osdep: Create qemu_getauxval and qemu_init_auxval

Abstract away dependence on a system implementation of getauxval.

Signed-off-by: Richard Henderson <rth@twiddle.net>

include/qemu/osdep.h

@@ -215,4 +215,29 @@ bool fips_get_state(void);
  */
 char *qemu_get_local_state_pathname(const char *relative_pathname);
 
+/**
+ * qemu_getauxval:
+ * @type: the auxiliary vector key to lookup
+ *
+ * Search the auxiliary vector for @type, returning the value
+ * or 0 if @type is not present.
+ */
+#if defined(CONFIG_GETAUXVAL) || defined(__linux__)
+unsigned long qemu_getauxval(unsigned long type);
+#else
+static inline unsigned long qemu_getauxval(unsigned long type) { return 0; }
+#endif
+
+/**
+ * qemu_init_auxval:
+ * @envp: the third argument to main
+ *
+ * If supported and required, locate the auxiliary vector at program startup.
+ */
+#if defined(CONFIG_GETAUXVAL) || !defined(__linux__)
+static inline void qemu_init_auxval(char **envp) { }
+#else
+void qemu_init_auxval(char **envp);
+#endif
+
 #endif

linux-user/main.c

@@ -3701,6 +3701,7 @@ int main(int argc, char **argv, char **envp)
 
     module_call_init(MODULE_INIT_QOM);
 
+    qemu_init_auxval(envp);
     qemu_cache_utils_init(envp);
 
     if ((envlist = envlist_create()) == NULL) {

util/Makefile.objs

@@ -12,3 +12,4 @@ util-obj-y += qemu-option.o qemu-progress.o
 util-obj-y += hexdump.o
 util-obj-y += crc32c.o
 util-obj-y += throttle.o
+util-obj-y += getauxval.o

util/getauxval.c

@@ -0,0 +1,74 @@
+/*
+ * QEMU access to the auxiliary vector
+ *
+ * Copyright (C) 2013 Red Hat, Inc
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+#include "qemu-common.h"
+#include "qemu/osdep.h"
+
+#ifdef CONFIG_GETAUXVAL
+/* Don't inline this in qemu/osdep.h, because pulling in <sys/auxv.h> for
+   the system declaration of getauxval pulls in the system <elf.h>, which
+   conflicts with qemu's version.  */
+
+#include <sys/auxv.h>
+
+unsigned long qemu_getauxval(unsigned long key)
+{
+    return getauxval(key);
+}
+#elif defined(__linux__)
+#include "elf.h"
+
+/* Our elf.h doesn't contain Elf32_auxv_t and Elf64_auxv_t, which is ok because
+   that just makes it easier to define it properly for the host here.  */
+typedef struct {
+    unsigned long a_type;
+    unsigned long a_val;
+} ElfW_auxv_t;
+
+static const ElfW_auxv_t *auxv;
+
+void qemu_init_auxval(char **envp)
+{
+    /* The auxiliary vector is located just beyond the initial environment.  */
+    while (*envp++ != NULL) {
+        continue;
+    }
+    auxv = (const ElfW_auxv_t *)envp;
+}
+
+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;
+            }
+        }
+    }
+
+    return 0;
+}
+#endif

vl.c

@@ -2894,6 +2894,7 @@ int main(int argc, char **argv, char **envp)
     init_clocks();
     rtc_clock = QEMU_CLOCK_HOST;
 
+    qemu_init_auxval(envp);
     qemu_cache_utils_init(envp);
 
     QLIST_INIT (&vm_change_state_head);