On Tue, May 07, 2019 at 03:01:53PM -0400, Steven Rostedt wrote: > How's this? > > -- Steve > > From d29dc2e9e0275c9857932b80cebc01551b669efb Mon Sep 17 00:00:00 2001 > From: Peter Zijlstra <[email protected]> > Date: Wed, 1 May 2019 15:11:17 +0200 > Subject: [PATCH] x86_64: Allow breakpoints to emulate call functions > > In order to allow breakpoints to emulate call functions, they need to push > the return address onto the stack. But because the breakpoint exception > frame is added to the stack when the breakpoint is hit, there's no room to > add the address onto the stack and return to the address of the emulated > called funtion.
The 2nd sentence can probably be removed since it's technically no longer true, thanks to the previous patch. > This helper functions are added: "These" > > 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") > 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]> > --- > arch/x86/include/asm/text-patching.h | 28 ++++++++++++++++++++++++++++ > 1 file changed, 28 insertions(+) > > diff --git a/arch/x86/include/asm/text-patching.h > b/arch/x86/include/asm/text-patching.h > index e85ff65c43c3..05861cc08787 100644 > --- 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_regs *regs); > 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; Looks good. -- Josh
