linux-kernel - [PATCH v4 08/12] s390/ptrace: Provide frame

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Message-ID: <20260127151926.2805123-9-jremus@linux.ibm.com>
Date: Tue, 27 Jan 2026 16:19:21 +0100
From: Jens Remus <jremus@...ux.ibm.com>
To: linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org,
        linux-s390@...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>,
        Josh Poimboeuf <jpoimboe@...nel.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...nel.org>,
        Jiri Olsa <jolsa@...nel.org>,
        Arnaldo Carvalho de Melo <acme@...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>,
        Florian Weimer <fweimer@...hat.com>, Kees Cook <kees@...nel.org>,
        "Carlos O'Donell" <codonell@...hat.com>, Sam James <sam@...too.org>,
        Dylan Hatch <dylanbhatch@...gle.com>
Subject: [PATCH v4 08/12] s390/ptrace: Provide frame_pointer()

On s390 64-bit the s390x ELF ABI [1] designates register 11 as the
"preferred" frame pointer (FP) register in user space.

[1]: s390x ELF ABI, https://github.com/IBM/s390x-abi/releases

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

Notes (jremus):
    Changes in v4:
    - Split out "while at it" changes into separate commit that can go
      upstream independently. (Heiko)
    
    Changes in RFC v2:
    - Separate provide frame_pointer() into this new commit.

 arch/s390/include/asm/ptrace.h | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/arch/s390/include/asm/ptrace.h b/arch/s390/include/asm/ptrace.h
index e6ec0ccf3d73..8f18d00b5fdb 100644
--- a/arch/s390/include/asm/ptrace.h
+++ b/arch/s390/include/asm/ptrace.h
@@ -250,6 +250,12 @@ static __always_inline unsigned long user_stack_pointer(const struct pt_regs *re
 	return regs->gprs[15];
 }
 
+static __always_inline unsigned long frame_pointer(const struct pt_regs *regs)
+{
+	/* Return ABI-designated "preferred" frame-pointer register value. */
+	return regs->gprs[11];
+}
+
 static __always_inline unsigned long regs_get_register(const struct pt_regs *regs,
 						       unsigned int offset)
 {
-- 
2.51.0