From 20a0bc10272fa17a44fc857c31574a8306f60d20 Mon Sep 17 00:00:00 2001 From: Jiri Olsa Date: Tue, 4 Nov 2025 22:54:03 +0100 Subject: x86/fgraph,bpf: Fix stack ORC unwind from kprobe_multi return probe Currently we don't get stack trace via ORC unwinder on top of fgraph exit handler. We can see that when generating stacktrace from kretprobe_multi bpf program which is based on fprobe/fgraph. The reason is that the ORC unwind code won't get pass the return_to_handler callback installed by fgraph return probe machinery. Solving this by creating stack frame in return_to_handler expected by ftrace_graph_ret_addr function to recover original return address and continue with the unwind. Also updating the pt_regs data with cs/flags/rsp which are needed for successful stack retrieval from ebpf bpf_get_stackid helper. - in get_perf_callchain we check user_mode(regs) so CS has to be set - in perf_callchain_kernel we call perf_hw_regs(regs), so EFLAGS/FIXED has to be unset Acked-by: Masami Hiramatsu (Google) Signed-off-by: Jiri Olsa Link: https://lore.kernel.org/r/20251104215405.168643-3-jolsa@kernel.org Signed-off-by: Alexei Starovoitov Acked-by: Steven Rostedt (Google) --- include/linux/ftrace.h | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) (limited to 'include/linux/ftrace.h') diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h index 7ded7df6e9b5..07f8c309e432 100644 --- a/include/linux/ftrace.h +++ b/include/linux/ftrace.h @@ -193,6 +193,10 @@ static __always_inline struct pt_regs *ftrace_get_regs(struct ftrace_regs *fregs #if !defined(CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS) || \ defined(CONFIG_HAVE_FTRACE_REGS_HAVING_PT_REGS) +#ifndef arch_ftrace_partial_regs +#define arch_ftrace_partial_regs(regs) do {} while (0) +#endif + static __always_inline struct pt_regs * ftrace_partial_regs(struct ftrace_regs *fregs, struct pt_regs *regs) { @@ -202,7 +206,11 @@ ftrace_partial_regs(struct ftrace_regs *fregs, struct pt_regs *regs) * Since arch_ftrace_get_regs() will check some members and may return * NULL, we can not use it. */ - return &arch_ftrace_regs(fregs)->regs; + regs = &arch_ftrace_regs(fregs)->regs; + + /* Allow arch specific updates to regs. */ + arch_ftrace_partial_regs(regs); + return regs; } #endif /* !CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS || CONFIG_HAVE_FTRACE_REGS_HAVING_PT_REGS */ -- cgit v1.2.3