From: Peter Zijlstra <peterz@infradead.org>
To: Jann Horn <jannh@google.com>
Cc: Andy Lutomirski <luto@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
"H. Peter Anvin" <hpa@zytor.com>,
the arch/x86 maintainers <x86@kernel.org>,
kernel list <linux-kernel@vger.kernel.org>,
Josh Poimboeuf <jpoimboe@redhat.com>
Subject: Re: x86 entry perf unwinding failure (missing IRET_REGS annotation on stack switch?)
Date: Mon, 2 Mar 2020 15:58:22 +0100 [thread overview]
Message-ID: <20200302145822.GC2562@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <CAG48ez1rkN0YU-ieBaUZDKFYG5XFnd7dhDjSDdRmVfWyQzsA5g@mail.gmail.com>
On Sun, Mar 01, 2020 at 07:02:15AM +0100, Jann Horn wrote:
> 0000000000000a2f <swapgs_restore_regs_and_return_to_usermode>:
> a2f: 41 5f pop %r15
> #######sp:sp-8 bp:(und) type:regs end:0
> a31: 41 5e pop %r14
> #######sp:sp-16 bp:(und) type:regs end:0
> a33: 41 5d pop %r13
> #######sp:sp-24 bp:(und) type:regs end:0
> a35: 41 5c pop %r12
> #######sp:sp-32 bp:(und) type:regs end:0
> a37: 5d pop %rbp
> #######sp:sp-40 bp:(und) type:regs end:0
> a38: 5b pop %rbx
> #######sp:sp-48 bp:(und) type:regs end:0
> a39: 41 5b pop %r11
> #######sp:sp-56 bp:(und) type:regs end:0
> a3b: 41 5a pop %r10
> #######sp:sp-64 bp:(und) type:regs end:0
> a3d: 41 59 pop %r9
> #######sp:sp-72 bp:(und) type:regs end:0
> a3f: 41 58 pop %r8
> #######sp:sp-80 bp:(und) type:regs end:0
> a41: 58 pop %rax
> #######sp:sp-88 bp:(und) type:regs end:0
> a42: 59 pop %rcx
> #######sp:sp-96 bp:(und) type:regs end:0
> a43: 5a pop %rdx
> #######sp:sp-104 bp:(und) type:regs end:0
> a44: 5e pop %rsi
> #######sp:sp-112 bp:(und) type:regs end:0
> a45: 48 89 e7 mov %rsp,%rdi
> a48: 65 48 8b 24 25 00 00 mov %gs:0x0,%rsp
> a4f: 00 00
Right, so here we flip stacks,
> a51: ff 77 30 pushq 0x30(%rdi)
> #######sp:sp-104 bp:(und) type:regs end:0
> a54: ff 77 28 pushq 0x28(%rdi)
> #######sp:sp-96 bp:(und) type:regs end:0
> a57: ff 77 20 pushq 0x20(%rdi)
> #######sp:sp-88 bp:(und) type:regs end:0
> a5a: ff 77 18 pushq 0x18(%rdi)
> #######sp:sp-80 bp:(und) type:regs end:0
> a5d: ff 77 10 pushq 0x10(%rdi)
And here we've pushed an IRET frame
> #######sp:sp-72 bp:(und) type:regs end:0
> a60: ff 37 pushq (%rdi)
> It looks to me like things go wrong at the point where we switch over
> to the trampoline stack? The ORC info claims that we have full user
> registers on the trampoline stack (and that we're clobbering them with
> our pushes - apparently objtool is not smart enough to realize that
> that looks bogus), but at that point we should probably actually use
> something like UNWIND_HINT_IRET_REGS, right?
I _think_ you've nailed it, but I'm somewhat new to this part of
objtool.
Josh?
next prev parent reply other threads:[~2020-03-02 14:58 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-01 6:02 x86 entry perf unwinding failure (missing IRET_REGS annotation on stack switch?) Jann Horn
2020-03-02 14:58 ` Peter Zijlstra [this message]
2020-03-02 15:18 ` Josh Poimboeuf
2020-03-02 15:52 ` Josh Poimboeuf
2020-04-28 7:04 ` Josh Poimboeuf
2020-04-28 12:46 ` Peter Zijlstra
2020-04-28 14:14 ` Josh Poimboeuf
2020-04-28 14:35 ` Peter Zijlstra
2020-04-28 14:16 ` Peter Zijlstra
2020-04-28 14:31 ` Josh Poimboeuf
2020-04-28 15:25 ` Peter Zijlstra
2020-04-28 15:49 ` Josh Poimboeuf
2020-04-28 15:54 ` Josh Poimboeuf
2020-04-28 16:25 ` Sean Christopherson
2020-04-28 16:33 ` Josh Poimboeuf
2020-04-28 18:28 ` Peter Zijlstra
2020-04-28 16:44 ` Peter Zijlstra
2020-04-28 17:01 ` Josh Poimboeuf
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