linux-kernel - [PATCH v9 06/11] unwind_user/sframe: Wire up unwind

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Message-ID: <20250717012936.619600891@kernel.org>
Date: Wed, 16 Jul 2025 21:28:54 -0400
From: Steven Rostedt <rostedt@...nel.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>,
 Jens Axboe <axboe@...nel.dk>,
 Florian Weimer <fweimer@...hat.com>,
 Sam James <sam@...too.org>
Subject: [PATCH v9 06/11] 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 v8: https://lore.kernel.org/20250708021159.386608979@kernel.org

- Rebased on the changes by Mathieu in the user.c file
  https://lore.kernel.org/all/20250710164301.3094-2-mathieu.desnoyers@efficios.com/

 arch/Kconfig                      |  1 +
 include/linux/unwind_user_types.h |  4 ++-
 kernel/unwind/user.c              | 41 +++++++++++++++++++++++++++++--
 3 files changed, 43 insertions(+), 3 deletions(-)

diff --git a/arch/Kconfig b/arch/Kconfig
index edd6393512f5..f3b3e5a91f6d 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -444,6 +444,7 @@ config HAVE_UNWIND_USER_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 a449f15be890..d30e8495eaa9 100644
--- a/include/linux/unwind_user_types.h
+++ b/include/linux/unwind_user_types.h
@@ -9,7 +9,8 @@
  * available.
  */
 enum unwind_user_type_bits {
-	UNWIND_USER_TYPE_FP_BIT =		0,
+	UNWIND_USER_TYPE_SFRAME_BIT =		0,
+	UNWIND_USER_TYPE_FP_BIT =		1,
 
 	NR_UNWIND_USER_TYPE_BITS,
 };
@@ -17,6 +18,7 @@ enum unwind_user_type_bits {
 enum unwind_user_type {
 	/* Type "none" for the start of stack walk iteration. */
 	UNWIND_USER_TYPE_NONE =			0,
+	UNWIND_USER_TYPE_SFRAME =		BIT(UNWIND_USER_TYPE_SFRAME_BIT),
 	UNWIND_USER_TYPE_FP =			BIT(UNWIND_USER_TYPE_FP_BIT),
 };
 
diff --git a/kernel/unwind/user.c b/kernel/unwind/user.c
index 85b8c764d2f7..e7ba01cf87a4 100644
--- a/kernel/unwind/user.c
+++ b/kernel/unwind/user.c
@@ -7,17 +7,24 @@
 #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
 };
 
+static struct unwind_user_frame *get_fp_frame(struct pt_regs *regs)
+{
+	return &fp_frame;
+}
+
 #define for_each_user_frame(state) \
 	for (unwind_user_start(state); !(state)->done; unwind_user_next(state))
 
-static int unwind_user_next_fp(struct unwind_user_state *state)
+static int unwind_user_next_common(struct unwind_user_state *state,
+				   struct unwind_user_frame *frame,
+				   struct pt_regs *regs)
 {
-	struct unwind_user_frame *frame = &fp_frame;
 	unsigned long cfa, fp, ra = 0;
 	unsigned int shift;
 
@@ -55,6 +62,24 @@ static int unwind_user_next_fp(struct unwind_user_state *state)
 	return 0;
 }
 
+static int unwind_user_next_sframe(struct unwind_user_state *state)
+{
+	struct unwind_user_frame _frame, *frame;
+
+	/* sframe expects the frame to be local storage */
+	frame = &_frame;
+	if (sframe_find(state->ip, frame))
+		return -ENOENT;
+	return unwind_user_next_common(state, frame, task_pt_regs(current));
+}
+
+static int unwind_user_next_fp(struct unwind_user_state *state)
+{
+	struct pt_regs *regs = task_pt_regs(current);
+
+	return unwind_user_next_common(state, get_fp_frame(regs), regs);
+}
+
 static int unwind_user_next(struct unwind_user_state *state)
 {
 	unsigned long iter_mask = state->available_types;
@@ -68,6 +93,16 @@ static int unwind_user_next(struct unwind_user_state *state)
 
 		state->current_type = type;
 		switch (type) {
+		case UNWIND_USER_TYPE_SFRAME:
+			switch (unwind_user_next_sframe(state)) {
+			case 0:
+				return 0;
+			case -ENOENT:
+				continue;	/* Try next method. */
+			default:
+				state->done = true;
+			}
+			break;
 		case UNWIND_USER_TYPE_FP:
 			if (!unwind_user_next_fp(state))
 				return 0;
@@ -96,6 +131,8 @@ static int unwind_user_start(struct unwind_user_state *state)
 		return -EINVAL;
 	}
 
+	if (current_has_sframe())
+		state->available_types |= UNWIND_USER_TYPE_SFRAME;
 	if (IS_ENABLED(CONFIG_HAVE_UNWIND_USER_FP))
 		state->available_types |= UNWIND_USER_TYPE_FP;
 
-- 
2.47.2