This patch series to support kernel relocation and KASLR (only 64bit).
Tested the kernel images built with new toolchain (Binutils-2.40 + patched
GCC-12.2) and old toolchain (kernel.org cross toolchain [1]) on a
3A5000-7A2000-EVB.
With CONFIG_RANDOMIZE_BASE=y, the results are:
1. first boot, new toolchain:
$ sudo cat /proc/iomem | grep Kernel
01080000-0189ffff : Kernel code
018a0000-01deb5ff : Kernel data
01deb600-01ef6e9f : Kernel bss
2. second boot, new toolchain:
$ sudo cat /proc/iomem | grep Kernel
012f0000-01b0ffff : Kernel code
01b10000-0205b5ff : Kernel data
0205b600-02166e9f : Kernel bss
3. first boot, old toolchain:
010e0000-018fffff : Kernel code
01900000-01e591ff : Kernel data
01e59200-01f56dcf : Kernel bss
4. second boot, old toolchain:
010b0000-018cffff : Kernel code
018d0000-01e291ff : Kernel data
01e29200-01f26dcf : Kernel bss
Changes from v2:
- Correctly fixup pcaddi12i/ori/lu32i.d/lu52i.d sequence generated by
GNU as <= 2.39 for la.pcrel.
Changes from v1 to v2:
- Relocate the handlers instead of using a trampoline, to avoid
performance issue on NUMA systems.
- Fix compiler warnings.
Xi Ruoyao (2):
LoongArch: Use la.pcrel instead of la.abs when it's trivially possible
LoongArch: Use la.pcrel instead of la.abs for exception handlers
Youling Tang (3):
LoongArch: Add JUMP_LINK_ADDR macro implementation to avoid using
la.abs
LoongArch: Add support for kernel relocation
LoongArch: Add support for kernel address space layout randomization
(KASLR)
arch/loongarch/Kconfig | 37 +++++
arch/loongarch/Makefile | 5 +
arch/loongarch/include/asm/inst.h | 1 +
arch/loongarch/include/asm/page.h | 6 +
arch/loongarch/include/asm/setup.h | 6 +-
arch/loongarch/include/asm/stackframe.h | 13 +-
arch/loongarch/include/asm/uaccess.h | 1 -
arch/loongarch/kernel/Makefile | 2 +
arch/loongarch/kernel/entry.S | 2 +-
arch/loongarch/kernel/genex.S | 40 ++++-
arch/loongarch/kernel/head.S | 30 +++-
arch/loongarch/kernel/relocate.c | 211 ++++++++++++++++++++++++
arch/loongarch/kernel/setup.c | 3 +
arch/loongarch/kernel/traps.c | 158 +++++++++++++++---
arch/loongarch/kernel/vmlinux.lds.S | 11 +-
arch/loongarch/mm/tlb.c | 23 +--
arch/loongarch/mm/tlbex.S | 72 +++++++-
arch/loongarch/power/suspend_asm.S | 5 +-
18 files changed, 564 insertions(+), 62 deletions(-)
create mode 100644 arch/loongarch/kernel/relocate.c
--
2.39.1
It's needed to build the kernel as a PIE, or the linker will complain.
For the consideration about performance, we copy the exception handlers
to a dedicated 64 KB area for each CPU. So, the PC-relative offset
calculated at link time will be incorrect and we need to relocate the
exception handlers after copying them.
For the simplicity, we don't use the ELF R_LARCH_* relocations, but code
an relocation entry as simply (offset_in_the_handler, symbol_addr). For
each exception handler, we also code the number of relocation entries.
Then we can use the relocation information to fix up the handlers after
copying them.
Signed-off-by: Xi Ruoyao <[email protected]>
---
arch/loongarch/include/asm/inst.h | 1 +
arch/loongarch/include/asm/setup.h | 6 +-
arch/loongarch/include/asm/stackframe.h | 3 +-
arch/loongarch/kernel/genex.S | 40 +++++-
arch/loongarch/kernel/traps.c | 158 ++++++++++++++++++++----
arch/loongarch/mm/tlb.c | 23 ++--
arch/loongarch/mm/tlbex.S | 69 +++++++++--
7 files changed, 255 insertions(+), 45 deletions(-)
diff --git a/arch/loongarch/include/asm/inst.h b/arch/loongarch/include/asm/inst.h
index 7eedd83fd0d7..426054518a3d 100644
--- a/arch/loongarch/include/asm/inst.h
+++ b/arch/loongarch/include/asm/inst.h
@@ -32,6 +32,7 @@ enum reg1i20_op {
lu12iw_op = 0x0a,
lu32id_op = 0x0b,
pcaddi_op = 0x0c,
+ pcalau12i_op = 0x0d,
pcaddu12i_op = 0x0e,
pcaddu18i_op = 0x0f,
};
diff --git a/arch/loongarch/include/asm/setup.h b/arch/loongarch/include/asm/setup.h
index 72ead58039f3..f0a2b34365f1 100644
--- a/arch/loongarch/include/asm/setup.h
+++ b/arch/loongarch/include/asm/setup.h
@@ -11,6 +11,9 @@
#define VECSIZE 0x200
+struct handler_reloc;
+
+extern struct handler_reloc *eentry_reloc[];
extern unsigned long eentry;
extern unsigned long tlbrentry;
extern char init_command_line[COMMAND_LINE_SIZE];
@@ -18,7 +21,8 @@ extern void tlb_init(int cpu);
extern void cpu_cache_init(void);
extern void cache_error_setup(void);
extern void per_cpu_trap_init(int cpu);
-extern void set_handler(unsigned long offset, void *addr, unsigned long len);
+extern void set_handler(unsigned long exccode, void *addr);
extern void set_merr_handler(unsigned long offset, void *addr, unsigned long len);
+extern void reloc_handler(unsigned long handler, struct handler_reloc *rel);
#endif /* __SETUP_H */
diff --git a/arch/loongarch/include/asm/stackframe.h b/arch/loongarch/include/asm/stackframe.h
index 7deb043ce387..bbec1e56b61b 100644
--- a/arch/loongarch/include/asm/stackframe.h
+++ b/arch/loongarch/include/asm/stackframe.h
@@ -77,7 +77,8 @@
* new value in sp.
*/
.macro get_saved_sp docfi=0
- la.abs t1, kernelsp
+ /* The label is used for generating reloc tables for handlers */
+514: la.pcrel t1, t0, kernelsp
#ifdef CONFIG_SMP
csrrd t0, PERCPU_BASE_KS
LONG_ADD t1, t1, t0
diff --git a/arch/loongarch/kernel/genex.S b/arch/loongarch/kernel/genex.S
index 7e5c293ed89f..005a10fe5a50 100644
--- a/arch/loongarch/kernel/genex.S
+++ b/arch/loongarch/kernel/genex.S
@@ -34,7 +34,7 @@ SYM_FUNC_END(__arch_cpu_idle)
SYM_FUNC_START(handle_vint)
BACKUP_T0T1
SAVE_ALL
- la.abs t1, __arch_cpu_idle
+0: la.pcrel t1, t2, __arch_cpu_idle
LONG_L t0, sp, PT_ERA
/* 32 byte rollback region */
ori t0, t0, 0x1f
@@ -43,11 +43,25 @@ SYM_FUNC_START(handle_vint)
LONG_S t0, sp, PT_ERA
1: move a0, sp
move a1, sp
- la.abs t0, do_vint
+2: la.pcrel t0, t2, do_vint
jirl ra, t0, 0
RESTORE_ALL_AND_RET
SYM_FUNC_END(handle_vint)
+SYM_DATA_START(rel_handle_vint)
+LONG 3
+
+LONG 514b - handle_vint
+LONG kernelsp
+
+LONG 0b - handle_vint
+LONG __arch_cpu_idle
+
+LONG 2b - handle_vint
+LONG do_vint
+
+SYM_DATA_END(rel_handle_vint)
+
SYM_FUNC_START(except_vec_cex)
b cache_parity_error
SYM_FUNC_END(except_vec_cex)
@@ -72,12 +86,24 @@ SYM_FUNC_END(except_vec_cex)
SAVE_ALL
build_prep_\prep
move a0, sp
- la.abs t0, do_\handler
+ 667:
+ la.pcrel t0, t1, do_\handler
jirl ra, t0, 0
668:
RESTORE_ALL_AND_RET
SYM_FUNC_END(handle_\exception)
SYM_DATA(unwind_hint_\exception, .word 668b - 666b)
+
+ SYM_DATA_START(rel_handle_\exception)
+ LONG 2
+
+ LONG 514b - 666b
+ LONG kernelsp
+
+ LONG 667b - 666b
+ LONG do_\handler
+
+ SYM_DATA_END(rel_handle_\exception)
.endm
BUILD_HANDLER ade ade badv
@@ -93,6 +119,12 @@ SYM_FUNC_END(except_vec_cex)
BUILD_HANDLER reserved reserved none /* others */
SYM_FUNC_START(handle_sys)
- la.abs t0, handle_syscall
+ la.pcrel t0, t1, handle_syscall
jr t0
SYM_FUNC_END(handle_sys)
+
+SYM_DATA_START(rel_handle_sys)
+LONG 1
+LONG 0
+LONG handle_syscall
+SYM_DATA_END(rel_handle_sys)
diff --git a/arch/loongarch/kernel/traps.c b/arch/loongarch/kernel/traps.c
index c38a146a973b..7e073854f493 100644
--- a/arch/loongarch/kernel/traps.c
+++ b/arch/loongarch/kernel/traps.c
@@ -62,6 +62,127 @@ extern asmlinkage void handle_reserved(void);
extern asmlinkage void handle_watch(void);
extern asmlinkage void handle_vint(void);
+struct handler_reloc_entry {
+ unsigned long offset;
+ unsigned long sym;
+};
+
+struct handler_reloc {
+ unsigned long cnt;
+ struct handler_reloc_entry entries[];
+};
+
+extern struct handler_reloc rel_handle_tlb_load;
+extern struct handler_reloc rel_handle_tlb_store;
+extern struct handler_reloc rel_handle_tlb_modify;
+extern struct handler_reloc rel_handle_tlb_protect;
+extern struct handler_reloc rel_handle_ade;
+extern struct handler_reloc rel_handle_ale;
+extern struct handler_reloc rel_handle_sys;
+extern struct handler_reloc rel_handle_bp;
+extern struct handler_reloc rel_handle_ri;
+extern struct handler_reloc rel_handle_fpu;
+extern struct handler_reloc rel_handle_lsx;
+extern struct handler_reloc rel_handle_lasx;
+extern struct handler_reloc rel_handle_fpe;
+extern struct handler_reloc rel_handle_lbt;
+extern struct handler_reloc rel_handle_watch;
+extern struct handler_reloc rel_handle_reserved;
+extern struct handler_reloc rel_handle_vint;
+
+struct handler_reloc *eentry_reloc[128] = {
+ [0] = NULL, /* merr handler */
+ [EXCCODE_TLBL] = &rel_handle_tlb_load,
+ [EXCCODE_TLBS] = &rel_handle_tlb_store,
+ [EXCCODE_TLBI] = &rel_handle_tlb_load,
+ [EXCCODE_TLBM] = &rel_handle_tlb_modify,
+ [EXCCODE_TLBNR] = &rel_handle_tlb_protect,
+ [EXCCODE_TLBNX] = &rel_handle_tlb_protect,
+ [EXCCODE_TLBPE] = &rel_handle_tlb_protect,
+ [EXCCODE_ADE] = &rel_handle_ade,
+ [EXCCODE_ALE] = &rel_handle_ale,
+ [EXCCODE_SYS] = &rel_handle_sys,
+ [EXCCODE_BP] = &rel_handle_bp,
+ [EXCCODE_INE] = &rel_handle_ri,
+ [EXCCODE_IPE] = &rel_handle_ri,
+ [EXCCODE_FPDIS] = &rel_handle_fpu,
+ [EXCCODE_LSXDIS] = &rel_handle_lsx,
+ [EXCCODE_LASXDIS] = &rel_handle_lasx,
+ [EXCCODE_FPE] = &rel_handle_fpe,
+ [EXCCODE_BTDIS] = &rel_handle_lbt,
+ [EXCCODE_WATCH] = &rel_handle_watch,
+ [(EXCCODE_WATCH + 1) ... (EXCCODE_INT_START - 1)] = &rel_handle_reserved,
+ [EXCCODE_INT_START ... (EXCCODE_INT_END - 1)] = &rel_handle_vint,
+};
+
+void reloc_handler(unsigned long handler, struct handler_reloc *rel)
+{
+ if (!rel)
+ return;
+
+ for (unsigned long i = 0; i < rel->cnt; i++) {
+ unsigned long pc = handler + rel->entries[i].offset;
+ union loongarch_instruction *insn =
+ (union loongarch_instruction *)pc;
+ u32 imm[4];
+ unsigned long v = rel->entries[i].sym;
+
+ /* GNU as >= 2.40 uses pcalau12i for la.pcrel, but GNU ld <= 2.39
+ * uses pcaddu12i.
+ */
+ if (insn->reg1i20_format.opcode == pcalau12i_op) {
+ /* Use s32 deliberately for sign extension. */
+ s32 offset_hi20 = ((v + 0x800) & ~0xfff) -
+ (pc & ~0xfff);
+ unsigned long anchor = (pc & ~0xfff) + offset_hi20;
+ unsigned long offset_rem = v - anchor;
+
+ imm[0] = (offset_hi20 >> 12) & 0xfffff;
+ imm[1] = v & 0xfff;
+ imm[2] = (offset_rem >> 32) & 0xfffff;
+ imm[3] = offset_rem >> 52;
+ } else if (insn->reg1i20_format.opcode == pcaddu12i_op) {
+ /* Use s32 deliberately for sign extension. */
+ s32 offset_lo = v - pc;
+ unsigned long offset_hi = v - pc - offset_lo;
+
+ imm[0] = (offset_lo >> 12) & 0xfffff;
+ imm[1] = offset_lo & 0xfff;
+ imm[2] = (offset_hi >> 32) & 0xfffff;
+ imm[3] = offset_hi >> 52;
+ } else
+ panic("Cannot fixup la.pcrel for exception handler at %lu: unexpected instruction %d!",
+ pc, insn->word);
+
+ insn[0].reg1i20_format.immediate = imm[0];
+ insn[1].reg2i12_format.immediate = imm[1];
+ insn[2].reg1i20_format.immediate = imm[2];
+ insn[3].reg2i12_format.immediate = imm[3];
+ }
+}
+
+/* Install CPU exception handler */
+static void do_set_handler(unsigned long exccode, void *addr,
+ struct handler_reloc *rel)
+{
+ unsigned long dest_addr = eentry + exccode * VECSIZE;
+
+ memcpy((void *)dest_addr, addr, VECSIZE);
+ reloc_handler(dest_addr, rel);
+ local_flush_icache_range(dest_addr, dest_addr + VECSIZE);
+}
+
+/* Install CPU exception handler, with the reloc table from eentry_reloc */
+void set_handler(unsigned long exccode, void *addr)
+{
+ do_set_handler(exccode, addr, eentry_reloc[exccode]);
+}
+
+static void set_handler_reserved(unsigned long exccode)
+{
+ do_set_handler(exccode, handle_reserved, &rel_handle_reserved);
+}
+
static void show_backtrace(struct task_struct *task, const struct pt_regs *regs,
const char *loglvl, bool user)
{
@@ -704,19 +825,12 @@ void per_cpu_trap_init(int cpu)
/* Initialise exception handlers */
if (cpu == 0)
for (i = 0; i < 64; i++)
- set_handler(i * VECSIZE, handle_reserved, VECSIZE);
+ set_handler_reserved(i);
tlb_init(cpu);
cpu_cache_init();
}
-/* Install CPU exception handler */
-void set_handler(unsigned long offset, void *addr, unsigned long size)
-{
- memcpy((void *)(eentry + offset), addr, size);
- local_flush_icache_range(eentry + offset, eentry + offset + size);
-}
-
static const char panic_null_cerr[] =
"Trying to set NULL cache error exception handler\n";
@@ -741,20 +855,20 @@ void __init trap_init(void)
/* Set interrupt vector handler */
for (i = EXCCODE_INT_START; i < EXCCODE_INT_END; i++)
- set_handler(i * VECSIZE, handle_vint, VECSIZE);
-
- set_handler(EXCCODE_ADE * VECSIZE, handle_ade, VECSIZE);
- set_handler(EXCCODE_ALE * VECSIZE, handle_ale, VECSIZE);
- set_handler(EXCCODE_SYS * VECSIZE, handle_sys, VECSIZE);
- set_handler(EXCCODE_BP * VECSIZE, handle_bp, VECSIZE);
- set_handler(EXCCODE_INE * VECSIZE, handle_ri, VECSIZE);
- set_handler(EXCCODE_IPE * VECSIZE, handle_ri, VECSIZE);
- set_handler(EXCCODE_FPDIS * VECSIZE, handle_fpu, VECSIZE);
- set_handler(EXCCODE_LSXDIS * VECSIZE, handle_lsx, VECSIZE);
- set_handler(EXCCODE_LASXDIS * VECSIZE, handle_lasx, VECSIZE);
- set_handler(EXCCODE_FPE * VECSIZE, handle_fpe, VECSIZE);
- set_handler(EXCCODE_BTDIS * VECSIZE, handle_lbt, VECSIZE);
- set_handler(EXCCODE_WATCH * VECSIZE, handle_watch, VECSIZE);
+ set_handler(i, handle_vint);
+
+ set_handler(EXCCODE_ADE, handle_ade);
+ set_handler(EXCCODE_ALE, handle_ale);
+ set_handler(EXCCODE_SYS, handle_sys);
+ set_handler(EXCCODE_BP, handle_bp);
+ set_handler(EXCCODE_INE, handle_ri);
+ set_handler(EXCCODE_IPE, handle_ri);
+ set_handler(EXCCODE_FPDIS, handle_fpu);
+ set_handler(EXCCODE_LSXDIS, handle_lsx);
+ set_handler(EXCCODE_LASXDIS, handle_lasx);
+ set_handler(EXCCODE_FPE, handle_fpe);
+ set_handler(EXCCODE_BTDIS, handle_lbt);
+ set_handler(EXCCODE_WATCH, handle_watch);
cache_error_setup();
diff --git a/arch/loongarch/mm/tlb.c b/arch/loongarch/mm/tlb.c
index 8bad6b0cff59..6f70aab7202a 100644
--- a/arch/loongarch/mm/tlb.c
+++ b/arch/loongarch/mm/tlb.c
@@ -253,7 +253,6 @@ static void output_pgtable_bits_defines(void)
#ifdef CONFIG_NUMA
unsigned long pcpu_handlers[NR_CPUS];
#endif
-extern long exception_handlers[VECSIZE * 128 / sizeof(long)];
void setup_tlb_handler(int cpu)
{
@@ -264,19 +263,20 @@ void setup_tlb_handler(int cpu)
if (cpu == 0) {
memcpy((void *)tlbrentry, handle_tlb_refill, 0x80);
local_flush_icache_range(tlbrentry, tlbrentry + 0x80);
- set_handler(EXCCODE_TLBI * VECSIZE, handle_tlb_load, VECSIZE);
- set_handler(EXCCODE_TLBL * VECSIZE, handle_tlb_load, VECSIZE);
- set_handler(EXCCODE_TLBS * VECSIZE, handle_tlb_store, VECSIZE);
- set_handler(EXCCODE_TLBM * VECSIZE, handle_tlb_modify, VECSIZE);
- set_handler(EXCCODE_TLBNR * VECSIZE, handle_tlb_protect, VECSIZE);
- set_handler(EXCCODE_TLBNX * VECSIZE, handle_tlb_protect, VECSIZE);
- set_handler(EXCCODE_TLBPE * VECSIZE, handle_tlb_protect, VECSIZE);
+ set_handler(EXCCODE_TLBI, handle_tlb_load);
+ set_handler(EXCCODE_TLBL, handle_tlb_load);
+ set_handler(EXCCODE_TLBS, handle_tlb_store);
+ set_handler(EXCCODE_TLBM, handle_tlb_modify);
+ set_handler(EXCCODE_TLBNR, handle_tlb_protect);
+ set_handler(EXCCODE_TLBNX, handle_tlb_protect);
+ set_handler(EXCCODE_TLBPE, handle_tlb_protect);
}
#ifdef CONFIG_NUMA
else {
void *addr;
+ unsigned long addr_ul;
struct page *page;
- const int vec_sz = sizeof(exception_handlers);
+ const int vec_sz = VECSIZE * 128;
if (pcpu_handlers[cpu])
return;
@@ -286,8 +286,11 @@ void setup_tlb_handler(int cpu)
return;
addr = page_address(page);
+ addr_ul = (unsigned long)addr;
pcpu_handlers[cpu] = (unsigned long)addr;
- memcpy((void *)addr, (void *)eentry, vec_sz);
+ memcpy(addr, (void *)eentry, vec_sz);
+ for (unsigned long i = 0; i < 128; i++)
+ reloc_handler(addr_ul + i * VECSIZE, eentry_reloc[i]);
local_flush_icache_range((unsigned long)addr, (unsigned long)addr + vec_sz);
csr_write64(pcpu_handlers[cpu], LOONGARCH_CSR_EENTRY);
csr_write64(pcpu_handlers[cpu], LOONGARCH_CSR_MERRENTRY);
diff --git a/arch/loongarch/mm/tlbex.S b/arch/loongarch/mm/tlbex.S
index 3dd2a9615cd9..044c2190771a 100644
--- a/arch/loongarch/mm/tlbex.S
+++ b/arch/loongarch/mm/tlbex.S
@@ -39,11 +39,21 @@ SYM_FUNC_START(handle_tlb_protect)
move a1, zero
csrrd a2, LOONGARCH_CSR_BADV
REG_S a2, sp, PT_BVADDR
- la.abs t0, do_page_fault
+1: la.pcrel t0, t1, do_page_fault
jirl ra, t0, 0
RESTORE_ALL_AND_RET
SYM_FUNC_END(handle_tlb_protect)
+SYM_DATA_START(rel_handle_tlb_protect)
+ LONG 2
+
+ LONG 514b - handle_tlb_protect
+ LONG kernelsp
+
+ LONG 1b - handle_tlb_protect
+ LONG do_page_fault
+SYM_DATA_END(rel_handle_tlb_protect)
+
SYM_FUNC_START(handle_tlb_load)
csrwr t0, EXCEPTION_KS0
csrwr t1, EXCEPTION_KS1
@@ -115,7 +125,8 @@ smp_pgtable_change_load:
#ifdef CONFIG_64BIT
vmalloc_load:
- la.abs t1, swapper_pg_dir
+ /* The first insn of vmalloc_done_load overwrites ra */
+1: la.pcrel t1, ra, swapper_pg_dir
b vmalloc_done_load
#endif
@@ -186,10 +197,24 @@ tlb_huge_update_load:
nopage_tlb_load:
dbar 0
csrrd ra, EXCEPTION_KS2
- la.abs t0, tlb_do_page_fault_0
+2: la.pcrel t0, t1, tlb_do_page_fault_0
jr t0
SYM_FUNC_END(handle_tlb_load)
+SYM_DATA_START(rel_handle_tlb_load)
+#ifdef CONFIG_64BIT
+ LONG 2
+
+ LONG 1b - handle_tlb_load
+ LONG swapper_pg_dir
+#else
+ LONG 1
+#endif
+
+ LONG 2b - handle_tlb_load
+ LONG tlb_do_page_fault_0
+SYM_DATA_END(rel_handle_tlb_load)
+
SYM_FUNC_START(handle_tlb_store)
csrwr t0, EXCEPTION_KS0
csrwr t1, EXCEPTION_KS1
@@ -262,7 +287,8 @@ smp_pgtable_change_store:
#ifdef CONFIG_64BIT
vmalloc_store:
- la.abs t1, swapper_pg_dir
+ /* The first insn of vmalloc_done_store overwrites ra */
+1: la.pcrel t1, ra, swapper_pg_dir
b vmalloc_done_store
#endif
@@ -335,10 +361,24 @@ tlb_huge_update_store:
nopage_tlb_store:
dbar 0
csrrd ra, EXCEPTION_KS2
- la.abs t0, tlb_do_page_fault_1
+2: la.pcrel t0, t1, tlb_do_page_fault_1
jr t0
SYM_FUNC_END(handle_tlb_store)
+SYM_DATA_START(rel_handle_tlb_store)
+#ifdef CONFIG_64BIT
+ LONG 2
+
+ LONG 1b - handle_tlb_store
+ LONG swapper_pg_dir
+#else
+ LONG 1
+#endif
+
+ LONG 2b - handle_tlb_store
+ LONG tlb_do_page_fault_1
+SYM_DATA_END(rel_handle_tlb_store)
+
SYM_FUNC_START(handle_tlb_modify)
csrwr t0, EXCEPTION_KS0
csrwr t1, EXCEPTION_KS1
@@ -410,7 +450,8 @@ smp_pgtable_change_modify:
#ifdef CONFIG_64BIT
vmalloc_modify:
- la.abs t1, swapper_pg_dir
+ /* The first insn of vmalloc_done_modify overwrites ra */
+1: la.pcrel t1, ra, swapper_pg_dir
b vmalloc_done_modify
#endif
@@ -482,10 +523,24 @@ tlb_huge_update_modify:
nopage_tlb_modify:
dbar 0
csrrd ra, EXCEPTION_KS2
- la.abs t0, tlb_do_page_fault_1
+2: la.pcrel t0, t1, tlb_do_page_fault_1
jr t0
SYM_FUNC_END(handle_tlb_modify)
+SYM_DATA_START(rel_handle_tlb_modify)
+#ifdef CONFIG_64BIT
+ LONG 2
+
+ LONG 1b - handle_tlb_modify
+ LONG swapper_pg_dir
+#else
+ LONG 1
+#endif
+
+ LONG 2b - handle_tlb_modify
+ LONG tlb_do_page_fault_1
+SYM_DATA_END(rel_handle_tlb_modify)
+
SYM_FUNC_START(handle_tlb_refill)
csrwr t0, LOONGARCH_CSR_TLBRSAVE
csrrd t0, LOONGARCH_CSR_PGD
--
2.39.1
From: Youling Tang <[email protected]>
Add JUMP_LINK_ADDR macro implementation to avoid using la.abs.
Signed-off-by: Youling Tang <[email protected]>
---
arch/loongarch/include/asm/stackframe.h | 8 ++++++++
arch/loongarch/kernel/head.S | 10 ++++------
arch/loongarch/power/suspend_asm.S | 5 ++---
3 files changed, 14 insertions(+), 9 deletions(-)
diff --git a/arch/loongarch/include/asm/stackframe.h b/arch/loongarch/include/asm/stackframe.h
index bbec1e56b61b..cd8240858599 100644
--- a/arch/loongarch/include/asm/stackframe.h
+++ b/arch/loongarch/include/asm/stackframe.h
@@ -217,4 +217,12 @@
RESTORE_SP_AND_RET \docfi
.endm
+/* Jump to the virtual address of the link. */
+ .macro JUMP_LINK_ADDR
+ li.d t0, CACHE_BASE
+ pcaddi t1, 0
+ or t0, t0, t1
+ jirl zero, t0, 0xc
+ .endm
+
#endif /* _ASM_STACKFRAME_H */
diff --git a/arch/loongarch/kernel/head.S b/arch/loongarch/kernel/head.S
index aa6181714ec3..e8a4bf9d7599 100644
--- a/arch/loongarch/kernel/head.S
+++ b/arch/loongarch/kernel/head.S
@@ -52,9 +52,8 @@ SYM_CODE_START(kernel_entry) # kernel entry point
/* We might not get launched at the address the kernel is linked to,
so we jump there. */
- la.abs t0, 0f
- jr t0
-0:
+ JUMP_LINK_ADDR
+
/* Enable PG */
li.w t0, 0xb0 # PLV=0, IE=0, PG=1
csrwr t0, LOONGARCH_CSR_CRMD
@@ -106,9 +105,8 @@ SYM_CODE_START(smpboot_entry)
li.d t0, CSR_DMW1_INIT # CA, PLV0
csrwr t0, LOONGARCH_CSR_DMWIN1
- la.abs t0, 0f
- jr t0
-0:
+ JUMP_LINK_ADDR
+
/* Enable PG */
li.w t0, 0xb0 # PLV=0, IE=0, PG=1
csrwr t0, LOONGARCH_CSR_CRMD
diff --git a/arch/loongarch/power/suspend_asm.S b/arch/loongarch/power/suspend_asm.S
index eb2675642f9f..596a682a7924 100644
--- a/arch/loongarch/power/suspend_asm.S
+++ b/arch/loongarch/power/suspend_asm.S
@@ -78,9 +78,8 @@ SYM_INNER_LABEL(loongarch_wakeup_start, SYM_L_GLOBAL)
li.d t0, CSR_DMW1_INIT # CA, PLV0
csrwr t0, LOONGARCH_CSR_DMWIN1
- la.abs t0, 0f
- jr t0
-0:
+ JUMP_LINK_ADDR
+
la.pcrel t0, acpi_saved_sp
ld.d sp, t0, 0
SETUP_WAKEUP
--
2.39.1
From: Youling Tang <[email protected]>
arch/loongarch/kernel/relocate.c contains the functions necessary to
relocate the kernel elsewhere in memory.
The kernel makes a copy of itself at the new address. It uses the
relocation table inserted by the relocs tool to fix symbol references
within the new image.
If copy/relocation is successful then the entry point of the new kernel
is returned, otherwise fall back to starting the kernel in place.
Signed-off-by: Youling Tang <[email protected]>
Signed-off-by: Xi Ruoyao <[email protected]> # Fix compiler warnings
---
arch/loongarch/Kconfig | 15 +++++
arch/loongarch/Makefile | 5 ++
arch/loongarch/kernel/Makefile | 2 +
arch/loongarch/kernel/head.S | 18 ++++++
arch/loongarch/kernel/relocate.c | 96 +++++++++++++++++++++++++++++
arch/loongarch/kernel/vmlinux.lds.S | 11 +++-
6 files changed, 145 insertions(+), 2 deletions(-)
create mode 100644 arch/loongarch/kernel/relocate.c
diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
index 9cc8b84f7eb0..089a4695b1b3 100644
--- a/arch/loongarch/Kconfig
+++ b/arch/loongarch/Kconfig
@@ -48,6 +48,7 @@ config LOONGARCH
select ARCH_SUPPORTS_ATOMIC_RMW
select ARCH_SUPPORTS_HUGETLBFS
select ARCH_SUPPORTS_NUMA_BALANCING
+ select SYS_SUPPORTS_RELOCATABLE
select ARCH_USE_BUILTIN_BSWAP
select ARCH_USE_CMPXCHG_LOCKREF
select ARCH_USE_QUEUED_RWLOCKS
@@ -229,6 +230,11 @@ config SCHED_OMIT_FRAME_POINTER
config AS_HAS_EXPLICIT_RELOCS
def_bool $(as-instr,x:pcalau12i \$t0$(comma)%pc_hi20(x))
+config SYS_SUPPORTS_RELOCATABLE
+ bool
+ help
+ Selected if the platform supports relocating the kernel.
+
menu "Kernel type and options"
source "kernel/Kconfig.hz"
@@ -474,6 +480,15 @@ config PHYSICAL_START
specified in the "crashkernel=YM@XM" command line boot parameter
passed to the panic-ed kernel).
+config RELOCATABLE
+ bool "Relocatable kernel"
+ depends on SYS_SUPPORTS_RELOCATABLE
+ help
+ This builds the kernel as a Position Independent Executable (PIE),
+ which retains all relocation metadata required to relocate the
+ kernel binary at runtime to a different virtual address than the
+ address it was linked at.
+
config SECCOMP
bool "Enable seccomp to safely compute untrusted bytecode"
depends on PROC_FS
diff --git a/arch/loongarch/Makefile b/arch/loongarch/Makefile
index 4402387d2755..27b5a70ff31c 100644
--- a/arch/loongarch/Makefile
+++ b/arch/loongarch/Makefile
@@ -71,6 +71,11 @@ KBUILD_AFLAGS_MODULE += -Wa,-mla-global-with-abs
KBUILD_CFLAGS_MODULE += -fplt -Wa,-mla-global-with-abs,-mla-local-with-abs
endif
+ifeq ($(CONFIG_RELOCATABLE),y)
+LDFLAGS_vmlinux += -static -pie --no-dynamic-linker -z notext
+KBUILD_CFLAGS_KERNEL += -fPIE
+endif
+
cflags-y += -ffreestanding
cflags-y += $(call cc-option, -mno-check-zero-division)
diff --git a/arch/loongarch/kernel/Makefile b/arch/loongarch/kernel/Makefile
index c8cfbd562921..3341dd5f0926 100644
--- a/arch/loongarch/kernel/Makefile
+++ b/arch/loongarch/kernel/Makefile
@@ -31,6 +31,8 @@ endif
obj-$(CONFIG_MODULES) += module.o module-sections.o
obj-$(CONFIG_STACKTRACE) += stacktrace.o
+obj-$(CONFIG_RELOCATABLE) += relocate.o
+
obj-$(CONFIG_PROC_FS) += proc.o
obj-$(CONFIG_SMP) += smp.o
diff --git a/arch/loongarch/kernel/head.S b/arch/loongarch/kernel/head.S
index e8a4bf9d7599..6db1549177ad 100644
--- a/arch/loongarch/kernel/head.S
+++ b/arch/loongarch/kernel/head.S
@@ -88,7 +88,25 @@ SYM_CODE_START(kernel_entry) # kernel entry point
PTR_ADD sp, sp, tp
set_saved_sp sp, t0, t1
+#ifdef CONFIG_RELOCATABLE
+ /* Copy kernel and apply the relocations */
+ bl relocate_kernel
+
+ /* Repoint the sp into the new kernel image */
+ PTR_LI sp, (_THREAD_SIZE - 32 - PT_SIZE)
+ PTR_ADD sp, sp, tp
+ set_saved_sp sp, t0, t1
+ PTR_ADDI sp, sp, -4 * SZREG # init stack pointer
+
+ /*
+ * relocate_kernel returns the entry point either
+ * in the relocated kernel or the original if for
+ * some reason relocation failed.
+ */
+ jr a0
+#else
bl start_kernel
+#endif
ASM_BUG()
SYM_CODE_END(kernel_entry)
diff --git a/arch/loongarch/kernel/relocate.c b/arch/loongarch/kernel/relocate.c
new file mode 100644
index 000000000000..9c61e03d3e91
--- /dev/null
+++ b/arch/loongarch/kernel/relocate.c
@@ -0,0 +1,96 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Support for Kernel relocation at boot time
+ *
+ * Copyright (C) 2023 Loongson Technology Corporation Limited
+ */
+
+#include <linux/elf.h>
+#include <linux/kernel.h>
+#include <linux/start_kernel.h>
+#include <linux/printk.h>
+#include <linux/panic_notifier.h>
+#include <asm/bootinfo.h>
+#include <asm/inst.h>
+#include <asm/sections.h>
+
+#define RELOCATED(x) ((void *)((long)x + offset))
+
+extern long __rela_dyn_start;
+extern long __rela_dyn_end;
+
+/*
+ * Choose a new address for the kernel, for now we'll hard
+ * code the destination.
+ */
+static inline void __init *determine_relocation_address(void)
+{
+ return (void *)(CACHE_BASE + 0x02000000);
+}
+
+static inline int __init relocation_addr_valid(void *loc_new)
+{
+ if ((unsigned long)loc_new & 0x0000ffff) {
+ /* Inappropriately aligned new location */
+ return 0;
+ }
+ if ((unsigned long)loc_new < (unsigned long)_end) {
+ /* New location overlaps original kernel */
+ return 0;
+ }
+ return 1;
+}
+
+void *__init relocate_kernel(void)
+{
+ Elf64_Rela *rela, *rela_end;
+ void *loc_new;
+ unsigned long kernel_length;
+ long offset = 0;
+ /* Default to original kernel entry point */
+ void *kernel_entry = start_kernel;
+
+ kernel_length = (long)(_end) - (long)(_text);
+
+ loc_new = determine_relocation_address();
+
+ /* Sanity check relocation address */
+ if (relocation_addr_valid(loc_new))
+ offset = (unsigned long)loc_new - (unsigned long)(_text);
+
+ if (offset) {
+ /* Copy the kernel to it's new location */
+ memcpy(loc_new, _text, kernel_length);
+
+ /* Sync the caches ready for execution of new kernel */
+ __asm__ __volatile__ (
+ "ibar 0 \t\n"
+ "dbar 0 \t\n");
+
+ rela = (Elf64_Rela *)RELOCATED(&__rela_dyn_start);
+ rela_end = (Elf64_Rela *)RELOCATED(&__rela_dyn_end);
+
+ for ( ; rela < rela_end; rela++) {
+ Elf64_Addr addr = rela->r_offset;
+ Elf64_Addr relocated_addr = rela->r_addend;
+
+ if (rela->r_info != R_LARCH_RELATIVE)
+ continue;
+
+ if (relocated_addr >= VMLINUX_LOAD_ADDRESS)
+ relocated_addr =
+ (Elf64_Addr)RELOCATED(relocated_addr);
+
+ *(Elf64_Addr *)RELOCATED(addr) = relocated_addr;
+
+ }
+
+ /* The current thread is now within the relocated image */
+ __current_thread_info = RELOCATED(__current_thread_info);
+
+ /* Return the new kernel's entry point */
+ kernel_entry = RELOCATED(start_kernel);
+ }
+
+ return kernel_entry;
+}
diff --git a/arch/loongarch/kernel/vmlinux.lds.S b/arch/loongarch/kernel/vmlinux.lds.S
index 733b16e8d55d..aec0b6567d24 100644
--- a/arch/loongarch/kernel/vmlinux.lds.S
+++ b/arch/loongarch/kernel/vmlinux.lds.S
@@ -70,6 +70,8 @@ SECTIONS
.plt : ALIGN(16) { *(.plt) }
.got.plt : ALIGN(16) { *(.got.plt) }
+ .data.rel : { *(.data.rel*) }
+
. = ALIGN(PECOFF_SEGMENT_ALIGN);
__init_begin = .;
__inittext_begin = .;
@@ -93,8 +95,6 @@ SECTIONS
PERCPU_SECTION(1 << CONFIG_L1_CACHE_SHIFT)
#endif
- .rela.dyn : ALIGN(8) { *(.rela.dyn) *(.rela*) }
-
.init.bss : {
*(.init.bss)
}
@@ -107,6 +107,12 @@ SECTIONS
RO_DATA(4096)
RW_DATA(1 << CONFIG_L1_CACHE_SHIFT, PAGE_SIZE, THREAD_SIZE)
+ .rela.dyn : ALIGN(8) {
+ __rela_dyn_start = .;
+ *(.rela.dyn) *(.rela*)
+ __rela_dyn_end = .;
+ }
+
.sdata : {
*(.sdata)
}
@@ -133,6 +139,7 @@ SECTIONS
DISCARDS
/DISCARD/ : {
+ *(.dynamic .dynsym .dynstr .hash .gnu.hash)
*(.gnu.attributes)
*(.options)
*(.eh_frame)
--
2.39.1
From: Youling Tang <[email protected]>
This patch adds support for relocating the kernel to a random address.
Entropy is derived from the banner, which will change every build and
random_get_entropy() which should provide additional runtime entropy.
The kernel is relocated by up to RANDOMIZE_BASE_MAX_OFFSET bytes from
its link address. Because relocation happens so early in the kernel boot,
the amount of physical memory has not yet been determined. This means
the only way to limit relocation within the available memory is via
Kconfig. Limit the maximum value of RANDOMIZE_BASE_MAX_OFFSET to
256M(0x10000000) because our memory layout has many holes.
KERNELOFFSET (kaslr_offset) is added to vmcoreinfo in the future, for
crash --kaslr support.
Signed-off-by: Youling Tang <[email protected]>
Signed-off-by: Xi Ruoyao <[email protected]> # Use arch_initcall
---
arch/loongarch/Kconfig | 22 ++++++
arch/loongarch/include/asm/page.h | 6 ++
arch/loongarch/kernel/relocate.c | 115 ++++++++++++++++++++++++++++++
arch/loongarch/kernel/setup.c | 3 +
4 files changed, 146 insertions(+)
diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
index 089a4695b1b3..cdf0535764ae 100644
--- a/arch/loongarch/Kconfig
+++ b/arch/loongarch/Kconfig
@@ -489,6 +489,28 @@ config RELOCATABLE
kernel binary at runtime to a different virtual address than the
address it was linked at.
+config RANDOMIZE_BASE
+ bool "Randomize the address of the kernel image (KASLR)"
+ depends on RELOCATABLE
+ help
+ Randomizes the physical and virtual address at which the
+ kernel image is loaded, as a security feature that
+ deters exploit attempts relying on knowledge of the location
+ of kernel internals.
+
+ The kernel will be offset by up to RANDOMIZE_BASE_MAX_OFFSET.
+
+ If unsure, say N.
+
+config RANDOMIZE_BASE_MAX_OFFSET
+ hex "Maximum KASLR offset" if EXPERT
+ depends on RANDOMIZE_BASE
+ range 0x0 0x10000000 if 64BIT
+ default "0x01000000"
+ help
+ When KASLR is active, this provides the maximum offset that will
+ be applied to the kernel image.
+
config SECCOMP
bool "Enable seccomp to safely compute untrusted bytecode"
depends on PROC_FS
diff --git a/arch/loongarch/include/asm/page.h b/arch/loongarch/include/asm/page.h
index 53f284a96182..6dda0d6271ca 100644
--- a/arch/loongarch/include/asm/page.h
+++ b/arch/loongarch/include/asm/page.h
@@ -106,6 +106,12 @@ extern int __virt_addr_valid(volatile void *kaddr);
((current->personality & READ_IMPLIES_EXEC) ? VM_EXEC : 0) | \
VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC)
+extern unsigned long __kaslr_offset;
+static inline unsigned long kaslr_offset(void)
+{
+ return __kaslr_offset;
+}
+
#include <asm-generic/memory_model.h>
#include <asm-generic/getorder.h>
diff --git a/arch/loongarch/kernel/relocate.c b/arch/loongarch/kernel/relocate.c
index 9c61e03d3e91..351168b70b7a 100644
--- a/arch/loongarch/kernel/relocate.c
+++ b/arch/loongarch/kernel/relocate.c
@@ -11,6 +11,7 @@
#include <linux/printk.h>
#include <linux/panic_notifier.h>
#include <asm/bootinfo.h>
+#include <asm/early_ioremap.h>
#include <asm/inst.h>
#include <asm/sections.h>
@@ -19,6 +20,70 @@
extern long __rela_dyn_start;
extern long __rela_dyn_end;
+#ifdef CONFIG_RANDOMIZE_BASE
+
+static inline __init unsigned long rotate_xor(unsigned long hash,
+ const void *area, size_t size)
+{
+ size_t i;
+ unsigned long *ptr = (unsigned long *)area;
+
+ for (i = 0; i < size / sizeof(hash); i++) {
+ /* Rotate by odd number of bits and XOR. */
+ hash = (hash << ((sizeof(hash) * 8) - 7)) | (hash >> 7);
+ hash ^= ptr[i];
+ }
+
+ return hash;
+}
+
+static inline __init unsigned long get_random_boot(void)
+{
+ unsigned long entropy = random_get_entropy();
+ unsigned long hash = 0;
+
+ /* Attempt to create a simple but unpredictable starting entropy. */
+ hash = rotate_xor(hash, linux_banner, strlen(linux_banner));
+
+ /* Add in any runtime entropy we can get */
+ hash = rotate_xor(hash, &entropy, sizeof(entropy));
+
+ return hash;
+}
+
+static inline __init bool kaslr_disabled(void)
+{
+ char *str;
+
+ str = strstr(boot_command_line, "nokaslr");
+ if (str == boot_command_line || (str > boot_command_line && *(str - 1) == ' '))
+ return true;
+
+ return false;
+}
+
+/* Choose a new address for the kernel */
+static inline void __init *determine_relocation_address(void)
+{
+ unsigned long kernel_length;
+ void *dest = _text;
+ unsigned long offset;
+
+ if (kaslr_disabled())
+ return dest;
+
+ kernel_length = (long)_end - (long)_text;
+
+ offset = get_random_boot() << 16;
+ offset &= (CONFIG_RANDOMIZE_BASE_MAX_OFFSET - 1);
+ if (offset < kernel_length)
+ offset += ALIGN(kernel_length, 0xffff);
+
+ return RELOCATED(dest);
+}
+
+#else
+
/*
* Choose a new address for the kernel, for now we'll hard
* code the destination.
@@ -28,6 +93,8 @@ static inline void __init *determine_relocation_address(void)
return (void *)(CACHE_BASE + 0x02000000);
}
+#endif
+
static inline int __init relocation_addr_valid(void *loc_new)
{
if ((unsigned long)loc_new & 0x0000ffff) {
@@ -41,6 +108,13 @@ static inline int __init relocation_addr_valid(void *loc_new)
return 1;
}
+static inline void __init update_kaslr_offset(unsigned long *addr, long offset)
+{
+ unsigned long *new_addr = (unsigned long *)RELOCATED(addr);
+
+ *new_addr = (unsigned long)offset;
+}
+
void *__init relocate_kernel(void)
{
Elf64_Rela *rela, *rela_end;
@@ -49,6 +123,10 @@ void *__init relocate_kernel(void)
long offset = 0;
/* Default to original kernel entry point */
void *kernel_entry = start_kernel;
+ char *cmdline = early_ioremap(fw_arg1, COMMAND_LINE_SIZE);
+
+ /* Boot command line was passed in fw_arg1 */
+ strscpy(boot_command_line, cmdline, COMMAND_LINE_SIZE);
kernel_length = (long)(_end) - (long)(_text);
@@ -90,7 +168,44 @@ void *__init relocate_kernel(void)
/* Return the new kernel's entry point */
kernel_entry = RELOCATED(start_kernel);
+
+ /* Error may occur before, so keep it at last */
+ update_kaslr_offset(&__kaslr_offset, offset);
}
return kernel_entry;
}
+
+/*
+ * Show relocation information on panic.
+ */
+static void show_kernel_relocation(const char *level)
+{
+ if (__kaslr_offset > 0) {
+ printk(level);
+ pr_cont("Kernel relocated offset @ 0x%lx\n", __kaslr_offset);
+ pr_cont(" .text @ 0x%lx\n", (unsigned long)&_text);
+ pr_cont(" .data @ 0x%lx\n", (unsigned long)&_sdata);
+ pr_cont(" .bss @ 0x%lx\n", (unsigned long)&__bss_start);
+ }
+}
+
+static int kernel_location_notifier_fn(struct notifier_block *self,
+ unsigned long v, void *p)
+{
+ show_kernel_relocation(KERN_EMERG);
+ return NOTIFY_DONE;
+}
+
+static struct notifier_block kernel_location_notifier = {
+ .notifier_call = kernel_location_notifier_fn
+};
+
+static int __init register_kernel_offset_dumper(void)
+{
+ atomic_notifier_chain_register(&panic_notifier_list,
+ &kernel_location_notifier);
+ return 0;
+}
+
+arch_initcall(register_kernel_offset_dumper);
diff --git a/arch/loongarch/kernel/setup.c b/arch/loongarch/kernel/setup.c
index 4344502c0b31..b2ba2741945c 100644
--- a/arch/loongarch/kernel/setup.c
+++ b/arch/loongarch/kernel/setup.c
@@ -82,6 +82,9 @@ static struct resource code_resource = { .name = "Kernel code", };
static struct resource data_resource = { .name = "Kernel data", };
static struct resource bss_resource = { .name = "Kernel bss", };
+unsigned long __kaslr_offset __ro_after_init;
+EXPORT_SYMBOL(__kaslr_offset);
+
const char *get_system_type(void)
{
return "generic-loongson-machine";
--
2.39.1