On 12/28/22 8:35 PM, Willy Tarreau wrote:
OK thanks!
I've pushed for you an update which starts to do what I proposed. Errno and environ are now marked weak for all archs, and _auxv is set for i386, x86_64, arm64 and arm for now:
https://git.kernel.org/pub/scm/linux/kernel/git/wtarreau/nolibc.git/log/?h=20221227-nolibc-weak-2You can already use it to implement getauxval(), it will normally work for these archs.
Will do and be back with two patch series.
I think we could avoid the asm specific stuff is we get rid of the frame pointer. Please look below:
__attribute__((weak,unused,noreturn,optimize("omit-frame-pointer"),section(".text.nolibc_rt_sigreturn"))) void sys_rt_sigreturn() { my_syscall0(__NR_rt_sigreturn); __builtin_unreachable(); }
Wow! You just taught me that we can force optimize a function with optimize("omit-frame-pointer") attribute. Nice to know this one!
I compile-tested it and it indeed gives the correct code on x86-64. Hopefully this approach works for all archs.
It gives me the correct code for x86_64 and i586. I don't know if other architectures will want to add a prologue. I tried with "naked" but it's ignored by the compiler since the function is not purely asm. Not very important but given that we already have everything to perform our calls it would make sense to stay on this. By the way, for the sake of consistency with other syscalls, I do think the function (or label if we can't do otherwise) should be called "sys_rt_sigreturn" as it just performs a syscall.
Will call that 'sys_rt_sigreturn' in the next series.
Thanks!