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x86/fgraph: Fix return_to_handler regs.rsp value

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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: 20a0bc1027 ("x86/fgraph,bpf: Fix stack ORC unwind from kprobe_multi return probe")
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Reviewed-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Link: https://lore.kernel.org/bpf/20260126211837.472802-2-jolsa@kernel.org
This commit is contained in:
Jiri Olsa 2026-01-26 22:18:32 +01:00 committed by Andrii Nakryiko
parent cd77618c41
commit 8bc11700e0
1 changed files with 4 additions and 1 deletions
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5
arch/x86/kernel/ftrace_64.S
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@ -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