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x86/unwind: Recover kretprobe trampoline entry

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Since the kretprobe replaces the function return address with
the kretprobe_trampoline on the stack, x86 unwinders can not
continue the stack unwinding at that point, or record
kretprobe_trampoline instead of correct return address.

To fix this issue, find the correct return address from task's
kretprobe_instances as like as function-graph tracer does.

With this fix, the unwinder can correctly unwind the stack
from kretprobe event on x86, as below.

           <...>-135     [003] ...1     6.722338: r_full_proxy_read_0: (vfs_read+0xab/0x1a0 <- full_proxy_read)
           <...>-135     [003] ...1     6.722377: <stack trace>
 => kretprobe_trace_func+0x209/0x2f0
 => kretprobe_dispatcher+0x4a/0x70
 => __kretprobe_trampoline_handler+0xca/0x150
 => trampoline_handler+0x44/0x70
 => kretprobe_trampoline+0x2a/0x50
 => vfs_read+0xab/0x1a0
 => ksys_read+0x5f/0xe0
 => do_syscall_64+0x33/0x40
 => entry_SYSCALL_64_after_hwframe+0x44/0xae

Link: https://lkml.kernel.org/r/163163055130.489837.5161749078833497255.stgit@devnote2

Reported-by: Daniel Xu <dxu@dxuuu.xyz>
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Suggested-by: Josh Poimboeuf <jpoimboe@redhat.com>
Tested-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
This commit is contained in:
Masami Hiramatsu
2021-09-14 23:42:31 +09:00
committed by Steven Rostedt (VMware)
parent 1f36839308
commit 19138af1bd
4 changed files with 42 additions and 8 deletions
Download Patch File Download Diff File Expand all files Collapse all files

23
arch/x86/include/asm/unwind.h
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@@ -4,6 +4,7 @@
#include <linux/sched.h>
#include <linux/ftrace.h>
#include <linux/kprobes.h>
#include <asm/ptrace.h>
#include <asm/stacktrace.h>
@@ -15,6 +16,7 @@ struct unwind_state {
unsigned long stack_mask;
struct task_struct *task;
int graph_idx;
struct llist_node *kr_cur;
bool error;
#if defined(CONFIG_UNWINDER_ORC)
bool signal, full_regs;
@@ -99,6 +101,27 @@ void unwind_module_init(struct module *mod, void *orc_ip, size_t orc_ip_size,
void *orc, size_t orc_size) {}
#endif
static inline
unsigned long unwind_recover_kretprobe(struct unwind_state *state,
unsigned long addr, unsigned long *addr_p)
{
return is_kretprobe_trampoline(addr) ?
kretprobe_find_ret_addr(state->task, addr_p, &state->kr_cur) :
addr;
}
/* Recover the return address modified by kretprobe and ftrace_graph. */
static inline
unsigned long unwind_recover_ret_addr(struct unwind_state *state,
unsigned long addr, unsigned long *addr_p)
{
unsigned long ret;
ret = ftrace_graph_ret_addr(state->task, &state->graph_idx,
addr, addr_p);
return unwind_recover_kretprobe(state, ret, addr_p);
}
/*
* This disables KASAN checking when reading a value from another task's stack,
* since the other task could be running on another CPU and could have poisoned