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s390/unwind: recover kretprobe modified return address in stacktrace 

Based on commit cd9bc2c925 ("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: Tobias Huschle <huschle@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
This commit is contained in:
Vasily Gorbik 2021-04-28 16:29:40 +02:00
parent 09bc20c8fb
commit d81675b60d
2 changed files with 15 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

13
arch/s390/include/asm/unwind.h
View File

@ -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);

8
arch/s390/kernel/unwind_bc.c
View File

@ -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;