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Message-ID: <20260206193642.1580787-7-jremus@linux.ibm.com>
Date: Fri, 6 Feb 2026 20:36:42 +0100
From: Jens Remus <jremus@...ux.ibm.com>
To: linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org,
bpf@...r.kernel.org, x86@...nel.org, linux-mm@...ck.org,
Steven Rostedt <rostedt@...nel.org>
Cc: Jens Remus <jremus@...ux.ibm.com>, Josh Poimboeuf <jpoimboe@...nel.org>,
Masami Hiramatsu <mhiramat@...nel.org>,
Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...nel.org>,
Jiri Olsa <jolsa@...nel.org>,
Arnaldo Carvalho de Melo <acme@...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>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Florian Weimer <fweimer@...hat.com>, Kees Cook <kees@...nel.org>,
"Carlos O'Donell" <codonell@...hat.com>, Sam James <sam@...too.org>,
Dylan Hatch <dylanbhatch@...gle.com>, Borislav Petkov <bp@...en8.de>,
Dave Hansen <dave.hansen@...ux.intel.com>,
David Hildenbrand <david@...nel.org>, "H. Peter Anvin" <hpa@...or.com>,
"Liam R. Howlett" <Liam.Howlett@...cle.com>,
Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
Michal Hocko <mhocko@...e.com>, Mike Rapoport <rppt@...nel.org>,
Suren Baghdasaryan <surenb@...gle.com>,
Vlastimil Babka <vbabka@...e.cz>, Heiko Carstens <hca@...ux.ibm.com>,
Vasily Gorbik <gor@...ux.ibm.com>,
"Steven Rostedt (Google)" <rostedt@...dmis.org>
Subject: [PATCH v8 6/6] x86/vdso: Enable sframe generation in VDSO
From: Josh Poimboeuf <jpoimboe@...nel.org>
Enable sframe generation in the VDSO library so kernel and user space
can unwind through it.
SFrame isn't supported for x32 or x86-32. Discard .sframe sections for
those VDSOs.
[ Jens Remus: Add support for SFrame V3. Prevent GNU_SFRAME program
table entry to empty .sframe section. ]
Signed-off-by: Josh Poimboeuf <jpoimboe@...nel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@...dmis.org>
Signed-off-by: Jens Remus <jremus@...ux.ibm.com>
---
Notes (jremus):
Changes in v8:
- Discard .sframe for x32 and x86-32 VDSOs. (Josh/Indu)
Note that the use of KEEP_SFRAME enables to define it for x86-64
VDSO only. Unlike CONFIG_AS_SFRAME, which may also be defined
for x32 and x86-32 VDSO. In x32 VDSO it would result in superfluous
.sframe (copied from the x86-64 build - could be removed in X32
build step). In x86-32 VDSO it would cause a bogus GNU_SFRAME
program table entry.
- Reword commit message (append Josh's private fix).
- Drop .cfi_sections .sframe in dwarf2.h in favor of the explicitly
specified more specific assembler option --gsframe-3. With this
it is not necessary to undefine CONFIG_AS_SFRAME in
fake_32bit_build.h.
arch/Kconfig | 7 +++++++
arch/x86/entry/vdso/common/vdso-layout.lds.S | 15 +++++++++++++++
arch/x86/entry/vdso/vdso64/Makefile | 1 +
arch/x86/entry/vdso/vdso64/vdso64.lds.S | 4 ++++
4 files changed, 27 insertions(+)
diff --git a/arch/Kconfig b/arch/Kconfig
index 31220f512b16..8170e492a44c 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/common/vdso-layout.lds.S b/arch/x86/entry/vdso/common/vdso-layout.lds.S
index 856b8b9d278c..47e6a6a0560a 100644
--- a/arch/x86/entry/vdso/common/vdso-layout.lds.S
+++ b/arch/x86/entry/vdso/common/vdso-layout.lds.S
@@ -60,6 +60,13 @@ SECTIONS
*(.eh_frame.*)
} :text
+#ifdef KEEP_SFRAME
+ .sframe : {
+ KEEP (*(.sframe))
+ *(.sframe.*)
+ } :text :sframe
+#endif
+
/*
* Text is well-separated from actual data: there's plenty of
* stuff that isn't used at runtime in between.
@@ -80,6 +87,10 @@ SECTIONS
*(.discard)
*(.discard.*)
*(__bug_table)
+#ifndef KEEP_SFRAME
+ *(.sframe)
+ *(.sframe.*)
+#endif
}
}
@@ -89,6 +100,7 @@ SECTIONS
#define PT_GNU_EH_FRAME 0x6474e550
#define PT_GNU_STACK 0x6474e551
#define PT_GNU_PROPERTY 0x6474e553
+#define PT_GNU_SFRAME 0x6474e554
/*
* We must supply the ELF program headers explicitly to get just one
@@ -104,6 +116,9 @@ PHDRS
dynamic PT_DYNAMIC PF_R;
note PT_NOTE PF_R;
eh_frame_hdr PT_GNU_EH_FRAME PF_R;
+#ifdef KEEP_SFRAME
+ sframe PT_GNU_SFRAME PF_R;
+#endif
gnu_stack PT_GNU_STACK PF_RW;
gnu_property PT_GNU_PROPERTY PF_R;
}
diff --git a/arch/x86/entry/vdso/vdso64/Makefile b/arch/x86/entry/vdso/vdso64/Makefile
index bfffaf1aeecc..459f8026531e 100644
--- a/arch/x86/entry/vdso/vdso64/Makefile
+++ b/arch/x86/entry/vdso/vdso64/Makefile
@@ -14,6 +14,7 @@ vobjs-$(CONFIG_X86_SGX) += vsgx.o
# Compilation flags
flags-y := -DBUILD_VDSO64 -m64 -mcmodel=small
+flags-$(CONFIG_AS_SFRAME3) += -Wa,--gsframe-3
# The location of this include matters!
include $(src)/../common/Makefile.include
diff --git a/arch/x86/entry/vdso/vdso64/vdso64.lds.S b/arch/x86/entry/vdso/vdso64/vdso64.lds.S
index 5ce3f2b6373a..13e30d3b4827 100644
--- a/arch/x86/entry/vdso/vdso64/vdso64.lds.S
+++ b/arch/x86/entry/vdso/vdso64/vdso64.lds.S
@@ -9,6 +9,10 @@
#define BUILD_VDSO64
+#ifdef CONFIG_AS_SFRAME
+# define KEEP_SFRAME
+#endif
+
#include "common/vdso-layout.lds.S"
/*
--
2.51.0
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