Commit aa44433a authored by Heiko Carstens's avatar Heiko Carstens Committed by Vasily Gorbik
Browse files

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 4d7bf939 ("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: default avatarHeiko Carstens <hca@linux.ibm.com>
Signed-off-by: default avatarVasily Gorbik <gor@linux.ibm.com>
parent 504b73d0

arch/s390/Kconfig

+1 −0
Original line number Diff line number Diff line
@@ -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

arch/s390/kernel/stacktrace.c

+43 −0
Original line number Diff line number Diff line
@@ -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();

}