[RFC 08/30] x86/asm: Re-add manual CFI infrastructure

[Andy Lutomirski <luto@kernel.org>]

Commit 131484c8da97 ("x86/debug: Remove perpetually broken,
unmaintainable dwarf annotations") removed all the manual DWARF
annotations outside the vDSO.  It also removed the macros we used
for the manual annotations.

Re-add the macros so that we can clean up the vDSO annotations.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
---
 arch/x86/Makefile             |  10 ++-
 arch/x86/include/asm/dwarf2.h | 170 ++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 178 insertions(+), 2 deletions(-)
 create mode 100644 arch/x86/include/asm/dwarf2.h

diff --git a/arch/x86/Makefile b/arch/x86/Makefile
index 054ff969fcdb..e4a537ed5350 100644
--- a/arch/x86/Makefile
+++ b/arch/x86/Makefile
@@ -159,6 +159,12 @@ endif
 sp-$(CONFIG_X86_32) := esp
 sp-$(CONFIG_X86_64) := rsp
 
+# do binutils support CFI?
+cfi := $(call as-instr,.cfi_startproc\n.cfi_rel_offset $(sp-y)$(comma)0\n.cfi_endproc,-DCONFIG_AS_CFI=1)
+# is .cfi_signal_frame supported too?
+cfi-sigframe := $(call as-instr,.cfi_startproc\n.cfi_signal_frame\n.cfi_endproc,-DCONFIG_AS_CFI_SIGNAL_FRAME=1)
+cfi-sections := $(call as-instr,.cfi_sections .debug_frame,-DCONFIG_AS_CFI_SECTIONS=1)
+
 # does binutils support specific instructions?
 asinstr := $(call as-instr,fxsaveq (%rax),-DCONFIG_AS_FXSAVEQ=1)
 asinstr += $(call as-instr,pshufb %xmm0$(comma)%xmm0,-DCONFIG_AS_SSSE3=1)
@@ -166,8 +172,8 @@ asinstr += $(call as-instr,crc32l %eax$(comma)%eax,-DCONFIG_AS_CRC32=1)
 avx_instr := $(call as-instr,vxorps %ymm0$(comma)%ymm1$(comma)%ymm2,-DCONFIG_AS_AVX=1)
 avx2_instr :=$(call as-instr,vpbroadcastb %xmm0$(comma)%ymm1,-DCONFIG_AS_AVX2=1)
 
-KBUILD_AFLAGS += $(asinstr) $(avx_instr) $(avx2_instr)
-KBUILD_CFLAGS += $(asinstr) $(avx_instr) $(avx2_instr)
+KBUILD_AFLAGS += $(cfi) $(cfi-sigframe) $(cfi-sections) $(asinstr) $(avx_instr) $(avx2_instr)
+KBUILD_CFLAGS += $(cfi) $(cfi-sigframe) $(cfi-sections) $(asinstr) $(avx_instr) $(avx2_instr)
 
 LDFLAGS := -m elf_$(UTS_MACHINE)
 
diff --git a/arch/x86/include/asm/dwarf2.h b/arch/x86/include/asm/dwarf2.h
new file mode 100644
index 000000000000..de1cdaf4d743
--- /dev/null
+++ b/arch/x86/include/asm/dwarf2.h
@@ -0,0 +1,170 @@
+#ifndef _ASM_X86_DWARF2_H
+#define _ASM_X86_DWARF2_H
+
+#ifndef __ASSEMBLY__
+#warning "asm/dwarf2.h should be only included in pure assembly files"
+#endif
+
+/*
+ * Macros for dwarf2 CFI unwind table entries.
+ * See "as.info" for details on these pseudo ops. Unfortunately
+ * they are only supported in very new binutils, so define them
+ * away for older version.
+ */
+
+#ifdef CONFIG_AS_CFI
+
+#define CFI_STARTPROC		.cfi_startproc
+#define CFI_ENDPROC		.cfi_endproc
+#define CFI_DEF_CFA		.cfi_def_cfa
+#define CFI_DEF_CFA_REGISTER	.cfi_def_cfa_register
+#define CFI_DEF_CFA_OFFSET	.cfi_def_cfa_offset
+#define CFI_ADJUST_CFA_OFFSET	.cfi_adjust_cfa_offset
+#define CFI_OFFSET		.cfi_offset
+#define CFI_REL_OFFSET		.cfi_rel_offset
+#define CFI_REGISTER		.cfi_register
+#define CFI_RESTORE		.cfi_restore
+#define CFI_REMEMBER_STATE	.cfi_remember_state
+#define CFI_RESTORE_STATE	.cfi_restore_state
+#define CFI_UNDEFINED		.cfi_undefined
+#define CFI_ESCAPE		.cfi_escape
+
+#ifdef CONFIG_AS_CFI_SIGNAL_FRAME
+#define CFI_SIGNAL_FRAME	.cfi_signal_frame
+#else
+#define CFI_SIGNAL_FRAME
+#endif
+
+#if defined(CONFIG_AS_CFI_SECTIONS) && defined(__ASSEMBLY__)
+	/*
+	 * 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 this
+	 * file is used in the vDSO assembly, or if vmlinux.lds.S gets
+	 * changed so it doesn't discard .eh_frame.
+	 */
+	.cfi_sections .debug_frame
+#endif
+
+#else
+
+/*
+ * Due to the structure of pre-exisiting code, don't use assembler line
+ * comment character # to ignore the arguments. Instead, use a dummy macro.
+ */
+.macro cfi_ignore a=0, b=0, c=0, d=0
+.endm
+
+#define CFI_STARTPROC		cfi_ignore
+#define CFI_ENDPROC		cfi_ignore
+#define CFI_DEF_CFA		cfi_ignore
+#define CFI_DEF_CFA_REGISTER	cfi_ignore
+#define CFI_DEF_CFA_OFFSET	cfi_ignore
+#define CFI_ADJUST_CFA_OFFSET	cfi_ignore
+#define CFI_OFFSET		cfi_ignore
+#define CFI_REL_OFFSET		cfi_ignore
+#define CFI_REGISTER		cfi_ignore
+#define CFI_RESTORE		cfi_ignore
+#define CFI_REMEMBER_STATE	cfi_ignore
+#define CFI_RESTORE_STATE	cfi_ignore
+#define CFI_UNDEFINED		cfi_ignore
+#define CFI_ESCAPE		cfi_ignore
+#define CFI_SIGNAL_FRAME	cfi_ignore
+
+#endif
+
+/*
+ * An attempt to make CFI annotations more or less
+ * correct and shorter. It is implied that you know
+ * what you're doing if you use them.
+ */
+#ifdef __ASSEMBLY__
+#ifdef CONFIG_X86_64
+	.macro pushq_cfi reg
+	pushq \reg
+	CFI_ADJUST_CFA_OFFSET 8
+	.endm
+
+	.macro pushq_cfi_reg reg
+	pushq %\reg
+	CFI_ADJUST_CFA_OFFSET 8
+	CFI_REL_OFFSET \reg, 0
+	.endm
+
+	.macro popq_cfi reg
+	popq \reg
+	CFI_ADJUST_CFA_OFFSET -8
+	.endm
+
+	.macro popq_cfi_reg reg
+	popq %\reg
+	CFI_ADJUST_CFA_OFFSET -8
+	CFI_RESTORE \reg
+	.endm
+
+	.macro pushfq_cfi
+	pushfq
+	CFI_ADJUST_CFA_OFFSET 8
+	.endm
+
+	.macro popfq_cfi
+	popfq
+	CFI_ADJUST_CFA_OFFSET -8
+	.endm
+
+	.macro movq_cfi reg offset=0
+	movq %\reg, \offset(%rsp)
+	CFI_REL_OFFSET \reg, \offset
+	.endm
+
+	.macro movq_cfi_restore offset reg
+	movq \offset(%rsp), %\reg
+	CFI_RESTORE \reg
+	.endm
+#else /*!CONFIG_X86_64*/
+	.macro pushl_cfi reg
+	pushl \reg
+	CFI_ADJUST_CFA_OFFSET 4
+	.endm
+
+	.macro pushl_cfi_reg reg
+	pushl %\reg
+	CFI_ADJUST_CFA_OFFSET 4
+	CFI_REL_OFFSET \reg, 0
+	.endm
+
+	.macro popl_cfi reg
+	popl \reg
+	CFI_ADJUST_CFA_OFFSET -4
+	.endm
+
+	.macro popl_cfi_reg reg
+	popl %\reg
+	CFI_ADJUST_CFA_OFFSET -4
+	CFI_RESTORE \reg
+	.endm
+
+	.macro pushfl_cfi
+	pushfl
+	CFI_ADJUST_CFA_OFFSET 4
+	.endm
+
+	.macro popfl_cfi
+	popfl
+	CFI_ADJUST_CFA_OFFSET -4
+	.endm
+
+	.macro movl_cfi reg offset=0
+	movl %\reg, \offset(%esp)
+	CFI_REL_OFFSET \reg, \offset
+	.endm
+
+	.macro movl_cfi_restore offset reg
+	movl \offset(%esp), %\reg
+	CFI_RESTORE \reg
+	.endm
+#endif /*!CONFIG_X86_64*/
+#endif /*__ASSEMBLY__*/
+
+#endif /* _ASM_X86_DWARF2_H */
-- 
2.4.3