| Message ID | 163369615714.636038.1154348556499203165.stgit@devnote2 (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | kprobes: Make KUnit and add stacktrace on kretprobe tests | expand |
On Fri, Oct 8, 2021 at 5:29 AM Masami Hiramatsu <mhiramat@kernel.org> wrote: > > Currently kretprobe on ARM just fills r0-r11 of pt_regs, but > that is not enough for the stacktrace. Moreover, from the user > kretprobe handler, stacktrace needs a frame pointer on the > __kretprobe_trampoline. > > This adds a frame pointer on __kretprobe_trampoline for both gcc > and clang case. Those have different frame pointer so we need > different but similar stack on pt_regs. > > Gcc makes the frame pointer (fp) to point the 'pc' address of > the {fp, ip (=sp), lr, pc}, this means {r11, r13, r14, r15}. > Thus if we save the r11 (fp) on pt_regs->r12, we can make this > set on the end of pt_regs. > > On the other hand, Clang makes the frame pointer to point the > 'fp' address of {fp, lr} on stack. Since the next to the > pt_regs->lr is pt_regs->sp, I reused the pair of pt_regs->fp > and pt_regs->ip. > So this stores the 'lr' on pt_regs->ip and make the fp to point > pt_regs->fp. > > For both cases, saves __kretprobe_trampoline address to > pt_regs->lr, so that the stack tracer can identify this frame > pointer has been made by the __kretprobe_trampoline. > > Note that if the CONFIG_FRAME_POINTER is not set, this keeps > fp as is. > > Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org> > --- > arch/arm/probes/kprobes/core.c | 29 ++++++++++++++++++++++++----- > 1 file changed, 24 insertions(+), 5 deletions(-) > > diff --git a/arch/arm/probes/kprobes/core.c b/arch/arm/probes/kprobes/core.c > index 95f23b47ba27..7cbd65a22769 100644 > --- a/arch/arm/probes/kprobes/core.c > +++ b/arch/arm/probes/kprobes/core.c > @@ -368,16 +368,35 @@ int __kprobes kprobe_exceptions_notify(struct notifier_block *self, > /* > * When a retprobed function returns, trampoline_handler() is called, > * calling the kretprobe's handler. We construct a struct pt_regs to > - * give a view of registers r0-r11 to the user return-handler. This is > - * not a complete pt_regs structure, but that should be plenty sufficient > - * for kretprobe handlers which should normally be interested in r0 only > - * anyway. > + * give a view of registers r0-r11, sp, lr, and pc to the user > + * return-handler. This is not a complete pt_regs structure, but that > + * should be enough for stacktrace from the return handler with or > + * without pt_regs. > */ > void __naked __kprobes __kretprobe_trampoline(void) > { > __asm__ __volatile__ ( > - "sub sp, sp, #16 \n\t" > + "ldr lr, =__kretprobe_trampoline \n\t" > + "stmdb sp!, {sp, lr, pc} \n\t" > +#ifdef CONFIG_FRAME_POINTER > + /* __kretprobe_trampoline makes a framepointer on pt_regs. */ > +#ifdef CONFIG_CC_IS_CLANG > + /* In clang case, pt_regs->ip = lr. */ > + "stmdb sp!, {lr} \n\t" > "stmdb sp!, {r0 - r11} \n\t" > + /* fp points regs->r11 (fp) */ > + "add fp, sp, #44 \n\t" > +#else /* !CONFIG_CC_IS_CLANG */ > + /* In gcc case, pt_regs->ip = fp. */ > + "stmdb sp!, {fp} \n\t" > + "stmdb sp!, {r0 - r11} \n\t" > + /* fp points regs->r15 (pc) */ > + "add fp, sp, #60 \n\t" Reviewed-by: Nick Desaulniers <ndesaulniers@google.com> > +#endif /* CONFIG_CC_IS_CLANG */ > +#else /* !CONFIG_FRAME_POINTER */ > + "sub sp, sp, #4 \n\t" > + "stmdb sp!, {r0 - r11} \n\t" > +#endif /* CONFIG_FRAME_POINTER */ > "mov r0, sp \n\t" > "bl trampoline_handler \n\t" > "mov lr, r0 \n\t" >
diff --git a/arch/arm/probes/kprobes/core.c b/arch/arm/probes/kprobes/core.c index 95f23b47ba27..7cbd65a22769 100644 --- a/arch/arm/probes/kprobes/core.c +++ b/arch/arm/probes/kprobes/core.c @@ -368,16 +368,35 @@ int __kprobes kprobe_exceptions_notify(struct notifier_block *self, /* * When a retprobed function returns, trampoline_handler() is called, * calling the kretprobe's handler. We construct a struct pt_regs to - * give a view of registers r0-r11 to the user return-handler. This is - * not a complete pt_regs structure, but that should be plenty sufficient - * for kretprobe handlers which should normally be interested in r0 only - * anyway. + * give a view of registers r0-r11, sp, lr, and pc to the user + * return-handler. This is not a complete pt_regs structure, but that + * should be enough for stacktrace from the return handler with or + * without pt_regs. */ void __naked __kprobes __kretprobe_trampoline(void) { __asm__ __volatile__ ( - "sub sp, sp, #16 \n\t" + "ldr lr, =__kretprobe_trampoline \n\t" + "stmdb sp!, {sp, lr, pc} \n\t" +#ifdef CONFIG_FRAME_POINTER + /* __kretprobe_trampoline makes a framepointer on pt_regs. */ +#ifdef CONFIG_CC_IS_CLANG + /* In clang case, pt_regs->ip = lr. */ + "stmdb sp!, {lr} \n\t" "stmdb sp!, {r0 - r11} \n\t" + /* fp points regs->r11 (fp) */ + "add fp, sp, #44 \n\t" +#else /* !CONFIG_CC_IS_CLANG */ + /* In gcc case, pt_regs->ip = fp. */ + "stmdb sp!, {fp} \n\t" + "stmdb sp!, {r0 - r11} \n\t" + /* fp points regs->r15 (pc) */ + "add fp, sp, #60 \n\t" +#endif /* CONFIG_CC_IS_CLANG */ +#else /* !CONFIG_FRAME_POINTER */ + "sub sp, sp, #4 \n\t" + "stmdb sp!, {r0 - r11} \n\t" +#endif /* CONFIG_FRAME_POINTER */ "mov r0, sp \n\t" "bl trampoline_handler \n\t" "mov lr, r0 \n\t"
Currently kretprobe on ARM just fills r0-r11 of pt_regs, but that is not enough for the stacktrace. Moreover, from the user kretprobe handler, stacktrace needs a frame pointer on the __kretprobe_trampoline. This adds a frame pointer on __kretprobe_trampoline for both gcc and clang case. Those have different frame pointer so we need different but similar stack on pt_regs. Gcc makes the frame pointer (fp) to point the 'pc' address of the {fp, ip (=sp), lr, pc}, this means {r11, r13, r14, r15}. Thus if we save the r11 (fp) on pt_regs->r12, we can make this set on the end of pt_regs. On the other hand, Clang makes the frame pointer to point the 'fp' address of {fp, lr} on stack. Since the next to the pt_regs->lr is pt_regs->sp, I reused the pair of pt_regs->fp and pt_regs->ip. So this stores the 'lr' on pt_regs->ip and make the fp to point pt_regs->fp. For both cases, saves __kretprobe_trampoline address to pt_regs->lr, so that the stack tracer can identify this frame pointer has been made by the __kretprobe_trampoline. Note that if the CONFIG_FRAME_POINTER is not set, this keeps fp as is. Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org> --- arch/arm/probes/kprobes/core.c | 29 ++++++++++++++++++++++++----- 1 file changed, 24 insertions(+), 5 deletions(-)