From 504b73d00a55a68c0d1bb0e7c12e56e5f908e906 Mon Sep 17 00:00:00 2001
From: Heiko Carstens <hca@linux.ibm.com>
Date: Mon, 30 Oct 2023 16:50:46 +0100
Subject: s390/perf: implement perf_callchain_user()
Daan De Meyer and Neal Gompa reported that s390 does not support perf user
stack unwinding.
This was never implemented since this requires user space to be compiled
with the -mbackchain compile option, which until now no distribution
did. However this is going to change with Fedora. Therefore provide a
perf_callchain_user() implementation.
Note that due to the way s390 sets up stack frames the provided call chains
can contain invalid values. This is especially true for the first stack
frame, where it is not possible to tell if the return address has been
written to the stack already or not.
Reported-by: Daan De Meyer <daan.j.demeyer@gmail.com>
Reported-by: Neal Gompa <ngompa@fedoraproject.org>
Closes: https://lore.kernel.org/all/CAO8sHcn3+_qrnvp0580aK7jN0Wion5F7KYeBAa4MnCY4mqABPA@mail.gmail.com/
Link: https://lore.kernel.org/all/20231030123558.10816-A-hca@linux.ibm.com
Reviewed-by: Neal Gompa <ngompa@fedoraproject.org>
Acked-by: Ilya Leoshkevich <iii@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
---
arch/s390/include/asm/stacktrace.h | 7 +++++++
1 file changed, 7 insertions(+)
(limited to 'arch/s390/include/asm/stacktrace.h')
diff --git a/arch/s390/include/asm/stacktrace.h b/arch/s390/include/asm/stacktrace.h
index 78f7b729b65f..31ec4f545e03 100644
--- a/arch/s390/include/asm/stacktrace.h
+++ b/arch/s390/include/asm/stacktrace.h
@@ -6,6 +6,13 @@
#include <linux/ptrace.h>
#include <asm/switch_to.h>
+struct stack_frame_user {
+ unsigned long back_chain;
+ unsigned long empty1[5];
+ unsigned long gprs[10];
+ unsigned long empty2[4];
+};
+
enum stack_type {
STACK_TYPE_UNKNOWN,
STACK_TYPE_TASK,
--
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