git: 9d436d9f2a22 - stable/15 - amd64/*sigtramp.S: re-enable some cfi annotations for special registers

The branch stable/15 has been updated by kib:

URL: https://cgit.FreeBSD.org/src/commit/?id=9d436d9f2a22bd0c39d0c47577dce1af0a732c57

commit 9d436d9f2a22bd0c39d0c47577dce1af0a732c57
Author:     Konstantin Belousov <kib@FreeBSD.org>
AuthorDate: 2026-09-19 09:46:19 +0000
Commit:     Konstantin Belousov <kib@FreeBSD.org>
CommitDate: 2026-09-28 01:03:26 +0000

    amd64/*sigtramp.S: re-enable some cfi annotations for special registers
    
    (cherry picked from commit 64a73d1b6dc93d92daea1e2d0603fda1dddadf4a)
---
 sys/amd64/amd64/sigtramp.S     | 44 ++++++++++++++++++++++++++----------------
 sys/amd64/ia32/ia32_sigtramp.S | 19 ++++++++++++------
 2 files changed, 40 insertions(+), 23 deletions(-)

diff --git a/sys/amd64/amd64/sigtramp.S b/sys/amd64/amd64/sigtramp.S
index 9aed66a199a1..13ad8eb1acca 100644
--- a/sys/amd64/amd64/sigtramp.S
+++ b/sys/amd64/amd64/sigtramp.S
@@ -34,6 +34,25 @@
 
 #include "assym.inc"
 
+/*
+ * Historical notes.  Keep it for now if problems with older versions
+ * of toolchains reappear.
+ *
+ * Gnu as complains about %fs/%gs/%es/%ds registers offsets not being
+ * multiple of 8, but gas + ld.bfd work for %cs/%ss.
+ *
+ * Clang IAS + ld.lld combination cannot handle any of the segment
+ * registers.  Also, clang IAS does not know %rflags/%fs.base/%gs.base
+ * registers names, use dwarf registers numbers from psABI directly.
+ *
+ * LLVM libunwind from stable/13 cannot parse register numbers higher
+ * than 32.  Disable %rflags, %fs.base, and %gs.base annotations.
+ */
+#if !defined(__clang__) || (__clang_major__ >= 17)
+#define	WORKING_CFI
+#endif
+
+	.cfi_sections	.eh_frame
 	.text
 /*
  * Signal trampoline, mapped as vdso into shared page.
@@ -57,33 +76,24 @@ ENTRY(__vdso_sigcode)
 	.cfi_offset	%r13, SIGF_UC + UC_R13
 	.cfi_offset	%r14, SIGF_UC + UC_R14
 	.cfi_offset	%r15, SIGF_UC + UC_R15
-#if 0
-/*
- * Gnu as complains about %fs/%gs/%es/%ds registers offsets not being
- * multiple of 8, but gas + ld.bfd work for %cs/%ss.
- *
- * Clang IAS + ld.lld combination cannot handle any of the segment
- * registers.  Also, clang IAS does not know %rflags/%fs.base/%gs.base
- * registers names, use dwarf registers numbers from psABI directly.
- *
- * LLVM libunwind from stable/13 cannot parse register numbers higher
- * than 32.  Disable %rflags, %fs.base, and %gs.base annotations.
- */
+#ifdef WORKING_CFI
+#ifdef __clang__
 	.cfi_offset	%fs,  SIGF_UC + UC_FS
 	.cfi_offset	%gs,  SIGF_UC + UC_GS
 	.cfi_offset	%es,  SIGF_UC + UC_ES
 	.cfi_offset	%ds,  SIGF_UC + UC_DS
+#endif
 #endif
 	.cfi_offset	%rip, SIGF_UC + UC_RIP
-#if 0
+#ifdef WORKING_CFI
 	.cfi_offset	%cs,  SIGF_UC + UC_CS
-	.cfi_offset	49 /* %rflags */, SIGF_UC + UC_RFLAGS
+	.cfi_offset	%rflags, SIGF_UC + UC_RFLAGS
 #endif
 	.cfi_offset	%rsp, SIGF_UC + UC_RSP
-#if 0
+#ifdef WORKING_CFI
 	.cfi_offset	%ss,  SIGF_UC + UC_SS
-	.cfi_offset	58 /* %fs.base */, SIGF_UC + UC_FSBASE
-	.cfi_offset	59 /* %gs.base */, SIGF_UC + UC_GSBASE
+	.cfi_offset	%fs.base, SIGF_UC + UC_FSBASE
+	.cfi_offset	%gs.base, SIGF_UC + UC_GSBASE
 #endif
 	call	*SIGF_HANDLER(%rsp)	/* call signal handler */
 	lea	SIGF_UC(%rsp),%rdi	/* get ucontext_t */
diff --git a/sys/amd64/ia32/ia32_sigtramp.S b/sys/amd64/ia32/ia32_sigtramp.S
index 1a80f78a3234..9f7df4ddd291 100644
--- a/sys/amd64/ia32/ia32_sigtramp.S
+++ b/sys/amd64/ia32/ia32_sigtramp.S
@@ -34,6 +34,11 @@
 
 #include "ia32_assym.h"
 
+#if !defined(__clang__) || (__clang_major__ >= 17)
+#define	WORKING_CFI
+#endif
+
+	.cfi_sections	.eh_frame
 	.text
 /*
  * Signal trampoline, mapped as vdso into shared page, or copied to
@@ -45,7 +50,7 @@ __vdso_ia32_sigcode:
 	.cfi_startproc
 	.cfi_signal_frame
 	.cfi_def_cfa	%esp, 0
-#if 0
+#ifdef WORKING_CFI
 	.cfi_offset	%gs,  IA32_SIGF_UC + IA32_UC_GS
 	.cfi_offset	%fs,  IA32_SIGF_UC + IA32_UC_FS
 	.cfi_offset	%es,  IA32_SIGF_UC + IA32_UC_ES
@@ -59,15 +64,17 @@ __vdso_ia32_sigcode:
 	.cfi_offset	%ecx, IA32_SIGF_UC + IA32_UC_ECX
 	.cfi_offset	%eax, IA32_SIGF_UC + IA32_UC_EAX
 	.cfi_offset	%eip, IA32_SIGF_UC + IA32_UC_EIP
-#if 0
+#ifdef WORKING_CFI
 	.cfi_offset	%cs,  IA32_SIGF_UC + IA32_UC_CS
-	.cfi_offset	%flags, IA32_SIGF_UC + IA32_UC_EFLAGS
+	.cfi_offset	%eflags, IA32_SIGF_UC + IA32_UC_EFLAGS
 #endif
 	.cfi_offset	%esp, IA32_SIGF_UC + IA32_UC_ESP
-#if 0
+#ifdef WORKING_CFI
 	.cfi_offset	%ss,  IA32_SIGF_UC + IA32_UC_SS
-	.cfi_offset	93 /* %fs.base */, IA32_SIGF_UC + IA32_UC_FSBASE
-	.cfi_offset	94 /* %gs.base */, IA32_SIGF_UC + IA32_UC_GSBASE
+#ifdef __clang__
+	.cfi_offset	%fs.base, IA32_SIGF_UC + IA32_UC_FSBASE
+	.cfi_offset	%gs.base, IA32_SIGF_UC + IA32_UC_GSBASE
+#endif
 #endif
 	calll	*IA32_SIGF_HANDLER(%esp)
 	leal	IA32_SIGF_UC(%esp),%eax	/* get ucontext */