bionic: add compatibility mode for properties

Allow a new bionic to work with an old init property area by supporting
the old format.

(cherry picked from commit ad76c85b9ca587084089d086f954158bc0eae905)

Change-Id: Ib496e818a62a5834d40c71eb4745783d998be893

libc/Android.mk

@@ -149,6 +149,7 @@ libc_common_src_files := \
 	bionic/strntoumax.c \
 	bionic/strtotimeval.c \
 	bionic/system_properties.c \
+	bionic/system_properties_compat.c \
 	bionic/tcgetpgrp.c \
 	bionic/tcsetpgrp.c \
 	bionic/thread_atexit.c \

libc/bionic/system_properties.c

@@ -109,6 +109,7 @@ typedef struct prop_bt prop_bt;
 
 static const char property_service_socket[] = "/dev/socket/" PROP_SERVICE_NAME;
 static char property_filename[PATH_MAX] = PROP_FILENAME;
+static bool compat_mode = false;
 
 prop_area *__system_property_area__ = NULL;
 
@@ -156,6 +157,7 @@ static int map_prop_area_rw()
 
     pa_size = PA_SIZE;
     pa_data_size = pa_size - sizeof(prop_area);
+    compat_mode = false;
 
     pa = mmap(NULL, pa_size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
     if(pa == MAP_FAILED)
@@ -246,11 +248,16 @@ static int map_prop_area()
         goto cleanup;
     }
 
-    if((pa->magic != PROP_AREA_MAGIC) || (pa->version != PROP_AREA_VERSION)) {
+    if((pa->magic != PROP_AREA_MAGIC) || (pa->version != PROP_AREA_VERSION &&
+                pa->version != PROP_AREA_VERSION_COMPAT)) {
         munmap(pa, pa_size);
         goto cleanup;
     }
 
+    if (pa->version == PROP_AREA_VERSION_COMPAT) {
+        compat_mode = true;
+    }
+
     result = 0;
 
     __system_property_area__ = pa;
@@ -425,6 +432,9 @@ static const prop_info *find_property(prop_bt *trie, const char *name,
 
 const prop_info *__system_property_find(const char *name)
 {
+    if (__predict_false(compat_mode)) {
+        return __system_property_find_compat(name);
+    }
     return find_property(root_node(), name, strlen(name), NULL, 0, false);
 }
 
@@ -432,6 +442,10 @@ int __system_property_read(const prop_info *pi, char *name, char *value)
 {
     unsigned serial, len;
 
+    if (__predict_false(compat_mode)) {
+        return __system_property_read_compat(pi, name, value);
+    }
+
     for(;;) {
         serial = pi->serial;
         while(SERIAL_DIRTY(serial)) {
@@ -688,5 +702,8 @@ static int foreach_property(prop_off_t off,
 int __system_property_foreach(void (*propfn)(const prop_info *pi, void *cookie),
         void *cookie)
 {
+    if (__predict_false(compat_mode)) {
+        return __system_property_foreach_compat(propfn, cookie);
+	}
     return foreach_property(0, propfn, cookie);
 }

libc/bionic/system_properties_compat.c

@@ -0,0 +1,131 @@
+/*
+ * Copyright (C) 2008 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.
+ */
+
+/*
+ * This file is only used to provide backwards compatibility to property areas
+ * created by old versions of init, which occurs when an ota runs.  The updater
+ * binary is compiled statically against the newest bionic, but the recovery
+ * ramdisk may be using an old version of init.  This can all be removed once
+ * OTAs from pre-K versions are no longer supported.
+ */
+
+#include <string.h>
+#include <sys/atomics.h>
+
+#define _REALLY_INCLUDE_SYS__SYSTEM_PROPERTIES_H_
+#include <sys/_system_properties.h>
+
+#define TOC_NAME_LEN(toc)       ((toc) >> 24)
+#define TOC_TO_INFO(area, toc)  ((prop_info_compat*) (((char*) area) + ((toc) & 0xFFFFFF)))
+
+struct prop_area_compat {
+    unsigned volatile count;
+    unsigned volatile serial;
+    unsigned magic;
+    unsigned version;
+    unsigned toc[1];
+};
+
+typedef struct prop_area_compat prop_area_compat;
+
+struct prop_area;
+typedef struct prop_area prop_area;
+
+struct prop_info_compat {
+    char name[PROP_NAME_MAX];
+    unsigned volatile serial;
+    char value[PROP_VALUE_MAX];
+};
+
+typedef struct prop_info_compat prop_info_compat;
+
+extern prop_area *__system_property_area__;
+
+const prop_info *__system_property_find_compat(const char *name)
+{
+    prop_area_compat *pa = (prop_area_compat *)__system_property_area__;
+    unsigned count = pa->count;
+    unsigned *toc = pa->toc;
+    unsigned len = strlen(name);
+    prop_info_compat *pi;
+
+    if (len >= PROP_NAME_MAX)
+        return 0;
+    if (len < 1)
+        return 0;
+
+    while(count--) {
+        unsigned entry = *toc++;
+        if(TOC_NAME_LEN(entry) != len) continue;
+
+        pi = TOC_TO_INFO(pa, entry);
+        if(memcmp(name, pi->name, len)) continue;
+
+        return (const prop_info *)pi;
+    }
+
+    return 0;
+}
+
+int __system_property_read_compat(const prop_info *_pi, char *name, char *value)
+{
+    unsigned serial, len;
+    const prop_info_compat *pi = (const prop_info_compat *)_pi;
+
+    for(;;) {
+        serial = pi->serial;
+        while(SERIAL_DIRTY(serial)) {
+            __futex_wait((volatile void *)&pi->serial, serial, 0);
+            serial = pi->serial;
+        }
+        len = SERIAL_VALUE_LEN(serial);
+        memcpy(value, pi->value, len + 1);
+        if(serial == pi->serial) {
+            if(name != 0) {
+                strcpy(name, pi->name);
+            }
+            return len;
+        }
+    }
+}
+
+int __system_property_foreach_compat(
+        void (*propfn)(const prop_info *pi, void *cookie),
+        void *cookie)
+{
+    prop_area_compat *pa = (prop_area_compat *)__system_property_area__;
+    unsigned i;
+
+    for (i = 0; i < pa->count; i++) {
+        unsigned entry = pa->toc[i];
+        prop_info_compat *pi = TOC_TO_INFO(pa, entry);
+        propfn((const prop_info *)pi, cookie);
+    }
+
+    return 0;
+}

libc/include/sys/_system_properties.h

@@ -38,6 +38,7 @@ typedef struct prop_msg prop_msg;
 
 #define PROP_AREA_MAGIC   0x504f5250
 #define PROP_AREA_VERSION 0xfc6ed0ab
+#define PROP_AREA_VERSION_COMPAT 0x45434f76
 
 #define PROP_SERVICE_NAME "property_service"
 #define PROP_FILENAME "/dev/__properties__"
@@ -129,6 +130,15 @@ unsigned int __system_property_serial(const prop_info *pi);
 ** successive call. */
 unsigned int __system_property_wait_any(unsigned int serial);
 
+/*  Compatibility functions to support using an old init with a new libc,
+ ** mostly for the OTA updater binary.  These can be deleted once OTAs from
+ ** a pre-K release no longer needed to be supported. */
+const prop_info *__system_property_find_compat(const char *name);
+int __system_property_read_compat(const prop_info *pi, char *name, char *value);
+int __system_property_foreach_compat(
+        void (*propfn)(const prop_info *pi, void *cookie),
+        void *cookie);
+
 __END_DECLS
 
 #endif