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cryptfs: Allow setting dm-crypt sector size

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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
This commit is contained in:
Greg Kaiser 2018-12-11 12:40:51 -08:00
parent 8cb4c9ff78
commit ab1e84ad5f
1 changed files with 18 additions and 0 deletions
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18
cryptfs.cpp
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@ -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 @@ extern "C" {
#include <crypto_scrypt.h>
}
using android::base::StringPrintf;
using namespace std::chrono_literals;
#define UNUSED __attribute__((unused))
@ -1044,6 +1046,21 @@ static std::string extra_params_as_string(const std::vector<std::string>& extra_
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 @@ static int create_crypto_blk_dev(struct crypt_mnt_ftr* crypt_ftr, const unsigned
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) {