btrfs: use full bootloader area
Signed-off-by: Robbie Harwood <rharwood@redhat.com>
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0213-fs-btrfs-Use-full-btrfs-bootloader-area.patch
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163
0213-fs-btrfs-Use-full-btrfs-bootloader-area.patch
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From 6e5b9bc2f1d2e3a10096716350fa67f48c199f5d Mon Sep 17 00:00:00 2001
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From: Michael Chang <mchang@suse.com>
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Date: Mon, 13 Dec 2021 14:25:49 +0800
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Subject: [PATCH] fs/btrfs: Use full btrfs bootloader area
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Up to now GRUB can only embed to the first 64 KiB before primary
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superblock of btrfs, effectively limiting the GRUB core size. That
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could consequently pose restrictions to feature enablement like
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advanced zstd compression.
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This patch attempts to utilize full unused area reserved by btrfs for
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the bootloader outlined in the document [1]:
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The first 1MiB on each device is unused with the exception of primary
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superblock that is on the offset 64KiB and spans 4KiB.
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Apart from that, adjacent sectors to superblock and first block group
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are not used for embedding in case of overflow and logged access to
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adjacent sectors could be useful for tracing it up.
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This patch has been tested to provide out of the box support for btrfs
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zstd compression with which GRUB has been installed to the partition.
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[1] https://btrfs.wiki.kernel.org/index.php/Manpage/btrfs(5)#BOOTLOADER_SUPPORT
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Signed-off-by: Michael Chang <mchang@suse.com>
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Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
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(cherry picked from commit b0f06a81c6f31b6fa20be67a96b6683bba8210c9)
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---
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grub-core/fs/btrfs.c | 90 +++++++++++++++++++++++++++++++++++++-------
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include/grub/disk.h | 2 +
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2 files changed, 79 insertions(+), 13 deletions(-)
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diff --git a/grub-core/fs/btrfs.c b/grub-core/fs/btrfs.c
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index 4cc86e9b7..07c0ff874 100644
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--- a/grub-core/fs/btrfs.c
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+++ b/grub-core/fs/btrfs.c
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@@ -2476,6 +2476,33 @@ grub_btrfs_label (grub_device_t device, char **label)
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}
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#ifdef GRUB_UTIL
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+
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+struct embed_region {
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+ unsigned int start;
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+ unsigned int secs;
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+};
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+
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+/*
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+ * https://btrfs.wiki.kernel.org/index.php/Manpage/btrfs(5)#BOOTLOADER_SUPPORT
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+ * The first 1 MiB on each device is unused with the exception of primary
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+ * superblock that is on the offset 64 KiB and spans 4 KiB.
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+ */
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+
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+static const struct {
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+ struct embed_region available;
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+ struct embed_region used[6];
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+} btrfs_head = {
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+ .available = {0, GRUB_DISK_KiB_TO_SECTORS (1024)}, /* The first 1 MiB. */
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+ .used = {
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+ {0, 1}, /* boot.S. */
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+ {GRUB_DISK_KiB_TO_SECTORS (64) - 1, 1}, /* Overflow guard. */
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+ {GRUB_DISK_KiB_TO_SECTORS (64), GRUB_DISK_KiB_TO_SECTORS (4)}, /* 4 KiB superblock. */
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+ {GRUB_DISK_KiB_TO_SECTORS (68), 1}, /* Overflow guard. */
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+ {GRUB_DISK_KiB_TO_SECTORS (1024) - 1, 1}, /* Overflow guard. */
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+ {0, 0} /* Array terminator. */
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+ }
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+};
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+
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static grub_err_t
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grub_btrfs_embed (grub_device_t device __attribute__ ((unused)),
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unsigned int *nsectors,
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@@ -2483,25 +2510,62 @@ grub_btrfs_embed (grub_device_t device __attribute__ ((unused)),
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grub_embed_type_t embed_type,
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grub_disk_addr_t **sectors)
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{
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- unsigned i;
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+ unsigned int i, j, n = 0;
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+ const struct embed_region *u;
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+ grub_disk_addr_t *map;
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if (embed_type != GRUB_EMBED_PCBIOS)
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return grub_error (GRUB_ERR_NOT_IMPLEMENTED_YET,
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"BtrFS currently supports only PC-BIOS embedding");
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- if (64 * 2 - 1 < *nsectors)
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- return grub_error (GRUB_ERR_OUT_OF_RANGE,
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- N_("your core.img is unusually large. "
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- "It won't fit in the embedding area"));
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-
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- *nsectors = 64 * 2 - 1;
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- if (*nsectors > max_nsectors)
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- *nsectors = max_nsectors;
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- *sectors = grub_calloc (*nsectors, sizeof (**sectors));
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- if (!*sectors)
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+ map = grub_calloc (btrfs_head.available.secs, sizeof (*map));
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+ if (map == NULL)
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return grub_errno;
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- for (i = 0; i < *nsectors; i++)
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- (*sectors)[i] = i + 1;
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+
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+ /*
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+ * Populating the map array so that it can be used to index if a disk
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+ * address is available to embed:
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+ * - 0: available,
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+ * - 1: unavailable.
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+ */
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+ for (u = btrfs_head.used; u->secs; ++u)
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+ {
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+ unsigned int end = u->start + u->secs;
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+
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+ if (end > btrfs_head.available.secs)
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+ end = btrfs_head.available.secs;
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+ for (i = u->start; i < end; ++i)
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+ map[i] = 1;
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+ }
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+
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+ /* Adding up n until it matches total size of available embedding area. */
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+ for (i = 0; i < btrfs_head.available.secs; ++i)
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+ if (map[i] == 0)
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+ n++;
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+
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+ if (n < *nsectors)
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+ {
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+ grub_free (map);
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+ return grub_error (GRUB_ERR_OUT_OF_RANGE,
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+ N_("your core.img is unusually large. "
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+ "It won't fit in the embedding area"));
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+ }
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+
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+ if (n > max_nsectors)
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+ n = max_nsectors;
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+
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+ /*
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+ * Populating the array so that it can used to index disk block address for
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+ * an image file's offset to be embedded on disk (the unit is in sectors):
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+ * - i: The disk block address relative to btrfs_head.available.start,
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+ * - j: The offset in image file.
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+ */
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+ for (i = 0, j = 0; i < btrfs_head.available.secs && j < n; ++i)
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+ if (map[i] == 0)
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+ map[j++] = btrfs_head.available.start + i;
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+
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+ *nsectors = n;
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+ *sectors = map;
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return GRUB_ERR_NONE;
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}
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diff --git a/include/grub/disk.h b/include/grub/disk.h
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index f95aca929..06210a704 100644
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--- a/include/grub/disk.h
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+++ b/include/grub/disk.h
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@@ -182,6 +182,8 @@ typedef struct grub_disk_memberlist *grub_disk_memberlist_t;
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/* Return value of grub_disk_native_sectors() in case disk size is unknown. */
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#define GRUB_DISK_SIZE_UNKNOWN 0xffffffffffffffffULL
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+#define GRUB_DISK_KiB_TO_SECTORS(x) ((x) << (10 - GRUB_DISK_SECTOR_BITS))
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+
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/* Convert sector number from one sector size to another. */
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static inline grub_disk_addr_t
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grub_convert_sector (grub_disk_addr_t sector,
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--
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2.34.1
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@ -210,3 +210,4 @@ Patch0209: 0209-fs-xfs-Fix-unreadable-filesystem-with-v4-superblock.patch
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Patch0210: 0210-Print-module-name-on-license-check-failure.patch
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Patch0211: 0211-powerpc-ieee1275-load-grub-at-4MB-not-2MB.patch
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Patch0212: 0212-grub-mkconfig-restore-umask-for-grub.cfg.patch
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Patch0213: 0213-fs-btrfs-Use-full-btrfs-bootloader-area.patch
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@ -14,7 +14,7 @@
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Name: grub2
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Epoch: 1
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Version: 2.06
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Release: 11%{?dist}
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Release: 12%{?dist}
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Summary: Bootloader with support for Linux, Multiboot and more
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License: GPLv3+
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URL: http://www.gnu.org/software/grub/
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@ -523,6 +523,9 @@ mv ${EFI_HOME}/grub.cfg.stb ${EFI_HOME}/grub.cfg
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%endif
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%changelog
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* Thu Jan 06 2022 Robbie Harwood <rharwood@redhat.com> - 2.06-12
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- btrfs: use full bootloader area
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* Fri Dec 10 2021 Robbie Harwood <rharwood@redhat.com> - 2.06-11
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- Bump to rerun signing (no code changes)
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