Subject: Re: fork1 and new stack
To: Robert Elz <kre@munnari.OZ.AU>
From: Emmanuel Dreyfus <firstname.lastname@example.org>
Date: 04/28/2002 18:07:11
> Is it possible you're attempting to use the child's stack, to call
> the function ...
> error = (*vmc.ev_proc)(p2, &vmc);
> before the stack has been mapped?
I checked a lot of things. By calling Debugger() the first time I enter
postsig() after a fork1(), I am able to see where the SIGSEGV is comming
The bad things happen in user mode. The child makes a fault in the libc
stub for sproc, before going to the child entry point in my program
(remember there is a child entry argument to sproc).
GP = 0x0fb582f0 SP = 0x7bffe900 PC = 0x0fa5c344
0xfa5c330: lui gp,0x10
0xfa5c334: addiu gp,gp,-16448
0xfa5c338: addu gp,gp,s2
0xfa5c33c: lw t9,-29592(gp)
0xfa5c340: addiu sp,sp,-64
0xfa5c344: sw gp,44(sp)
0xfa5c348: jalr t9
As far as I understand, accessing stack at 0x7bffe944 causes a
fault. The way I map memory is wrong.
The exec_vmcmd parameters are addr = 0x79ffe000, len = 0x02000000. This
maps a stack between 0x79ffe000 and 0x7bffe000, and 0x7bffe944 is
outside the stack.
Si la reponse est NT, c'est probablement
que vous n'avez pas compris la question.