| From 4b33dadf37666c0860b88f9e52a16d07bf6d0b03 Mon Sep 17 00:00:00 2001 |
| From: Peter Zijlstra <peterz@infradead.org> |
| Date: Wed, 1 May 2019 15:11:17 +0200 |
| Subject: x86_64: Allow breakpoints to emulate call instructions |
| |
| From: Peter Zijlstra <peterz@infradead.org> |
| |
| 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 <luto@kernel.org> |
| Cc: Nicolai Stange <nstange@suse.de> |
| Cc: Thomas Gleixner <tglx@linutronix.de> |
| Cc: Ingo Molnar <mingo@redhat.com> |
| Cc: Borislav Petkov <bp@alien8.de> |
| Cc: "H. Peter Anvin" <hpa@zytor.com> |
| Cc: the arch/x86 maintainers <x86@kernel.org> |
| Cc: Josh Poimboeuf <jpoimboe@redhat.com> |
| Cc: Jiri Kosina <jikos@kernel.org> |
| Cc: Miroslav Benes <mbenes@suse.cz> |
| Cc: Petr Mladek <pmladek@suse.com> |
| Cc: Joe Lawrence <joe.lawrence@redhat.com> |
| Cc: Shuah Khan <shuah@kernel.org> |
| Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> |
| Cc: Tim Chen <tim.c.chen@linux.intel.com> |
| Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de> |
| Cc: Mimi Zohar <zohar@linux.ibm.com> |
| Cc: Juergen Gross <jgross@suse.com> |
| Cc: Nick Desaulniers <ndesaulniers@google.com> |
| Cc: Nayna Jain <nayna@linux.ibm.com> |
| Cc: Masahiro Yamada <yamada.masahiro@socionext.com> |
| Cc: Joerg Roedel <jroedel@suse.de> |
| Cc: "open list:KERNEL SELFTEST FRAMEWORK" <linux-kselftest@vger.kernel.org> |
| Cc: stable@vger.kernel.org |
| Fixes: b700e7f03df5 ("livepatch: kernel: add support for live patching") |
| Tested-by: Nicolai Stange <nstange@suse.de> |
| Reviewed-by: Nicolai Stange <nstange@suse.de> |
| Reviewed-by: Masami Hiramatsu <mhiramat@kernel.org> |
| Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> |
| [ Modified to only work for x86_64 and added comment to int3_emulate_push() ] |
| Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| |
| --- |
| 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 |
| @@ -39,4 +39,32 @@ extern int poke_int3_handler(struct pt_r |
| extern void *text_poke_bp(void *addr, const void *opcode, size_t len, void *handler); |
| extern int after_bootmem; |
| |
| +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 */ |