linux-kernel - [tip:x86/urgent] perf/x86: Always store regs->ip in perf_callchain

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Message-ID: <tip-83f44ae0f8afcc9da659799db8693f74847e66b3@git.kernel.org>
Date:   Thu, 27 Jun 2019 15:22:01 -0700
From:   tip-bot for Song Liu <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     jpoimboe@...hat.com, tglx@...utronix.de, songliubraving@...com,
        kasong@...hat.com, peterz@...radead.org,
        linux-kernel@...r.kernel.org, rostedt@...dmis.org, hpa@...or.com,
        bp@...en8.de, mingo@...nel.org
Subject: [tip:x86/urgent] perf/x86: Always store regs->ip in
 perf_callchain_kernel()

Commit-ID:  83f44ae0f8afcc9da659799db8693f74847e66b3
Gitweb:     https://git.kernel.org/tip/83f44ae0f8afcc9da659799db8693f74847e66b3
Author:     Song Liu <songliubraving@...com>
AuthorDate: Wed, 26 Jun 2019 19:33:52 -0500
Committer:  Thomas Gleixner <tglx@...utronix.de>
CommitDate: Fri, 28 Jun 2019 00:11:20 +0200

perf/x86: Always store regs->ip in perf_callchain_kernel()

The stacktrace_map_raw_tp BPF selftest is failing because the RIP saved by
perf_arch_fetch_caller_regs() isn't getting saved by perf_callchain_kernel().

This was broken by the following commit:

  d15d356887e7 ("perf/x86: Make perf callchains work without CONFIG_FRAME_POINTER")

With that change, when starting with non-HW regs, the unwinder starts
with the current stack frame and unwinds until it passes up the frame
which called perf_arch_fetch_caller_regs().  So regs->ip needs to be
saved deliberately.

Fixes: d15d356887e7 ("perf/x86: Make perf callchains work without CONFIG_FRAME_POINTER")
Signed-off-by: Song Liu <songliubraving@...com>
Signed-off-by: Josh Poimboeuf <jpoimboe@...hat.com>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Cc: Kairui Song <kasong@...hat.com>
Cc: Steven Rostedt <rostedt@...dmis.org>
Cc: Borislav Petkov <bp@...en8.de>
Link: https://lkml.kernel.org/r/3975a298fa52b506fea32666d8ff6a13467eee6d.1561595111.git.jpoimboe@redhat.com

---
 arch/x86/events/core.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/arch/x86/events/core.c b/arch/x86/events/core.c
index f315425d8468..4fb3ca1e699d 100644
--- a/arch/x86/events/core.c
+++ b/arch/x86/events/core.c
@@ -2402,13 +2402,13 @@ perf_callchain_kernel(struct perf_callchain_entry_ctx *entry, struct pt_regs *re
 		return;
 	}
 
-	if (perf_hw_regs(regs)) {
-		if (perf_callchain_store(entry, regs->ip))
-			return;
+	if (perf_callchain_store(entry, regs->ip))
+		return;
+
+	if (perf_hw_regs(regs))
 		unwind_start(&state, current, regs, NULL);
-	} else {
+	else
 		unwind_start(&state, current, NULL, (void *)regs->sp);
-	}
 
 	for (; !unwind_done(&state); unwind_next_frame(&state)) {
 		addr = unwind_get_return_address(&state);