From 2ab4aa487b93d9d994b4a20382848a4041f00d78 Mon Sep 17 00:00:00 2001 From: Willy Tarreau Date: Tue, 10 Jan 2023 08:24:25 +0100 Subject: tools/nolibc: add auxiliary vector retrieval for i386 In the _start block we now iterate over envp to find the auxiliary vector after the NULL. The pointer is saved into an _auxv variable that is marked as weak so that it's accessible from multiple units. Signed-off-by: Willy Tarreau Signed-off-by: Paul E. McKenney --- tools/include/nolibc/arch-i386.h | 7 +++++++ 1 file changed, 7 insertions(+) (limited to 'tools/include') diff --git a/tools/include/nolibc/arch-i386.h b/tools/include/nolibc/arch-i386.h index 60b586120727..e8d0cf545bf1 100644 --- a/tools/include/nolibc/arch-i386.h +++ b/tools/include/nolibc/arch-i386.h @@ -179,6 +179,7 @@ struct sys_stat_struct { }) char **environ __attribute__((weak)); +const unsigned long *_auxv __attribute__((weak)); /* startup code */ /* @@ -195,6 +196,12 @@ void __attribute__((weak,noreturn,optimize("omit-frame-pointer"))) _start(void) "lea 4(%ebx,%eax,4),%ecx\n" // then a NULL then envp (third arg, %ecx) "mov %ecx, environ\n" // save environ "xor %ebp, %ebp\n" // zero the stack frame + "mov %ecx, %edx\n" // search for auxv (follows NULL after last env) + "0:\n" + "add $4, %edx\n" // search for auxv using edx, it follows the + "cmp -4(%edx), %ebp\n" // ... NULL after last env (ebp is zero here) + "jnz 0b\n" + "mov %edx, _auxv\n" // save it into _auxv "and $-16, %esp\n" // x86 ABI : esp must be 16-byte aligned before "sub $4, %esp\n" // the call instruction (args are aligned) "push %ecx\n" // push all registers on the stack so that we -- cgit v1.2.3