[PATCH v14 18/19] unwind_user/sframe/x86: Enable sframe unwinding on x86

[Jens Remus]

From: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>

The x86 SFrame V3 implementation works fairly well, starting with
binutils 2.46.  Enable it.

[ Jens Remus: Reword commit message for SFrame V3, starting with
binutils 2.46. ]

Signed-off-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Signed-off-by: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx>
Reviewed-by: Indu Bhagat <ibhagatgnu@xxxxxxxxx>
Signed-off-by: Jens Remus <jremus@xxxxxxxxxxxxx>
---

Notes (jremus):
    Changes in v14:
    - Drop superfluous empty line in unwind_user_get_reg().
    
    Changes in v13:
    - Naive implementation of unwind_user_get_reg() to support SFrame V3
      flexible FDEs (e.g. used to represent DRAP pattern).
    - Define SFRAME_REG_SP and SFRAME_REG_FP to the respective x86-64
      DWARF register numbers.
    - Reword commit message for SFrame V3 and (upcoming) binutils 2.46.

 arch/x86/Kconfig                          |  1 +
 arch/x86/include/asm/unwind_user.h        | 33 +++++++++++++++++++++++
 arch/x86/include/asm/unwind_user_sframe.h | 12 +++++++++
 3 files changed, 46 insertions(+)
 create mode 100644 arch/x86/include/asm/unwind_user_sframe.h

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index f3f7cb01d69d..51286dfdb5f4 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -302,6 +302,7 @@ config X86
 	select HAVE_UACCESS_VALIDATION		if HAVE_OBJTOOL
 	select HAVE_UNSTABLE_SCHED_CLOCK
 	select HAVE_UNWIND_USER_FP		if X86_64
+	select HAVE_UNWIND_USER_SFRAME		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
index f38f7c5ff1de..b80f0ec0f7a7 100644
--- a/arch/x86/include/asm/unwind_user.h
+++ b/arch/x86/include/asm/unwind_user.h
@@ -15,6 +15,39 @@ static inline int unwind_user_word_size(struct pt_regs *regs)
 	return user_64bit_mode(regs) ? 8 : 4;
 }
 
+static inline int unwind_user_get_reg(unsigned long *val, unsigned int regnum)
+{
+#ifdef CONFIG_X86_64
+	const struct pt_regs *regs = task_pt_regs(current);
+
+	switch (regnum) {
+	/* DWARF register numbers 0..15 */
+	case  0: *val = regs->ax; break;
+	case  1: *val = regs->dx; break;
+	case  2: *val = regs->cx; break;
+	case  3: *val = regs->bx; break;
+	case  4: *val = regs->si; break;
+	case  5: *val = regs->di; break;
+	case  6: *val = regs->bp; break;
+	case  7: *val = regs->sp; break;
+	case  8: *val = regs->r8; break;
+	case  9: *val = regs->r9; break;
+	case 10: *val = regs->r10; break;
+	case 11: *val = regs->r11; break;
+	case 12: *val = regs->r12; break;
+	case 13: *val = regs->r13; break;
+	case 14: *val = regs->r14; break;
+	case 15: *val = regs->r15; break;
+	default:
+		return -EINVAL;
+	}
+	return 0;
+#else /* !CONFIG_X86_64 */
+	return -EINVAL;
+#endif /* !CONFIG_X86_64 */
+}
+#define unwind_user_get_reg unwind_user_get_reg
+
 #endif /* CONFIG_UNWIND_USER */
 
 #ifdef CONFIG_HAVE_UNWIND_USER_FP
diff --git a/arch/x86/include/asm/unwind_user_sframe.h b/arch/x86/include/asm/unwind_user_sframe.h
new file mode 100644
index 000000000000..d828ae1a4aac
--- /dev/null
+++ b/arch/x86/include/asm/unwind_user_sframe.h
@@ -0,0 +1,12 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ASM_X86_UNWIND_USER_SFRAME_H
+#define _ASM_X86_UNWIND_USER_SFRAME_H
+
+#ifdef CONFIG_X86_64
+
+#define SFRAME_REG_SP	7
+#define SFRAME_REG_FP	6
+
+#endif
+
+#endif /* _ASM_X86_UNWIND_USER_SFRAME_H */
-- 
2.51.0