[PATCH v6 0/6] x86/vdso: VDSO updates and fixes for sframes

[PATCH v6 0/6] x86/vdso: VDSO updates and fixes for sframes

[Jens Remus]

This enables generation of SFrame V3 stack trace information for VDSO on
x86-64.  It's a continuation of Josh's and Steve's work:

   https://lore.kernel.org/all/cover.1737511963.git.jpoimboe@kernel.org/
   https://lore.kernel.org/all/20250422183439.895236512@goodmis.org/

This series focuses only on the VDSO code. They are helpful fixes
and updates that doesn't rely on sframes (although the last patch
is sframe related).

This series applies on top of the latest unwind user sframe series
"[PATCH v13 00/18] unwind_deferred: Implement sframe handling":
https://lore.kernel.org/all/20260127150554.2760964-1-jremus@linux.ibm.com/

Like above series it depends on the upcoming binutils 2.46 release to
be used to build executables and libraries such as VDSO with SFrame V3
stack trace information (using the assembler option --gsframe-3).

Changes in v6:
- SFrame V3 support (SFrame V2 is not supported).
- Prevent GNU_SFRAME program table entry to empty .sframe section.
- Integrate v5 review feedback. (Josh)

Regards,
Jens


Josh Poimboeuf (6):
  x86/vdso: Fix DWARF generation for getrandom()
  x86/asm: Avoid emitting DWARF CFI for non-VDSO
  x86/asm: Simplify VDSO DWARF generation
  x86/vdso: Use SYM_FUNC_{START,END} in __kernel_vsyscall()
  x86/vdso: Use CFI macros in __vdso_sgx_enter_enclave()
  x86/vdso: Enable sframe generation in VDSO

 arch/Kconfig                             |  7 +++
 arch/x86/entry/vdso/Makefile             | 10 +++--
 arch/x86/entry/vdso/vdso-layout.lds.S    |  9 +++-
 arch/x86/entry/vdso/vdso32/system_call.S | 10 +----
 arch/x86/entry/vdso/vgetrandom-chacha.S  |  3 +-
 arch/x86/entry/vdso/vsgx.S               | 19 +++------
 arch/x86/include/asm/dwarf2.h            | 54 +++++++++++++++++-------
 arch/x86/include/asm/linkage.h           | 33 ++++++++++++---
 arch/x86/include/asm/vdso.h              |  1 -
 9 files changed, 97 insertions(+), 49 deletions(-)

-- 
2.51.0

[PATCH v6 1/6] x86/vdso: Fix DWARF generation for getrandom()

[Jens Remus]

From: Josh Poimboeuf <jpoimboe@kernel.org>

Add CFI annotations to the VDSO implementation of getrandom() so it will
have valid DWARF unwinding metadata.

Fixes: 33385150ac45 ("x86: vdso: Wire up getrandom() vDSO implementation")
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Jens Remus <jremus@linux.ibm.com>
---
 arch/x86/entry/vdso/vgetrandom-chacha.S | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/arch/x86/entry/vdso/vgetrandom-chacha.S b/arch/x86/entry/vdso/vgetrandom-chacha.S
index bcba5639b8ee..cc82da9216fb 100644
--- a/arch/x86/entry/vdso/vgetrandom-chacha.S
+++ b/arch/x86/entry/vdso/vgetrandom-chacha.S
@@ -4,7 +4,7 @@
  */
 
 #include <linux/linkage.h>
-#include <asm/frame.h>
+#include <asm/dwarf2.h>
 
 .section	.rodata, "a"
 .align 16
@@ -22,7 +22,7 @@ CONSTANTS:	.octa 0x6b20657479622d323320646e61707865
  *	rcx: number of 64-byte blocks to write to output
  */
 SYM_FUNC_START(__arch_chacha20_blocks_nostack)
-
+	CFI_STARTPROC
 .set	output,		%rdi
 .set	key,		%rsi
 .set	counter,	%rdx
@@ -175,4 +175,5 @@ SYM_FUNC_START(__arch_chacha20_blocks_nostack)
 	pxor		temp,temp
 
 	ret
+	CFI_ENDPROC
 SYM_FUNC_END(__arch_chacha20_blocks_nostack)
-- 
2.51.0

[PATCH v6 2/6] x86/asm: Avoid emitting DWARF CFI for non-VDSO

[Jens Remus]

From: Josh Poimboeuf <jpoimboe@kernel.org>

It was decided years ago that .cfi_* annotations aren't maintainable in
the kernel.  They were replaced by objtool unwind hints.  For the kernel
proper, ensure the CFI_* macros don't do anything.

On the other hand the VDSO library *does* use them, so user space can
unwind through it.

Make sure these macros only work for VDSO.  They aren't actually being
used outside of VDSO anyway, so there's no functional change.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Jens Remus <jremus@linux.ibm.com>
---
 arch/x86/include/asm/dwarf2.h | 51 ++++++++++++++++++++++++-----------
 1 file changed, 35 insertions(+), 16 deletions(-)

diff --git a/arch/x86/include/asm/dwarf2.h b/arch/x86/include/asm/dwarf2.h
index 302e11b15da8..65d958ef1178 100644
--- a/arch/x86/include/asm/dwarf2.h
+++ b/arch/x86/include/asm/dwarf2.h
@@ -6,6 +6,15 @@
 #warning "asm/dwarf2.h should be only included in pure assembly files"
 #endif
 
+#ifdef BUILD_VDSO
+
+	/*
+	 * For the vDSO, emit both runtime unwind information and debug
+	 * symbols for the .dbg file.
+	 */
+
+	.cfi_sections .eh_frame, .debug_frame
+
 #define CFI_STARTPROC		.cfi_startproc
 #define CFI_ENDPROC		.cfi_endproc
 #define CFI_DEF_CFA		.cfi_def_cfa
@@ -21,21 +30,31 @@
 #define CFI_UNDEFINED		.cfi_undefined
 #define CFI_ESCAPE		.cfi_escape
 
-#ifndef BUILD_VDSO
-	/*
-	 * Emit CFI data in .debug_frame sections, not .eh_frame sections.
-	 * The latter we currently just discard since we don't do DWARF
-	 * unwinding at runtime.  So only the offline DWARF information is
-	 * useful to anyone.  Note we should not use this directive if we
-	 * ever decide to enable DWARF unwinding at runtime.
-	 */
-	.cfi_sections .debug_frame
-#else
-	 /*
-	  * For the vDSO, emit both runtime unwind information and debug
-	  * symbols for the .dbg file.
-	  */
-	.cfi_sections .eh_frame, .debug_frame
-#endif
+#else /* !BUILD_VDSO */
+
+/*
+ * On x86, these macros aren't used outside VDSO.  As well they shouldn't be:
+ * they're fragile and very difficult to maintain.
+ */
+
+.macro nocfi args:vararg
+.endm
+
+#define CFI_STARTPROC		nocfi
+#define CFI_ENDPROC		nocfi
+#define CFI_DEF_CFA		nocfi
+#define CFI_DEF_CFA_REGISTER	nocfi
+#define CFI_DEF_CFA_OFFSET	nocfi
+#define CFI_ADJUST_CFA_OFFSET	nocfi
+#define CFI_OFFSET		nocfi
+#define CFI_REL_OFFSET		nocfi
+#define CFI_REGISTER		nocfi
+#define CFI_RESTORE		nocfi
+#define CFI_REMEMBER_STATE	nocfi
+#define CFI_RESTORE_STATE	nocfi
+#define CFI_UNDEFINED		nocfi
+#define CFI_ESCAPE		nocfi
+
+#endif /* !BUILD_VDSO */
 
 #endif /* _ASM_X86_DWARF2_H */
-- 
2.51.0

[PATCH v6 3/6] x86/asm: Simplify VDSO DWARF generation

[Jens Remus]

From: Josh Poimboeuf <jpoimboe@kernel.org>

Add CFI_STARTPROC and CFI_ENDPROC annotations to the SYM_FUNC_* macros
so the VDSO asm functions don't need to add them manually.  Note this
only affects VDSO, the CFI_* macros are empty for the kernel proper.

[ Jens Remus: Reword commit subject and message as suggested by Josh. ]

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Jens Remus <jremus@linux.ibm.com>
---
 arch/x86/entry/vdso/vdso-layout.lds.S   |  2 +-
 arch/x86/entry/vdso/vgetrandom-chacha.S |  2 --
 arch/x86/entry/vdso/vsgx.S              |  4 ---
 arch/x86/include/asm/linkage.h          | 33 ++++++++++++++++++++-----
 arch/x86/include/asm/vdso.h             |  1 -
 5 files changed, 28 insertions(+), 14 deletions(-)

diff --git a/arch/x86/entry/vdso/vdso-layout.lds.S b/arch/x86/entry/vdso/vdso-layout.lds.S
index ec1ac191a057..60747905de2b 100644
--- a/arch/x86/entry/vdso/vdso-layout.lds.S
+++ b/arch/x86/entry/vdso/vdso-layout.lds.S
@@ -1,5 +1,5 @@
 /* SPDX-License-Identifier: GPL-2.0 */
-#include <asm/vdso.h>
+#include <asm/page_types.h>
 #include <asm/vdso/vsyscall.h>
 #include <vdso/datapage.h>
 
diff --git a/arch/x86/entry/vdso/vgetrandom-chacha.S b/arch/x86/entry/vdso/vgetrandom-chacha.S
index cc82da9216fb..a33212594731 100644
--- a/arch/x86/entry/vdso/vgetrandom-chacha.S
+++ b/arch/x86/entry/vdso/vgetrandom-chacha.S
@@ -22,7 +22,6 @@ CONSTANTS:	.octa 0x6b20657479622d323320646e61707865
  *	rcx: number of 64-byte blocks to write to output
  */
 SYM_FUNC_START(__arch_chacha20_blocks_nostack)
-	CFI_STARTPROC
 .set	output,		%rdi
 .set	key,		%rsi
 .set	counter,	%rdx
@@ -175,5 +174,4 @@ SYM_FUNC_START(__arch_chacha20_blocks_nostack)
 	pxor		temp,temp
 
 	ret
-	CFI_ENDPROC
 SYM_FUNC_END(__arch_chacha20_blocks_nostack)
diff --git a/arch/x86/entry/vdso/vsgx.S b/arch/x86/entry/vdso/vsgx.S
index 37a3d4c02366..c0342238c976 100644
--- a/arch/x86/entry/vdso/vsgx.S
+++ b/arch/x86/entry/vdso/vsgx.S
@@ -24,8 +24,6 @@
 .section .text, "ax"
 
 SYM_FUNC_START(__vdso_sgx_enter_enclave)
-	/* Prolog */
-	.cfi_startproc
 	push	%rbp
 	.cfi_adjust_cfa_offset	8
 	.cfi_rel_offset		%rbp, 0
@@ -143,8 +141,6 @@ SYM_FUNC_START(__vdso_sgx_enter_enclave)
 	jle	.Lout
 	jmp	.Lenter_enclave
 
-	.cfi_endproc
-
 _ASM_VDSO_EXTABLE_HANDLE(.Lenclu_eenter_eresume, .Lhandle_exception)
 
 SYM_FUNC_END(__vdso_sgx_enter_enclave)
diff --git a/arch/x86/include/asm/linkage.h b/arch/x86/include/asm/linkage.h
index 9d38ae744a2e..9d7f90c57451 100644
--- a/arch/x86/include/asm/linkage.h
+++ b/arch/x86/include/asm/linkage.h
@@ -40,6 +40,10 @@
 
 #ifdef __ASSEMBLER__
 
+#ifndef LINKER_SCRIPT
+#include <asm/dwarf2.h>
+#endif
+
 #if defined(CONFIG_MITIGATION_RETHUNK) && !defined(__DISABLE_EXPORTS) && !defined(BUILD_VDSO)
 #define RET	jmp __x86_return_thunk
 #else /* CONFIG_MITIGATION_RETPOLINE */
@@ -112,34 +116,51 @@
 # define SYM_FUNC_ALIAS_MEMFUNC	SYM_FUNC_ALIAS
 #endif
 
+#define __SYM_FUNC_START				\
+	CFI_STARTPROC ASM_NL
+
+#define __SYM_FUNC_END					\
+	CFI_ENDPROC ASM_NL
+
 /* SYM_TYPED_FUNC_START -- use for indirectly called globals, w/ CFI type */
 #define SYM_TYPED_FUNC_START(name)				\
 	SYM_TYPED_START(name, SYM_L_GLOBAL, SYM_F_ALIGN)	\
+	__SYM_FUNC_START					\
 	ENDBR
 
 /* SYM_FUNC_START -- use for global functions */
 #define SYM_FUNC_START(name)				\
-	SYM_START(name, SYM_L_GLOBAL, SYM_F_ALIGN)
+	SYM_START(name, SYM_L_GLOBAL, SYM_F_ALIGN)	\
+	__SYM_FUNC_START
 
 /* SYM_FUNC_START_NOALIGN -- use for global functions, w/o alignment */
 #define SYM_FUNC_START_NOALIGN(name)			\
-	SYM_START(name, SYM_L_GLOBAL, SYM_A_NONE)
+	SYM_START(name, SYM_L_GLOBAL, SYM_A_NONE)	\
+	__SYM_FUNC_START
 
 /* SYM_FUNC_START_LOCAL -- use for local functions */
 #define SYM_FUNC_START_LOCAL(name)			\
-	SYM_START(name, SYM_L_LOCAL, SYM_F_ALIGN)
+	SYM_START(name, SYM_L_LOCAL, SYM_F_ALIGN)	\
+	__SYM_FUNC_START
 
 /* SYM_FUNC_START_LOCAL_NOALIGN -- use for local functions, w/o alignment */
 #define SYM_FUNC_START_LOCAL_NOALIGN(name)		\
-	SYM_START(name, SYM_L_LOCAL, SYM_A_NONE)
+	SYM_START(name, SYM_L_LOCAL, SYM_A_NONE)	\
+	__SYM_FUNC_START
 
 /* SYM_FUNC_START_WEAK -- use for weak functions */
 #define SYM_FUNC_START_WEAK(name)			\
-	SYM_START(name, SYM_L_WEAK, SYM_F_ALIGN)
+	SYM_START(name, SYM_L_WEAK, SYM_F_ALIGN)	\
+	__SYM_FUNC_START
 
 /* SYM_FUNC_START_WEAK_NOALIGN -- use for weak functions, w/o alignment */
 #define SYM_FUNC_START_WEAK_NOALIGN(name)		\
-	SYM_START(name, SYM_L_WEAK, SYM_A_NONE)
+	SYM_START(name, SYM_L_WEAK, SYM_A_NONE)		\
+	__SYM_FUNC_START
+
+#define SYM_FUNC_END(name)				\
+	__SYM_FUNC_END					\
+	SYM_END(name, SYM_T_FUNC)
 
 /*
  * Expose 'sym' to the startup code in arch/x86/boot/startup/, by emitting an
diff --git a/arch/x86/include/asm/vdso.h b/arch/x86/include/asm/vdso.h
index b7253ef3205a..c4290dadba66 100644
--- a/arch/x86/include/asm/vdso.h
+++ b/arch/x86/include/asm/vdso.h
@@ -2,7 +2,6 @@
 #ifndef _ASM_X86_VDSO_H
 #define _ASM_X86_VDSO_H
 
-#include <asm/page_types.h>
 #include <linux/linkage.h>
 #include <linux/init.h>
 
-- 
2.51.0

[PATCH v6 4/6] x86/vdso: Use SYM_FUNC_{START,END} in __kernel_vsyscall()

[Jens Remus]

From: Josh Poimboeuf <jpoimboe@kernel.org>

Use SYM_FUNC_{START,END} instead of all the boilerplate.  No functional
change.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Jens Remus <jremus@linux.ibm.com>
---
 arch/x86/entry/vdso/vdso32/system_call.S | 10 ++--------
 1 file changed, 2 insertions(+), 8 deletions(-)

diff --git a/arch/x86/entry/vdso/vdso32/system_call.S b/arch/x86/entry/vdso/vdso32/system_call.S
index d33c6513fd2c..bdc576548240 100644
--- a/arch/x86/entry/vdso/vdso32/system_call.S
+++ b/arch/x86/entry/vdso/vdso32/system_call.S
@@ -9,11 +9,7 @@
 #include <asm/alternative.h>
 
 	.text
-	.globl __kernel_vsyscall
-	.type __kernel_vsyscall,@function
-	ALIGN
-__kernel_vsyscall:
-	CFI_STARTPROC
+SYM_FUNC_START(__kernel_vsyscall)
 	/*
 	 * Reshuffle regs so that all of any of the entry instructions
 	 * will preserve enough state.
@@ -79,7 +75,5 @@ SYM_INNER_LABEL(int80_landing_pad, SYM_L_GLOBAL)
 	CFI_RESTORE		ecx
 	CFI_ADJUST_CFA_OFFSET	-4
 	RET
-	CFI_ENDPROC
-
-	.size __kernel_vsyscall,.-__kernel_vsyscall
+SYM_FUNC_END(__kernel_vsyscall)
 	.previous
-- 
2.51.0

[PATCH v6 5/6] x86/vdso: Use CFI macros in __vdso_sgx_enter_enclave()

[Jens Remus]

From: Josh Poimboeuf <jpoimboe@kernel.org>

Use the CFI macros instead of the raw .cfi_* directives to be consistent
with the rest of the VDSO asm.  It's also easier on the eyes.

No functional changes.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Jens Remus <jremus@linux.ibm.com>
---
 arch/x86/entry/vdso/vsgx.S | 15 +++++++--------
 1 file changed, 7 insertions(+), 8 deletions(-)

diff --git a/arch/x86/entry/vdso/vsgx.S b/arch/x86/entry/vdso/vsgx.S
index c0342238c976..8d7b8eb45c50 100644
--- a/arch/x86/entry/vdso/vsgx.S
+++ b/arch/x86/entry/vdso/vsgx.S
@@ -24,13 +24,14 @@
 .section .text, "ax"
 
 SYM_FUNC_START(__vdso_sgx_enter_enclave)
+	SYM_F_ALIGN
 	push	%rbp
-	.cfi_adjust_cfa_offset	8
-	.cfi_rel_offset		%rbp, 0
+	CFI_ADJUST_CFA_OFFSET	8
+	CFI_REL_OFFSET		%rbp, 0
 	mov	%rsp, %rbp
-	.cfi_def_cfa_register	%rbp
+	CFI_DEF_CFA_REGISTER	%rbp
 	push	%rbx
-	.cfi_rel_offset		%rbx, -8
+	CFI_REL_OFFSET		%rbx, -8
 
 	mov	%ecx, %eax
 .Lenter_enclave:
@@ -77,13 +78,11 @@ SYM_FUNC_START(__vdso_sgx_enter_enclave)
 .Lout:
 	pop	%rbx
 	leave
-	.cfi_def_cfa		%rsp, 8
+	CFI_DEF_CFA		%rsp, 8
 	RET
 
-	/* The out-of-line code runs with the pre-leave stack frame. */
-	.cfi_def_cfa		%rbp, 16
-
 .Linvalid_input:
+	CFI_DEF_CFA		%rbp, 16
 	mov	$(-EINVAL), %eax
 	jmp	.Lout
 
-- 
2.51.0

[PATCH v6 6/6] x86/vdso: Enable sframe generation in VDSO

[Jens Remus]

From: Josh Poimboeuf <jpoimboe@kernel.org>

Enable sframe generation in the VDSO library so kernel and user space
can unwind through it.

[ Jens Remus: Add support for SFrame V3.  Prevent GNU_SFRAME program
table entry to empty .sframe section. ]

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Jens Remus <jremus@linux.ibm.com>
---
 arch/Kconfig                          |  7 +++++++
 arch/x86/entry/vdso/Makefile          | 10 +++++++---
 arch/x86/entry/vdso/vdso-layout.lds.S |  7 +++++++
 arch/x86/include/asm/dwarf2.h         |  5 ++++-
 4 files changed, 25 insertions(+), 4 deletions(-)

diff --git a/arch/Kconfig b/arch/Kconfig
index dcb553136e0c..b5b3a83072f7 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -479,6 +479,13 @@ config HAVE_HARDLOCKUP_DETECTOR_ARCH
 	  It uses the same command line parameters, and sysctl interface,
 	  as the generic hardlockup detectors.
 
+config AS_SFRAME
+	bool
+
+config AS_SFRAME3
+	def_bool $(as-instr,.cfi_startproc\n.cfi_endproc,-Wa$(comma)--gsframe-3)
+	select AS_SFRAME
+
 config UNWIND_USER
 	bool
 
diff --git a/arch/x86/entry/vdso/Makefile b/arch/x86/entry/vdso/Makefile
index f247f5f5cb44..748e0a630e81 100644
--- a/arch/x86/entry/vdso/Makefile
+++ b/arch/x86/entry/vdso/Makefile
@@ -47,13 +47,17 @@ quiet_cmd_vdso2c = VDSO2C  $@
 $(obj)/vdso-image-%.c: $(obj)/vdso%.so.dbg $(obj)/vdso%.so $(obj)/vdso2c FORCE
 	$(call if_changed,vdso2c)
 
+ifeq ($(CONFIG_AS_SFRAME3),y)
+  SFRAME_CFLAGS := -Wa,--gsframe-3
+endif
+
 #
 # Don't omit frame pointers for ease of userspace debugging, but do
 # optimize sibling calls.
 #
 CFL := $(PROFILING) -mcmodel=small -fPIC -O2 -fasynchronous-unwind-tables -m64 \
        $(filter -g%,$(KBUILD_CFLAGS)) -fno-stack-protector \
-       -fno-omit-frame-pointer -foptimize-sibling-calls \
+       -fno-omit-frame-pointer $(SFRAME_CFLAGS) -foptimize-sibling-calls \
        -DDISABLE_BRANCH_PROFILING -DBUILD_VDSO
 
 ifdef CONFIG_MITIGATION_RETPOLINE
@@ -63,7 +67,7 @@ endif
 endif
 
 $(vobjs): KBUILD_CFLAGS := $(filter-out $(PADDING_CFLAGS) $(CC_FLAGS_LTO) $(CC_FLAGS_CFI) $(RANDSTRUCT_CFLAGS) $(KSTACK_ERASE_CFLAGS) $(GCC_PLUGINS_CFLAGS) $(RETPOLINE_CFLAGS),$(KBUILD_CFLAGS)) $(CFL)
-$(vobjs): KBUILD_AFLAGS += -DBUILD_VDSO
+$(vobjs): KBUILD_AFLAGS += -DBUILD_VDSO $(SFRAME_CFLAGS)
 
 #
 # vDSO code runs in userspace and -pg doesn't help with profiling anyway.
@@ -104,7 +108,7 @@ $(obj)/%-x32.o: $(obj)/%.o FORCE
 
 targets += vdsox32.lds $(vobjx32s-y)
 
-$(obj)/%.so: OBJCOPYFLAGS := -S --remove-section __ex_table
+$(obj)/%.so: OBJCOPYFLAGS := -g --remove-section __ex_table
 $(obj)/%.so: $(obj)/%.so.dbg FORCE
 	$(call if_changed,objcopy)
 
diff --git a/arch/x86/entry/vdso/vdso-layout.lds.S b/arch/x86/entry/vdso/vdso-layout.lds.S
index 60747905de2b..acdc55435d99 100644
--- a/arch/x86/entry/vdso/vdso-layout.lds.S
+++ b/arch/x86/entry/vdso/vdso-layout.lds.S
@@ -59,6 +59,9 @@ SECTIONS
 	.eh_frame_hdr	: { *(.eh_frame_hdr) }		:text	:eh_frame_hdr
 	.eh_frame	: { KEEP (*(.eh_frame)) }	:text
 
+#ifdef CONFIG_AS_SFRAME
+	.sframe		: { *(.sframe) }		:text	:sframe
+#endif
 
 	/*
 	 * Text is well-separated from actual data: there's plenty of
@@ -87,6 +90,7 @@ SECTIONS
  * Very old versions of ld do not recognize this name token; use the constant.
  */
 #define PT_GNU_EH_FRAME	0x6474e550
+#define PT_GNU_SFRAME	0x6474e554
 
 /*
  * We must supply the ELF program headers explicitly to get just one
@@ -98,4 +102,7 @@ PHDRS
 	dynamic		PT_DYNAMIC	FLAGS(4);		/* PF_R */
 	note		PT_NOTE		FLAGS(4);		/* PF_R */
 	eh_frame_hdr	PT_GNU_EH_FRAME;
+#ifdef CONFIG_AS_SFRAME
+	sframe		PT_GNU_SFRAME;
+#endif
 }
diff --git a/arch/x86/include/asm/dwarf2.h b/arch/x86/include/asm/dwarf2.h
index 65d958ef1178..ce294e6c9017 100644
--- a/arch/x86/include/asm/dwarf2.h
+++ b/arch/x86/include/asm/dwarf2.h
@@ -12,8 +12,11 @@
 	 * For the vDSO, emit both runtime unwind information and debug
 	 * symbols for the .dbg file.
 	 */
-
+#if defined(__x86_64__) && defined(CONFIG_AS_SFRAME)
+	.cfi_sections .eh_frame, .debug_frame, .sframe
+#else
 	.cfi_sections .eh_frame, .debug_frame
+#endif
 
 #define CFI_STARTPROC		.cfi_startproc
 #define CFI_ENDPROC		.cfi_endproc
-- 
2.51.0

Re: [PATCH v6 0/6] x86/vdso: VDSO updates and fixes for sframes

[H. Peter Anvin]

On January 29, 2026 3:27:20 AM PST, Jens Remus <jremus@linux.ibm.com> wrote:
>This enables generation of SFrame V3 stack trace information for VDSO on
>x86-64.  It's a continuation of Josh's and Steve's work:
>
>   https://lore.kernel.org/all/cover.1737511963.git.jpoimboe@kernel.org/
>   https://lore.kernel.org/all/20250422183439.895236512@goodmis.org/
>
>This series focuses only on the VDSO code. They are helpful fixes
>and updates that doesn't rely on sframes (although the last patch
>is sframe related).
>
>This series applies on top of the latest unwind user sframe series
>"[PATCH v13 00/18] unwind_deferred: Implement sframe handling":
>https://lore.kernel.org/all/20260127150554.2760964-1-jremus@linux.ibm.com/
>
>Like above series it depends on the upcoming binutils 2.46 release to
>be used to build executables and libraries such as VDSO with SFrame V3
>stack trace information (using the assembler option --gsframe-3).
>
>Changes in v6:
>- SFrame V3 support (SFrame V2 is not supported).
>- Prevent GNU_SFRAME program table entry to empty .sframe section.
>- Integrate v5 review feedback. (Josh)
>
>Regards,
>Jens
>
>
>Josh Poimboeuf (6):
>  x86/vdso: Fix DWARF generation for getrandom()
>  x86/asm: Avoid emitting DWARF CFI for non-VDSO
>  x86/asm: Simplify VDSO DWARF generation
>  x86/vdso: Use SYM_FUNC_{START,END} in __kernel_vsyscall()
>  x86/vdso: Use CFI macros in __vdso_sgx_enter_enclave()
>  x86/vdso: Enable sframe generation in VDSO
>
> arch/Kconfig                             |  7 +++
> arch/x86/entry/vdso/Makefile             | 10 +++--
> arch/x86/entry/vdso/vdso-layout.lds.S    |  9 +++-
> arch/x86/entry/vdso/vdso32/system_call.S | 10 +----
> arch/x86/entry/vdso/vgetrandom-chacha.S  |  3 +-
> arch/x86/entry/vdso/vsgx.S               | 19 +++------
> arch/x86/include/asm/dwarf2.h            | 54 +++++++++++++++++-------
> arch/x86/include/asm/linkage.h           | 33 ++++++++++++---
> arch/x86/include/asm/vdso.h              |  1 -
> 9 files changed, 97 insertions(+), 49 deletions(-)
>

This patchset clashes *hard* with the changes already in tip:x86/entry.

Re: [PATCH v6 0/6] x86/vdso: VDSO updates and fixes for sframes

[Jens Remus]

On 2/1/2026 9:23 AM, H. Peter Anvin wrote:
> On January 29, 2026 3:27:20 AM PST, Jens Remus <jremus@linux.ibm.com> wrote:
>> This enables generation of SFrame V3 stack trace information for VDSO on
>> x86-64.  It's a continuation of Josh's and Steve's work:
>>
>>   https://lore.kernel.org/all/cover.1737511963.git.jpoimboe@kernel.org/
>>   https://lore.kernel.org/all/20250422183439.895236512@goodmis.org/
>>
>> This series focuses only on the VDSO code. They are helpful fixes
>> and updates that doesn't rely on sframes (although the last patch
>> is sframe related).
>>
>> This series applies on top of the latest unwind user sframe series
>> "[PATCH v13 00/18] unwind_deferred: Implement sframe handling":
>> https://lore.kernel.org/all/20260127150554.2760964-1-jremus@linux.ibm.com/
>>
>> Like above series it depends on the upcoming binutils 2.46 release to
>> be used to build executables and libraries such as VDSO with SFrame V3
>> stack trace information (using the assembler option --gsframe-3).

>> Josh Poimboeuf (6):
>>  x86/vdso: Fix DWARF generation for getrandom()
>>  x86/asm: Avoid emitting DWARF CFI for non-VDSO
>>  x86/asm: Simplify VDSO DWARF generation
>>  x86/vdso: Use SYM_FUNC_{START,END} in __kernel_vsyscall()
>>  x86/vdso: Use CFI macros in __vdso_sgx_enter_enclave()
>>  x86/vdso: Enable sframe generation in VDSO
>>
>> arch/Kconfig                             |  7 +++
>> arch/x86/entry/vdso/Makefile             | 10 +++--
>> arch/x86/entry/vdso/vdso-layout.lds.S    |  9 +++-
>> arch/x86/entry/vdso/vdso32/system_call.S | 10 +----
>> arch/x86/entry/vdso/vgetrandom-chacha.S  |  3 +-
>> arch/x86/entry/vdso/vsgx.S               | 19 +++------
>> arch/x86/include/asm/dwarf2.h            | 54 +++++++++++++++++-------
>> arch/x86/include/asm/linkage.h           | 33 ++++++++++++---
>> arch/x86/include/asm/vdso.h              |  1 -
>> 9 files changed, 97 insertions(+), 49 deletions(-)
>>
> 
> This patchset clashes *hard* with the changes already in tip:x86/entry.

Thank you for the hint!  I have rebased the series on top of
tip:x86/entry and sent a v7 for review:

[PATCH v7 0/6] x86/vdso: VDSO updates and fixes for sframes
https://lore.kernel.org/all/20260203171958.1522030-1-jremus@linux.ibm.com/

Regards,
Jens
-- 
Jens Remus
Linux on Z Development (D3303)
jremus@de.ibm.com / jremus@linux.ibm.com

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