linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Masami Hiramatsu <mhiramat@kernel.org>
To: Steven Rostedt <rostedt@goodmis.org>,
	Josh Poimboeuf <jpoimboe@redhat.com>,
	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,
	Thomas Gleixner <tglx@linutronix.de>,
	Borislav Petkov <bp@alien8.de>,
	Peter Zijlstra <peterz@infradead.org>,
	kernel-team@fb.com, yhs@fb.com, linux-ia64@vger.kernel.org,
	Abhishek Sagar <sagar.abhishek@gmail.com>,
	Andrii Nakryiko <andrii.nakryiko@gmail.com>
Subject: [PATCH -tip v10 13/16] x86/kprobes: Push a fake return address at kretprobe_trampoline
Date: Thu, 29 Jul 2021 23:07:58 +0900	[thread overview]
Message-ID: <162756767828.301564.16335053369674561101.stgit@devnote2> (raw)
In-Reply-To: <162756755600.301564.4957591913842010341.stgit@devnote2>

Change __kretprobe_trampoline() to push the address of the
__kretprobe_trampoline() as a fake return address at the bottom
of the stack frame. This fake return address will be replaced
with the correct return address in the trampoline_handler().

With this change, the ORC unwinder can check whether the return
address is modified by kretprobes or not.

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>
---
 Changes in v9:
  - Update changelog and comment.
  - Remove unneeded type casting.
---
 arch/x86/kernel/kprobes/core.c |   34 +++++++++++++++++++++++++---------
 1 file changed, 25 insertions(+), 9 deletions(-)

diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c
index d1436d7463fd..7e1111c19605 100644
--- a/arch/x86/kernel/kprobes/core.c
+++ b/arch/x86/kernel/kprobes/core.c
@@ -1022,28 +1022,33 @@ 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 a 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
+	/* In trampoline_handler(), 'regs->flags' is copied to 'regs->sp'. */
+	"	addq $8, %rsp\n"
 	"	popfq\n"
 #else
-	"	pushl %esp\n"
+	/* Push a 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
+	/* In trampoline_handler(), 'regs->flags' is copied to 'regs->sp'. */
+	"	addl $4, %esp\n"
 	"	popfl\n"
 #endif
 	"	ret\n"
@@ -1063,8 +1068,10 @@ STACK_FRAME_NON_STANDARD_FP(__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
@@ -1072,8 +1079,17 @@ __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 = &regs->sp + 1;
+
+	/* Replace fake return address with real one. */
+	*frame_pointer = kretprobe_trampoline_handler(regs, frame_pointer);
 
-	return (void *)kretprobe_trampoline_handler(regs, &regs->sp);
+	/*
+	 * Copy FLAGS to 'pt_regs::sp' so that __kretprobe_trapmoline()
+	 * can do RET right after POPF.
+	 */
+	regs->sp = regs->flags;
 }
 NOKPROBE_SYMBOL(trampoline_handler);
 


  parent reply	other threads:[~2021-07-29 14:10 UTC|newest]

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-29 14:05 [PATCH -tip v10 00/16] kprobes: Fix stacktrace with kretprobes on x86 Masami Hiramatsu
2021-07-29 14:06 ` [PATCH -tip v10 01/16] ia64: kprobes: Fix to pass correct trampoline address to the handler Masami Hiramatsu
2021-07-29 14:06 ` [PATCH -tip v10 02/16] kprobes: treewide: Replace arch_deref_entry_point() with dereference_symbol_descriptor() Masami Hiramatsu
2021-07-29 14:06 ` [PATCH -tip v10 03/16] kprobes: treewide: Remove trampoline_address from kretprobe_trampoline_handler() Masami Hiramatsu
2021-07-29 14:06 ` [PATCH -tip v10 04/16] kprobes: treewide: Make it harder to refer kretprobe_trampoline directly Masami Hiramatsu
2021-07-29 14:06 ` [PATCH -tip v10 05/16] kprobes: Add kretprobe_find_ret_addr() for searching return address Masami Hiramatsu
2021-07-29 14:06 ` [PATCH -tip v10 06/16] objtool: Add frame-pointer-specific function ignore Masami Hiramatsu
2021-07-29 14:07 ` [PATCH -tip v10 07/16] objtool: Ignore unwind hints for ignored functions Masami Hiramatsu
2021-07-29 14:07 ` [PATCH -tip v10 08/16] x86/kprobes: Add UNWIND_HINT_FUNC on kretprobe_trampoline() Masami Hiramatsu
2021-07-29 14:07 ` [PATCH -tip v10 09/16] ARC: Add instruction_pointer_set() API Masami Hiramatsu
2021-07-29 14:07 ` [PATCH -tip v10 10/16] ia64: " Masami Hiramatsu
2021-07-29 14:07 ` [PATCH -tip v10 11/16] arm: kprobes: Make space for instruction pointer on stack Masami Hiramatsu
2021-07-29 14:07 ` [PATCH -tip v10 12/16] kprobes: Enable stacktrace from pt_regs in kretprobe handler Masami Hiramatsu
2021-07-29 14:07 ` Masami Hiramatsu [this message]
2021-07-29 14:08 ` [PATCH -tip v10 14/16] x86/unwind: Recover kretprobe trampoline entry Masami Hiramatsu
2021-07-29 14:08 ` [PATCH -tip v10 15/16] tracing: Show kretprobe unknown indicator only for kretprobe_trampoline Masami Hiramatsu
2021-07-29 14:08 ` [PATCH -tip v10 16/16] x86/kprobes: Fixup return address in generic trampoline handler Masami Hiramatsu
2021-07-29 23:35 ` [PATCH -tip v10 00/16] kprobes: Fix stacktrace with kretprobes on x86 Masami Hiramatsu
2021-08-24  5:12   ` Andrii Nakryiko
2021-08-24  5:32     ` Masami Hiramatsu
2021-09-13 17:14       ` Andrii Nakryiko
2021-09-14  0:38         ` Masami Hiramatsu
2021-09-14  1:36           ` Andrii Nakryiko
2021-09-14  5:10             ` Masami Hiramatsu
2021-08-29 14:22 ` [RFC PATCH 0/1] Non stack-intrusive return probe event Masami Hiramatsu
2021-08-29 14:22   ` [RFC PATCH 1/1] [PoC] tracing: kprobe: Add non-stack intrusion " Masami Hiramatsu
2021-08-30 19:04   ` [RFC PATCH 0/1] Non stack-intrusive " Andrii Nakryiko
2021-08-31  6:06     ` Masami Hiramatsu

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=162756767828.301564.16335053369674561101.stgit@devnote2 \
    --to=mhiramat@kernel.org \
    --cc=andrii.nakryiko@gmail.com \
    --cc=ast@kernel.org \
    --cc=bp@alien8.de \
    --cc=bpf@vger.kernel.org \
    --cc=dxu@dxuuu.xyz \
    --cc=jpoimboe@redhat.com \
    --cc=kernel-team@fb.com \
    --cc=kuba@kernel.org \
    --cc=linux-ia64@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=mingo@kernel.org \
    --cc=mingo@redhat.com \
    --cc=peterz@infradead.org \
    --cc=rostedt@goodmis.org \
    --cc=sagar.abhishek@gmail.com \
    --cc=tglx@linutronix.de \
    --cc=x86@kernel.org \
    --cc=yhs@fb.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).