[PATCH 6.18 096/314] unwind_user/x86: Enable frame pointer unwinding on x86

Sasha Levin
2026-03-10T11:26:11Z

From: Josh Poimboeuf <jpoimboe@kernel.org>

[ Upstream commit 49cf34c0815f93fb2ea3ab5cfbac1124bd9b45d0 ]

Use ARCH_INIT_USER_FP_FRAME to describe how frame pointers are unwound
on x86, and enable CONFIG_HAVE_UNWIND_USER_FP accordingly so the
unwind_user interfaces can be used.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/20250827193828.347397433@kernel.org
Stable-dep-of: d55c571e4333 ("x86/uprobes: Fix XOL allocation failure for 32-bit tasks")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
arch/x86/Kconfig | 1 +
arch/x86/include/asm/unwind_user.h | 25 +++++++++++++++++++++++++
2 files changed, 26 insertions(+)
create mode 100644 arch/x86/include/asm/unwind_user.h

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index a3700766a8c08..ee41af778a9dc 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -298,6 +298,7 @@ config X86
select HAVE_SYSCALL_TRACEPOINTS
select HAVE_UACCESS_VALIDATION if HAVE_OBJTOOL
select HAVE_UNSTABLE_SCHED_CLOCK
+ select HAVE_UNWIND_USER_FP if X86_64
select HAVE_USER_RETURN_NOTIFIER
select HAVE_GENERIC_VDSO
select VDSO_GETRANDOM if X86_64
diff --git a/arch/x86/include/asm/unwind_user.h b/arch/x86/include/asm/unwind_user.h
new file mode 100644
index 0000000000000..b166e102d4445
--- /dev/null
+++ b/arch/x86/include/asm/unwind_user.h
@@ -0,0 +1,25 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ASM_X86_UNWIND_USER_H
+#define _ASM_X86_UNWIND_USER_H
+
+#include <asm/ptrace.h>
+
+#define ARCH_INIT_USER_FP_FRAME(ws) \
+ .cfa_off = 2*(ws), \
+ .ra_off = -1*(ws), \
+ .fp_off = -2*(ws), \
+ .use_fp = true,
+
+static inline int unwind_user_word_size(struct pt_regs *regs)
+{
+ /* We can't unwind VM86 stacks */
+ if (regs->flags & X86_VM_MASK)
+ return 0;
+#ifdef CONFIG_X86_64
+ if (!user_64bit_mode(regs))
+ return sizeof(int);
+#endif
+ return sizeof(long);
+}
+
+#endif /* _ASM_X86_UNWIND_USER_H */
--
2.51.0