Andi Kleen wrote: > From: Jeff Dike <[EMAIL PROTECTED]> > The patch below copies %r9 (where the sixth argument has been > stashed) into the RBP slot of pt_regs before syscall_trace_enter is > called. This fixes ptrace. > > To allow a successful return to userspace, the original value of rbp > must be restored. This is done by storing the current value of rbp > into the RBP slot of pt_regs before the RESTORE_REST. > > --- linux.orig/arch/x86_64/ia32/ia32entry.S > +++ linux/arch/x86_64/ia32/ia32entry.S > @@ -148,11 +148,23 @@ sysenter_do_call: > sysenter_tracesys: > CFI_RESTORE_STATE > SAVE_REST > + /* > + * We need the 6th system call argument to be in regs->rbp at > + * this point so that ptrace will see it. It's in r9 now, so copy > + * it to the rbp slot now. > + */ > + movq %r9, RBP(%rsp) > CLEAR_RREGS > movq $-ENOSYS,RAX(%rsp) /* really needed? */ > movq %rsp,%rdi /* &pt_regs -> arg1 */ > call syscall_trace_enter > LOAD_ARGS ARGOFFSET /* reload args from stack in case ptrace changed > it */ > + /* > + * Now, we need the correct value of rbp to be restored. It > + * was never munged, so we can save it to the rbp slot and > + * just have it restored. > + */ > + movq %rbp, RBP(%rsp) > RESTORE_REST > movl %ebp, %ebp > /* no need to do an access_ok check here because rbp has been
Didn't we have problems with this exact approach before? This one was dropped because it caused 32-bit programs to crash: http://www2.kernel.org/pub/linux/kernel/people/akpm/patches/2.6/2.6.13/2.6.13-mm2/broken-out/x86-64-ptrace-ia32-bp-fix.patch See: http://lkml.org/lkml/2005/09/16/261 for the one I proposed instead. And in any case doesn't cstar_tracesys() need the same fix? - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
