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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 4d7bf939df ("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>
This commit is contained in:
Heiko Carstens 2023-10-30 16:50:47 +01:00 committed by Vasily Gorbik
parent 504b73d00a
commit aa44433ac4
2 changed files with 44 additions and 0 deletions
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1
arch/s390/Kconfig
View File

@ -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

43
arch/s390/kernel/stacktrace.c
View File

@ -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();
}