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Diffstat (limited to 'arch/x86/include/asm/text-patching.h')
| -rw-r--r-- | arch/x86/include/asm/text-patching.h | 219 |
1 files changed, 219 insertions, 0 deletions
diff --git a/arch/x86/include/asm/text-patching.h b/arch/x86/include/asm/text-patching.h new file mode 100644 index 000000000..85b85a275 --- /dev/null +++ b/arch/x86/include/asm/text-patching.h @@ -0,0 +1,219 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef _ASM_X86_TEXT_PATCHING_H +#define _ASM_X86_TEXT_PATCHING_H + +#include <linux/types.h> +#include <linux/stddef.h> +#include <asm/ptrace.h> + +struct paravirt_patch_site; +#ifdef CONFIG_PARAVIRT +void apply_paravirt(struct paravirt_patch_site *start, + struct paravirt_patch_site *end); +#else +static inline void apply_paravirt(struct paravirt_patch_site *start, + struct paravirt_patch_site *end) +{} +#define __parainstructions NULL +#define __parainstructions_end NULL +#endif + +/* + * Currently, the max observed size in the kernel code is + * JUMP_LABEL_NOP_SIZE/RELATIVEJUMP_SIZE, which are 5. + * Raise it if needed. + */ +#define POKE_MAX_OPCODE_SIZE 5 + +extern void text_poke_early(void *addr, const void *opcode, size_t len); + +/* + * Clear and restore the kernel write-protection flag on the local CPU. + * Allows the kernel to edit read-only pages. + * Side-effect: any interrupt handler running between save and restore will have + * the ability to write to read-only pages. + * + * Warning: + * Code patching in the UP case is safe if NMIs and MCE handlers are stopped and + * no thread can be preempted in the instructions being modified (no iret to an + * invalid instruction possible) or if the instructions are changed from a + * consistent state to another consistent state atomically. + * On the local CPU you need to be protected against NMI or MCE handlers seeing + * an inconsistent instruction while you patch. + */ +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 void *text_poke_set(void *addr, int c, 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); + +extern void text_poke_queue(void *addr, const void *opcode, size_t len, const void *emulate); +extern void text_poke_finish(void); + +#define INT3_INSN_SIZE 1 +#define INT3_INSN_OPCODE 0xCC + +#define RET_INSN_SIZE 1 +#define RET_INSN_OPCODE 0xC3 + +#define CALL_INSN_SIZE 5 +#define CALL_INSN_OPCODE 0xE8 + +#define JMP32_INSN_SIZE 5 +#define JMP32_INSN_OPCODE 0xE9 + +#define JMP8_INSN_SIZE 2 +#define JMP8_INSN_OPCODE 0xEB + +#define DISP32_SIZE 4 + +static __always_inline int text_opcode_size(u8 opcode) +{ + int size = 0; + +#define __CASE(insn) \ + case insn##_INSN_OPCODE: size = insn##_INSN_SIZE; break + + switch(opcode) { + __CASE(INT3); + __CASE(RET); + __CASE(CALL); + __CASE(JMP32); + __CASE(JMP8); + } + +#undef __CASE + + return size; +} + +union text_poke_insn { + u8 text[POKE_MAX_OPCODE_SIZE]; + struct { + u8 opcode; + s32 disp; + } __attribute__((packed)); +}; + +static __always_inline +void __text_gen_insn(void *buf, u8 opcode, const void *addr, const void *dest, int size) +{ + union text_poke_insn *insn = buf; + + BUG_ON(size < text_opcode_size(opcode)); + + /* + * Hide the addresses to avoid the compiler folding in constants when + * referencing code, these can mess up annotations like + * ANNOTATE_NOENDBR. + */ + OPTIMIZER_HIDE_VAR(insn); + OPTIMIZER_HIDE_VAR(addr); + OPTIMIZER_HIDE_VAR(dest); + + insn->opcode = opcode; + + if (size > 1) { + insn->disp = (long)dest - (long)(addr + size); + if (size == 2) { + /* + * Ensure that for JMP8 the displacement + * actually fits the signed byte. + */ + BUG_ON((insn->disp >> 31) != (insn->disp >> 7)); + } + } +} + +static __always_inline +void *text_gen_insn(u8 opcode, const void *addr, const void *dest) +{ + static union text_poke_insn insn; /* per instance */ + __text_gen_insn(&insn, opcode, addr, dest, text_opcode_size(opcode)); + return &insn.text; +} + +extern int after_bootmem; +extern __ro_after_init struct mm_struct *poking_mm; +extern __ro_after_init unsigned long poking_addr; + +#ifndef CONFIG_UML_X86 +static __always_inline +void int3_emulate_jmp(struct pt_regs *regs, unsigned long ip) +{ + regs->ip = ip; +} + +static __always_inline +void int3_emulate_push(struct pt_regs *regs, unsigned long val) +{ + /* + * The int3 handler in entry_64.S adds a gap between the + * stack where the break point happened, and the saving of + * pt_regs. We can extend the original stack because of + * this gap. See the idtentry macro's create_gap option. + * + * Similarly entry_32.S will have a gap on the stack for (any) hardware + * exception and pt_regs; see FIXUP_FRAME. + */ + regs->sp -= sizeof(unsigned long); + *(unsigned long *)regs->sp = val; +} + +static __always_inline +unsigned long int3_emulate_pop(struct pt_regs *regs) +{ + unsigned long val = *(unsigned long *)regs->sp; + regs->sp += sizeof(unsigned long); + return val; +} + +static __always_inline +void int3_emulate_call(struct pt_regs *regs, unsigned long func) +{ + int3_emulate_push(regs, regs->ip - INT3_INSN_SIZE + CALL_INSN_SIZE); + int3_emulate_jmp(regs, func); +} + +static __always_inline +void int3_emulate_ret(struct pt_regs *regs) +{ + unsigned long ip = int3_emulate_pop(regs); + int3_emulate_jmp(regs, ip); +} + +static __always_inline +void int3_emulate_jcc(struct pt_regs *regs, u8 cc, unsigned long ip, unsigned long disp) +{ + static const unsigned long jcc_mask[6] = { + [0] = X86_EFLAGS_OF, + [1] = X86_EFLAGS_CF, + [2] = X86_EFLAGS_ZF, + [3] = X86_EFLAGS_CF | X86_EFLAGS_ZF, + [4] = X86_EFLAGS_SF, + [5] = X86_EFLAGS_PF, + }; + + bool invert = cc & 1; + bool match; + + if (cc < 0xc) { + match = regs->flags & jcc_mask[cc >> 1]; + } else { + match = ((regs->flags & X86_EFLAGS_SF) >> X86_EFLAGS_SF_BIT) ^ + ((regs->flags & X86_EFLAGS_OF) >> X86_EFLAGS_OF_BIT); + if (cc >= 0xe) + match = match || (regs->flags & X86_EFLAGS_ZF); + } + + if ((match && !invert) || (!match && invert)) + ip += disp; + + int3_emulate_jmp(regs, ip); +} + +#endif /* !CONFIG_UML_X86 */ + +#endif /* _ASM_X86_TEXT_PATCHING_H */ |