Changes v6 => v7:
1. Redesign the interface between generic and arch logic, based on feedback
from Alexei and Ilya.
2. Split 6/7 of v6 to 7/9 and 8/9 in v7, for cleaner logic.
3. Add bpf_arch_text_copy in 6/9.
Changes v5 => v6:
1. Make jit_hole_buffer 128 byte long. Only fill the first and last 128
bytes of header with INT3. (Alexei)
2. Use kvmalloc for temporary buffer. (Alexei)
3. Rename tmp_header/tmp_image => rw_header/rw_image. Remove tmp_image from
x64_jit_data. (Alexei)
4. Change fall back round_up_to in bpf_jit_binary_alloc_pack() from
BPF_PROG_MAX_PACK_PROG_SIZE to PAGE_SIZE.
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 1-6 prepare the work. Patch 7 contains key logic of bpf_prog_pack
allocator. Patch 8 contains bpf_jit_binary_pack_alloc logic on top of
bpf_prog_pack allocator. Patch 9 uses this allocator in x86_64 jit.
Song Liu (9):
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: use prog->jited_len in bpf_prog_ksym_set_addr()
x86/alternative: introduce text_poke_copy
bpf: introduce bpf_arch_text_copy
bpf: introduce bpf_prog_pack allocator
bpf: introduce bpf_jit_binary_pack_[alloc|finalize|free]
bpf, x86_64: use bpf_jit_binary_pack_alloc
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 | 66 ++++---
include/linux/bpf.h | 7 +-
include/linux/filter.h | 27 +--
kernel/bpf/core.c | 269 +++++++++++++++++++++++++--
kernel/bpf/trampoline.c | 6 +-
8 files changed, 346 insertions(+), 63 deletions(-)
--
2.30.2
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]>
---
kernel/bpf/core.c | 127 ++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 127 insertions(+)
diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index dc0142e20c72..25e34caa9a95 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -805,6 +805,133 @@ 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_MASK (~(BPF_PROG_CHUNK_SIZE - 1))
+#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->ptr);
+ 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;
+
+ if (size > BPF_PROG_MAX_PACK_PROG_SIZE) {
+ size = round_up(size, PAGE_SIZE);
+ ptr = module_alloc(size);
+ if (ptr) {
+ set_vm_flush_reset_perms(ptr);
+ set_memory_ro((unsigned long)ptr, size / PAGE_SIZE);
+ set_memory_x((unsigned long)ptr, size / PAGE_SIZE);
+ }
+ return ptr;
+ }
+ 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)
+{
+ struct bpf_prog_pack *pack = NULL, *tmp;
+ unsigned int nbits;
+ unsigned long pos;
+ void *pack_ptr;
+
+ if (hdr->size > BPF_PROG_MAX_PACK_PROG_SIZE) {
+ module_memfree(hdr);
+ return;
+ }
+
+ pack_ptr = (void *)((unsigned long)hdr & ~(BPF_PROG_PACK_SIZE - 1));
+ 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,
--
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
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 d96ad87f0a2c..69f348d9f816 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
From: Song Liu <[email protected]>
This is the jit binary allocator built on top of bpf_prog_pack.
bpf_prog_pack allocates RO memory, which cannot be used directly by the
JIT engine. Therefore, a temporary rw buffer is allocated for the JIT
engine. Once JIT is done, bpf_jit_binary_pack_finalize is used to copy
the program to the RO memory.
bpf_jit_binary_pack_alloc reserves 16 bytes of extra space for illegal
instructions, which is small than the 128 bytes space reserved by
bpf_jit_binary_alloc. This change is necessary for bpf_jit_binary_hdr
to find the correct header. Also, flag use_bpf_prog_pack is added to
differentiate a program allocated by bpf_jit_binary_pack_alloc.
Signed-off-by: Song Liu <[email protected]>
---
include/linux/bpf.h | 1 +
include/linux/filter.h | 21 ++++----
kernel/bpf/core.c | 108 ++++++++++++++++++++++++++++++++++++++++-
3 files changed, 120 insertions(+), 10 deletions(-)
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 7f58fe256671..06d119c472e7 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -945,6 +945,7 @@ struct bpf_prog_aux {
bool sleepable;
bool tail_call_reachable;
bool xdp_has_frags;
+ bool use_bpf_prog_pack;
struct hlist_node tramp_hlist;
/* BTF_KIND_FUNC_PROTO for valid attach_btf_id */
const struct btf_type *attach_func_proto;
diff --git a/include/linux/filter.h b/include/linux/filter.h
index 5855eb474c62..1cb1af917617 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -890,15 +890,6 @@ static inline void bpf_jit_binary_lock_ro(struct bpf_binary_header *hdr)
set_memory_x((unsigned long)hdr, hdr->size >> PAGE_SHIFT);
}
-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;
-
- return (void *)addr;
-}
-
int sk_filter_trim_cap(struct sock *sk, struct sk_buff *skb, unsigned int cap);
static inline int sk_filter(struct sock *sk, struct sk_buff *skb)
{
@@ -1068,6 +1059,18 @@ 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_pack_alloc(unsigned int proglen, u8 **ro_image,
+ unsigned int alignment,
+ struct bpf_binary_header **rw_hdr,
+ u8 **rw_image,
+ bpf_jit_fill_hole_t bpf_fill_ill_insns);
+int bpf_jit_binary_pack_finalize(struct bpf_prog *prog,
+ struct bpf_binary_header *ro_header,
+ struct bpf_binary_header *rw_header);
+void bpf_jit_binary_pack_free(struct bpf_binary_header *ro_header,
+ struct bpf_binary_header *rw_header);
+
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 25e34caa9a95..ff0c51ef1cb7 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -1031,6 +1031,109 @@ void bpf_jit_binary_free(struct bpf_binary_header *hdr)
bpf_jit_uncharge_modmem(size);
}
+/* Allocate jit binary from bpf_prog_pack allocator.
+ * Since the allocated meory is RO+X, the JIT engine cannot write directly
+ * to the memory. To solve this problem, a RW buffer is also allocated at
+ * as the same time. The JIT engine should calculate offsets based on the
+ * RO memory address, but write JITed program to the RW buffer. Once the
+ * JIT engine finishes, it calls bpf_jit_binary_pack_finalize, which copies
+ * the JITed program to the RO memory.
+ */
+struct bpf_binary_header *
+bpf_jit_binary_pack_alloc(unsigned int proglen, u8 **image_ptr,
+ unsigned int alignment,
+ struct bpf_binary_header **rw_header,
+ u8 **rw_image,
+ bpf_jit_fill_hole_t bpf_fill_ill_insns)
+{
+ struct bpf_binary_header *ro_header;
+ u32 size, hole, start;
+
+ WARN_ON_ONCE(!is_power_of_2(alignment) ||
+ alignment > BPF_IMAGE_ALIGNMENT);
+
+ /* add 16 bytes for a random section of illegal instructions */
+ size = round_up(proglen + sizeof(*ro_header) + 16, BPF_PROG_CHUNK_SIZE);
+
+ if (bpf_jit_charge_modmem(size))
+ return NULL;
+ ro_header = bpf_prog_pack_alloc(size);
+ if (!ro_header) {
+ bpf_jit_uncharge_modmem(size);
+ return NULL;
+ }
+
+ *rw_header = kvmalloc(size, GFP_KERNEL);
+ if (!*rw_header) {
+ bpf_prog_pack_free(ro_header);
+ bpf_jit_uncharge_modmem(size);
+ return NULL;
+ }
+
+ /* Fill space with illegal/arch-dep instructions. */
+ bpf_fill_ill_insns(*rw_header, size);
+ (*rw_header)->size = size;
+
+ hole = min_t(unsigned int, size - (proglen + sizeof(*ro_header)),
+ BPF_PROG_CHUNK_SIZE - sizeof(*ro_header));
+ start = (get_random_int() % hole) & ~(alignment - 1);
+
+ *image_ptr = &ro_header->image[start];
+ *rw_image = &(*rw_header)->image[start];
+
+ return ro_header;
+}
+
+/* Copy JITed text from rw_header to its final location, the ro_header. */
+int bpf_jit_binary_pack_finalize(struct bpf_prog *prog,
+ struct bpf_binary_header *ro_header,
+ struct bpf_binary_header *rw_header)
+{
+ void *ptr;
+
+ ptr = bpf_arch_text_copy(ro_header, rw_header, rw_header->size);
+
+ kvfree(rw_header);
+
+ if (IS_ERR(ptr)) {
+ bpf_prog_pack_free(ro_header);
+ return PTR_ERR(ptr);
+ }
+ prog->aux->use_bpf_prog_pack = true;
+ return 0;
+}
+
+/* bpf_jit_binary_pack_free is called in two different scenarios:
+ * 1) when the program is freed after;
+ * 2) when the JIT engine fails (before bpf_jit_binary_pack_finalize).
+ * For case 2), we need to free both the RO memory and the RW buffer.
+ * Also, ro_header->size in 2) is not properly set yet, so rw_header->size
+ * is used for uncharge.
+ */
+void bpf_jit_binary_pack_free(struct bpf_binary_header *ro_header,
+ struct bpf_binary_header *rw_header)
+{
+ u32 size = rw_header ? rw_header->size : ro_header->size;
+
+ bpf_prog_pack_free(ro_header);
+ kvfree(rw_header);
+ bpf_jit_uncharge_modmem(size);
+}
+
+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;
+
+ if (fp->aux->use_bpf_prog_pack)
+ addr = real_start & BPF_PROG_CHUNK_MASK;
+ else
+ addr = real_start & PAGE_MASK;
+
+ return (void *)addr;
+}
+
/* 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.
@@ -1040,7 +1143,10 @@ void __weak bpf_jit_free(struct bpf_prog *fp)
if (fp->jited) {
struct bpf_binary_header *hdr = bpf_jit_binary_hdr(fp);
- bpf_jit_binary_free(hdr);
+ if (fp->aux->use_bpf_prog_pack)
+ bpf_jit_binary_pack_free(hdr, NULL /* rw_buffer */);
+ else
+ bpf_jit_binary_free(hdr);
WARN_ON_ONCE(!bpf_prog_kallsyms_verify_off(fp));
}
--
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 e8ec8d2f2fe3..28ac752f21ba 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -838,8 +838,8 @@ 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 0a1cfd8544b9..d96ad87f0a2c 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]>
Use bpf_jit_binary_pack_alloc in x86_64 jit. The jit engine first writes
the program to the rw buffer. When the jit is done, the program is copied
to the final location with bpf_jit_binary_pack_finalize.
Note that we need to do bpf_tail_call_direct_fixup after finalize.
Therefore, the text_live = false logic in __bpf_arch_text_poke is no
longer needed.
Signed-off-by: Song Liu <[email protected]>
---
arch/x86/net/bpf_jit_comp.c | 59 +++++++++++++++++++------------------
1 file changed, 31 insertions(+), 28 deletions(-)
diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c
index 9792bf10d881..afb957e63e3d 100644
--- a/arch/x86/net/bpf_jit_comp.c
+++ b/arch/x86/net/bpf_jit_comp.c
@@ -330,8 +330,7 @@ static int emit_jump(u8 **pprog, void *func, void *ip)
}
static int __bpf_arch_text_poke(void *ip, enum bpf_text_poke_type t,
- void *old_addr, void *new_addr,
- const bool text_live)
+ void *old_addr, void *new_addr)
{
const u8 *nop_insn = x86_nops[5];
u8 old_insn[X86_PATCH_SIZE];
@@ -365,10 +364,7 @@ static int __bpf_arch_text_poke(void *ip, enum bpf_text_poke_type t,
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:
@@ -384,7 +380,7 @@ int bpf_arch_text_poke(void *ip, enum bpf_text_poke_type t,
/* BPF poking in modules is not supported */
return -EINVAL;
- return __bpf_arch_text_poke(ip, t, old_addr, new_addr, true);
+ return __bpf_arch_text_poke(ip, t, old_addr, new_addr);
}
#define EMIT_LFENCE() EMIT3(0x0F, 0xAE, 0xE8)
@@ -558,24 +554,15 @@ 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);
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);
BUG_ON(ret < 0);
}
WRITE_ONCE(poke->tailcall_target_stable, true);
@@ -867,7 +854,7 @@ 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 *rw_image,
int oldproglen, struct jit_context *ctx, bool jmp_padding)
{
bool tail_call_reachable = bpf_prog->aux->tail_call_reachable;
@@ -894,8 +881,8 @@ 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 (rw_image)
+ memcpy(rw_image + proglen, temp, ilen);
proglen += ilen;
addrs[0] = proglen;
prog = temp;
@@ -1324,8 +1311,10 @@ 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 rw buffer for writes */
+ ex = (void *)rw_image + ((void *)ex - (void *)image);
+ ex->insn = delta;
ex->type = EX_TYPE_BPF;
if (dst_reg > BPF_REG_9) {
@@ -1706,7 +1695,7 @@ st: if (is_imm8(insn->off))
pr_err("bpf_jit: fatal error\n");
return -EFAULT;
}
- memcpy(image + proglen, temp, ilen);
+ memcpy(rw_image + proglen, temp, ilen);
}
proglen += ilen;
addrs[i] = proglen;
@@ -2247,6 +2236,7 @@ int arch_prepare_bpf_dispatcher(void *image, s64 *funcs, int num_funcs)
}
struct x64_jit_data {
+ struct bpf_binary_header *rw_header;
struct bpf_binary_header *header;
int *addrs;
u8 *image;
@@ -2259,6 +2249,7 @@ struct x64_jit_data {
struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog)
{
+ struct bpf_binary_header *rw_header = NULL;
struct bpf_binary_header *header = NULL;
struct bpf_prog *tmp, *orig_prog = prog;
struct x64_jit_data *jit_data;
@@ -2267,6 +2258,7 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog)
bool tmp_blinded = false;
bool extra_pass = false;
bool padding = false;
+ u8 *rw_image = NULL;
u8 *image = NULL;
int *addrs;
int pass;
@@ -2302,6 +2294,8 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog)
oldproglen = jit_data->proglen;
image = jit_data->image;
header = jit_data->header;
+ rw_header = jit_data->rw_header;
+ rw_image = (void *)rw_header + ((void *)image - (void *)header);
extra_pass = true;
padding = true;
goto skip_init_addrs;
@@ -2332,12 +2326,12 @@ 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, rw_image, oldproglen, &ctx, padding);
if (proglen <= 0) {
out_image:
image = NULL;
if (header)
- bpf_jit_binary_free(header);
+ bpf_jit_binary_pack_free(header, rw_header);
prog = orig_prog;
goto out_addrs;
}
@@ -2361,8 +2355,9 @@ 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_pack_alloc(roundup(proglen, align) + extable_size,
+ &image, align, &rw_header, &rw_image,
+ jit_fill_hole);
if (!header) {
prog = orig_prog;
goto out_addrs;
@@ -2378,14 +2373,22 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog)
if (image) {
if (!prog->is_func || extra_pass) {
+ /*
+ * bpf_jit_binary_pack_finalize fails in two scenarios:
+ * 1) header is not pointing to proper module memory;
+ * 2) the arch doesn't support bpf_arch_text_copy().
+ *
+ * Both cases are serious bugs that we should not continue.
+ */
+ BUG_ON(bpf_jit_binary_pack_finalize(prog, header, rw_header));
bpf_tail_call_direct_fixup(prog);
- 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->header = header;
+ jit_data->rw_header = rw_header;
}
prog->bpf_func = (void *)image;
prog->jited = 1;
--
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.
Acked-by: Peter Zijlstra (Intel) <[email protected]>
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
This will be used to copy JITed text to RO protected module memory. On
x86, bpf_arch_text_copy is implemented with text_poke_copy.
bpf_arch_text_copy returns pointer to dst on success, and ERR_PTR(errno)
on errors.
Signed-off-by: Song Liu <[email protected]>
---
arch/x86/net/bpf_jit_comp.c | 7 +++++++
include/linux/bpf.h | 2 ++
kernel/bpf/core.c | 5 +++++
3 files changed, 14 insertions(+)
diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c
index ce1f86f245c9..9792bf10d881 100644
--- a/arch/x86/net/bpf_jit_comp.c
+++ b/arch/x86/net/bpf_jit_comp.c
@@ -2413,3 +2413,10 @@ bool bpf_jit_supports_kfunc_call(void)
{
return true;
}
+
+void *bpf_arch_text_copy(void *dst, void *src, size_t len)
+{
+ if (text_poke_copy(dst, src, len) == NULL)
+ return ERR_PTR(-EINVAL);
+ return dst;
+}
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 28ac752f21ba..7f58fe256671 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -2350,6 +2350,8 @@ enum bpf_text_poke_type {
int bpf_arch_text_poke(void *ip, enum bpf_text_poke_type t,
void *addr1, void *addr2);
+void *bpf_arch_text_copy(void *dst, void *src, size_t len);
+
struct btf_id_set;
bool btf_id_set_contains(const struct btf_id_set *set, u32 id);
diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index 7cbcf6bfbb52..dc0142e20c72 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -2448,6 +2448,11 @@ int __weak bpf_arch_text_poke(void *ip, enum bpf_text_poke_type t,
return -ENOTSUPP;
}
+void * __weak bpf_arch_text_copy(void *dst, void *src, size_t len)
+{
+ return ERR_PTR(-ENOTSUPP);
+}
+
DEFINE_STATIC_KEY_FALSE(bpf_stats_enabled_key);
EXPORT_SYMBOL(bpf_stats_enabled_key);
--
2.30.2
On 1/29/22 12:45 AM, Song Liu wrote:
> 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.
Did you benchmark the program load times under this API, e.g. how much
overhead is expected for very large programs?
> Signed-off-by: Song Liu <[email protected]>
> ---
> kernel/bpf/core.c | 127 ++++++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 127 insertions(+)
>
> diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
> index dc0142e20c72..25e34caa9a95 100644
> --- a/kernel/bpf/core.c
> +++ b/kernel/bpf/core.c
> @@ -805,6 +805,133 @@ 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_MASK (~(BPF_PROG_CHUNK_SIZE - 1))
> +#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->ptr);
> + 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;
> +
> + if (size > BPF_PROG_MAX_PACK_PROG_SIZE) {
> + size = round_up(size, PAGE_SIZE);
> + ptr = module_alloc(size);
> + if (ptr) {
> + set_vm_flush_reset_perms(ptr);
> + set_memory_ro((unsigned long)ptr, size / PAGE_SIZE);
> + set_memory_x((unsigned long)ptr, size / PAGE_SIZE);
> + }
> + return ptr;
> + }
> + 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;
Will this effectively disable the JIT for all bpf_prog_pack_alloc requests <=
BPF_PROG_MAX_PACK_PROG_SIZE when vmap_allow_huge is false (e.g. boot param via
nohugevmalloc) ?
> + 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)
> +{
> + struct bpf_prog_pack *pack = NULL, *tmp;
> + unsigned int nbits;
> + unsigned long pos;
> + void *pack_ptr;
> +
> + if (hdr->size > BPF_PROG_MAX_PACK_PROG_SIZE) {
> + module_memfree(hdr);
> + return;
> + }
> +
> + pack_ptr = (void *)((unsigned long)hdr & ~(BPF_PROG_PACK_SIZE - 1));
> + 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,
>
On 1/29/22 12:45 AM, Song Liu wrote:
[...]
> diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
> index 25e34caa9a95..ff0c51ef1cb7 100644
> --- a/kernel/bpf/core.c
> +++ b/kernel/bpf/core.c
> @@ -1031,6 +1031,109 @@ void bpf_jit_binary_free(struct bpf_binary_header *hdr)
> bpf_jit_uncharge_modmem(size);
> }
>
> +/* Allocate jit binary from bpf_prog_pack allocator.
> + * Since the allocated meory is RO+X, the JIT engine cannot write directly
nit: meory
> + * to the memory. To solve this problem, a RW buffer is also allocated at
> + * as the same time. The JIT engine should calculate offsets based on the
> + * RO memory address, but write JITed program to the RW buffer. Once the
> + * JIT engine finishes, it calls bpf_jit_binary_pack_finalize, which copies
> + * the JITed program to the RO memory.
> + */
> +struct bpf_binary_header *
> +bpf_jit_binary_pack_alloc(unsigned int proglen, u8 **image_ptr,
> + unsigned int alignment,
> + struct bpf_binary_header **rw_header,
> + u8 **rw_image,
> + bpf_jit_fill_hole_t bpf_fill_ill_insns)
> +{
> + struct bpf_binary_header *ro_header;
> + u32 size, hole, start;
> +
> + WARN_ON_ONCE(!is_power_of_2(alignment) ||
> + alignment > BPF_IMAGE_ALIGNMENT);
> +
> + /* add 16 bytes for a random section of illegal instructions */
> + size = round_up(proglen + sizeof(*ro_header) + 16, BPF_PROG_CHUNK_SIZE);
> +
> + if (bpf_jit_charge_modmem(size))
> + return NULL;
> + ro_header = bpf_prog_pack_alloc(size);
> + if (!ro_header) {
> + bpf_jit_uncharge_modmem(size);
> + return NULL;
> + }
> +
> + *rw_header = kvmalloc(size, GFP_KERNEL);
> + if (!*rw_header) {
> + bpf_prog_pack_free(ro_header);
> + bpf_jit_uncharge_modmem(size);
> + return NULL;
> + }
> +
> + /* Fill space with illegal/arch-dep instructions. */
> + bpf_fill_ill_insns(*rw_header, size);
> + (*rw_header)->size = size;
> +
> + hole = min_t(unsigned int, size - (proglen + sizeof(*ro_header)),
> + BPF_PROG_CHUNK_SIZE - sizeof(*ro_header));
> + start = (get_random_int() % hole) & ~(alignment - 1);
> +
> + *image_ptr = &ro_header->image[start];
> + *rw_image = &(*rw_header)->image[start];
> +
> + return ro_header;
> +}
> +
> +/* Copy JITed text from rw_header to its final location, the ro_header. */
> +int bpf_jit_binary_pack_finalize(struct bpf_prog *prog,
> + struct bpf_binary_header *ro_header,
> + struct bpf_binary_header *rw_header)
> +{
> + void *ptr;
> +
> + ptr = bpf_arch_text_copy(ro_header, rw_header, rw_header->size);
Does this need to be wrapped with a text_mutex lock/unlock pair given
text_poke_copy() internally relies on __text_poke() ?
> + kvfree(rw_header);
> +
> + if (IS_ERR(ptr)) {
> + bpf_prog_pack_free(ro_header);
> + return PTR_ERR(ptr);
> + }
> + prog->aux->use_bpf_prog_pack = true;
> + return 0;
> +}
> +
[...]
On Mon, Jan 31, 2022 at 4:21 PM Daniel Borkmann <[email protected]> wrote:
>
> On 1/29/22 12:45 AM, Song Liu wrote:
> [...]
[...]
> > +}
> > +
> > +/* Copy JITed text from rw_header to its final location, the ro_header. */
> > +int bpf_jit_binary_pack_finalize(struct bpf_prog *prog,
> > + struct bpf_binary_header *ro_header,
> > + struct bpf_binary_header *rw_header)
> > +{
> > + void *ptr;
> > +
> > + ptr = bpf_arch_text_copy(ro_header, rw_header, rw_header->size);
>
> Does this need to be wrapped with a text_mutex lock/unlock pair given
> text_poke_copy() internally relies on __text_poke() ?
Yes... Good catch. I guess we may do the lock in text_poke_copy().
Thanks,
Song
On Mon, Jan 31, 2022 at 4:06 PM Daniel Borkmann <[email protected]> wrote:
>
> On 1/29/22 12:45 AM, Song Liu wrote:
> > 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.
>
> Did you benchmark the program load times under this API, e.g. how much
> overhead is expected for very large programs?
For the two scale tests in test_verifier:
./test_verifier 965 966
#965/p scale: scale test 1 OK
#966/p scale: scale test 2 OK
The runtime is about 0.6 second before the set and 0.7 second after.
Is this a good benchmark?
>
> > Signed-off-by: Song Liu <[email protected]>
> > ---
> > kernel/bpf/core.c | 127 ++++++++++++++++++++++++++++++++++++++++++++++
> > 1 file changed, 127 insertions(+)
> >
[...]
> > + }
> > + 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;
>
> Will this effectively disable the JIT for all bpf_prog_pack_alloc requests <=
> BPF_PROG_MAX_PACK_PROG_SIZE when vmap_allow_huge is false (e.g. boot param via
> nohugevmalloc) ?
This won't disable JIT. It will just allocate 512x 4k pages for a 2MB pack. We
will mark the whole 2MB RO, same as a 2MB huge page. We still benefit
from this as this avoids poking the linear mapping (1GB pages) to 4kB pages
with set_memory_ro().
Thanks,
Song