From 8bc11700e0d23d4fdb7d8d5a73b2e95de427cabc Mon Sep 17 00:00:00 2001 From: Jiri Olsa Date: Mon, 26 Jan 2026 22:18:32 +0100 Subject: [PATCH] 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: 20a0bc10272f ("x86/fgraph,bpf: Fix stack ORC unwind from kprobe_multi return probe") Signed-off-by: Jiri Olsa Signed-off-by: Andrii Nakryiko Reviewed-by: Steven Rostedt (Google) Link: https://lore.kernel.org/bpf/20260126211837.472802-2-jolsa@kernel.org --- arch/x86/kernel/ftrace_64.S | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/arch/x86/kernel/ftrace_64.S b/arch/x86/kernel/ftrace_64.S index a132608265f6c..62c1c93aa1c6a 100644 --- a/arch/x86/kernel/ftrace_64.S +++ b/arch/x86/kernel/ftrace_64.S @@ -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 -- 2.47.3