From: Masami Hiramatsu <mhiramat@kernel.org>
To: Steven Rostedt <rostedt@goodmis.org>, Ingo Molnar <mingo@kernel.org>
Cc: X86 ML <x86@kernel.org>, Masami Hiramatsu <mhiramat@kernel.org>,
Daniel Xu <dxu@dxuuu.xyz>,
linux-kernel@vger.kernel.org, bpf@vger.kernel.org,
kuba@kernel.org, mingo@redhat.com, ast@kernel.org,
tglx@linutronix.de, kernel-team@fb.com, yhs@fb.com,
Josh Poimboeuf <jpoimboe@redhat.com>,
linux-ia64@vger.kernel.org,
Abhishek Sagar <sagar.abhishek@gmail.com>
Subject: [PATCH -tip v5 10/12] x86/kprobes: Push a fake return address at kretprobe_trampoline
Date: Fri, 26 Mar 2021 21:30:20 +0900 [thread overview]
Message-ID: <161676182049.330141.1300212263028157733.stgit@devnote2> (raw)
In-Reply-To: <161676170650.330141.6214727134265514123.stgit@devnote2>
This changes x86/kretprobe stack frame on kretprobe_trampoline
a bit, which now push the kretprobe_trampoline as a fake return
address at the bottom of the stack frame. With this fix, the ORC
unwinder will see the kretprobe_trampoline as a return address.
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Suggested-by: Josh Poimboeuf <jpoimboe@redhat.com>
---
arch/x86/kernel/kprobes/core.c | 31 ++++++++++++++++++++++---------
1 file changed, 22 insertions(+), 9 deletions(-)
diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c
index 02b602f894e4..00c5944ae8f6 100644
--- a/arch/x86/kernel/kprobes/core.c
+++ b/arch/x86/kernel/kprobes/core.c
@@ -1041,28 +1041,31 @@ asm(
".global kretprobe_trampoline\n"
".type kretprobe_trampoline, @function\n"
"kretprobe_trampoline:\n"
- /* We don't bother saving the ss register */
#ifdef CONFIG_X86_64
- " pushq %rsp\n"
+ /* Push fake return address to tell the unwinder it's a kretprobe */
+ " pushq $kretprobe_trampoline\n"
UNWIND_HINT_FUNC
+ /* Save the sp-8, this will be fixed later */
+ " pushq %rsp\n"
" pushfq\n"
SAVE_REGS_STRING
" movq %rsp, %rdi\n"
" call trampoline_handler\n"
- /* Replace saved sp with true return address. */
- " movq %rax, 19*8(%rsp)\n"
RESTORE_REGS_STRING
+ " addq $8, %rsp\n"
" popfq\n"
#else
- " pushl %esp\n"
+ /* Push fake return address to tell the unwinder it's a kretprobe */
+ " pushl $kretprobe_trampoline\n"
UNWIND_HINT_FUNC
+ /* Save the sp-4, this will be fixed later */
+ " pushl %esp\n"
" pushfl\n"
SAVE_REGS_STRING
" movl %esp, %eax\n"
" call trampoline_handler\n"
- /* Replace saved sp with true return address. */
- " movl %eax, 15*4(%esp)\n"
RESTORE_REGS_STRING
+ " addl $4, %esp\n"
" popfl\n"
#endif
" ret\n"
@@ -1073,8 +1076,10 @@ NOKPROBE_SYMBOL(kretprobe_trampoline);
/*
* Called from kretprobe_trampoline
*/
-__used __visible void *trampoline_handler(struct pt_regs *regs)
+__used __visible void trampoline_handler(struct pt_regs *regs)
{
+ unsigned long *frame_pointer;
+
/* fixup registers */
regs->cs = __KERNEL_CS;
#ifdef CONFIG_X86_32
@@ -1082,8 +1087,16 @@ __used __visible void *trampoline_handler(struct pt_regs *regs)
#endif
regs->ip = (unsigned long)&kretprobe_trampoline;
regs->orig_ax = ~0UL;
+ regs->sp += sizeof(long);
+ frame_pointer = ((unsigned long *)®s->sp) + 1;
- return (void *)kretprobe_trampoline_handler(regs, ®s->sp);
+ /* Replace fake return address with real one. */
+ *frame_pointer = kretprobe_trampoline_handler(regs, frame_pointer);
+ /*
+ * Move flags to sp so that kretprobe_trapmoline can return
+ * right after popf.
+ */
+ regs->sp = regs->flags;
}
NOKPROBE_SYMBOL(trampoline_handler);
next prev parent reply other threads:[~2021-03-26 12:31 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-26 12:28 [PATCH -tip v5 00/12] kprobes: Fix stacktrace with kretprobes on x86 Masami Hiramatsu
2021-03-26 12:28 ` [PATCH -tip v5 01/12] ia64: kprobes: Fix to pass correct trampoline address to the handler Masami Hiramatsu
2021-03-26 12:28 ` [PATCH -tip v5 02/12] kprobes: treewide: Replace arch_deref_entry_point() with dereference_function_descriptor() Masami Hiramatsu
2021-03-26 12:28 ` [PATCH -tip v5 03/12] kprobes: treewide: Remove trampoline_address from kretprobe_trampoline_handler() Masami Hiramatsu
2021-03-26 12:29 ` [PATCH -tip v5 04/12] kprobes: Add kretprobe_find_ret_addr() for searching return address Masami Hiramatsu
2021-03-26 12:29 ` [PATCH -tip v5 05/12] x86/kprobes: Add UNWIND_HINT_FUNC on kretprobe_trampoline code Masami Hiramatsu
2021-03-26 12:29 ` [PATCH -tip v5 06/12] ARC: Add instruction_pointer_set() API Masami Hiramatsu
2021-03-26 12:29 ` [PATCH -tip v5 07/12] ia64: " Masami Hiramatsu
2021-03-26 12:30 ` [PATCH -tip v5 08/12] arm: kprobes: Make a space for regs->ARM_pc at kretprobe_trampoline Masami Hiramatsu
2021-03-26 12:30 ` [PATCH -tip v5 09/12] kprobes: Setup instruction pointer in __kretprobe_trampoline_handler Masami Hiramatsu
2021-03-26 12:30 ` Masami Hiramatsu [this message]
2021-03-26 12:30 ` [PATCH -tip v5 11/12] x86/unwind: Recover kretprobe trampoline entry Masami Hiramatsu
2021-03-26 12:30 ` [PATCH -tip v5 12/12] tracing: Show kretprobe unknown indicator only for kretprobe_trampoline Masami Hiramatsu
2021-03-26 23:49 ` [PATCH -tip v5 00/12] kprobes: Fix stacktrace with kretprobes on x86 Masami Hiramatsu
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