Re: [PATCH 6/6] x86/vdso: Enable sframe generation in VDSO
From: Jens Remus <hidden>
Date: 2025-10-20 14:07:08
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lkml
On 4/25/2025 4:37 AM, Steven Rostedt wrote:
From: Josh Poimboeuf <jpoimboe@kernel.org> Enable sframe generation in the VDSO library so kernel and user space can unwind through it. Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
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diff --git a/arch/x86/entry/vdso/vdso-layout.lds.S b/arch/x86/entry/vdso/vdso-layout.lds.S
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@@ -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;
On s390 I found that the respective s390-change needs to be guarded to prevent the vDSO from erroneously getting generated with a bogus GNU_SFRAME program table entry, if CONFIG_AS_SFRAME is not enabled: $ readelf -Wl arch/s390/kernel/vdso64/vdso64.so ... Program Headers: Type Offset VirtAddr PhysAddr FileSiz MemSiz Flg Align LOAD 0x000000 0x0000000000000000 0x0000000000000000 0x001508 0x001508 R E 0x1000 DYNAMIC 0x001190 0x0000000000001190 0x0000000000001190 0x000100 0x000100 R 0x8 NOTE 0x000420 0x0000000000000420 0x0000000000000420 0x00003c 0x00003c R 0x4 GNU_EH_FRAME 0x000000 0x0000000000000000 0x0000000000000000 0x000000 0x000000 0x8 GNU_SFRAME 0x0014f0 0x00000000000014f0 0x00000000000014f0 0x000018 0x000018 RW 0x8 ... $ xxd arch/s390/kernel/vdso64/vdso64.so ... 000014f0: 0000 0000 0000 1190 0000 0000 0000 0000 ................ 00001500: 0000 0000 0000 0000 4743 433a 2028 5562 ........GCC: (Ub 00001510: 756e 7475 2031 342e 322e 302d 3139 7562 untu 14.2.0-19ub 00001520: 756e 7475 3229 2031 342e 322e 3000 0000 untu2) 14.2.0... ... Following would be the guard for x86 (same as the one used below in arch/x86/include/asm/dwarf2.h): #if defined(__x86_64__) && defined(CONFIG_AS_SFRAME)
+ sframe PT_GNU_SFRAME;
#endif
}
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diff --git a/arch/x86/include/asm/dwarf2.h b/arch/x86/include/asm/dwarf2.h
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@@ -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
Regards, Jens -- Jens Remus Linux on Z Development (D3303) +49-7031-16-1128 Office jremus@de.ibm.com IBM IBM Deutschland Research & Development GmbH; Vorsitzender des Aufsichtsrats: Wolfgang Wendt; Geschäftsführung: David Faller; Sitz der Gesellschaft: Böblingen; Registergericht: Amtsgericht Stuttgart, HRB 243294 IBM Data Privacy Statement: https://www.ibm.com/privacy/