From: Josh Poimboeuf <jpoim...@kernel.org>
Enable sframe generation in the VDSO library so kernel and user space
can unwind through it.
Signed-off-by: Josh Poimboeuf <jpoim...@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rost...@goodmis.org>
---
Notes (jremus):
Link: https://lore.kernel.org/all/20250425024023.173709...@goodmis.org/
This is a prerequisite for patch "s390/vdso: Enable SFrame generation in
vDSO" to actually generate SFrame in vDSO, as it introduces config
option CONFIG_AS_SFRAME.
arch/Kconfig | 3 +++
arch/x86/entry/vdso/Makefile | 10 +++++++---
arch/x86/entry/vdso/vdso-layout.lds.S | 3 +++
arch/x86/include/asm/dwarf2.h | 5 ++++-
4 files changed, 17 insertions(+), 4 deletions(-)
diff --git a/arch/Kconfig b/arch/Kconfig
index 4fe16ad6f053..1c3daccd9072 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -435,6 +435,9 @@ config HAVE_HARDLOCKUP_DETECTOR_ARCH
It uses the same command line parameters, and sysctl interface,
as the generic hardlockup detectors.
+config AS_SFRAME
+ def_bool $(as-instr,.cfi_sections .sframe\n.cfi_startproc\n.cfi_endproc)
+
config UNWIND_USER
bool
diff --git a/arch/x86/entry/vdso/Makefile b/arch/x86/entry/vdso/Makefile
index 54d3e9774d62..2dc0e0ca19a7 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_SFRAME),y)
+ SFRAME_CFLAGS := -Wa,-gsframe
+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) $(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 ec1ac191a057..c57cfddfc37d 100644
--- a/arch/x86/entry/vdso/vdso-layout.lds.S
+++ b/arch/x86/entry/vdso/vdso-layout.lds.S
@@ -59,6 +59,7 @@ SECTIONS
.eh_frame_hdr : { *(.eh_frame_hdr) } :text :eh_frame_hdr
.eh_frame : { KEEP (*(.eh_frame)) } :text
+ .sframe : { *(.sframe) } :text :sframe
/*
* Text is well-separated from actual data: there's plenty of
@@ -87,6 +88,7 @@ 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 +100,5 @@ PHDRS
dynamic PT_DYNAMIC FLAGS(4); /* PF_R */
note PT_NOTE FLAGS(4); /* PF_R */
eh_frame_hdr PT_GNU_EH_FRAME;
+ sframe PT_GNU_SFRAME;
}
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
--
2.48.1
