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kprobes: Enable stacktrace from pt_regs in kretprobe handler 

Since the ORC unwinder from pt_regs requires setting up regs->ip
correctly, set the correct return address to the regs->ip before
calling user kretprobe handler.

This allows the kretrprobe handler to trace stack from the
kretprobe's pt_regs by stack_trace_save_regs() (eBPF will do
this), instead of stack tracing from the handler context by
stack_trace_save() (ftrace will do this).

Link: https://lkml.kernel.org/r/163163053237.489837.4272653874525136832.stgit@devnote2

Suggested-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Tested-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
This commit is contained in:
Masami Hiramatsu 2021-09-14 23:42:12 +09:00 committed by Steven Rostedt (VMware)
parent 7391dd1902
commit df91c5bccb
1 changed files with 7 additions and 0 deletions
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7
kernel/kprobes.c
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@ -1937,6 +1937,13 @@ unsigned long __kretprobe_trampoline_handler(struct pt_regs *regs,
BUG_ON(1);
}
/*
* Set the return address as the instruction pointer, because if the
* user handler calls stack_trace_save_regs() with this 'regs',
* the stack trace will start from the instruction pointer.
*/
instruction_pointer_set(regs, (unsigned long)correct_ret_addr);
/* Run the user handler of the nodes. */
first = current->kretprobe_instances.first;
while (first) {