Commit 8bc11700 authored by Jiri Olsa's avatar Jiri Olsa Committed by Andrii Nakryiko
Browse files

x86/fgraph: Fix return_to_handler regs.rsp value 



The previous change (Fixes commit) messed up the rsp register value,
which is wrong because it's already adjusted with FRAME_SIZE, we need
the original rsp value.

This change does not affect fprobe current kernel unwind, the !perf_hw_regs
path perf_callchain_kernel:

        if (perf_hw_regs(regs)) {
                if (perf_callchain_store(entry, regs->ip))
                        return;
                unwind_start(&state, current, regs, NULL);
        } else {
                unwind_start(&state, current, NULL, (void *)regs->sp);
        }

which uses pt_regs.sp as first_frame boundary (FRAME_SIZE shift makes
no difference, unwind stil stops at the right frame).

This change fixes the other path when we want to unwind directly from
pt_regs sp/fp/ip state, which is coming in following change.

Fixes: 20a0bc10 ("x86/fgraph,bpf: Fix stack ORC unwind from kprobe_multi return probe")
Signed-off-by: default avatarJiri Olsa <jolsa@kernel.org>
Signed-off-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Reviewed-by: default avatarSteven Rostedt (Google) <rostedt@goodmis.org>
Link: https://lore.kernel.org/bpf/20260126211837.472802-2-jolsa@kernel.org
parent cd77618c

arch/x86/kernel/ftrace_64.S

+4 −1
Original line number Diff line number Diff line
@@ -364,6 +364,9 @@ SYM_CODE_START(return_to_handler) 
	UNWIND_HINT_UNDEFINED

	ANNOTATE_NOENDBR



	/* Store original rsp for pt_regs.sp value. */

	movq %rsp, %rdi



	/* Restore return_to_handler value that got eaten by previous ret instruction. */

	subq $8, %rsp

	UNWIND_HINT_FUNC
@@ -374,7 +377,7 @@ SYM_CODE_START(return_to_handler) 
	movq %rax, RAX(%rsp)

	movq %rdx, RDX(%rsp)

	movq %rbp, RBP(%rsp)

	movq %rsp, RSP(%rsp)

	movq %rdi, RSP(%rsp)

	movq %rsp, %rdi



	call ftrace_return_to_handler