tools/bootconfig: Align the bootconfig applied initrd
Subsystems (2)
Masami Hiramatsu
maintainerv5 cover tools/bootconfig: Align the bootconfig applied initrd
Hi,
This is the 5th version of the bootconfig tool update to align the total size of initrd + bootconfig to 4.
Previous version is here;
https://lkml.kernel.org/r/160571371674.277955.11736890010190945946.stgit@devnote2
This version fixes bugs in [2/4] and [3/4] and cleans up code in [3/4].
To adjust the file size, the bootconfig tool adds padding null characters in between the boot configuration data and the footer.
The changing points are
- The bootconfig applied initrd image size is aligned to 4.
- To insert the padding null ('\0') bytes, the size in the footer can be bigger than the actual bootconfig file size.
- But the max size of the boot configuration file is same, because the max size doesn't include the last null characters.
In this series I keep 4 bytes aligned instead of longer size, because only I could found was that the grub might align the initrd filesize to 4, and U-Boot/EDK2 would not change it. So I couldn't say what is the best size.
Anyway, I updated the documentation too, which clearly says that the above changing points, and if the bootloader pass the wrong size, kernel will not find bootconfig from the initrd.
Thank you,
---
Masami Hiramatsu (4):
tools/bootconfig: Fix errno reference after printf() tools/bootconfig: Fix to check the write failure correctly tools/bootconfig: Align the bootconfig applied initrd image size to 4
docs: bootconfig: Update file format on initrd image
tools/bootconfig/main.c | 121 +++++++++++++++++++++++------------ tools/bootconfig/test-bootconfig.sh | 6 +- 2 files changed, 85 insertions(+), 42 deletions(-)
--
Masami Hiramatsu (Linaro) <[email protected]>
Masami Hiramatsu
maintainerPATCH v5 1/4 tools/bootconfig: Fix errno reference after printf()
Fix not to refer the errno variable as the result of previous libc functions after printf() because printf() can change the errno.
--- tools/bootconfig/main.c | 52 ++++++++++++++++++++++++++--------------------- 1 file changed, 29 insertions(+), 23 deletions(-)
tools/bootconfig/main.c +29 -23
@@ -147,6 +147,12 @@ static int load_xbc_file(const char *path, char **buf)return ret; } +static int pr_errno (const char *msg,int err) +{ +pr_err ("%s: %d\n" , msg, err); +return err; +} +static int load_xbc_from_initrd (int fd,char **buf) {struct stat stat;
@@ -162,26 +168,24 @@ static int load_xbc_from_initrd(int fd, char **buf)if (stat.st_size <8 +BOOTCONFIG_MAGIC_LEN )return 0 ; -if (lseek (fd, -BOOTCONFIG_MAGIC_LEN ,SEEK_END ) <0 ) { -pr_err ("Failed to lseek: %d\n" , -errno); -return -errno; - } +if (lseek (fd, -BOOTCONFIG_MAGIC_LEN ,SEEK_END ) <0 ) +return pr_errno ("Failed to lseek for magic" , -errno); +if (read (fd, magic,BOOTCONFIG_MAGIC_LEN ) <0 ) -return -errno; +return pr_errno ("Failed to read" , -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; - } +if (lseek (fd, -(8 +BOOTCONFIG_MAGIC_LEN ),SEEK_END ) <0 ) +return pr_errno ("Failed to lseek for size" , -errno);if (read (fd, &size,sizeof (u32)) <0 ) -return -errno; +return pr_errno ("Failed to read size" , -errno);if (read (fd, &csum,sizeof (u32)) <0 ) -return -errno; +return pr_errno ("Failed to read checksum" , -errno);/* Wrong size error */ if (stat.st_size < size +8 +BOOTCONFIG_MAGIC_LEN ) {
@@ -190,10 +194,8 @@ static int load_xbc_from_initrd(int fd, char **buf) }if (lseek (fd, stat.st_size - (size +8 +BOOTCONFIG_MAGIC_LEN ), -SEEK_SET ) <0 ) { -pr_err ("Failed to lseek: %d\n" , -errno); -return -errno; - } +SEEK_SET ) <0 ) +return pr_errno ("Failed to lseek" , -errno); ret =load_xbc_fd (fd, buf, size);if (ret <0 )
@@ -262,14 +264,16 @@ static int show_xbc(const char *path, bool list) ret =stat (path, &st);if (ret <0 ) { -pr_err ("Failed to stat %s: %d\n" , path, -errno); -return -errno; + ret = -errno; +pr_err ("Failed to stat %s: %d\n" , path, ret); +return ret; } fd =open (path,O_RDONLY );if (fd <0 ) { -pr_err ("Failed to open initrd %s: %d\n" , path, fd); -return -errno; + ret = -errno; +pr_err ("Failed to open initrd %s: %d\n" , path, ret); +return ret; } ret =load_xbc_from_initrd (fd, &buf);
@@ -307,8 +311,9 @@ static int delete_xbc(const char *path) fd =open (path,O_RDWR );if (fd <0 ) { -pr_err ("Failed to open initrd %s: %d\n" , path, fd); -return -errno; + ret = -errno; +pr_err ("Failed to open initrd %s: %d\n" , path, ret); +return ret; } size =load_xbc_from_initrd (fd, &buf);
@@ -383,9 +388,10 @@ static int apply_xbc(const char *path, const char *xbc_path)/* Apply new one */ fd =open (path,O_RDWR |O_APPEND );if (fd <0 ) { -pr_err ("Failed to open %s: %d\n" , path, fd); + ret = -errno; +pr_err ("Failed to open %s: %d\n" , path, ret);free (data); -return fd; +return ret; }/* TODO: Ensure the @path is initramfs/initrd image */ ret =write (fd, data, size +8 );
Masami Hiramatsu
maintainerPATCH v5 2/4 tools/bootconfig: Fix to check the write failure correctly
In reply to Masami HiramatsuFix to check the write(2) failure including partial write correctly and try to rollback the partial write, because if there is no BOOTCONFIG_MAGIC string, we can not remove it.
---
Changes in v5:
- Return -ENOSPC for partial write.
--- tools/bootconfig/main.c | 30 ++++++++++++++++++++++++++---- 1 file changed, 26 insertions(+), 4 deletions(-)
tools/bootconfig/main.c +26 -4
@@ -337,6 +337,7 @@ static int delete_xbc(const char *path)static int apply_xbc (const char *path,const char *xbc_path) { +struct stat stat;u32 size, csum;char *buf, *data;int ret, fd;
@@ -394,16 +395,26 @@ static int apply_xbc(const char *path, const char *xbc_path)return ret; }/* TODO: Ensure the @path is initramfs/initrd image */ +if (fstat (fd, &stat) <0 ) { +pr_err ("Failed to get the size of %s\n" , path); + goto out; + } ret =write (fd, data, size +8 ); -if (ret <0 ) { +if (ret < size +8 ) { +if (ret <0 ) + ret = -errno;pr_err ("Failed to apply a boot config: %d\n" , ret); - goto out; +if (ret <0 ) + goto out; + goto out_rollback; }/* Write a magic word of the bootconfig */ ret =write (fd,BOOTCONFIG_MAGIC ,BOOTCONFIG_MAGIC_LEN ); -if (ret <0 ) { +if (ret <BOOTCONFIG_MAGIC_LEN ) { +if (ret <0 ) + ret = -errno;pr_err ("Failed to apply a boot config magic: %d\n" , ret); - goto out; + goto out_rollback; } ret =0 ; out:
@@ -411,6 +422,17 @@ static int apply_xbc(const char *path, const char *xbc_path)free (data);return ret; + +out_rollback: +/* Map the partial write to -ENOSPC */ +if (ret >=0 ) + ret = -ENOSPC ; +if (ftruncate (fd, stat.st_size) <0 ) { + ret = -errno; +pr_err ("Failed to rollback the write error: %d\n" , ret); +pr_err ("The initrd %s may be corrupted. Recommend to rebuild.\n" , path); + } + goto out; }static int usage (void )
Masami Hiramatsu
maintainerPATCH v5 3/4 tools/bootconfig: Align the bootconfig applied initrd image size to 4
In reply to Masami HiramatsuAlign the bootconfig applied initrd image size to 4. To fill the gap, the bootconfig command uses null characters in between the bootconfig data and the footer. This will expands the footer size but don't change the checksum.
Thus the block image of the initrd file with bootconfig is as follows.
[initrd][bootconfig][(pad)][size][csum]["#BOOTCONFIG\n"]
---
Changes in v5:
- Sort the local variables by length.
- Remove if from padding size calculation (alignment should be power of two)
- Cleanup footer setup code.
- Fix a bug if write() == 0 case.
Changes in v3:
- Fix patch description
- Fix a typo.
- Consolidate several write()s to 1 time write to fix/simplify the error check.
Changes in v2:
- Fix to add the footer size.
--- tools/bootconfig/main.c | 57 +++++++++++++++++++++-------------- tools/bootconfig/test-bootconfig.sh | 6 +++- 2 files changed, 39 insertions(+), 24 deletions(-)
include/linux/bootconfig.h +3 -0
@@ -12,6 +12,9 @@#define BOOTCONFIG_MAGIC "#BOOTCONFIG\n"#define BOOTCONFIG_MAGIC_LEN 12 +#define BOOTCONFIG_ALIGN_SHIFT 2 +#define BOOTCONFIG_ALIGN (1 << BOOTCONFIG_ALIGN_SHIFT) +#define BOOTCONFIG_ALIGN_MASK (BOOTCONFIG_ALIGN - 1)/* XBC tree node */ struct xbc_node {
tools/bootconfig/main.c +34 -23
83 lines not on this page · raw message
tools/bootconfig/test-bootconfig.sh +5 -1
@@ -9,6 +9,7 @@ else TESTDIR=. fi BOOTCONF=${TESTDIR}/bootconfig +ALIGN=4 INITRD=`mktemp ${TESTDIR}/initrd-XXXX` TEMPCONF=`mktemp ${TESTDIR}/temp-XXXX.bconf`
@@ -59,7 +60,10 @@ echo "Show command test" xpass $BOOTCONF $INITRD echo "File size check" -xpass test $new_size -eq $(expr $bconf_size + $initrd_size + 9 + 12) +total_size=$(expr $bconf_size + $initrd_size + 9 + 12 + $ALIGN - 1 ) +total_size=$(expr $total_size / $ALIGN) +total_size=$(expr $total_size \* $ALIGN) +xpass test $new_size -eq $total_size echo "Apply command repeat test" xpass $BOOTCONF -a $TEMPCONF $INITRD
Masami Hiramatsu
maintainerPATCH v5 4/4 docs: bootconfig: Update file format on initrd image
In reply to Masami HiramatsuTo align the total file size, add padding null character when appending the bootconfig to initrd image.
---
0 files changed
Documentation/admin-guide/bootconfig.rst +13 -5
@@ -137,15 +137,22 @@ 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 with size, checksum and -12-byte magic word as below. +to the end of the initrd (initramfs) image file with padding, size, +checksum and 12-byte magic word as below. -[initrd][bootconfig][size(u32)][checksum(u32)][#BOOTCONFIG\n] +[initrd][bootconfig][padding][size(u32)][checksum(u32)][#BOOTCONFIG\n] + +When the boot configuration is added to the initrd image, the total +file size is aligned to 4 bytes. To fill the gap, null characters +(``\0``) will be added. Thus the ``size`` is the length of the bootconfig +file + padding bytes. 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. +update the boot loader and the kernel image itself as long as the boot +loader passes the correct initrd file size. If by any chance, the boot +loader passes a longer size, the kernel feils to find the bootconfig data. To do this operation, Linux kernel provides "bootconfig" command under tools/bootconfig, which allows admin to apply or delete the config file
@@ -176,7 +183,8 @@ up to 512 key-value pairs. If keys contains 3 words in average, it can contain 256 key-value pairs. In most cases, the number of config items will be under 100 entries and smaller than 8KB, so it would be enough. If the node number exceeds 1024, parser returns an error even if the file -size is smaller than 32KB. +size is smaller than 32KB. (Note that this maximum size is not including +the padding null characters.) Anyway, since bootconfig command verifies it when appending a boot config to initrd image, user can notice it before boot.