Log the file format of cros_install on postinstall action
This patch adds a new function to utils which determines the format
of a file based on magic constants on the header and returns a
human-readable description of it. This currently only supports ELF
files and is used to log the file format of the cros_install
binary on post-install.
BUG=chromium:356187
TEST=Unittests.
Change-Id: Ie6e91c3f5fa398c39894704db9071489560a8ff7
Reviewed-on: https://chromium-review.googlesource.com/191609
Tested-by: Alex Deymo <[email protected]>
Reviewed-by: Don Garrett <[email protected]>
Commit-Queue: Alex Deymo <[email protected]>
diff --git a/utils.cc b/utils.cc
index 7558f35..70b9c75 100644
--- a/utils.cc
+++ b/utils.cc
@@ -56,6 +56,11 @@
// one second.
const int kUnmountMaxNumOfRetries = 5;
const int kUnmountRetryIntervalInMicroseconds = 200 * 1000; // 200 ms
+
+// Number of bytes to read from a file to attempt to detect its contents. Used
+// in GetFileFormat.
+const int kGetFileFormatMaxHeaderSize = 32;
+
} // namespace
namespace utils {
@@ -665,6 +670,83 @@
return true;
}
+// Tries to parse the header of an ELF file to obtain a human-readable
+// description of it on the |output| string.
+static bool GetFileFormatELF(const char* buffer, size_t size, string* output) {
+ // 0x00: EI_MAG - ELF magic header, 4 bytes.
+ if (size < 4 || memcmp(buffer, "\x7F""ELF", 4) != 0)
+ return false;
+ *output = "ELF";
+
+ // 0x04: EI_CLASS, 1 byte.
+ if (size < 0x04 + 1)
+ return true;
+ switch (buffer[4]) {
+ case 1:
+ *output += " 32-bit";
+ break;
+ case 2:
+ *output += " 64-bit";
+ break;
+ default:
+ *output += " ?-bit";
+ }
+
+ // 0x05: EI_DATA, endianness, 1 byte.
+ if (size < 0x05 + 1)
+ return true;
+ char ei_data = buffer[5];
+ switch (ei_data) {
+ case 1:
+ *output += " little-endian";
+ break;
+ case 2:
+ *output += " big-endian";
+ break;
+ default:
+ *output += " ?-endian";
+ // Don't parse anything after the 0x10 offset if endianness is unknown.
+ return true;
+ }
+
+ // 0x12: e_machine, 2 byte endianness based on ei_data
+ if (size < 0x12 + 2)
+ return true;
+ uint16 e_machine = *reinterpret_cast<const uint16*>(buffer+0x12);
+ // Fix endianess regardless of the host endianess.
+ if (ei_data == 1)
+ e_machine = le16toh(e_machine);
+ else
+ e_machine = be16toh(e_machine);
+
+ switch (e_machine) {
+ case 0x03:
+ *output += " x86";
+ break;
+ case 0x28:
+ *output += " arm";
+ break;
+ case 0x3E:
+ *output += " x86-64";
+ break;
+ default:
+ *output += " unknown-arch";
+ }
+ return true;
+}
+
+string GetFileFormat(const string& path) {
+ vector<char> buffer;
+ if (!ReadFileChunkAndAppend(path, 0, kGetFileFormatMaxHeaderSize, &buffer))
+ return "File not found.";
+
+ string result;
+ if (GetFileFormatELF(buffer.data(), buffer.size(), &result))
+ return result;
+
+ return "data";
+}
+
bool GetBootloader(BootLoader* out_bootloader) {
// For now, hardcode to syslinux.
*out_bootloader = BootLoader_SYSLINUX;
