Introduce a new partition parser for U-Boot's Flattened-Image-Tree (FIT) in
order to allow Linux to mount the filesystem part of a uImage.FIT.
uImage.FIT needs to be created with external data and aligned to the
system's memory page size. e.g.
mkimage -E -B 0x1000 -p 0x1000 ...
Signed-off-by: Daniel Golle <[email protected]>
---
MAINTAINERS | 6 +
block/partitions/Kconfig | 15 ++
block/partitions/Makefile | 1 +
block/partitions/check.h | 4 +
block/partitions/core.c | 3 +
block/partitions/fit.c | 353 ++++++++++++++++++++++++++++++++++++++
6 files changed, 382 insertions(+)
create mode 100644 block/partitions/fit.c
diff --git a/MAINTAINERS b/MAINTAINERS
index f6108373680e..556183a9d112 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -8044,6 +8044,12 @@ F: Documentation/firmware_class/
F: drivers/base/firmware_loader/
F: include/linux/firmware.h
+FIT PARTITION TABLE (uImage.FIT)
+M: Daniel Golle <[email protected]>
+L: [email protected]
+S: Maintained
+F: block/partitions/fit.c
+
FLEXTIMER FTM-QUADDEC DRIVER
M: Patrick Havelange <[email protected]>
L: [email protected]
diff --git a/block/partitions/Kconfig b/block/partitions/Kconfig
index 7aff4eb81c60..77dc85d3797d 100644
--- a/block/partitions/Kconfig
+++ b/block/partitions/Kconfig
@@ -103,6 +103,21 @@ config ATARI_PARTITION
Say Y here if you would like to use hard disks under Linux which
were partitioned under the Atari OS.
+config FIT_PARTITION
+ bool "Flattened-Image-Tree (FIT) partition support" if PARTITION_ADVANCED
+ default n
+ select LIBFDT
+ help
+ Say Y here if your system needs to mount the filesystem part of
+ a Flattened-Image-Tree (FIT) image commonly used with Das U-Boot.
+
+ uImage.FIT needs to be created with external data and aligned to
+ the systems memory page size. e.g.
+ mkimage -E -B 0x1000 -p 0x1000 ...
+
+ If your system doesn't use U-Boot or you don't need to mount uImage.FIT
+ filesystem sub-images in Linux, say N.
+
config IBM_PARTITION
bool "IBM disk label and partition support"
depends on PARTITION_ADVANCED && S390
diff --git a/block/partitions/Makefile b/block/partitions/Makefile
index a7f05cdb02a8..d319eb1deba9 100644
--- a/block/partitions/Makefile
+++ b/block/partitions/Makefile
@@ -8,6 +8,7 @@ obj-$(CONFIG_ACORN_PARTITION) += acorn.o
obj-$(CONFIG_AMIGA_PARTITION) += amiga.o
obj-$(CONFIG_ATARI_PARTITION) += atari.o
obj-$(CONFIG_AIX_PARTITION) += aix.o
+obj-$(CONFIG_FIT_PARTITION) += fit.o
obj-$(CONFIG_CMDLINE_PARTITION) += cmdline.o
obj-$(CONFIG_MAC_PARTITION) += mac.o
obj-$(CONFIG_LDM_PARTITION) += ldm.o
diff --git a/block/partitions/check.h b/block/partitions/check.h
index 8d70a880c372..76b006d3cb27 100644
--- a/block/partitions/check.h
+++ b/block/partitions/check.h
@@ -57,6 +57,7 @@ int amiga_partition(struct parsed_partitions *state);
int atari_partition(struct parsed_partitions *state);
int cmdline_partition(struct parsed_partitions *state);
int efi_partition(struct parsed_partitions *state);
+int fit_partition(struct parsed_partitions *state);
int ibm_partition(struct parsed_partitions *);
int karma_partition(struct parsed_partitions *state);
int ldm_partition(struct parsed_partitions *state);
@@ -67,3 +68,6 @@ int sgi_partition(struct parsed_partitions *state);
int sun_partition(struct parsed_partitions *state);
int sysv68_partition(struct parsed_partitions *state);
int ultrix_partition(struct parsed_partitions *state);
+
+int parse_fit_partitions(struct parsed_partitions *state, u64 fit_start_sector,
+ u64 sectors, int *slot, int max_slot, bool add_remain);
diff --git a/block/partitions/core.c b/block/partitions/core.c
index 355646b0707d..9d4bb8f48d35 100644
--- a/block/partitions/core.c
+++ b/block/partitions/core.c
@@ -43,6 +43,9 @@ static int (*check_part[])(struct parsed_partitions *) = {
#ifdef CONFIG_CMDLINE_PARTITION
cmdline_partition,
#endif
+#ifdef CONFIG_FIT_PARTITION
+ fit_partition,
+#endif
#ifdef CONFIG_EFI_PARTITION
efi_partition, /* this must come before msdos */
#endif
diff --git a/block/partitions/fit.c b/block/partitions/fit.c
new file mode 100644
index 000000000000..095faa5fa69a
--- /dev/null
+++ b/block/partitions/fit.c
@@ -0,0 +1,353 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * fs/partitions/fit.c
+ * Copyright (C) 2021 Daniel Golle
+ *
+ * headers extracted from U-Boot mkimage sources
+ * (C) Copyright 2008 Semihalf
+ * (C) Copyright 2000-2005
+ * Wolfgang Denk, DENX Software Engineering, [email protected].
+ *
+ * based on existing partition parsers
+ * Copyright (C) 1991-1998 Linus Torvalds
+ * Re-organised Feb 1998 Russell King
+ */
+
+#include <linux/libfdt.h>
+#include <linux/of.h>
+#include <linux/of_device.h>
+#include <linux/of_fdt.h>
+#include <linux/types.h>
+
+#include "check.h"
+
+#define FIT_IMAGES_PATH "/images"
+#define FIT_CONFS_PATH "/configurations"
+
+/* hash/signature/key node */
+#define FIT_HASH_NODENAME "hash"
+#define FIT_ALGO_PROP "algo"
+#define FIT_VALUE_PROP "value"
+#define FIT_IGNORE_PROP "uboot-ignore"
+#define FIT_SIG_NODENAME "signature"
+#define FIT_KEY_REQUIRED "required"
+#define FIT_KEY_HINT "key-name-hint"
+
+/* cipher node */
+#define FIT_CIPHER_NODENAME "cipher"
+#define FIT_ALGO_PROP "algo"
+
+/* image node */
+#define FIT_DATA_PROP "data"
+#define FIT_DATA_POSITION_PROP "data-position"
+#define FIT_DATA_OFFSET_PROP "data-offset"
+#define FIT_DATA_SIZE_PROP "data-size"
+#define FIT_TIMESTAMP_PROP "timestamp"
+#define FIT_DESC_PROP "description"
+#define FIT_ARCH_PROP "arch"
+#define FIT_TYPE_PROP "type"
+#define FIT_OS_PROP "os"
+#define FIT_COMP_PROP "compression"
+#define FIT_ENTRY_PROP "entry"
+#define FIT_LOAD_PROP "load"
+
+/* configuration node */
+#define FIT_KERNEL_PROP "kernel"
+#define FIT_FILESYSTEM_PROP "filesystem"
+#define FIT_RAMDISK_PROP "ramdisk"
+#define FIT_FDT_PROP "fdt"
+#define FIT_LOADABLE_PROP "loadables"
+#define FIT_DEFAULT_PROP "default"
+#define FIT_SETUP_PROP "setup"
+#define FIT_FPGA_PROP "fpga"
+#define FIT_FIRMWARE_PROP "firmware"
+#define FIT_STANDALONE_PROP "standalone"
+
+#define MIN_FREE_SECT 16
+#define REMAIN_VOLNAME "rootfs_data"
+#define MAX_FIT_LOADABLES 16
+
+/**
+ * parse_fit_partitions - map uImage.FIT filesystem sub-images into sub-partitions
+ * @state: pointer to partition parser state
+ * @fit_start_sector: start sector of the FIT structure on disk
+ * @sectors: number of sectors of the uImage.FIT partition or 0 if whole device
+ * @slot: pointer to the current partition slot number
+ * @add_remain: map unused sectors into additional partition
+ *
+ * To be called by other partition parsers on physical block devices or using
+ * wrapper function int fit_partition(struct parsed_partitions *state) for the
+ * whole disk, relevant typically for ubiblock or mtdblock devices.
+ */
+int parse_fit_partitions(struct parsed_partitions *state, u64 fit_start_sector,
+ u64 sectors, int *slot, int max_slot, bool add_remain)
+{
+ struct block_device *bdev = state->disk->part0;
+ struct address_space *mapping = bdev->bd_inode->i_mapping;
+ struct page *page;
+ void *fit, *init_fit;
+ struct partition_meta_info *info;
+ char tmp[sizeof(info->volname)];
+ u64 dsize, dsectors, imgmaxsect = 0;
+ u32 size, image_pos, image_len;
+ const __be32 *image_offset_be, *image_len_be, *image_pos_be;
+ int ret = 1, node, images, config;
+ const char *image_name, *image_type, *image_description,
+ *config_default, *config_description, *config_loadables;
+ u32 image_name_len, image_type_len, image_description_len,
+ config_default_len, config_description_len,
+ config_loadables_len;
+ sector_t start_sect, nr_sects;
+ size_t label_min;
+ struct device_node *np = NULL;
+ const char *bootconf;
+ const char *loadable;
+ bool found;
+ int loadables_rem_len, loadable_len;
+ u16 loadcnt;
+
+ /* uImage.FIT should be aligned to page boundaries */
+ if (fit_start_sector % (1 << (PAGE_SHIFT - SECTOR_SHIFT)))
+ return 0;
+
+ /* map first page */
+ page = read_mapping_page(
+ mapping, fit_start_sector >> (PAGE_SHIFT - SECTOR_SHIFT), NULL);
+
+ if (IS_ERR(page))
+ return -EFAULT;
+
+ if (PageError(page))
+ return -EFAULT;
+
+ init_fit = page_address(page);
+
+ if (!init_fit) {
+ put_page(page);
+ return -EFAULT;
+ }
+
+ /* uImage.FIT is based on flattened device tree structure */
+ if (fdt_check_header(init_fit)) {
+ put_page(page);
+ return 0;
+ }
+
+ /* acquire disk or partition size */
+ dsectors = get_capacity(bdev->bd_disk);
+ if (sectors)
+ dsectors = min_t(u64, sectors, dsectors);
+
+ dsize = dsectors << SECTOR_SHIFT;
+ size = fdt_totalsize(init_fit);
+
+ /* silently skip non-external-data legacy uImage.FIT */
+ if (size > PAGE_SIZE) {
+ put_page(page);
+ return 0;
+ }
+
+ /* abort if FIT structure is larger than disk or partition size */
+ if (size >= dsize) {
+ state->access_beyond_eod = 1;
+ put_page(page);
+ return -EFBIG;
+ }
+
+ /*
+ * copy FIT structure for further processing
+ * this is necessary for libfdt to work
+ */
+ fit = kmemdup(init_fit, size, GFP_KERNEL);
+ put_page(page);
+ if (!fit)
+ return -ENOMEM;
+
+ /* set boot config node name U-Boot may have added to the device tree */
+ np = of_find_node_by_path("/chosen");
+ if (np)
+ bootconf = of_get_property(np, "u-boot,bootconf", NULL);
+ else
+ bootconf = NULL;
+
+ /* find configuration path in uImage.FIT */
+ config = fdt_path_offset(fit, FIT_CONFS_PATH);
+ if (config < 0) {
+ pr_err("FIT: Cannot find %s node: %d\n",
+ FIT_CONFS_PATH, config);
+ ret = -ENOENT;
+ goto ret_out;
+ }
+
+ /* get default configuration node name */
+ config_default =
+ fdt_getprop(fit, config, FIT_DEFAULT_PROP, &config_default_len);
+
+ /* make sure we got either default or selected boot config node name */
+ if (!config_default && !bootconf) {
+ pr_err("FIT: Cannot find default configuration\n");
+ ret = -ENOENT;
+ goto ret_out;
+ }
+
+ /* find selected boot config node, fallback on default config node */
+ node = fdt_subnode_offset(fit, config, bootconf ?: config_default);
+ if (node < 0) {
+ pr_err("FIT: Cannot find %s node: %d\n",
+ bootconf ?: config_default, node);
+ ret = -ENOENT;
+ goto ret_out;
+ }
+
+ /* get selected configuration data */
+ config_description =
+ fdt_getprop(fit, node, FIT_DESC_PROP, &config_description_len);
+ config_loadables = fdt_getprop(fit, node, FIT_LOADABLE_PROP,
+ &config_loadables_len);
+
+ pr_info("FIT: %s configuration: \"%s\"%s%s%s\n",
+ bootconf ? "Selected" : "Default", bootconf ?: config_default,
+ config_description ? " (" : "", config_description ?: "",
+ config_description ? ")" : "");
+
+ if (!config_loadables || !config_loadables_len) {
+ pr_err("FIT: No loadables configured in \"%s\"\n",
+ bootconf ?: config_default);
+ ret = -ENOENT;
+ goto ret_out;
+ }
+
+ /* get images path in uImage.FIT */
+ images = fdt_path_offset(fit, FIT_IMAGES_PATH);
+ if (images < 0) {
+ pr_err("FIT: Cannot find %s node: %d\n", FIT_IMAGES_PATH, images);
+ ret = -EINVAL;
+ goto ret_out;
+ }
+
+ /* allocate one slot for mapping remaing space */
+ if (add_remain)
+ --max_slot;
+
+ /* iterate over images in uImage.FIT */
+ fdt_for_each_subnode(node, fit, images) {
+ image_name = fdt_get_name(fit, node, &image_name_len);
+ image_type = fdt_getprop(fit, node, FIT_TYPE_PROP, &image_type_len);
+ image_offset_be = fdt_getprop(fit, node, FIT_DATA_OFFSET_PROP, NULL);
+ image_pos_be = fdt_getprop(fit, node, FIT_DATA_POSITION_PROP, NULL);
+ image_len_be = fdt_getprop(fit, node, FIT_DATA_SIZE_PROP, NULL);
+
+ if (!image_name || !image_type || !image_len_be)
+ continue;
+
+ image_len = be32_to_cpu(*image_len_be);
+ if (!image_len)
+ continue;
+
+ if (image_offset_be)
+ image_pos = be32_to_cpu(*image_offset_be) + size;
+ else if (image_pos_be)
+ image_pos = be32_to_cpu(*image_pos_be);
+ else
+ continue;
+
+ image_description = fdt_getprop(fit, node, FIT_DESC_PROP,
+ &image_description_len);
+
+ pr_info("FIT: %16s sub-image 0x%08x..0x%08x \"%.*s\"%s%.*s%s\n",
+ image_type, image_pos, image_pos + image_len - 1,
+ image_name_len, image_name, image_description ? " (" : "",
+ image_description ? image_description_len : 0,
+ image_description ?: "", image_description ? ") " : "");
+
+ /* only 'filesystem' images should be mapped as partitions */
+ if (strncmp(image_type, FIT_FILESYSTEM_PROP, image_type_len))
+ continue;
+
+ /* check if sub-image is part of configured loadables */
+ found = false;
+ loadable = config_loadables;
+ loadables_rem_len = config_loadables_len;
+ for (loadcnt = 0; loadables_rem_len > 1 &&
+ loadcnt < MAX_FIT_LOADABLES; ++loadcnt) {
+ loadable_len =
+ strnlen(loadable, loadables_rem_len - 1) + 1;
+ loadables_rem_len -= loadable_len;
+ if (!strncmp(image_name, loadable, loadable_len)) {
+ found = true;
+ break;
+ }
+ loadable += loadable_len;
+ }
+ if (!found)
+ continue;
+
+ if (image_pos % (1 << PAGE_SHIFT)) {
+ pr_err("FIT: image %.*s start not aligned to page boundaries, skipping\n",
+ image_name_len, image_name);
+ continue;
+ }
+
+ if (image_len % (1 << PAGE_SHIFT)) {
+ pr_err("FIT: sub-image %.*s end not aligned to page boundaries, skipping\n",
+ image_name_len, image_name);
+ continue;
+ }
+
+ start_sect = image_pos >> SECTOR_SHIFT;
+ nr_sects = image_len >> SECTOR_SHIFT;
+ imgmaxsect = (imgmaxsect < (start_sect + nr_sects)) ?
+ (start_sect + nr_sects) :
+ imgmaxsect;
+
+ if (start_sect + nr_sects > dsectors) {
+ state->access_beyond_eod = 1;
+ continue;
+ }
+
+ put_partition(state, *slot, fit_start_sector + start_sect,
+ nr_sects);
+ state->parts[*slot].flags = ADDPART_FLAG_READONLY;
+ state->parts[*slot].has_info = true;
+ info = &state->parts[*slot].info;
+
+ label_min = min_t(int, sizeof(info->volname) - 1, image_name_len);
+ strncpy(info->volname, image_name, label_min);
+ info->volname[label_min] = '\0';
+
+ snprintf(tmp, sizeof(tmp), "(%s)", info->volname);
+ strlcat(state->pp_buf, tmp, PAGE_SIZE);
+
+ if (++(*slot) > max_slot)
+ break;
+ }
+
+ /* in case uImage.FIT is stored in a partition, map the remaining space */
+ if (add_remain && (imgmaxsect + MIN_FREE_SECT) < dsectors) {
+ put_partition(state, *slot, fit_start_sector + imgmaxsect,
+ dsectors - imgmaxsect);
+ state->parts[*slot].flags = 0;
+ info = &state->parts[*slot].info;
+ strcpy(info->volname, REMAIN_VOLNAME);
+ snprintf(tmp, sizeof(tmp), "(%s)", REMAIN_VOLNAME);
+ strlcat(state->pp_buf, tmp, PAGE_SIZE);
+ ++(*slot);
+ }
+ret_out:
+ kfree(fit);
+ return ret;
+}
+
+/**
+ * fit_partition - map uImage.FIT filesystem sub-images into partitions
+ * @state: pointer to partition parser state
+ *
+ * Used to parse uImage.FIT structure for images directly stored on
+ * the whole block device (typically ubiblock or mtdblock).
+ */
+int fit_partition(struct parsed_partitions *state)
+{
+ int slot = 1;
+
+ return parse_fit_partitions(state, 0, 0, &slot, MAX_FIT_LOADABLES, false);
+}
--
2.38.1
On Tue, Nov 08, 2022 at 11:03:16PM +0000, Daniel Golle wrote:
> + /* map first page */
> + page = read_mapping_page(
> + mapping, fit_start_sector >> (PAGE_SHIFT - SECTOR_SHIFT), NULL);
> +
> + if (IS_ERR(page))
> + return -EFAULT;
> +
> + if (PageError(page))
> + return -EFAULT;
Why are you checking for PageError? You won't ever get a page with an
error back from read_mapping_page(). And you have the real error in
'page', so why return -EFAUlT, which would indicate a problem copying
from the user. Also, this is a great place to use the new folio APIs
instead of the old page APIs. So:
folio = read_mapping_folio(mapping,
fit_start_sector >> PAGE_SECTORS_SHIFT, NULL);
if (IS_ERR(folio))
return PTR_ERR(folio);
> + init_fit = page_address(page);
init_fit = folio_address(folio) +
offset_in_folio(folio, fit_start_sector * SECTOR_SIZE);
> + if (!init_fit) {
> + put_page(page);
> + return -EFAULT;
> + }
page_address() or folio_address() can't ever return NULL, you should
just drop this nonsense check.
... actually, why can't you call read_part_sector() and avoid all of
this?
On Wed, Nov 09, 2022 at 01:58:29PM +0000, Matthew Wilcox wrote:
> On Tue, Nov 08, 2022 at 11:03:16PM +0000, Daniel Golle wrote:
> > + /* map first page */
> > + page = read_mapping_page(
> > + mapping, fit_start_sector >> (PAGE_SHIFT - SECTOR_SHIFT), NULL);
> > +
> > + if (IS_ERR(page))
> > + return -EFAULT;
> > +
> > + if (PageError(page))
> > + return -EFAULT;
>
> Why are you checking for PageError? You won't ever get a page with an
> error back from read_mapping_page(). And you have the real error in
> 'page', so why return -EFAUlT, which would indicate a problem copying
> from the user. Also, this is a great place to use the new folio APIs
> instead of the old page APIs. So:
>
> folio = read_mapping_folio(mapping,
> fit_start_sector >> PAGE_SECTORS_SHIFT, NULL);
> if (IS_ERR(folio))
> return PTR_ERR(folio);
>
> > + init_fit = page_address(page);
>
> init_fit = folio_address(folio) +
> offset_in_folio(folio, fit_start_sector * SECTOR_SIZE);
>
> > + if (!init_fit) {
> > + put_page(page);
> > + return -EFAULT;
> > + }
>
> page_address() or folio_address() can't ever return NULL, you should
> just drop this nonsense check.
Thank you for the pointers, I will implement your suggestions and post
v5 after the upcoming weekend.
>
> ... actually, why can't you call read_part_sector() and avoid all of
> this?
I've tried that before and the problem is that read_part_sector()
returns a pointer to one sector (typically 512 bytes) of data.
And this pointer should not be accesses beyond sector boundaries,
right? You'd have to call read_part_sector() again for the next
sector.
The FIT structure, however, usually exceeds the size of one sector,
and having a continous memory area covering the structure as a whole
is crucial for libfdt to do its job.
I could, of course, use read_part_sector() to copy all sectors
covering the FIT structure into a buffer, but that seemed strange
given that read_part_sector() actually used read_mapping_page()
(and now uses read_mapping_folio()) internally and then returns a
pointer to the offset within the page/folio. So why not read it in one
piece in first place instead of having it first split up to sectors
by read_part_sector() just to then having to reassemble it into a
continous buffer again.
On Wed, Nov 09, 2022 at 02:36:11PM +0000, Daniel Golle wrote:
> On Wed, Nov 09, 2022 at 01:58:29PM +0000, Matthew Wilcox wrote:
> > ... actually, why can't you call read_part_sector() and avoid all of
> > this?
>
> I've tried that before and the problem is that read_part_sector()
> returns a pointer to one sector (typically 512 bytes) of data.
> And this pointer should not be accesses beyond sector boundaries,
> right? You'd have to call read_part_sector() again for the next
> sector.
>
> The FIT structure, however, usually exceeds the size of one sector,
> and having a continous memory area covering the structure as a whole
> is crucial for libfdt to do its job.
>
> I could, of course, use read_part_sector() to copy all sectors
> covering the FIT structure into a buffer, but that seemed strange
> given that read_part_sector() actually used read_mapping_page()
> (and now uses read_mapping_folio()) internally and then returns a
> pointer to the offset within the page/folio. So why not read it in one
> piece in first place instead of having it first split up to sectors
> by read_part_sector() just to then having to reassemble it into a
> continous buffer again.
Are you guaranteed that it's "sufficiently" aligned on storage so
that it fits entirely within a single page? If not, you'll have
to copy it, vmap it, or fix libfdt to handle a segmented buffer.
On Wed, Nov 09, 2022 at 05:21:01PM +0000, Matthew Wilcox wrote:
> On Wed, Nov 09, 2022 at 02:36:11PM +0000, Daniel Golle wrote:
> > On Wed, Nov 09, 2022 at 01:58:29PM +0000, Matthew Wilcox wrote:
> > > ... actually, why can't you call read_part_sector() and avoid all of
> > > this?
> >
> > I've tried that before and the problem is that read_part_sector()
> > returns a pointer to one sector (typically 512 bytes) of data.
> > And this pointer should not be accesses beyond sector boundaries,
> > right? You'd have to call read_part_sector() again for the next
> > sector.
> >
> > The FIT structure, however, usually exceeds the size of one sector,
> > and having a continous memory area covering the structure as a whole
> > is crucial for libfdt to do its job.
> >
> > I could, of course, use read_part_sector() to copy all sectors
> > covering the FIT structure into a buffer, but that seemed strange
> > given that read_part_sector() actually used read_mapping_page()
> > (and now uses read_mapping_folio()) internally and then returns a
> > pointer to the offset within the page/folio. So why not read it in one
> > piece in first place instead of having it first split up to sectors
> > by read_part_sector() just to then having to reassemble it into a
> > continous buffer again.
>
> Are you guaranteed that it's "sufficiently" aligned on storage so
> that it fits entirely within a single page? If not, you'll have
> to copy it, vmap it, or fix libfdt to handle a segmented buffer.
Yes, for the uImage.FIT to be usable for the partition parser it has
to be page-aligned.
There is a check which makes sure that this is the case:
> + /* uImage.FIT should be aligned to page boundaries */
> + if (fit_start_sector % (1 << (PAGE_SHIFT - SECTOR_SHIFT)))
> + return 0;
In case of mtdblock or ubiblock devices, the image always starts at
offset 0, so this is never a problem.
In case of the image being stored in a GPT partition, one has to make
sure that the start sector of the partition is page aligned, otherwise
the above check will fail and the partition parser will bail out.
On Thu, Nov 10, 2022 at 01:52:43AM +0000, Daniel Golle wrote:
> On Wed, Nov 09, 2022 at 05:21:01PM +0000, Matthew Wilcox wrote:
> > On Wed, Nov 09, 2022 at 02:36:11PM +0000, Daniel Golle wrote:
> > > On Wed, Nov 09, 2022 at 01:58:29PM +0000, Matthew Wilcox wrote:
> > > > ... actually, why can't you call read_part_sector() and avoid all of
> > > > this?
> > >
> > > I've tried that before and the problem is that read_part_sector()
> > > returns a pointer to one sector (typically 512 bytes) of data.
> > > And this pointer should not be accesses beyond sector boundaries,
> > > right? You'd have to call read_part_sector() again for the next
> > > sector.
> > >
> > > The FIT structure, however, usually exceeds the size of one sector,
> > > and having a continous memory area covering the structure as a whole
> > > is crucial for libfdt to do its job.
> > >
> > > I could, of course, use read_part_sector() to copy all sectors
> > > covering the FIT structure into a buffer, but that seemed strange
> > > given that read_part_sector() actually used read_mapping_page()
> > > (and now uses read_mapping_folio()) internally and then returns a
> > > pointer to the offset within the page/folio. So why not read it in one
> > > piece in first place instead of having it first split up to sectors
> > > by read_part_sector() just to then having to reassemble it into a
> > > continous buffer again.
> >
> > Are you guaranteed that it's "sufficiently" aligned on storage so
> > that it fits entirely within a single page? If not, you'll have
> > to copy it, vmap it, or fix libfdt to handle a segmented buffer.
>
> Yes, for the uImage.FIT to be usable for the partition parser it has
> to be page-aligned.
>
> There is a check which makes sure that this is the case:
> > + /* uImage.FIT should be aligned to page boundaries */
> > + if (fit_start_sector % (1 << (PAGE_SHIFT - SECTOR_SHIFT)))
> > + return 0;
>
> In case of mtdblock or ubiblock devices, the image always starts at
> offset 0, so this is never a problem.
> In case of the image being stored in a GPT partition, one has to make
> sure that the start sector of the partition is page aligned, otherwise
> the above check will fail and the partition parser will bail out.
OK. Then I think open coding it is the right idea, just with all
the cruft removed ;-) I looked at extracting parts of
read_part_sector() into read_part_page(), but it ended up being
a two line function that wasn't terribly useful.