[PATCH v2 19/22] tools/nolibc: add auxiliary vector retrieval for s390

Willy Tarreau
2023-01-10T07:25:21Z

From: Sven Schnelle <svens@linux.ibm.com>

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: Sven Schnelle <svens@linux.ibm.com>
Signed-off-by: Willy Tarreau <w@1wt.eu>
---
tools/include/nolibc/arch-s390.h | 10 ++++++++++
1 file changed, 10 insertions(+)

diff --git a/tools/include/nolibc/arch-s390.h b/tools/include/nolibc/arch-s390.h
index 039b454e79f0..6b0e54ed543d 100644
--- a/tools/include/nolibc/arch-s390.h
+++ b/tools/include/nolibc/arch-s390.h
@@ -160,6 +160,7 @@ 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)
@@ -179,6 +180,15 @@ void __attribute__((weak,noreturn,optimize("omit-frame-pointer"))) _start(void)
"larl %r1,environ\n"
"stg %r4,0(%r1)\n"

+ /* search for auxv */
+ "lgr %r5,%r4\n" /* start at envp */
+ "1:\n"
+ "clg %r0,0(%r5)\n" /* entry zero? */
+ "la %r5,8(%r5)\n" /* advance pointer */
+ "jnz 1b\n" /* no -> test next pointer */
+ "larl %r1,_auxv\n" /* yes -> store value in _auxv */
+ "stg %r5,0(%r1)\n"
+
"aghi %r15,-160\n" /* allocate new stackframe */
"xc 0(8,%r15),0(%r15)\n" /* clear backchain */
"brasl %r14,main\n" /* ret value of main is arg to exit */
--
2.17.5