Commit d81675b6 authored by Vasily Gorbik's avatar Vasily Gorbik
Browse files

s390/unwind: recover kretprobe modified return address in stacktrace 

Based on commit cd9bc2c9 ("arm64: Recover kretprobe modified return
address in stacktrace").

"""
Since the kretprobe replaces the function return address with
the __kretprobe_trampoline on the stack, stack unwinder shows it
instead of the correct return address.

This checks whether the next return address is the
__kretprobe_trampoline(), and if so, try to find the correct
return address from the kretprobe instance list.
"""

Original patch series:
https://lore.kernel.org/all/163163030719.489837.2236069935502195491.stgit@devnote2/



Reviewed-by: default avatarTobias Huschle <huschle@linux.ibm.com>
Signed-off-by: default avatarVasily Gorbik <gor@linux.ibm.com>
parent 09bc20c8

arch/s390/include/asm/unwind.h

+13 −0
Original line number Diff line number Diff line
@@ -4,6 +4,8 @@ 


#include <linux/sched.h>

#include <linux/ftrace.h>

#include <linux/kprobes.h>

#include <linux/llist.h>

#include <asm/ptrace.h>

#include <asm/stacktrace.h>
@@ -36,10 +38,21 @@ struct unwind_state { 
	struct pt_regs *regs;

	unsigned long sp, ip;

	int graph_idx;

	struct llist_node *kr_cur;

	bool reliable;

	bool error;

};



/* Recover the return address modified by kretprobe and ftrace_graph. */

static inline unsigned long unwind_recover_ret_addr(struct unwind_state *state,

						    unsigned long ip)

{

	ip = ftrace_graph_ret_addr(state->task, &state->graph_idx, ip, NULL);

	if (is_kretprobe_trampoline(ip))

		ip = kretprobe_find_ret_addr(state->task, (void *)state->sp, &state->kr_cur);

	return ip;

}



void __unwind_start(struct unwind_state *state, struct task_struct *task,

		    struct pt_regs *regs, unsigned long first_frame);

bool unwind_next_frame(struct unwind_state *state);

arch/s390/kernel/unwind_bc.c

+2 −6
Original line number Diff line number Diff line
@@ -103,13 +103,11 @@ bool unwind_next_frame(struct unwind_state *state) 
	if (sp & 0x7)

		goto out_err;



	ip = ftrace_graph_ret_addr(state->task, &state->graph_idx, ip, (void *) sp);



	/* Update unwind state */

	state->sp = sp;

	state->ip = ip;

	state->regs = regs;

	state->reliable = reliable;

	state->ip = unwind_recover_ret_addr(state, ip);

	return true;



out_err:
@@ -161,12 +159,10 @@ void __unwind_start(struct unwind_state *state, struct task_struct *task, 
		ip = READ_ONCE_NOCHECK(sf->gprs[8]);

	}



	ip = ftrace_graph_ret_addr(state->task, &state->graph_idx, ip, NULL);



	/* Update unwind state */

	state->sp = sp;

	state->ip = ip;

	state->reliable = true;

	state->ip = unwind_recover_ret_addr(state, ip);



	if (!first_frame)

		return;