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Re: [PATCH] disk: Move hardcoded max disk size literal to a GRUB_DISK_MA
From: |
Daniel Kiper |
Subject: |
Re: [PATCH] disk: Move hardcoded max disk size literal to a GRUB_DISK_MAX_SECTORS in disk.h |
Date: |
Mon, 30 Nov 2020 15:42:14 +0100 |
User-agent: |
NeoMutt/20170113 (1.7.2) |
On Fri, Nov 27, 2020 at 02:36:23AM -0600, Glenn Washburn wrote:
> There is a hardcoded maximum disk size that can be read or written from,
> currently set at 1EiB in grub_disk_adjust_range. Move the literal into a
> macro in disk.h, so our assumptions are more visible. This hard coded limit
> does not prevent using larger disks, just grub won't read/write past the
> limit. The comment accompanying this restriction didn't quite make sense to
> me, so its been modified.
>
> Signed-off-by: Glenn Washburn <development@efficientek.com>
> ---
> grub-core/kern/disk_common.c | 13 +++++++------
> include/grub/disk.h | 6 ++++++
> 2 files changed, 13 insertions(+), 6 deletions(-)
>
> diff --git a/grub-core/kern/disk_common.c b/grub-core/kern/disk_common.c
> index 5b92f670b..d20ed20d2 100644
> --- a/grub-core/kern/disk_common.c
> +++ b/grub-core/kern/disk_common.c
> @@ -32,13 +32,14 @@ grub_disk_adjust_range (grub_disk_t disk,
> grub_disk_addr_t *sector,
> /* Transform total_sectors to number of 512B blocks. */
> total_sectors = grub_disk_from_native_sector (disk, disk->total_sectors);
>
> - /* Some drivers have problems with disks above reasonable.
> - Treat unknown as 1EiB disk. While on it, clamp the size to 1EiB.
> - Just one condition is enough since GRUB_DISK_UNKNOWN_SIZE << ls is
> always
> - above 9EiB.
> + /*
> + Some drivers have problems with disks above reasonable sizes.
> + Clamp the size to GRUB_DISK_MAX_SECTORS. Just one condition is enough
> + since GRUB_DISK_UNKNOWN_SIZE is always above GRUB_DISK_MAX_SECTORS,
> + assuming a maximum 4KiB sector size.
> */
> - if (total_sectors > (1ULL << 51))
> - total_sectors = (1ULL << 51);
> + if (total_sectors > GRUB_DISK_MAX_SECTORS)
> + total_sectors = GRUB_DISK_MAX_SECTORS;
>
> if ((total_sectors <= *sector
> || ((*offset + size + GRUB_DISK_SECTOR_SIZE - 1)
> diff --git a/include/grub/disk.h b/include/grub/disk.h
> index 1a9e8fcf4..0bf08091f 100644
> --- a/include/grub/disk.h
> +++ b/include/grub/disk.h
> @@ -157,6 +157,12 @@ struct grub_disk_memberlist
> typedef struct grub_disk_memberlist *grub_disk_memberlist_t;
> #endif
>
> +/*
> + Some drivers have problems with disks above reasonable sizes.
> + Set max disk size at 1EiB.
The comment is formatted incorrectly [1].
> +*/
> +#define GRUB_DISK_MAX_SECTORS (1ULL << (60 - 9))
> +
> /* The sector size. */
> #define GRUB_DISK_SECTOR_SIZE 0x200
> #define GRUB_DISK_SECTOR_BITS 9
Please move the constant below these definitions and do this:
#define GRUB_DISK_MAX_SECTORS (1ULL << (60 - GRUB_DISK_SECTOR_BITS))
[1] https://www.gnu.org/software/grub/manual/grub-dev/grub-dev.html#Comments