| Message ID | 161615659174.306069.12736134222759644948.stgit@devnote2 (mailing list archive) |
|---|---|
| State | Superseded |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | kprobes: Fix stacktrace with kretprobes on x86 | expand |
| Context | Check | Description |
|---|---|---|
| netdev/tree_selection | success | Not a local patch |
On Fri, 19 Mar 2021 21:23:12 +0900 Masami Hiramatsu <mhiramat@kernel.org> wrote: > To simplify the stacktrace with pt_regs from kretprobe handler, > set the correct return address to the instruction pointer in > the pt_regs before calling kretprobe handlers. > Oops, now I also find this breaks kretprobe for arm. It seems not enough registers stores. I need to fix the arm kprobe code too. In arch/arm/include/uapi/asm/ptrace.h, --- #define ARM_pc uregs[15] --- And in arch/arm/probes/kprobes/core.c, --- /* * 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. */ void __naked __kprobes kretprobe_trampoline(void) { __asm__ __volatile__ ( "stmdb sp!, {r0 - r11} \n\t" --- So, changing regs->ARM_pc will break a stack entry. I need to expand it to r15. Thanks, > Suggested-by: Josh Poimboeuf <jpoimboe@redhat.com> > Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org> > --- > Changes in v3: > - Cast the correct_ret_addr to unsigned long. > --- > kernel/kprobes.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/kernel/kprobes.c b/kernel/kprobes.c > index cf19edc038e4..4ce3e6f5d28d 100644 > --- a/kernel/kprobes.c > +++ b/kernel/kprobes.c > @@ -1914,6 +1914,9 @@ unsigned long __kretprobe_trampoline_handler(struct pt_regs *regs, > BUG_ON(1); > } > > + /* Set the instruction pointer to the correct address */ > + instruction_pointer_set(regs, (unsigned long)correct_ret_addr); > + > /* Run them. */ > first = current->kretprobe_instances.first; > while (first) { >
diff --git a/kernel/kprobes.c b/kernel/kprobes.c index cf19edc038e4..4ce3e6f5d28d 100644 --- a/kernel/kprobes.c +++ b/kernel/kprobes.c @@ -1914,6 +1914,9 @@ unsigned long __kretprobe_trampoline_handler(struct pt_regs *regs, BUG_ON(1); } + /* Set the instruction pointer to the correct address */ + instruction_pointer_set(regs, (unsigned long)correct_ret_addr); + /* Run them. */ first = current->kretprobe_instances.first; while (first) {
To simplify the stacktrace with pt_regs from kretprobe handler, set the correct return address to the instruction pointer in the pt_regs before calling kretprobe handlers. Suggested-by: Josh Poimboeuf <jpoimboe@redhat.com> Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org> --- Changes in v3: - Cast the correct_ret_addr to unsigned long. --- kernel/kprobes.c | 3 +++ 1 file changed, 3 insertions(+)