On Fri, Feb 28, 2014 at 05:58:54PM +0100, Florian Weimer wrote:
On 02/28/2014 05:49 PM, Richard Henderson wrote:
On 02/28/2014 03:49 AM, Florian Weimer wrote:
In all cases (kernel and glibc implementation), we can use a tail call to make
sure that the stack layout looks like it is at present (at least on
architectures with an available callee-saved register), and we would not have
to adjust GDB and other tools.
How's that? A tail call would not be able to "restore" anything afterward.
We already have the restorer that calls sigreturn, and could add
movq errno@gottpoff(%rip), %rdi
movl %r12d, %fs:(%rdi)
right before that.
This does not support nested signal handlers. The saved errno must be
on the stack frame of the trampoline calling the real signal handler,
not a fixed TLS location.