linux-kernel - Re: [tip:x86/vdso] x86/vdso32/syscall.S: Do not load __USER32

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Date:	Thu, 23 Apr 2015 13:46:36 +0200
From:	Denys Vlasenko <dvlasenk@...hat.com>
To:	Brian Gerst <brgerst@...il.com>
CC:	Steven Rostedt <rostedt@...dmis.org>,
	Oleg Nesterov <oleg@...hat.com>,
	Ingo Molnar <mingo@...nel.org>,
	"H. Peter Anvin" <hpa@...or.com>, Borislav Petkov <bp@...en8.de>,
	Andy Lutomirski <luto@...capital.net>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andy Lutomirski <luto@...nel.org>,
	Will Drewry <wad@...omium.org>,
	Frédéric Weisbecker <fweisbec@...il.com>,
	Alexei Starovoitov <ast@...mgrid.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Kees Cook <keescook@...omium.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	linux-tip-commits@...r.kernel.org
Subject: Re: [tip:x86/vdso] x86/vdso32/syscall.S: Do not load __USER32_DS
 to %ss

On 04/23/2015 01:28 PM, Brian Gerst wrote:
>> Looking at the error message:
>>
>>> Unhandled exception: stack overflow in 32-bit code (0xf779bc07).
>>> Register dump:
>>>  CS:0023 SS:002b DS:002b ES:002b FS:0063 GS:006b
>>>  EIP:f779bc07 ESP:00aed60c EBP:00aed750 EFLAGS:00010216(  R- --  I   -A-P- )
>>>  EAX:00000040 EBX:00000010 ECX:00aed750 EDX:00000040
>>>  ESI:00000040 EDI:7ffd4000
>>
>> it is not coming from Wine itself, looks like it's from Windows code,
>> and I'd guess it just tells us that they got exception 12,
>> without further information on the cause.
> 
> The backtrace shows the fault is in the VDSO, the first pop
> instruction after returning from the kernel.

Yes, I understand at which insn exception happens.

I meant that *the message* is not generated by Wine or kernel.
grep for "Unhandled exception:" comes up empty
on their source trees.

After much grepping, I see that I'm wrong.
It does come from wine:

void info_win32_exception(void)
{
    const EXCEPTION_RECORD*     rec;
    ADDRESS64                   addr;
    char                        hexbuf[MAX_OFFSET_TO_STR_LEN];

    if (!dbg_curr_thread->in_exception)
    {
        dbg_printf("Thread isn't in an exception\n");
        return;
    }
    rec = &dbg_curr_thread->excpt_record;
    memory_get_current_pc(&addr);

    /* print some infos */
    dbg_printf("%s: ",
               dbg_curr_thread->first_chance ? "First chance exception" : "Unhandled exception");
    switch (rec->ExceptionCode)
    {
    case EXCEPTION_BREAKPOINT:
        dbg_printf("breakpoint");
        break;
    case EXCEPTION_SINGLE_STEP:
        dbg_printf("single step");
        break;
    case EXCEPTION_INT_DIVIDE_BY_ZERO:
        dbg_printf("divide by zero");
        break;
    case EXCEPTION_INT_OVERFLOW:
        dbg_printf("overflow");
        break;
    case EXCEPTION_ARRAY_BOUNDS_EXCEEDED:
        dbg_printf("array bounds");
        break;
    case EXCEPTION_ILLEGAL_INSTRUCTION:
        dbg_printf("illegal instruction");
        break;
    case EXCEPTION_STACK_OVERFLOW:
        dbg_printf("stack overflow");
        break;
    ...

I hoped we can easily make Wine show exception's error code.
Not that easy :/

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