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Re: Gdbserver syscall clobber
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:
li r10,-_LAST_ERRNO
cmpl 0,r3,r10
blt 30f
neg r3,r3
cmpi 0,r3,ERESTARTNOHAND
bne 22f
li r3,EINTR
22: lwz r10,_CCR(r1) /* Set SO bit in CR */
oris r10,r10,0x1000
stw r10,_CCR(r1)
30: stw r3,GPR3(r1) /* Update return value */
b ret_from_except
66: li r3,ENOSYS
b 22b
?
--
Bill Gatliff
bgat@billgatliff.com