linux-kernel - [PATCH 09/16] selftests: vDSO: vdso_standalone_test_x86: Use vdso_init_form_sysinfo

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Message-Id: <20250203-parse_vdso-nolibc-v1-9-9cb6268d77be@linutronix.de>
Date: Mon, 03 Feb 2025 10:05:10 +0100
From: Thomas Weißschuh <thomas.weissschuh@...utronix.de>
To: Kees Cook <kees@...nel.org>, Eric Biederman <ebiederm@...ssion.com>, 
 Shuah Khan <shuah@...nel.org>, Nathan Chancellor <nathan@...nel.org>, 
 Nick Desaulniers <ndesaulniers@...gle.com>, 
 Bill Wendling <morbo@...gle.com>, Justin Stitt <justinstitt@...gle.com>, 
 Andy Lutomirski <luto@...nel.org>, Thomas Gleixner <tglx@...utronix.de>, 
 Vincenzo Frascino <vincenzo.frascino@....com>
Cc: linux-mm@...ck.org, linux-kernel@...r.kernel.org, 
 linux-kselftest@...r.kernel.org, llvm@...ts.linux.dev, 
 Thomas Weißschuh <thomas.weissschuh@...utronix.de>
Subject: [PATCH 09/16] selftests: vDSO: vdso_standalone_test_x86: Use
 vdso_init_form_sysinfo_ehdr

vdso_standalone_test_x86 is the only user of vdso_init_from_auxv().
Instead of combining the parsing the aux vector with the parsing of the
vDSO, split them apart into getauxval() and the regular
vdso_init_from_sysinfo_ehdr().

The implementation of getauxval() is taken from
tools/include/nolibc/stdlib.h.

Signed-off-by: Thomas Weißschuh <thomas.weissschuh@...utronix.de>

---
All of this code will be deleted later again.
---
 .../selftests/vDSO/vdso_standalone_test_x86.c      | 27 +++++++++++++++++++++-
 1 file changed, 26 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/vDSO/vdso_standalone_test_x86.c b/tools/testing/selftests/vDSO/vdso_standalone_test_x86.c
index 644915862af8883131e5defd336f1bd80736fc0f..500608f89c66b5747e3d845ebc54e4c3a35b6ccd 100644
--- a/tools/testing/selftests/vDSO/vdso_standalone_test_x86.c
+++ b/tools/testing/selftests/vDSO/vdso_standalone_test_x86.c
@@ -15,6 +15,7 @@
 #include <sys/time.h>
 #include <unistd.h>
 #include <stdint.h>
+#include <linux/auxvec.h>
 
 #include "parse_vdso.h"
 
@@ -84,6 +85,30 @@ void to_base10(char *lastdig, time_t n)
 	}
 }
 
+unsigned long getauxval(const unsigned long *auxv, unsigned long type)
+{
+	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;
+}
+
 void c_main(void **stack)
 {
 	/* Parse the stack */
@@ -96,7 +121,7 @@ void c_main(void **stack)
 	stack++;
 
 	/* Now we're pointing at auxv.  Initialize the vDSO parser. */
-	vdso_init_from_auxv((void *)stack);
+	vdso_init_from_sysinfo_ehdr(getauxval((unsigned long *)stack, AT_SYSINFO_EHDR));
 
 	/* Find gettimeofday. */
 	typedef long (*gtod_t)(struct timeval *tv, struct timezone *tz);

-- 
2.48.1