From: Peter Zijlstra <[email protected]> commit 4b33dadf37666c0860b88f9e52a16d07bf6d0b03 upstream.
In order to allow breakpoints to emulate call instructions, they need to push the return address onto the stack. The x86_64 int3 handler adds a small gap to allow the stack to grow some. Use this gap to add the return address to be able to emulate a call instruction at the breakpoint location. These helper functions are added: int3_emulate_jmp(): changes the location of the regs->ip to return there. (The next two are only for x86_64) int3_emulate_push(): to push the address onto the gap in the stack int3_emulate_call(): push the return address and change regs->ip Cc: Andy Lutomirski <[email protected]> Cc: Nicolai Stange <[email protected]> Cc: Thomas Gleixner <[email protected]> Cc: Ingo Molnar <[email protected]> Cc: Borislav Petkov <[email protected]> Cc: "H. Peter Anvin" <[email protected]> Cc: the arch/x86 maintainers <[email protected]> Cc: Josh Poimboeuf <[email protected]> Cc: Jiri Kosina <[email protected]> Cc: Miroslav Benes <[email protected]> Cc: Petr Mladek <[email protected]> Cc: Joe Lawrence <[email protected]> Cc: Shuah Khan <[email protected]> Cc: Konrad Rzeszutek Wilk <[email protected]> Cc: Tim Chen <[email protected]> Cc: Sebastian Andrzej Siewior <[email protected]> Cc: Mimi Zohar <[email protected]> Cc: Juergen Gross <[email protected]> Cc: Nick Desaulniers <[email protected]> Cc: Nayna Jain <[email protected]> Cc: Masahiro Yamada <[email protected]> Cc: Joerg Roedel <[email protected]> Cc: "open list:KERNEL SELFTEST FRAMEWORK" <[email protected]> Cc: [email protected] Fixes: b700e7f03df5 ("livepatch: kernel: add support for live patching") Tested-by: Nicolai Stange <[email protected]> Reviewed-by: Nicolai Stange <[email protected]> Reviewed-by: Masami Hiramatsu <[email protected]> Signed-off-by: Peter Zijlstra (Intel) <[email protected]> [ Modified to only work for x86_64 and added comment to int3_emulate_push() ] Signed-off-by: Steven Rostedt (VMware) <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]> --- arch/x86/include/asm/text-patching.h | 28 ++++++++++++++++++++++++++++ 1 file changed, 28 insertions(+) --- a/arch/x86/include/asm/text-patching.h +++ b/arch/x86/include/asm/text-patching.h @@ -38,4 +38,32 @@ extern void *text_poke(void *addr, const extern int poke_int3_handler(struct pt_regs *regs); extern void *text_poke_bp(void *addr, const void *opcode, size_t len, void *handler); +static inline void int3_emulate_jmp(struct pt_regs *regs, unsigned long ip) +{ + regs->ip = ip; +} + +#define INT3_INSN_SIZE 1 +#define CALL_INSN_SIZE 5 + +#ifdef CONFIG_X86_64 +static 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. + */ + regs->sp -= sizeof(unsigned long); + *(unsigned long *)regs->sp = val; +} + +static 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); +} +#endif + #endif /* _ASM_X86_TEXT_PATCHING_H */
