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tools/nolibc: add auxiliary vector retrieval for arm64

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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 <w@1wt.eu>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit is contained in:
Willy Tarreau 2023-01-10 08:24:27 +01:00 committed by Paul E. McKenney
parent 1cce162ab4
commit 2a39a53245
1 changed files with 7 additions and 0 deletions
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7
tools/include/nolibc/arch-aarch64.h
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@ -170,6 +170,7 @@ 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)
@ -182,6 +183,12 @@ void __attribute__((weak,noreturn,optimize("omit-frame-pointer"))) _start(void)
"add x2, x2, x1\n" // + argv
"adrp x3, environ\n" // x3 = &environ (high bits)
"str x2, [x3, #:lo12:environ]\n" // store envp into environ
"mov x4, x2\n" // search for auxv (follows NULL after last env)
"0:\n"
"ldr x5, [x4], 8\n" // x5 = *x4; x4 += 8
"cbnz x5, 0b\n" // and stop at NULL after last env
"adrp x3, _auxv\n" // x3 = &_auxv (high bits)
"str x4, [x3, #:lo12:_auxv]\n" // store x4 into _auxv
"and sp, x1, -16\n" // sp must be 16-byte aligned in the callee
"bl main\n" // main() returns the status code, we'll exit with it.
"mov x8, 93\n" // NR_exit == 93