linux-kernel - [PATCH v6 07/12] unwind_user/sframe: Wire up unwind

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Message-ID: <20250617225118.194027083@goodmis.org>
Date: Tue, 17 Jun 2025 18:50:16 -0400
From: Steven Rostedt <rostedt@...dmis.org>
To: linux-kernel@...r.kernel.org,
 linux-trace-kernel@...r.kernel.org,
 bpf@...r.kernel.org,
 x86@...nel.org
Cc: Masami Hiramatsu <mhiramat@...nel.org>,
 Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
 Josh Poimboeuf <jpoimboe@...nel.org>,
 Peter Zijlstra <peterz@...radead.org>,
 Ingo Molnar <mingo@...nel.org>,
 Jiri Olsa <jolsa@...nel.org>,
 Namhyung Kim <namhyung@...nel.org>,
 Thomas Gleixner <tglx@...utronix.de>,
 Andrii Nakryiko <andrii@...nel.org>,
 Indu Bhagat <indu.bhagat@...cle.com>,
 "Jose E. Marchesi" <jemarch@....org>,
 Beau Belgrave <beaub@...ux.microsoft.com>,
 Jens Remus <jremus@...ux.ibm.com>,
 Linus Torvalds <torvalds@...ux-foundation.org>,
 Andrew Morton <akpm@...ux-foundation.org>
Subject: [PATCH v6 07/12] unwind_user/sframe: Wire up unwind_user to sframe

From: Josh Poimboeuf <jpoimboe@...nel.org>

Now that the sframe infrastructure is fully in place, make it work by
hooking it up to the unwind_user interface.

Signed-off-by: Josh Poimboeuf <jpoimboe@...nel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@...dmis.org>
---
Changes since v5: https://lore.kernel.org/20250424201824.638379190@goodmis.org

- Have sframe use initialize the frame = &_frame

  The unwind code had the on stack _frame storage removed since it wasn't
  being used. The sframe code needs it. Add it back but only assign it
  when sframe is used.

 arch/Kconfig                      |  1 +
 include/linux/unwind_user_types.h |  1 +
 kernel/unwind/user.c              | 25 ++++++++++++++++++++++---
 3 files changed, 24 insertions(+), 3 deletions(-)

diff --git a/arch/Kconfig b/arch/Kconfig
index c54d35e2f860..0c6056ef13de 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -448,6 +448,7 @@ config HAVE_UNWIND_USER_COMPAT_FP
 
 config HAVE_UNWIND_USER_SFRAME
 	bool
+	select UNWIND_USER
 
 config HAVE_PERF_REGS
 	bool
diff --git a/include/linux/unwind_user_types.h b/include/linux/unwind_user_types.h
index 0b6563951ca4..4d50476e950e 100644
--- a/include/linux/unwind_user_types.h
+++ b/include/linux/unwind_user_types.h
@@ -13,6 +13,7 @@ enum unwind_user_type {
 	UNWIND_USER_TYPE_NONE,
 	UNWIND_USER_TYPE_FP,
 	UNWIND_USER_TYPE_COMPAT_FP,
+	UNWIND_USER_TYPE_SFRAME,
 };
 
 struct unwind_stacktrace {
diff --git a/kernel/unwind/user.c b/kernel/unwind/user.c
index 29e1f497a26e..e9e1e584753e 100644
--- a/kernel/unwind/user.c
+++ b/kernel/unwind/user.c
@@ -7,6 +7,7 @@
 #include <linux/sched/task_stack.h>
 #include <linux/unwind_user.h>
 #include <linux/uaccess.h>
+#include <linux/sframe.h>
 
 static struct unwind_user_frame fp_frame = {
 	ARCH_INIT_USER_FP_FRAME
@@ -28,6 +29,12 @@ static inline bool compat_state(struct unwind_user_state *state)
 	       state->type == UNWIND_USER_TYPE_COMPAT_FP;
 }
 
+static inline bool sframe_state(struct unwind_user_state *state)
+{
+	return IS_ENABLED(CONFIG_HAVE_UNWIND_USER_SFRAME) &&
+	       state->type == UNWIND_USER_TYPE_SFRAME;
+}
+
 #define UNWIND_GET_USER_LONG(to, from, state)				\
 ({									\
 	int __ret;							\
@@ -41,17 +48,27 @@ static inline bool compat_state(struct unwind_user_state *state)
 int unwind_user_next(struct unwind_user_state *state)
 {
 	struct unwind_user_frame *frame;
+	struct unwind_user_frame _frame;
 	unsigned long cfa = 0, fp, ra = 0;
 
 	if (state->done)
 		return -EINVAL;
 
-	if (compat_state(state))
+	if (compat_state(state)) {
 		frame = &compat_fp_frame;
-	else if (fp_state(state))
+	} else if (sframe_state(state)) {
+		/* sframe expects the frame to be local storage */
+		frame = &_frame;
+		if (sframe_find(state->ip, frame)) {
+			if (!IS_ENABLED(CONFIG_HAVE_UNWIND_USER_FP))
+				goto the_end;
+			frame = &fp_frame;
+		}
+	} else if (fp_state(state)) {
 		frame = &fp_frame;
-	else
+	} else {
 		goto the_end;
+	}
 
 	cfa = (frame->use_fp ? state->fp : state->sp) + frame->cfa_off;
 
@@ -92,6 +109,8 @@ int unwind_user_start(struct unwind_user_state *state)
 
 	if (IS_ENABLED(CONFIG_HAVE_UNWIND_USER_COMPAT_FP) && in_compat_mode(regs))
 		state->type = UNWIND_USER_TYPE_COMPAT_FP;
+	else if (current_has_sframe())
+		state->type = UNWIND_USER_TYPE_SFRAME;
 	else if (IS_ENABLED(CONFIG_HAVE_UNWIND_USER_FP))
 		state->type = UNWIND_USER_TYPE_FP;
 	else
-- 
2.47.2