[PATCH v2 20/22] nolibc/stdlib: Implement `getauxval(3)` function

Willy Tarreau
2023-01-10T07:27:30Z

From: Ammar Faizi <ammarfaizi2@gnuweeb.org>

Previous commits save the address of the auxiliary vector into a global
variable @_auxv. This commit creates a new function 'getauxval()' as a
helper function to get the auxv value based on the given key.

The behavior of this function is identic with the function documented
in 'man 3 getauxval'. This function is also needed to implement
'getpagesize()' function that we will wire up in the next patches.

Signed-off-by: Ammar Faizi <ammarfaizi2@gnuweeb.org>
Signed-off-by: Willy Tarreau <w@1wt.eu>
---
tools/include/nolibc/stdlib.h | 27 +++++++++++++++++++++++++++
1 file changed, 27 insertions(+)

diff --git a/tools/include/nolibc/stdlib.h b/tools/include/nolibc/stdlib.h
index a24000d1e822..894c955d027e 100644
--- a/tools/include/nolibc/stdlib.h
+++ b/tools/include/nolibc/stdlib.h
@@ -12,6 +12,7 @@
#include "types.h"
#include "sys.h"
#include "string.h"
+#include <linux/auxvec.h>

struct nolibc_heap {
size_t len;
@@ -108,6 +109,32 @@ char *getenv(const char *name)
return _getenv(name, environ);
}

+static __attribute__((unused))
+unsigned long getauxval(unsigned long type)
+{
+ const unsigned long *auxv = _auxv;
+ unsigned long ret;
+
+ if (!auxv)
+ return 0;
+
+ while (1) {
+ if (!auxv[0] && !auxv[1]) {
+ ret = 0;
+ break;
+ }
+
+ if (auxv[0] == type) {
+ ret = auxv[1];
+ break;
+ }
+
+ auxv += 2;
+ }
+
+ return ret;
+}
+
static __attribute__((unused))
void *malloc(size_t len)
{
--
2.17.5