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Message-ID: <20250708012400.023290498@kernel.org>
Date: Mon, 07 Jul 2025 21:22:53 -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 v13 14/14] unwind_user/x86: Enable compat mode frame pointer unwinding on x86
From: Josh Poimboeuf <jpoimboe@...nel.org>
Use ARCH_INIT_USER_COMPAT_FP_FRAME to describe how frame pointers are
unwound on x86, and implement the hooks needed to add the segment base
addresses. Enable HAVE_UNWIND_USER_COMPAT_FP if the system has compat
mode compiled in.
Signed-off-by: Josh Poimboeuf <jpoimboe@...nel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@...dmis.org>
---
arch/x86/Kconfig | 1 +
arch/x86/include/asm/unwind_user.h | 31 ++++++++++++++++++++++++
arch/x86/include/asm/unwind_user_types.h | 17 +++++++++++++
arch/x86/kernel/stacktrace.c | 28 +++++++++++++++++++++
include/linux/unwind_user.h | 20 +++++++++++++++
kernel/unwind/user.c | 4 +++
6 files changed, 101 insertions(+)
create mode 100644 arch/x86/include/asm/unwind_user_types.h
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 5862433c81e1..17d4094c821b 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -302,6 +302,7 @@ config X86
select HAVE_SYSCALL_TRACEPOINTS
select HAVE_UACCESS_VALIDATION if HAVE_OBJTOOL
select HAVE_UNSTABLE_SCHED_CLOCK
+ select HAVE_UNWIND_USER_COMPAT_FP if IA32_EMULATION
select HAVE_UNWIND_USER_FP if X86_64
select HAVE_USER_RETURN_NOTIFIER
select HAVE_GENERIC_VDSO
diff --git a/arch/x86/include/asm/unwind_user.h b/arch/x86/include/asm/unwind_user.h
index 8597857bf896..19634a73612d 100644
--- a/arch/x86/include/asm/unwind_user.h
+++ b/arch/x86/include/asm/unwind_user.h
@@ -2,10 +2,41 @@
#ifndef _ASM_X86_UNWIND_USER_H
#define _ASM_X86_UNWIND_USER_H
+#include <linux/unwind_user_types.h>
+
#define ARCH_INIT_USER_FP_FRAME \
.cfa_off = (s32)sizeof(long) * 2, \
.ra_off = (s32)sizeof(long) * -1, \
.fp_off = (s32)sizeof(long) * -2, \
.use_fp = true,
+#ifdef CONFIG_IA32_EMULATION
+
+#define ARCH_INIT_USER_COMPAT_FP_FRAME \
+ .cfa_off = (s32)sizeof(u32) * 2, \
+ .ra_off = (s32)sizeof(u32) * -1, \
+ .fp_off = (s32)sizeof(u32) * -2, \
+ .use_fp = true,
+
+#define in_compat_mode(regs) !user_64bit_mode(regs)
+
+void arch_unwind_user_init(struct unwind_user_state *state,
+ struct pt_regs *regs);
+
+static inline void arch_unwind_user_next(struct unwind_user_state *state)
+{
+ if (state->type != UNWIND_USER_TYPE_COMPAT_FP)
+ return;
+
+ state->ip += state->arch.cs_base;
+ state->fp += state->arch.ss_base;
+}
+
+#define arch_unwind_user_init arch_unwind_user_init
+#define arch_unwind_user_next arch_unwind_user_next
+
+#endif /* CONFIG_IA32_EMULATION */
+
+#include <asm-generic/unwind_user.h>
+
#endif /* _ASM_X86_UNWIND_USER_H */
diff --git a/arch/x86/include/asm/unwind_user_types.h b/arch/x86/include/asm/unwind_user_types.h
new file mode 100644
index 000000000000..f93d535f900e
--- /dev/null
+++ b/arch/x86/include/asm/unwind_user_types.h
@@ -0,0 +1,17 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ASM_X86_UNWIND_USER_TYPES_H
+#define _ASM_X86_UNWIND_USER_TYPES_H
+
+#ifdef CONFIG_IA32_EMULATION
+
+struct arch_unwind_user_state {
+ unsigned long ss_base;
+ unsigned long cs_base;
+};
+#define arch_unwind_user_state arch_unwind_user_state
+
+#endif /* CONFIG_IA32_EMULATION */
+
+#include <asm-generic/unwind_user_types.h>
+
+#endif /* _ASM_UNWIND_USER_TYPES_H */
diff --git a/arch/x86/kernel/stacktrace.c b/arch/x86/kernel/stacktrace.c
index ee117fcf46ed..8ef9d8c71df9 100644
--- a/arch/x86/kernel/stacktrace.c
+++ b/arch/x86/kernel/stacktrace.c
@@ -9,7 +9,10 @@
#include <linux/stacktrace.h>
#include <linux/export.h>
#include <linux/uaccess.h>
+#include <asm/unwind_user.h>
#include <asm/stacktrace.h>
+#include <asm/insn.h>
+#include <asm/insn-eval.h>
#include <asm/unwind.h>
void arch_stack_walk(stack_trace_consume_fn consume_entry, void *cookie,
@@ -128,3 +131,28 @@ void arch_stack_walk_user(stack_trace_consume_fn consume_entry, void *cookie,
}
}
+#ifdef CONFIG_IA32_EMULATION
+void arch_unwind_user_init(struct unwind_user_state *state,
+ struct pt_regs *regs)
+{
+ unsigned long cs_base, ss_base;
+
+ if (state->type != UNWIND_USER_TYPE_COMPAT_FP)
+ return;
+
+ cs_base = insn_get_seg_base(regs, INAT_SEG_REG_CS);
+ ss_base = insn_get_seg_base(regs, INAT_SEG_REG_SS);
+
+ if (cs_base == -1)
+ cs_base = 0;
+ if (ss_base == -1)
+ ss_base = 0;
+
+ state->arch.cs_base = cs_base;
+ state->arch.ss_base = ss_base;
+
+ state->ip += cs_base;
+ state->sp += ss_base;
+ state->fp += ss_base;
+}
+#endif /* CONFIG_IA32_EMULATION */
diff --git a/include/linux/unwind_user.h b/include/linux/unwind_user.h
index 834b643afd3a..8a4af0214ecb 100644
--- a/include/linux/unwind_user.h
+++ b/include/linux/unwind_user.h
@@ -14,6 +14,26 @@
#define in_compat_mode(regs) false
#endif
+/*
+ * If an architecture needs to initialize the state for a specific
+ * reason, for example, it may need to do something different
+ * in compat mode, it can define a macro named arch_unwind_user_init
+ * with the name of the function that will perform this initialization.
+ */
+#ifndef arch_unwind_user_init
+static inline void arch_unwind_user_init(struct unwind_user_state *state, struct pt_regs *reg) {}
+#endif
+
+/*
+ * If an architecture requires some more updates to the state between
+ * stack frames, it can define a macro named arch_unwind_user_next
+ * with the name of the function that will update the state between
+ * reading stack frames during the user space stack walk.
+ */
+#ifndef arch_unwind_user_next
+static inline void arch_unwind_user_next(struct unwind_user_state *state) {}
+#endif
+
int unwind_user(struct unwind_stacktrace *trace, unsigned int max_entries);
#endif /* _LINUX_UNWIND_USER_H */
diff --git a/kernel/unwind/user.c b/kernel/unwind/user.c
index 03775191447c..249d9e32fad7 100644
--- a/kernel/unwind/user.c
+++ b/kernel/unwind/user.c
@@ -89,6 +89,8 @@ static int unwind_user_next(struct unwind_user_state *state)
if (frame->fp_off)
state->fp = fp;
+ arch_unwind_user_next(state);
+
return 0;
done:
@@ -118,6 +120,8 @@ static int unwind_user_start(struct unwind_user_state *state)
state->sp = user_stack_pointer(regs);
state->fp = frame_pointer(regs);
+ arch_unwind_user_init(state, regs);
+
return 0;
}
--
2.47.2
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