am 2c5153b0: libc: add getauxval()

* commit '2c5153b043b44e9935a334ae9b2d5a4bc5258b40':
  libc: add getauxval()

libc/Android.mk

@@ -275,6 +275,7 @@ libc_bionic_src_files := \
     bionic/dirent.cpp \
     bionic/eventfd.cpp \
     bionic/__fgets_chk.cpp \
+    bionic/getauxval.cpp \
     bionic/getcwd.cpp \
     bionic/libgen.cpp \
     bionic/__memcpy_chk.cpp \

libc/bionic/getauxval.cpp

@@ -0,0 +1,48 @@
+/*
+ * Copyright (C) 2013 The Android Open Source Project
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *  * Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *  * Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <stddef.h>
+#include <sys/cdefs.h>
+#include <sys/auxv.h>
+#include <private/bionic_auxv.h>
+#include <elf.h>
+
+__LIBC_HIDDEN__
+Elf32_auxv_t* __libc_auxv = NULL;
+
+extern "C" unsigned long int getauxval(unsigned long int type) {
+  Elf32_auxv_t* v;
+
+  for (v = __libc_auxv; v->a_type != AT_NULL; v++) {
+    if (v->a_type == type) {
+      return v->a_un.a_val;
+    }
+  }
+
+  return 0;
+}

libc/bionic/libc_init_common.c

@@ -38,6 +38,7 @@
 
 #include <bionic_tls.h>
 #include <errno.h>
+#include <private/bionic_auxv.h>
 
 extern unsigned __get_sp(void);
 extern pid_t gettid(void);
@@ -95,6 +96,15 @@ void __libc_init_common(uintptr_t* elf_data) {
   __progname = argv[0] ? argv[0] : "<unknown>";
   environ = envp;
 
+  // The auxiliary vector is at the end of the environment block
+  while(*envp != NULL) {
+    envp++;
+  }
+  /* The end of the environment block is marked by two NULL pointers */
+  envp++;
+
+  __libc_auxv = (Elf32_auxv_t*) envp;
+
   __system_properties_init(); // Requires 'environ'.
 }
 

libc/bionic/libc_init_static.c

@@ -49,6 +49,7 @@
 #include <bionic_tls.h>
 #include <errno.h>
 #include <sys/mman.h>
+#include <sys/auxv.h>
 
 // Returns the address of the page containing address 'x'.
 #define PAGE_START(x)  ((x) & PAGE_MASK)
@@ -65,27 +66,13 @@ static void call_array(void(**list)())
     }
 }
 
-/*
+static void apply_gnu_relro() {
- * Find the value of the AT_* variable passed to us by the kernel.
- */
-static unsigned find_aux(unsigned *vecs, unsigned type) {
-    while (vecs[0]) {
-        if (vecs[0] == type) {
-            return vecs[1];
-        }
-        vecs += 2;
-    }
-
-    return 0; // should never happen
-}
-
-static void apply_gnu_relro(unsigned *vecs) {
     Elf32_Phdr *phdr_start;
-    unsigned phdr_ct;
+    unsigned long int phdr_ct;
     Elf32_Phdr *phdr;
 
-    phdr_start = (Elf32_Phdr *) find_aux(vecs, AT_PHDR);
+    phdr_start = (Elf32_Phdr *) getauxval(AT_PHDR);
-    phdr_ct    = find_aux(vecs, AT_PHNUM);
+    phdr_ct    = getauxval(AT_PHNUM);
 
     for (phdr = phdr_start; phdr < (phdr_start + phdr_ct); phdr++) {
         if (phdr->p_type != PT_GNU_RELRO)
@@ -108,7 +95,6 @@ __noreturn void __libc_init(uintptr_t *elfdata,
 {
     int  argc;
     char **argv, **envp;
-    unsigned *vecs;
 
     __libc_init_tls(NULL);
 
@@ -129,14 +115,6 @@ __noreturn void __libc_init(uintptr_t *elfdata,
     argv = (char**)(elfdata + 1);
     envp = argv + argc + 1;
 
-    // The auxiliary vector is at the end of the environment block
-    vecs = (unsigned *) envp;
-    while (vecs[0] != 0) {
-        vecs++;
-    }
-    /* The end of the environment block is marked by two NULL pointers */
-    vecs++;
-
     /* The executable may have its own destructors listed in its .fini_array
      * so we need to ensure that these are called when the program exits
      * normally.
@@ -144,6 +122,6 @@ __noreturn void __libc_init(uintptr_t *elfdata,
     if (structors->fini_array)
         __cxa_atexit(__libc_fini,structors->fini_array,NULL);
 
-    apply_gnu_relro(vecs);
+    apply_gnu_relro();
     exit(slingshot(argc, argv, envp));
 }

libc/include/elf.h

@@ -28,8 +28,23 @@
 #ifndef _ELF_H
 #define _ELF_H
 
+#include <stdint.h>
 #include <linux/auxvec.h>
 #include <sys/exec_elf.h>
 
+typedef struct {
+  uint32_t a_type;
+  union {
+    uint32_t a_val;
+  } a_un;
+} Elf32_auxv_t;
+
+typedef struct {
+  uint64_t a_type;
+  union {
+    uint64_t a_val;
+  } a_un;
+} Elf64_auxv_t;
+
 #endif /* _ELF_H */
 

libc/include/sys/auxv.h

@@ -0,0 +1,39 @@
+/*
+ * Copyright (C) 2013 The Android Open Source Project
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *  * Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *  * Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+#ifndef _SYS_AUXV_H_
+#define _SYS_AUXV_H_
+
+#include <linux/auxvec.h>
+
+__BEGIN_DECLS
+
+unsigned long int getauxval(unsigned long int type);
+
+__END_DECLS
+
+#endif /* _SYS_AUXV_H_ */

libc/private/bionic_auxv.h

@@ -0,0 +1,39 @@
+/*
+ * Copyright (C) 2013 The Android Open Source Project
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *  * Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *  * Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+#ifndef _SYS_AUXV_H_
+#define _SYS_AUXV_H_
+
+#include <elf.h>
+
+__BEGIN_DECLS
+
+extern Elf32_auxv_t* __libc_auxv;
+
+__END_DECLS
+
+#endif /* _SYS_AUXV_H_ */

tests/Android.mk

@@ -55,6 +55,7 @@ test_c_flags = \
 test_src_files = \
     dirent_test.cpp \
     fenv_test.cpp \
+    getauxval_test.cpp \
     getcwd_test.cpp \
     libgen_test.cpp \
     pthread_test.cpp \

tests/getauxval_test.cpp

@@ -0,0 +1,55 @@
+/*
+ * Copyright (C) 2013 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <sys/cdefs.h>
+#include <features.h>
+#include <gtest/gtest.h>
+
+// getauxval() was only added as of glibc version 2.16.
+// See: http://lwn.net/Articles/519085/
+// Don't try to compile this code on older glibc versions.
+
+#if defined(__BIONIC__)
+  #define GETAUXVAL_CAN_COMPILE 1
+#elif defined(__GLIBC_PREREQ)
+  #if __GLIBC_PREREQ(2, 16)
+    #define GETAUXVAL_CAN_COMPILE 1
+  #endif
+#endif
+
+#if defined(GETAUXVAL_CAN_COMPILE)
+
+#include <sys/auxv.h>
+
+TEST(getauxval, expected_values) {
+  ASSERT_EQ((unsigned long int) 0, getauxval(AT_SECURE));
+  ASSERT_EQ(getuid(), getauxval(AT_UID));
+  ASSERT_EQ(geteuid(), getauxval(AT_EUID));
+  ASSERT_EQ(getgid(), getauxval(AT_GID));
+  ASSERT_EQ(getegid(), getauxval(AT_EGID));
+  ASSERT_EQ((unsigned long int) getpagesize(), getauxval(AT_PAGESZ));
+
+  ASSERT_NE((unsigned long int) 0, getauxval(AT_PHDR));
+  ASSERT_NE((unsigned long int) 0, getauxval(AT_PHNUM));
+  ASSERT_NE((unsigned long int) 0, getauxval(AT_ENTRY));
+  ASSERT_NE((unsigned long int) 0, getauxval(AT_PAGESZ));
+}
+
+TEST(getauxval, unexpected_values) {
+  ASSERT_EQ((unsigned long int) 0, getauxval(0xdeadbeef));
+}
+
+#endif /* GETAUXVAL_CAN_COMPILE */