cryptfs: Allow setting dm-crypt sector size
We add the property ro.crypto.fde_sector_size to allow devices
to pass the "sector_size:<size>" argument to dm-crypt in the kernel.
We also pass "iv_large_sectors" when setting the sector size.
Using 4096-byte sectors rather than the default of 512 improves
dm-crypt performance, especially when the Adiantum encryption mode
is used.
Bug: 112010205
Test: Run on a device
Change-Id: I144ec7088a0aad3430369dc7158370d7ff3ef5d2
diff --git a/cryptfs.cpp b/cryptfs.cpp
index 2ac20e1..28facac 100644
--- a/cryptfs.cpp
+++ b/cryptfs.cpp
@@ -36,6 +36,7 @@
#include "secontext.h"
#include <android-base/properties.h>
+#include <android-base/stringprintf.h>
#include <bootloader_message/bootloader_message.h>
#include <cutils/android_reboot.h>
#include <cutils/properties.h>
@@ -74,6 +75,7 @@
#include <crypto_scrypt.h>
}
+using android::base::StringPrintf;
using namespace std::chrono_literals;
#define UNUSED __attribute__((unused))
@@ -1044,6 +1046,21 @@
return extra_params;
}
+// Only adds parameters if the property is set.
+static void add_sector_size_param(std::vector<std::string>* extra_params_vec) {
+ constexpr char DM_CRYPT_SECTOR_SIZE[] = "ro.crypto.fde_sector_size";
+ char sector_size[PROPERTY_VALUE_MAX];
+
+ if (property_get(DM_CRYPT_SECTOR_SIZE, sector_size, "") > 0) {
+ std::string param = StringPrintf("sector_size:%s", sector_size);
+ extra_params_vec->push_back(std::move(param));
+
+ // With this option, IVs will match the sector numbering, instead
+ // of being hard-coded to being based on 512-byte sectors.
+ extra_params_vec->emplace_back("iv_large_sectors");
+ }
+}
+
static int create_crypto_blk_dev(struct crypt_mnt_ftr* crypt_ftr, const unsigned char* master_key,
const char* real_blk_name, char* crypto_blk_name, const char* name,
uint32_t flags) {
@@ -1089,6 +1106,7 @@
if (flags & CREATE_CRYPTO_BLK_DEV_FLAGS_ALLOW_ENCRYPT_OVERRIDE) {
extra_params_vec.emplace_back("allow_encrypt_override");
}
+ add_sector_size_param(&extra_params_vec);
load_count = load_crypto_mapping_table(crypt_ftr, master_key, real_blk_name, name, fd,
extra_params_as_string(extra_params_vec).c_str());
if (load_count < 0) {