linux-kernel - [PATCH RFC 08/10] perf/x86: Use user

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Date:   Wed,  8 Nov 2023 16:41:13 -0800
From:   Josh Poimboeuf <jpoimboe@...nel.org>
To:     Peter Zijlstra <peterz@...radead.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ingo Molnar <mingo@...nel.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:     linux-kernel@...r.kernel.org, x86@...nel.org,
        Indu Bhagat <indu.bhagat@...cle.com>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Ian Rogers <irogers@...gle.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        linux-perf-users@...r.kernel.org, Mark Brown <broonie@...nel.org>,
        linux-toolchains@...r.kernel.org
Subject: [PATCH RFC 08/10] perf/x86: Use user_unwind interface

Simplify __perf_callchain_user() and prepare for sframe user space
unwinding by switching to the generic user unwind interface.

Signed-off-by: Josh Poimboeuf <jpoimboe@...nel.org>
---
 arch/x86/events/core.c | 20 +++++---------------
 1 file changed, 5 insertions(+), 15 deletions(-)

diff --git a/arch/x86/events/core.c b/arch/x86/events/core.c
index ae264437f794..5c41a11f058f 100644
--- a/arch/x86/events/core.c
+++ b/arch/x86/events/core.c
@@ -29,6 +29,7 @@
 #include <linux/device.h>
 #include <linux/nospec.h>
 #include <linux/static_call.h>
+#include <linux/user_unwind.h>
 
 #include <asm/apic.h>
 #include <asm/stacktrace.h>
@@ -2856,8 +2857,7 @@ static inline int __perf_callchain_user32(struct pt_regs *regs,
 void __perf_callchain_user(struct perf_callchain_entry_ctx *entry,
 			   struct pt_regs *regs, bool atomic)
 {
-	struct stack_frame frame;
-	const struct stack_frame __user *fp;
+	struct user_unwind_state state;
 
 	if (perf_guest_state()) {
 		/* TODO: We don't support guest os callchain now */
@@ -2870,8 +2870,6 @@ void __perf_callchain_user(struct perf_callchain_entry_ctx *entry,
 	if (regs->flags & (X86_VM_MASK | PERF_EFLAGS_VM))
 		return;
 
-	fp = (void __user *)regs->bp;
-
 	perf_callchain_store(entry, regs->ip);
 
 	if (atomic && !nmi_uaccess_okay())
@@ -2883,17 +2881,9 @@ void __perf_callchain_user(struct perf_callchain_entry_ctx *entry,
 	if (__perf_callchain_user32(regs, entry))
 		goto done;
 
-	while (entry->nr < entry->max_stack) {
-		if (!valid_user_frame(fp, sizeof(frame)))
-			break;
-
-		if (__get_user(frame.next_frame, &fp->next_frame))
-			break;
-		if (__get_user(frame.return_address, &fp->return_address))
-			break;
-
-		perf_callchain_store(entry, frame.return_address);
-		fp = (void __user *)frame.next_frame;
+	for_each_user_frame(state, USER_UNWIND_TYPE_AUTO) {
+		if (perf_callchain_store(entry, state.ip))
+			goto done;
 	}
 done:
 	if (atomic)
-- 
2.41.0