linux-kernel - [RFC PATCH v1 05/16] s390/vdso: Keep function symbols in vDSO

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Message-ID: <20250710163522.3195293-6-jremus@linux.ibm.com>
Date: Thu, 10 Jul 2025 18:35:11 +0200
From: Jens Remus <jremus@...ux.ibm.com>
To: linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org,
        bpf@...r.kernel.org, x86@...nel.org,
        Steven Rostedt <rostedt@...nel.org>
Cc: Jens Remus <jremus@...ux.ibm.com>, Heiko Carstens <hca@...ux.ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Ilya Leoshkevich <iii@...ux.ibm.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Josh Poimboeuf <jpoimboe@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...nel.org>,
        Jiri Olsa <jolsa@...nel.org>, Namhyung Kim <namhyung@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Andrii Nakryiko <andrii@...nel.org>,
        Indu Bhagat <indu.bhagat@...cle.com>,
        "Jose E. Marchesi" <jemarch@....org>,
        Beau Belgrave <beaub@...ux.microsoft.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Jens Axboe <axboe@...nel.dk>, Florian Weimer <fweimer@...hat.com>,
        Sam James <sam@...too.org>
Subject: [RFC PATCH v1 05/16] s390/vdso: Keep function symbols in vDSO

Keep all function symbols in the vDSO .symtab for stack trace purposes.
This enables perf to lookup these function symbols in addition to those
already exported in vDSO .dynsym.

Signed-off-by: Jens Remus <jremus@...ux.ibm.com>
---

Notes (jremus):
    Alternatively use objcopy option -g instead of -S (and the -w -K
    filters), as Josh did in "x86/vdso: Enable sframe generation in VDSO":
    https://lore.kernel.org/all/20250425024023.173709192@goodmis.org/
    
    Note that this change does not cause the vDSO build-id to change.
    perf record may therefore not dump an updated copy of the vDSO to
    ~/.debug/[vdso]/<build-id>/vdso, so that perf script may use a
    stale copy without .symtab. Resolve by deleting ~/.debug/.

 arch/s390/kernel/vdso64/Makefile | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/s390/kernel/vdso64/Makefile b/arch/s390/kernel/vdso64/Makefile
index e96156b9c4df..067753352697 100644
--- a/arch/s390/kernel/vdso64/Makefile
+++ b/arch/s390/kernel/vdso64/Makefile
@@ -58,7 +58,7 @@ $(obj)/vdso64.so.dbg: $(obj)/vdso64.lds $(obj-vdso64) $(obj-cvdso64) FORCE
 	$(call if_changed,vdso_and_check)
 
 # strip rule for the .so file
-$(obj)/%.so: OBJCOPYFLAGS := -S
+$(obj)/%.so: OBJCOPYFLAGS := -S -w -K "__arch_*" -K "__cvdso_*" -K "__s390_vdso_*"
 $(obj)/%.so: $(obj)/%.so.dbg FORCE
 	$(call if_changed,objcopy)
 
-- 
2.48.1