(-)
diff --git a/include/linux/filter.h b/include/linux/filter.h
index d23e999dc032..5855eb474c62 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -548,7 +548,7 @@ struct sock_fprog_kern {
#define BPF_IMAGE_ALIGNMENT 8
struct bpf_binary_header {
- u32 pages;
+ u32 size;
u8 image[] __aligned(BPF_IMAGE_ALIGNMENT);
};
@@ -886,8 +886,8 @@ static inline void bpf_prog_lock_ro(struct bpf_prog *fp)
static inline void bpf_jit_binary_lock_ro(struct bpf_binary_header *hdr)
{
set_vm_flush_reset_perms(hdr);
- set_memory_ro((unsigned long)hdr, hdr->pages);
- set_memory_x((unsigned long)hdr, hdr->pages);
+ set_memory_ro((unsigned long)hdr, hdr->size >> PAGE_SHIFT);
+ set_memory_x((unsigned long)hdr, hdr->size >> PAGE_SHIFT);
}
static inline struct bpf_binary_header *
diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index b9c6a426a7dd..f252d8529b0b 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -543,7 +543,7 @@ bpf_prog_ksym_set_addr(struct bpf_prog *prog)
WARN_ON_ONCE(!bpf_prog_ebpf_jited(prog));
prog->aux->ksym.start = (unsigned long) prog->bpf_func;
- prog->aux->ksym.end = addr + hdr->pages * PAGE_SIZE;
+ prog->aux->ksym.end = addr + hdr->size;
}
static void
@@ -866,7 +866,7 @@ bpf_jit_binary_alloc(unsigned int proglen, u8 **image_ptr,
bpf_jit_fill_hole_t bpf_fill_ill_insns)
{
struct bpf_binary_header *hdr;
- u32 size, hole, start, pages;
+ u32 size, hole, start;
WARN_ON_ONCE(!is_power_of_2(alignment) ||
alignment > BPF_IMAGE_ALIGNMENT);
@@ -876,7 +876,6 @@ bpf_jit_binary_alloc(unsigned int proglen, u8 **image_ptr,
* random section of illegal instructions.
*/
size = round_up(proglen + sizeof(*hdr) + 128, PAGE_SIZE);
- pages = size / PAGE_SIZE;
if (bpf_jit_charge_modmem(size))
return NULL;
@@ -889,7 +888,7 @@ bpf_jit_binary_alloc(unsigned int proglen, u8 **image_ptr,
/* Fill space with illegal/arch-dep instructions. */
bpf_fill_ill_insns(hdr, size);
- hdr->pages = pages;
+ hdr->size = size;
hole = min_t(unsigned int, size - (proglen + sizeof(*hdr)),
PAGE_SIZE - sizeof(*hdr));
start = (get_random_int() % hole) & ~(alignment - 1);
@@ -902,10 +901,10 @@ bpf_jit_binary_alloc(unsigned int proglen, u8 **image_ptr,
void bpf_jit_binary_free(struct bpf_binary_header *hdr)
{
- u32 pages = hdr->pages;
+ u32 size = hdr->size;
bpf_jit_free_exec(hdr);
- bpf_jit_uncharge_modmem(pages << PAGE_SHIFT);
+ bpf_jit_uncharge_modmem(size);
}
/* This symbol is only overridden by archs that have different
--
2.30.2
This will be used by BPF jit compiler to dump JITed binary to a RX huge
page, and thus allow multiple BPF programs sharing the a huge (2MB) page.
Signed-off-by: Song Liu <[email protected]>
---
arch/x86/include/asm/text-patching.h | 1 +
arch/x86/kernel/alternative.c | 32 ++++++++++++++++++++++++++++
2 files changed, 33 insertions(+)
diff --git a/arch/x86/include/asm/text-patching.h b/arch/x86/include/asm/text-patching.h
index b7421780e4e9..4cc18ba1b75e 100644
--- a/arch/x86/include/asm/text-patching.h
+++ b/arch/x86/include/asm/text-patching.h
@@ -44,6 +44,7 @@ extern void text_poke_early(void *addr, const void *opcode, size_t len);
extern void *text_poke(void *addr, const void *opcode, size_t len);
extern void text_poke_sync(void);
extern void *text_poke_kgdb(void *addr, const void *opcode, size_t len);
+extern void *text_poke_copy(void *addr, const void *opcode, size_t len);
extern int poke_int3_handler(struct pt_regs *regs);
extern void text_poke_bp(void *addr, const void *opcode, size_t len, const void *emulate);
diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c
index 23fb4d51a5da..903a415c19fa 100644
--- a/arch/x86/kernel/alternative.c
+++ b/arch/x86/kernel/alternative.c
@@ -1102,6 +1102,38 @@ void *text_poke_kgdb(void *addr, const void *opcode, size_t len)
return __text_poke(addr, opcode, len);
}
+/**
+ * text_poke_copy - Copy instructions into (an unused part of) RX memory
+ * @addr: address to modify
+ * @opcode: source of the copy
+ * @len: length to copy, could be more than 2x PAGE_SIZE
+ *
+ * Not safe against concurrent execution; useful for JITs to dump
+ * new code blocks into unused regions of RX memory. Can be used in
+ * conjunction with synchronize_rcu_tasks() to wait for existing
+ * execution to quiesce after having made sure no existing functions
+ * pointers are live.
+ */
+void *text_poke_copy(void *addr, const void *opcode, size_t len)
+{
+ unsigned long start = (unsigned long)addr;
+ size_t patched = 0;
+
+ if (WARN_ON_ONCE(core_kernel_text(start)))
+ return NULL;
+
+ while (patched < len) {
+ unsigned long ptr = start + patched;
+ size_t s;
+
+ s = min_t(size_t, PAGE_SIZE * 2 - offset_in_page(ptr), len - patched);
+
+ __text_poke((void *)ptr, opcode + patched, s);
+ patched += s;
+ }
+ return addr;
+}
+
static void do_sync_core(void *info)
{
sync_core();
--
2.30.2
Hi Peter,
> On Jan 20, 2022, at 11:12 AM, Song Liu <[email protected]> wrote:
>
> Changes v4 => v5:
> 1. Do not use atomic64 for bpf_jit_current. (Alexei)
>
> Changes v3 => v4:
> 1. Rename text_poke_jit() => text_poke_copy(). (Peter)
> 2. Change comment style. (Peter)
>
> Changes v2 => v3:
> 1. Fix tailcall.
>
> Changes v1 => v2:
> 1. Use text_poke instead of writing through linear mapping. (Peter)
> 2. Avoid making changes to non-x86_64 code.
>
> Most BPF programs are small, but they consume a page each. For systems
> with busy traffic and many BPF programs, this could also add significant
> pressure to instruction TLB.
>
> This set tries to solve this problem with customized allocator that pack
> multiple programs into a huge page.
>
> Patches 1-5 prepare the work. Patch 6 contains key logic of the allocator.
> Patch 7 uses this allocator in x86_64 jit compiler.
>
> Song Liu (7):
> x86/Kconfig: select HAVE_ARCH_HUGE_VMALLOC with HAVE_ARCH_HUGE_VMAP
> bpf: use bytes instead of pages for bpf_jit_[charge|uncharge]_modmem
> bpf: use size instead of pages in bpf_binary_header
> bpf: add a pointer of bpf_binary_header to bpf_prog
> x86/alternative: introduce text_poke_copy
> bpf: introduce bpf_prog_pack allocator
> bpf, x86_64: use bpf_prog_pack allocator
Could you please share your feedback for and/or ack this set?
Thanks,
Song
On Thu, Jan 20, 2022 at 11:13 AM Song Liu <[email protected]> wrote:
>
> From: Song Liu <[email protected]>
>
> Use bpf_prog_pack allocator in x86_64 jit.
>
> The program header from bpf_prog_pack is read only during the jit process.
> Therefore, the binary is first written to a temporary buffer, and later
> copied to final location with text_poke_copy().
>
> Similarly, jit_fill_hole() is updated to fill the hole with 0xcc using
> text_poke_copy().
>
> Signed-off-by: Song Liu <[email protected]>
> ---
> arch/x86/net/bpf_jit_comp.c | 134 +++++++++++++++++++++++++++---------
> 1 file changed, 103 insertions(+), 31 deletions(-)
>
> diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c
> index fe4f08e25a1d..6d97f7c24df2 100644
> --- a/arch/x86/net/bpf_jit_comp.c
> +++ b/arch/x86/net/bpf_jit_comp.c
> @@ -216,11 +216,34 @@ static u8 simple_alu_opcodes[] = {
> [BPF_ARSH] = 0xF8,
> };
>
> +static char jit_hole_buffer[PAGE_SIZE] = {};
Let's not waste a page filled with 0xcc.
The pack allocator will reserve 128 bytes at the front
and will round up the tail to 64 bytes.
So this can be a 128 byte array?
> +
> static void jit_fill_hole(void *area, unsigned int size)
> +{
> + struct bpf_binary_header *hdr = area;
> + int i;
> +
> + for (i = 0; i < roundup(size, PAGE_SIZE); i += PAGE_SIZE) {
multi page 0xcc-ing?
Is it because bpf_jit_binary_alloc_pack() allocates 2MB
and then populates the whole thing with this?
Seems overkill.
0xcc in the front of the prog and in the back is there
to catch JIT bugs.
No need to fill 2MB with it.
> + int s;
> +
> + s = min_t(int, PAGE_SIZE, size - i);
> + text_poke_copy(area + i, jit_hole_buffer, s);
> + }
> +
> + /*
> + * bpf_jit_binary_alloc_pack cannot write size directly to the ro
> + * mapping. Write it here with text_poke_copy().
> + */
> + text_poke_copy(&hdr->size, &size, sizeof(size));
> +}
> +
> +static int __init x86_jit_fill_hole_init(void)
> {
> /* Fill whole space with INT3 instructions */
> - memset(area, 0xcc, size);
> + memset(jit_hole_buffer, 0xcc, PAGE_SIZE);
> + return 0;
> }
> +pure_initcall(x86_jit_fill_hole_init);
>
> struct jit_context {
> int cleanup_addr; /* Epilogue code offset */
> @@ -361,14 +384,11 @@ static int __bpf_arch_text_poke(void *ip, enum bpf_text_poke_type t,
>
> ret = -EBUSY;
> mutex_lock(&text_mutex);
> - if (memcmp(ip, old_insn, X86_PATCH_SIZE))
> + if (text_live && memcmp(ip, old_insn, X86_PATCH_SIZE))
> goto out;
> ret = 1;
> if (memcmp(ip, new_insn, X86_PATCH_SIZE)) {
> - if (text_live)
> - text_poke_bp(ip, new_insn, X86_PATCH_SIZE, NULL);
> - else
> - memcpy(ip, new_insn, X86_PATCH_SIZE);
> + text_poke_bp(ip, new_insn, X86_PATCH_SIZE, NULL);
> ret = 0;
> }
> out:
> @@ -537,7 +557,7 @@ static void emit_bpf_tail_call_direct(struct bpf_jit_poke_descriptor *poke,
> *pprog = prog;
> }
>
> -static void bpf_tail_call_direct_fixup(struct bpf_prog *prog)
> +static void bpf_tail_call_direct_fixup(struct bpf_prog *prog, bool text_live)
> {
> struct bpf_jit_poke_descriptor *poke;
> struct bpf_array *array;
> @@ -558,24 +578,15 @@ static void bpf_tail_call_direct_fixup(struct bpf_prog *prog)
> mutex_lock(&array->aux->poke_mutex);
> target = array->ptrs[poke->tail_call.key];
> if (target) {
> - /* Plain memcpy is used when image is not live yet
> - * and still not locked as read-only. Once poke
> - * location is active (poke->tailcall_target_stable),
> - * any parallel bpf_arch_text_poke() might occur
> - * still on the read-write image until we finally
> - * locked it as read-only. Both modifications on
> - * the given image are under text_mutex to avoid
> - * interference.
> - */
> ret = __bpf_arch_text_poke(poke->tailcall_target,
> BPF_MOD_JUMP, NULL,
> (u8 *)target->bpf_func +
> - poke->adj_off, false);
> + poke->adj_off, text_live);
> BUG_ON(ret < 0);
> ret = __bpf_arch_text_poke(poke->tailcall_bypass,
> BPF_MOD_JUMP,
> (u8 *)poke->tailcall_target +
> - X86_PATCH_SIZE, NULL, false);
> + X86_PATCH_SIZE, NULL, text_live);
> BUG_ON(ret < 0);
> }
> WRITE_ONCE(poke->tailcall_target_stable, true);
> @@ -867,7 +878,7 @@ static void emit_nops(u8 **pprog, int len)
>
> #define INSN_SZ_DIFF (((addrs[i] - addrs[i - 1]) - (prog - temp)))
>
> -static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image,
> +static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image, u8 *tmp_image,
> int oldproglen, struct jit_context *ctx, bool jmp_padding)
> {
> bool tail_call_reachable = bpf_prog->aux->tail_call_reachable;
> @@ -894,8 +905,8 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image,
> push_callee_regs(&prog, callee_regs_used);
>
> ilen = prog - temp;
> - if (image)
> - memcpy(image + proglen, temp, ilen);
> + if (tmp_image)
> + memcpy(tmp_image + proglen, temp, ilen);
> proglen += ilen;
> addrs[0] = proglen;
> prog = temp;
> @@ -1324,8 +1335,10 @@ st: if (is_imm8(insn->off))
> pr_err("extable->insn doesn't fit into 32-bit\n");
> return -EFAULT;
> }
> - ex->insn = delta;
> + /* switch ex to temporary buffer for writes */
> + ex = (void *)tmp_image + ((void *)ex - (void *)image);
>
> + ex->insn = delta;
> ex->type = EX_TYPE_BPF;
>
> if (dst_reg > BPF_REG_9) {
> @@ -1706,7 +1719,7 @@ st: if (is_imm8(insn->off))
> pr_err("bpf_jit: fatal error\n");
> return -EFAULT;
> }
> - memcpy(image + proglen, temp, ilen);
> + memcpy(tmp_image + proglen, temp, ilen);
> }
> proglen += ilen;
> addrs[i] = proglen;
> @@ -2248,8 +2261,10 @@ int arch_prepare_bpf_dispatcher(void *image, s64 *funcs, int num_funcs)
>
> struct x64_jit_data {
> struct bpf_binary_header *header;
> + struct bpf_binary_header *tmp_header;
> int *addrs;
> u8 *image;
> + u8 *tmp_image;
Why add these two fields here?
With new logic header and image will be zero always?
Maybe rename them instead?
Or both used during JIT-ing?
> int proglen;
> struct jit_context ctx;
> };
> @@ -2259,6 +2274,7 @@ struct x64_jit_data {
>
> struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog)
> {
> + struct bpf_binary_header *tmp_header = NULL;
> struct bpf_binary_header *header = NULL;
> struct bpf_prog *tmp, *orig_prog = prog;
> struct x64_jit_data *jit_data;
> @@ -2267,6 +2283,7 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog)
> bool tmp_blinded = false;
> bool extra_pass = false;
> bool padding = false;
> + u8 *tmp_image = NULL;
> u8 *image = NULL;
> int *addrs;
> int pass;
> @@ -2301,7 +2318,9 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog)
> ctx = jit_data->ctx;
> oldproglen = jit_data->proglen;
> image = jit_data->image;
> + tmp_image = jit_data->tmp_image;
> header = jit_data->header;
> + tmp_header = jit_data->tmp_header;
> extra_pass = true;
> padding = true;
> goto skip_init_addrs;
> @@ -2332,14 +2351,18 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog)
> for (pass = 0; pass < MAX_PASSES || image; pass++) {
> if (!padding && pass >= PADDING_PASSES)
> padding = true;
> - proglen = do_jit(prog, addrs, image, oldproglen, &ctx, padding);
> + proglen = do_jit(prog, addrs, image, tmp_image, oldproglen, &ctx, padding);
> if (proglen <= 0) {
> out_image:
> image = NULL;
> - if (header)
> - bpf_jit_binary_free(header);
> + tmp_image = NULL;
> + if (header) {
> + bpf_jit_binary_free_pack(header);
> + kfree(tmp_header);
> + }
> prog = orig_prog;
> header = NULL;
> + tmp_header = NULL;
> goto out_addrs;
> }
> if (image) {
> @@ -2362,13 +2385,27 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog)
> sizeof(struct exception_table_entry);
>
> /* allocate module memory for x86 insns and extable */
> - header = bpf_jit_binary_alloc(roundup(proglen, align) + extable_size,
> - &image, align, jit_fill_hole);
> + header = bpf_jit_binary_alloc_pack(roundup(proglen, align) + extable_size,
> + &image, align, jit_fill_hole);
> if (!header) {
> prog = orig_prog;
> goto out_addrs;
> }
> - prog->aux->extable = (void *) image + roundup(proglen, align);
> + if (header->size > bpf_prog_pack_max_size()) {
> + tmp_header = header;
> + tmp_image = image;
> + } else {
> + tmp_header = kzalloc(header->size, GFP_KERNEL);
the header->size could be just below 2MB.
I don't think kzalloc() can handle that.
> + if (!tmp_header) {
> + bpf_jit_binary_free_pack(header);
> + header = NULL;
> + prog = orig_prog;
> + goto out_addrs;
> + }
> + tmp_header->size = header->size;
> + tmp_image = (void *)tmp_header + ((void *)image - (void *)header);
Why is 'tmp_image' needed at all?
The above math can be done where necessary.
> + }
> + prog->aux->extable = (void *)image + roundup(proglen, align);
I suspect if you didn't remove the space between (void *) and image
the diff would be less confusing.
This line didn't change, right?
> }
> oldproglen = proglen;
> cond_resched();
> @@ -2379,14 +2416,24 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog)
>
> if (image) {
> if (!prog->is_func || extra_pass) {
> - bpf_tail_call_direct_fixup(prog);
> - bpf_jit_binary_lock_ro(header);
> + if (header->size > bpf_prog_pack_max_size()) {
> + /*
> + * bpf_prog_pack cannot handle too big
> + * program (> ~2MB). Fall back to regular
> + * module_alloc(), and do the fixup and
> + * lock_ro here.
> + */
> + bpf_tail_call_direct_fixup(prog, false);
> + bpf_jit_binary_lock_ro(header);
> + }
> } else {
> jit_data->addrs = addrs;
> jit_data->ctx = ctx;
> jit_data->proglen = proglen;
> jit_data->image = image;
> + jit_data->tmp_image = tmp_image;
> jit_data->header = header;
> + jit_data->tmp_header = tmp_header;
> }
> prog->bpf_func = (void *)image;
> prog->jited = 1;
> @@ -2402,6 +2449,17 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog)
> kvfree(addrs);
> kfree(jit_data);
> prog->aux->jit_data = NULL;
> + jit_data = NULL;
> + if (tmp_header != header) {
> + text_poke_copy(header, tmp_header, header->size);
> + kfree(tmp_header);
> + /*
> + * Do the fixup after final text_poke_copy().
> + * Otherwise, the fix up will be overwritten by
> + * text_poke_copy().
> + */
> + bpf_tail_call_direct_fixup(prog, true);
> + }
> }
> out:
> if (tmp_blinded)
> @@ -2415,3 +2473,17 @@ bool bpf_jit_supports_kfunc_call(void)
> {
> return true;
> }
> +
> +void bpf_jit_free(struct bpf_prog *fp)
> +{
> + if (fp->jited) {
> + struct bpf_binary_header *hdr = bpf_jit_binary_hdr(fp);
> +
> + if (hdr->size > bpf_prog_pack_max_size())
> + bpf_jit_binary_free(hdr);
> + else
> + bpf_jit_binary_free_pack(hdr);
> + }
> +
> + bpf_prog_unlock_free(fp);
> +}
> --
> 2.30.2
>
On Thu, Jan 20, 2022 at 11:13:03AM -0800, Song Liu wrote:
> This will be used by BPF jit compiler to dump JITed binary to a RX huge
> page, and thus allow multiple BPF programs sharing the a huge (2MB) page.
>
> Signed-off-by: Song Liu <[email protected]>
Acked-by: Peter Zijlstra (Intel) <[email protected]>
> On Jan 20, 2022, at 8:59 PM, Alexei Starovoitov <[email protected]> wrote:
>
> On Thu, Jan 20, 2022 at 11:13 AM Song Liu <[email protected]> wrote:
>>
>> From: Song Liu <[email protected]>
>>
>> Use bpf_prog_pack allocator in x86_64 jit.
>>
>> The program header from bpf_prog_pack is read only during the jit process.
>> Therefore, the binary is first written to a temporary buffer, and later
>> copied to final location with text_poke_copy().
>>
>> Similarly, jit_fill_hole() is updated to fill the hole with 0xcc using
>> text_poke_copy().
>>
>> Signed-off-by: Song Liu <[email protected]>
>> ---
>> arch/x86/net/bpf_jit_comp.c | 134 +++++++++++++++++++++++++++---------
>> 1 file changed, 103 insertions(+), 31 deletions(-)
>>
>> diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c
>> index fe4f08e25a1d..6d97f7c24df2 100644
>> --- a/arch/x86/net/bpf_jit_comp.c
>> +++ b/arch/x86/net/bpf_jit_comp.c
>> @@ -216,11 +216,34 @@ static u8 simple_alu_opcodes[] = {
>> [BPF_ARSH] = 0xF8,
>> };
>>
>> +static char jit_hole_buffer[PAGE_SIZE] = {};
>
> Let's not waste a page filled with 0xcc.
> The pack allocator will reserve 128 bytes at the front
> and will round up the tail to 64 bytes.
> So this can be a 128 byte array?
>
>> +
>> static void jit_fill_hole(void *area, unsigned int size)
>> +{
>> + struct bpf_binary_header *hdr = area;
>> + int i;
>> +
>> + for (i = 0; i < roundup(size, PAGE_SIZE); i += PAGE_SIZE) {
>
> multi page 0xcc-ing?
> Is it because bpf_jit_binary_alloc_pack() allocates 2MB
> and then populates the whole thing with this?
> Seems overkill.
> 0xcc in the front of the prog and in the back is there
> to catch JIT bugs.
> No need to fill 2MB with it.
I got this logic because current code memset(0xcc) for the whole
buffer. We can change the logic to only 0xcc the first 128 bytes
and the last 64 bytes.
>
>
>> + int s;
>> +
>> + s = min_t(int, PAGE_SIZE, size - i);
>> + text_poke_copy(area + i, jit_hole_buffer, s);
>> + }
>> +
>> + /*
>> + * bpf_jit_binary_alloc_pack cannot write size directly to the ro
>> + * mapping. Write it here with text_poke_copy().
>> + */
>> + text_poke_copy(&hdr->size, &size, sizeof(size));
>> +}
[...]
>> @@ -2248,8 +2261,10 @@ int arch_prepare_bpf_dispatcher(void *image, s64 *funcs, int num_funcs)
>>
>> struct x64_jit_data {
>> struct bpf_binary_header *header;
>> + struct bpf_binary_header *tmp_header;
>> int *addrs;
>> u8 *image;
>> + u8 *tmp_image;
>
> Why add these two fields here?
> With new logic header and image will be zero always?
header and image point to a section of the 2MB page; while tmp_header
and tmp_image point to a temporary buffer from kzalloc. We need them
in x86_jit_data, so that we can reuse the temporary buffer between
multiple calls of bpf_int_jit_compile(). It is used as:
bpf_int_jit_compile(...)
{
/* ... */
jit_data = prog->aux->jit_data;
if (!jit_data) {
/* kzalloc jit_data */
}
addrs = jit_data->addrs;
if (addrs) {
/* reuse previous jit_data */
}
> Maybe rename them instead?
> Or both used during JIT-ing?
>
>> int proglen;
>> struct jit_context ctx;
>> };
>> @@ -2259,6 +2274,7 @@ struct x64_jit_data {
>>
[...]
>> }
>> - prog->aux->extable = (void *) image + roundup(proglen, align);
>> + if (header->size > bpf_prog_pack_max_size()) {
>> + tmp_header = header;
>> + tmp_image = image;
>> + } else {
>> + tmp_header = kzalloc(header->size, GFP_KERNEL);
>
> the header->size could be just below 2MB.
> I don't think kzalloc() can handle that.
Technically, kzalloc can handle 2MB allocation via:
kzalloc() => kmalloc() => kmalloc_large() => kmalloc_order()
But this would fail when the memory is fragmented. I guess we should use
kvmalloc() instead?
>
>> + if (!tmp_header) {
>> + bpf_jit_binary_free_pack(header);
>> + header = NULL;
>> + prog = orig_prog;
>> + goto out_addrs;
>> + }
>> + tmp_header->size = header->size;
>> + tmp_image = (void *)tmp_header + ((void *)image - (void *)header);
>
> Why is 'tmp_image' needed at all?
> The above math can be done where necessary.
We pass both image and tmp_image to do_jit(), as it needs both of them.
I think maintaining a tmp_image variable makes the logic cleaner. We can
remove it from x64_jit_data, I guess.
>
>> + }
>> + prog->aux->extable = (void *)image + roundup(proglen, align);
>
> I suspect if you didn't remove the space between (void *) and image
> the diff would be less confusing.
> This line didn't change, right?
Yeah, I forgot why I changed it in the first place. Let me undo it.
Thanks,
Song
[...]
On Fri, Jan 21, 2022 at 9:53 AM Song Liu <[email protected]> wrote:
> >
> > the header->size could be just below 2MB.
> > I don't think kzalloc() can handle that.
>
> Technically, kzalloc can handle 2MB allocation via:
> kzalloc() => kmalloc() => kmalloc_large() => kmalloc_order()
>
> But this would fail when the memory is fragmented. I guess we should use
> kvmalloc() instead?
Contiguous 2MB allocation?
> >
> >> + if (!tmp_header) {
> >> + bpf_jit_binary_free_pack(header);
> >> + header = NULL;
> >> + prog = orig_prog;
> >> + goto out_addrs;
> >> + }
> >> + tmp_header->size = header->size;
> >> + tmp_image = (void *)tmp_header + ((void *)image - (void *)header);
> >
> > Why is 'tmp_image' needed at all?
> > The above math can be done where necessary.
>
> We pass both image and tmp_image to do_jit(), as it needs both of them.
> I think maintaining a tmp_image variable makes the logic cleaner. We can
> remove it from x64_jit_data, I guess.
I'd remove from x64_jit_data. The recompute is cheap.
Speaking of tmp_header name... would be great to come up
with something more descriptive.
Here both tmp_header/tmp_image and header/image are used at the same time.
My initial confusion with the patch was due to the name 'tmp'.
The "tmp" prefix implies that the tmp_image will be used first
and then it will become an image.
But it's not the case.
Maybe call it 'rw_header' and add a comment that 'header/image'
are not writeable directly ?
Or call it 'poke_header' ?
Other ideas?
> On Jan 21, 2022, at 10:29 AM, Alexei Starovoitov <[email protected]> wrote:
>
> On Fri, Jan 21, 2022 at 9:53 AM Song Liu <[email protected]> wrote:
>>>
>>> the header->size could be just below 2MB.
>>> I don't think kzalloc() can handle that.
>>
>> Technically, kzalloc can handle 2MB allocation via:
>> kzalloc() => kmalloc() => kmalloc_large() => kmalloc_order()
>>
>> But this would fail when the memory is fragmented. I guess we should use
>> kvmalloc() instead?
>
> Contiguous 2MB allocation?
Yeah, I tried that both kzalloc() and kvmalloc() could get 2MB memory.
I think kzalloc will fail when the memory is fragmented, but I haven't
confirmed it yet.
>
>>>
>>>> + if (!tmp_header) {
>>>> + bpf_jit_binary_free_pack(header);
>>>> + header = NULL;
>>>> + prog = orig_prog;
>>>> + goto out_addrs;
>>>> + }
>>>> + tmp_header->size = header->size;
>>>> + tmp_image = (void *)tmp_header + ((void *)image - (void *)header);
>>>
>>> Why is 'tmp_image' needed at all?
>>> The above math can be done where necessary.
>>
>> We pass both image and tmp_image to do_jit(), as it needs both of them.
>> I think maintaining a tmp_image variable makes the logic cleaner. We can
>> remove it from x64_jit_data, I guess.
>
> I'd remove from x64_jit_data. The recompute is cheap.
Will do.
>
> Speaking of tmp_header name... would be great to come up
> with something more descriptive.
> Here both tmp_header/tmp_image and header/image are used at the same time.
> My initial confusion with the patch was due to the name 'tmp'.
> The "tmp" prefix implies that the tmp_image will be used first
> and then it will become an image.
> But it's not the case.
> Maybe call it 'rw_header' and add a comment that 'header/image'
> are not writeable directly ?
> Or call it 'poke_header' ?
> Other ideas?
I think rw_header/rw_image is good. poke_header is confusing, as we will
text_poke "header".
Thanks,
Song