unwind_user/x86: Enable frame pointer unwinding on x86

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

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index fa3b616af03a2d50eaf5f922bc8cd4e08a284045..5cf1afc0a974c862305ade32dc050f56122d683a 100644 (file)
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -297,6 +297,7 @@ 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 (file)
index 0000000..b166e10
--- /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 */