Enable sframe generation in the VDSO library so kernel and user space
can unwind through it.
Signed-off-by: Josh Poimboeuf <jpoim...@kernel.org>
---
 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 6682b2a53e34..65228c78fef0 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 HAVE_PERF_REGS
        bool
        help
diff --git a/arch/x86/entry/vdso/Makefile b/arch/x86/entry/vdso/Makefile
index c9216ac4fb1e..478de89029d1 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)
 
+#ifdef CONFIG_AS_SFRAME
+SFRAME_CFLAGS := -Wa$(comma)-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 506c9800a5aa..4dcde4747b07 100644
--- a/arch/x86/entry/vdso/vdso-layout.lds.S
+++ b/arch/x86/entry/vdso/vdso-layout.lds.S
@@ -63,6 +63,7 @@ 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
@@ -91,6 +92,7 @@ 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
@@ -102,4 +104,5 @@ 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 b195b3c8677e..1c354f648505 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.
         */
-
+#ifdef __x86_64__
+       .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


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