Add a .note.android.ident section to Android ELF binaries.

This allows debugging tools to know they are working with Android
binaries and adapt accordingly.

Signed-off-by: Thiago Jung Bauermann <thiago.bauermann@linaro.org>
Signed-off-by: Michael Hope <michael.hope@linaro.org>

Change-Id: Ic906992fcad61c028bb765821637a3e1333bf52b

1 files changed, 63 insertions, 0 deletions

diff --git a/libc/bionic/crtbrand.c b/libc/bionic/crtbrand.c
new file mode 100644
index 000000000..31fcbc7b3
--- /dev/null
+++ b/libc/bionic/crtbrand.c
@@ -0,0 +1,63 @@
+/*-
+ * Copyright 2000 David E. O'Brien, John D. Polstra.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. 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 AUTHOR ``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 AUTHOR 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 <stdint.h>
+
+#define ABI_VENDOR	"Android"
+#define ABI_SECTION	".note.android.ident"
+#define ABI_NOTETYPE	1
+#define ABI_ANDROID_API	PLATFORM_SDK_VERSION
+
+/*
+ * Special ".note" entry to tag an Android binary and specify the ABI version.
+ *
+ * For all arches except sparc, gcc emits the section directive for the
+ * following struct with a PROGBITS type.  However, the section should be
+ * of NOTE type, according to the Generic SysV ABI spec.
+ *
+ * Unfortunately, there is no clean way to tell gcc to use another section type,
+ * so this C file (or the C file that includes it) must be compiled in multiple
+ * steps:
+ *
+ * - Compile the .c file to a .s file.
+ * - Edit the .s file to change the 'progbits' type to 'note', for the section
+ *   directive that defines the .note.ABI-tag section.
+ * - Compile the .s file to an object file.
+ *
+ * These steps are done in the invididual Makefiles for each applicable arch.
+ */
+static const struct {
+    int32_t	namesz;
+    int32_t	descsz;
+    int32_t	type;
+    char	name[sizeof ABI_VENDOR];
+    int32_t	android_api;
+} abitag __attribute__ ((section (ABI_SECTION), aligned(4), used)) = {
+    sizeof ABI_VENDOR,
+    sizeof(int32_t),
+    ABI_NOTETYPE,
+    ABI_VENDOR,
+    ABI_ANDROID_API,
+};