Re: Gdbserver syscall clobber
On Mon, Jul 23, 2007 at 11:06:13AM -0500, Bill Gatliff wrote: Daniel Jacobowitz wrote: On Wed, Jul 18, 2007 at 12:59:42PM -0500, Bill Gatliff wrote: Now, I'm a little rusty on PPC asm (I've been doing a lot of ARM lately), but it looks to me like the kernel is setting bit 0 in CR0 (oris r10, r10, 0x1000) a.k.a LT, but the user side is looking at CR0 (bnslr+) bit 3 a.k.a. SO. Or maybe the other way around, I'm not sure after reading Sections 1.2 and 2.1 of the Programming Environments manual. It's not checking for restart here - userspace isn't supposed to have to. It's probably checking for error. Check for the bit of kernel code that's supposed to back you up two instructions. I don't see it in this kernel. What I see is this after the call to the syscall handler: Look around do_signal: regs-nip -= 4; /* Back up retry system call */ If your kernel has corrupted the register containing the syscall number at this point, that would explain your problem. It will then do the wrong syscall. I guess PPC only backs up one instruction. -- Daniel Jacobowitz CodeSourcery ___ Linuxppc-embedded mailing list Linuxppc-embedded@ozlabs.org https://ozlabs.org/mailman/listinfo/linuxppc-embedded
Re: Gdbserver syscall clobber
On Wed, Jul 18, 2007 at 12:59:42PM -0500, Bill Gatliff wrote: Now, I'm a little rusty on PPC asm (I've been doing a lot of ARM lately), but it looks to me like the kernel is setting bit 0 in CR0 (oris r10, r10, 0x1000) a.k.a LT, but the user side is looking at CR0 (bnslr+) bit 3 a.k.a. SO. Or maybe the other way around, I'm not sure after reading Sections 1.2 and 2.1 of the Programming Environments manual. It's not checking for restart here - userspace isn't supposed to have to. It's probably checking for error. Check for the bit of kernel code that's supposed to back you up two instructions. -- Daniel Jacobowitz CodeSourcery ___ Linuxppc-embedded mailing list Linuxppc-embedded@ozlabs.org https://ozlabs.org/mailman/listinfo/linuxppc-embedded
Re: Gdbserver syscall clobber
On Mon, Jul 16, 2007 at 10:43:41AM -0500, Bill Gatliff wrote: recv(4, 0x7d60, 1, 0) = ? ERESTARTSYS (To be restarted) --- SIGIO (I/O possible) @ 0 (0) --- syscall_4294966784(0xa, 0x7d34, 0x1, 0, 0x1008a3c7, 0x1008b5a3, 0x1008b5a4, That's -512, a.k.a. the errno value used by syscall restarting. I'd say your glibc does not obey the restartable syscall convention used by your kernel, and when it tries to restart the syscall the errno value is not being replaced by the syscall number. Check the assembly for recv. -- Daniel Jacobowitz CodeSourcery ___ Linuxppc-embedded mailing list Linuxppc-embedded@ozlabs.org https://ozlabs.org/mailman/listinfo/linuxppc-embedded
