selftests/powerpc: Add a routine for retrieving an AUXV entry

Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

2 files changed, 49 insertions, 0 deletions

diff --git a/tools/testing/selftests/powerpc/pmu/lib.c b/tools/testing/selftests/powerpc/pmu/lib.c
index 11e26e8cf33a..9768dea37bf3 100644
--- a/tools/testing/selftests/powerpc/pmu/lib.c
+++ b/tools/testing/selftests/powerpc/pmu/lib.c
@@ -5,10 +5,15 @@
 
 #define _GNU_SOURCE     /* For CPU_ZERO etc. */
 
+#include <elf.h>
 #include <errno.h>
+#include <fcntl.h>
+#include <link.h>
 #include <sched.h>
 #include <setjmp.h>
 #include <stdlib.h>
+#include <sys/stat.h>
+#include <sys/types.h>
 #include <sys/wait.h>
 
 #include "utils.h"
@@ -250,3 +255,46 @@ out_close:
 out:
         return rc;
 }
+
+static char auxv[4096];
+
+void *get_auxv_entry(int type)
+{
+        ElfW(auxv_t) *p;
+        void *result;
+        ssize_t num;
+        int fd;
+
+        fd = open("/proc/self/auxv", O_RDONLY);
+        if (fd == -1) {
+                perror("open");
+                return NULL;
+        }
+
+        result = NULL;
+
+        num = read(fd, auxv, sizeof(auxv));
+        if (num < 0) {
+                perror("read");
+                goto out;
+        }
+
+        if (num > sizeof(auxv)) {
+                printf("Overflowed auxv buffer\n");
+                goto out;
+        }
+
+        p = (ElfW(auxv_t) *)auxv;
+
+        while (p->a_type != AT_NULL) {
+                if (p->a_type == type) {
+                        result = (void *)p->a_un.a_val;
+                        break;
+                }
+
+                p++;
+        }
+out:
+        close(fd);
+        return result;
+}
diff --git a/tools/testing/selftests/powerpc/pmu/lib.h b/tools/testing/selftests/powerpc/pmu/lib.h
index ca5d72ae3be6..0f0339c8a6f6 100644
--- a/tools/testing/selftests/powerpc/pmu/lib.h
+++ b/tools/testing/selftests/powerpc/pmu/lib.h
@@ -29,6 +29,7 @@ extern int notify_parent(union pipe write_pipe);
 extern int notify_parent_of_error(union pipe write_pipe);
 extern pid_t eat_cpu(int (test_function)(void));
 extern bool require_paranoia_below(int level);
+extern void *get_auxv_entry(int type);
 
 struct addr_range {
         uint64_t first, last;