qemu/osdep: Remove the need for qemu_init_auxval

Instead of getting backup auxv data from the env pointer given to main,
read it from /proc/self/auxv.  We can do this at any time, so we're not
tied to any ordering wrt a call to qemu_init_auxval from main.

Tested-by: Tom Musta <tommusta@gmail.com>
Signed-off-by: Richard Henderson <rth@twiddle.net>

1 files changed, 39 insertions, 12 deletions

diff --git a/util/getauxval.c b/util/getauxval.c
index 476c883b32..25f48e5456 100644
--- a/util/getauxval.c
+++ b/util/getauxval.c
@@ -48,24 +48,51 @@ typedef struct {
 
 static const ElfW_auxv_t *auxv;
 
-void qemu_init_auxval(char **envp)
+static const ElfW_auxv_t *qemu_init_auxval(void)
 {
-    /* The auxiliary vector is located just beyond the initial environment.  */
-    while (*envp++ != NULL) {
-        continue;
+    ElfW_auxv_t *a;
+    ssize_t size = 512, r, ofs;
+    int fd;
+
+    /* Allocate some initial storage.  Make sure the first entry is set
+       to end-of-list, so that we've got a valid list in case of error.  */
+    auxv = a = g_malloc(size);
+    a[0].a_type = 0;
+    a[0].a_val = 0;
+
+    fd = open("/proc/self/auxv", O_RDONLY);
+    if (fd < 0) {
+        return a;
+    }
+
+    /* Read the first SIZE bytes.  Hopefully, this covers everything.  */
+    r = read(fd, a, size);
+
+    if (r == size) {
+        /* Continue to expand until we do get a partial read.  */
+        do {
+            ofs = size;
+            size *= 2;
+            auxv = a = g_realloc(a, size);
+            r = read(fd, (char *)a + ofs, ofs);
+        } while (r == ofs);
     }
-    auxv = (const ElfW_auxv_t *)envp;
+
+    close(fd);
+    return a;
 }
 
 unsigned long qemu_getauxval(unsigned long type)
 {
-    /* If we were able to find the auxiliary vector, use it.  */
-    if (auxv) {
-        const ElfW_auxv_t *a;
-        for (a = auxv; a->a_type != 0; a++) {
-            if (a->a_type == type) {
-                return a->a_val;
-            }
+    const ElfW_auxv_t *a = auxv;
+
+    if (unlikely(a == NULL)) {
+        a = qemu_init_auxval();
+    }
+
+    for (; a->a_type != 0; a++) {
+        if (a->a_type == type) {
+            return a->a_val;
         }
     }