diff options
| -rw-r--r-- | Documentation/admin-guide/bootconfig.rst | 10 | ||||
| -rw-r--r-- | include/linux/bootconfig.h | 3 | ||||
| -rw-r--r-- | init/Kconfig | 2 | ||||
| -rw-r--r-- | init/main.c | 6 | ||||
| -rw-r--r-- | tools/bootconfig/main.c | 43 | ||||
| -rwxr-xr-x | tools/bootconfig/test-bootconfig.sh | 2 |
6 files changed, 49 insertions, 17 deletions
diff --git a/Documentation/admin-guide/bootconfig.rst b/Documentation/admin-guide/bootconfig.rst index b342a6796392..5e7609936507 100644 --- a/Documentation/admin-guide/bootconfig.rst +++ b/Documentation/admin-guide/bootconfig.rst @@ -102,9 +102,13 @@ Boot Kernel With a Boot Config ============================== Since the boot configuration file is loaded with initrd, it will be added -to the end of the initrd (initramfs) image file. The Linux kernel decodes -the last part of the initrd image in memory to get the boot configuration -data. +to the end of the initrd (initramfs) image file with size, checksum and +12-byte magic word as below. + +[initrd][bootconfig][size(u32)][checksum(u32)][#BOOTCONFIG\n] + +The Linux kernel decodes the last part of the initrd image in memory to +get the boot configuration data. Because of this "piggyback" method, there is no need to change or update the boot loader and the kernel image itself. diff --git a/include/linux/bootconfig.h b/include/linux/bootconfig.h index 7e18c939663e..d11e183fcb54 100644 --- a/include/linux/bootconfig.h +++ b/include/linux/bootconfig.h @@ -10,6 +10,9 @@ #include <linux/kernel.h> #include <linux/types.h> +#define BOOTCONFIG_MAGIC "#BOOTCONFIG\n" +#define BOOTCONFIG_MAGIC_LEN 12 + /* XBC tree node */ struct xbc_node { u16 next; diff --git a/init/Kconfig b/init/Kconfig index f586878410d2..a84e7aa89a29 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -1222,7 +1222,7 @@ config BOOT_CONFIG Extra boot config allows system admin to pass a config file as complemental extension of kernel cmdline when booting. The boot config file must be attached at the end of initramfs - with checksum and size. + with checksum, size and magic word. See <file:Documentation/admin-guide/bootconfig.rst> for details. If unsure, say Y. diff --git a/init/main.c b/init/main.c index d96cc5f65022..2fe8dec93e68 100644 --- a/init/main.c +++ b/init/main.c @@ -374,7 +374,11 @@ static void __init setup_boot_config(const char *cmdline) if (!initrd_end) goto not_found; - hdr = (u32 *)(initrd_end - 8); + data = (char *)initrd_end - BOOTCONFIG_MAGIC_LEN; + if (memcmp(data, BOOTCONFIG_MAGIC, BOOTCONFIG_MAGIC_LEN)) + goto not_found; + + hdr = (u32 *)(data - 8); size = hdr[0]; csum = hdr[1]; diff --git a/tools/bootconfig/main.c b/tools/bootconfig/main.c index e18eeb070562..742271f019a9 100644 --- a/tools/bootconfig/main.c +++ b/tools/bootconfig/main.c @@ -131,15 +131,26 @@ int load_xbc_from_initrd(int fd, char **buf) struct stat stat; int ret; u32 size = 0, csum = 0, rcsum; + char magic[BOOTCONFIG_MAGIC_LEN]; ret = fstat(fd, &stat); if (ret < 0) return -errno; - if (stat.st_size < 8) + if (stat.st_size < 8 + BOOTCONFIG_MAGIC_LEN) return 0; - if (lseek(fd, -8, SEEK_END) < 0) { + if (lseek(fd, -BOOTCONFIG_MAGIC_LEN, SEEK_END) < 0) { + pr_err("Failed to lseek: %d\n", -errno); + return -errno; + } + if (read(fd, magic, BOOTCONFIG_MAGIC_LEN) < 0) + return -errno; + /* Check the bootconfig magic bytes */ + if (memcmp(magic, BOOTCONFIG_MAGIC, BOOTCONFIG_MAGIC_LEN) != 0) + return 0; + + if (lseek(fd, -(8 + BOOTCONFIG_MAGIC_LEN), SEEK_END) < 0) { pr_err("Failed to lseek: %d\n", -errno); return -errno; } @@ -150,11 +161,14 @@ int load_xbc_from_initrd(int fd, char **buf) if (read(fd, &csum, sizeof(u32)) < 0) return -errno; - /* Wrong size, maybe no boot config here */ - if (stat.st_size < size + 8) - return 0; + /* Wrong size error */ + if (stat.st_size < size + 8 + BOOTCONFIG_MAGIC_LEN) { + pr_err("bootconfig size is too big\n"); + return -E2BIG; + } - if (lseek(fd, stat.st_size - 8 - size, SEEK_SET) < 0) { + if (lseek(fd, stat.st_size - (size + 8 + BOOTCONFIG_MAGIC_LEN), + SEEK_SET) < 0) { pr_err("Failed to lseek: %d\n", -errno); return -errno; } @@ -163,17 +177,17 @@ int load_xbc_from_initrd(int fd, char **buf) if (ret < 0) return ret; - /* Wrong Checksum, maybe no boot config here */ + /* Wrong Checksum */ rcsum = checksum((unsigned char *)*buf, size); if (csum != rcsum) { pr_err("checksum error: %d != %d\n", csum, rcsum); - return 0; + return -EINVAL; } ret = xbc_init(*buf); - /* Wrong data, maybe no boot config here */ + /* Wrong data */ if (ret < 0) - return 0; + return ret; return size; } @@ -226,7 +240,8 @@ int delete_xbc(const char *path) } else if (size > 0) { ret = fstat(fd, &stat); if (!ret) - ret = ftruncate(fd, stat.st_size - size - 8); + ret = ftruncate(fd, stat.st_size + - size - 8 - BOOTCONFIG_MAGIC_LEN); if (ret) ret = -errno; } /* Ignore if there is no boot config in initrd */ @@ -295,6 +310,12 @@ int apply_xbc(const char *path, const char *xbc_path) pr_err("Failed to apply a boot config: %d\n", ret); return ret; } + /* Write a magic word of the bootconfig */ + ret = write(fd, BOOTCONFIG_MAGIC, BOOTCONFIG_MAGIC_LEN); + if (ret < 0) { + pr_err("Failed to apply a boot config magic: %d\n", ret); + return ret; + } close(fd); free(data); diff --git a/tools/bootconfig/test-bootconfig.sh b/tools/bootconfig/test-bootconfig.sh index 1de06de328e2..adafb7c50940 100755 --- a/tools/bootconfig/test-bootconfig.sh +++ b/tools/bootconfig/test-bootconfig.sh @@ -49,7 +49,7 @@ xpass $BOOTCONF -a $TEMPCONF $INITRD new_size=$(stat -c %s $INITRD) echo "File size check" -xpass test $new_size -eq $(expr $bconf_size + $initrd_size + 9) +xpass test $new_size -eq $(expr $bconf_size + $initrd_size + 9 + 12) echo "Apply command repeat test" xpass $BOOTCONF -a $TEMPCONF $INITRD |