From aa44433ac4ee2ae59b4b11e01eddb6241ae24ef5 Mon Sep 17 00:00:00 2001
From: Heiko Carstens <hca@linux.ibm.com>
Date: Mon, 30 Oct 2023 16:50:47 +0100
Subject: [PATCH] s390: add USER_STACKTRACE support
Use the perf_callchain_user() code as blueprint to also add support for
USER_STACKTRACE. To describe how to use this cite the commit message of the
LoongArch implementation which came with commit 4d7bf939df08 ("LoongArch:
Add USER_STACKTRACE support"), but replace -fno-omit-frame-pointer option
with the s390 specific -mbackchain option:
====================================================================== To
get the best stacktrace output, you can compile your userspace programs
with frame pointers (at least glibc + the app you are tracing).
1, export "CC = gcc -mbackchain";
2, compile your programs with "CC";
3, use uprobe to get stacktrace output.
...
echo 'p:malloc /usr/lib64/libc.so.6:0x0a4704 size=%r2:u64' > uprobe_events
echo 'p:free /usr/lib64/libc.so.6:0x0a4d50 ptr=%r2:u64' >> uprobe_events
echo 'comm == "demo"' > ./events/uprobes/malloc/filter
echo 'comm == "demo"' > ./events/uprobes/free/filter
echo 1 > ./options/userstacktrace
echo 1 > ./options/sym-userobj
...
======================================================================
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
---
arch/s390/Kconfig | 1 +
arch/s390/kernel/stacktrace.c | 43 +++++++++++++++++++++++++++++++++++
2 files changed, 44 insertions(+)
diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
index b0d67ac8695f9..3bec98d20283b 100644
--- a/arch/s390/Kconfig
+++ b/arch/s390/Kconfig
@@ -236,6 +236,7 @@ config S390
select THREAD_INFO_IN_TASK
select TRACE_IRQFLAGS_SUPPORT
select TTY
+ select USER_STACKTRACE_SUPPORT
select VIRT_CPU_ACCOUNTING
select ZONE_DMA
# Note: keep the above list sorted alphabetically
diff --git a/arch/s390/kernel/stacktrace.c b/arch/s390/kernel/stacktrace.c
index 0787010139f77..94f440e383031 100644
--- a/arch/s390/kernel/stacktrace.c
+++ b/arch/s390/kernel/stacktrace.c
@@ -6,9 +6,12 @@
*/
#include <linux/stacktrace.h>
+#include <linux/uaccess.h>
+#include <linux/compat.h>
#include <asm/stacktrace.h>
#include <asm/unwind.h>
#include <asm/kprobes.h>
+#include <asm/ptrace.h>
void arch_stack_walk(stack_trace_consume_fn consume_entry, void *cookie,
struct task_struct *task, struct pt_regs *regs)
@@ -58,3 +61,43 @@ int arch_stack_walk_reliable(stack_trace_consume_fn consume_entry,
return -EINVAL;
return 0;
}
+
+void arch_stack_walk_user(stack_trace_consume_fn consume_entry, void *cookie,
+ const struct pt_regs *regs)
+{
+ struct stack_frame_user __user *sf;
+ unsigned long ip, sp;
+ bool first = true;
+
+ if (is_compat_task())
+ return;
+ if (!consume_entry(cookie, instruction_pointer(regs)))
+ return;
+ sf = (void __user *)user_stack_pointer(regs);
+ pagefault_disable();
+ while (1) {
+ if (__get_user(sp, &sf->back_chain))
+ break;
+ if (__get_user(ip, &sf->gprs[8]))
+ break;
+ if (ip & 0x1) {
+ /*
+ * If the instruction address is invalid, and this
+ * is the first stack frame, assume r14 has not
+ * been written to the stack yet. Otherwise exit.
+ */
+ if (first && !(regs->gprs[14] & 0x1))
+ ip = regs->gprs[14];
+ else
+ break;
+ }
+ if (!consume_entry(cookie, ip))
+ break;
+ /* Sanity check: ABI requires SP to be aligned 8 bytes. */
+ if (!sp || sp & 0x7)
+ break;
+ sf = (void __user *)sp;
+ first = false;
+ }
+ pagefault_enable();
+}
--
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