Commit 59ea1876 authored by Willy Tarreau's avatar Willy Tarreau Committed by Paul E. McKenney
Browse files

tools/nolibc: add auxiliary vector retrieval for arm 



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: default avatarWilly Tarreau <w@1wt.eu>

It was tested in arm, thumb1 and thumb2 modes.

Signed-off-by: default avatarPaul E. McKenney <paulmck@kernel.org>
parent 2a39a532

tools/include/nolibc/arch-arm.h

+13 −0
Original line number Diff line number Diff line
@@ -197,6 +197,7 @@ struct sys_stat_struct { 
})



char **environ __attribute__((weak));

const unsigned long *_auxv __attribute__((weak));



/* startup code */

void __attribute__((weak,noreturn,optimize("omit-frame-pointer"))) _start(void)
@@ -211,6 +212,16 @@ void __attribute__((weak,noreturn,optimize("omit-frame-pointer"))) _start(void) 
		"ldr %r3, 1f\n"               // r3 = &environ (see below)

		"str %r2, [r3]\n"             // store envp into environ



		"mov r4, r2\n"                // search for auxv (follows NULL after last env)

		"0:\n"

		"mov r5, r4\n"                // r5 = r4

		"add r4, r4, #4\n"            // r4 += 4

		"ldr r5,[r5]\n"               // r5 = *r5 = *(r4-4)

		"cmp r5, #0\n"                // and stop at NULL after last env

		"bne 0b\n"

		"ldr %r3, 2f\n"               // r3 = &_auxv (low bits)

		"str r4, [r3]\n"              // store r4 into _auxv



		"mov %r3, $8\n"               // AAPCS : sp must be 8-byte aligned in the

		"neg %r3, %r3\n"              //         callee, and bl doesn't push (lr=pc)

		"and %r3, %r3, %r1\n"         // so we do sp = r1(=sp) & r3(=-8);
@@ -222,6 +233,8 @@ void __attribute__((weak,noreturn,optimize("omit-frame-pointer"))) _start(void) 
		".align 2\n"                  // below are the pointers to a few variables

		"1:\n"

		".word environ\n"

		"2:\n"

		".word _auxv\n"

	);

	__builtin_unreachable();

}