Re: [Qemu-devel] [PATCH v7] pflash: Require backend size to match device, improve errors

[Alex Bennée]

Markus Armbruster <address@hidden> writes:

> From: Alex Bennée <address@hidden>
>
> We reject undersized backends with a rather enigmatic "failed to read
> the initial flash content" error.
>
> We happily accept oversized images, ignoring their tail.  Throwing
> away parts of firmware that way is pretty much certain to end in an
> even more enigmatic failure to boot.
>
> Require the backend's size to match the device's size exactly.  Report
> mismatch as "device requires N bytes, block backend 'NAME' provides M
> bytes".
>
> Improve the error for actual read failures to "can't read initial
> flash content from block backend 'NAME'.
>
> We disabled code to limit device sizes to 8, 16, 32 or 64MiB more than
> a decade ago in commit 95d1f3edd5e and c8b153d7949, v0.9.1.  Bury.
>
> Signed-off-by: Alex Bennée <address@hidden>
> Signed-off-by: Markus Armbruster <address@hidden>
> ---
>  hw/block/pflash_cfi01.c | 31 ++++++++++++++++++++++---------
>  hw/block/pflash_cfi02.c | 31 +++++++++++++++++++++++--------
>  2 files changed, 45 insertions(+), 17 deletions(-)
>
> diff --git a/hw/block/pflash_cfi01.c b/hw/block/pflash_cfi01.c
> index 9d1c356eb6..2e3a05c0b3 100644
> --- a/hw/block/pflash_cfi01.c
> +++ b/hw/block/pflash_cfi01.c
> @@ -730,13 +730,6 @@ static void pflash_cfi01_realize(DeviceState *dev, Error 
> **errp)
>      }
>      device_len = sector_len_per_device * blocks_per_device;
>
> -    /* XXX: to be fixed */
> -#if 0
> -    if (total_len != (8 * 1024 * 1024) && total_len != (16 * 1024 * 1024) &&
> -        total_len != (32 * 1024 * 1024) && total_len != (64 * 1024 * 1024))
> -        return NULL;
> -#endif
> -
>      memory_region_init_rom_device(
>          &pfl->mem, OBJECT(dev),
>          &pflash_cfi01_ops,
> @@ -763,12 +756,32 @@ static void pflash_cfi01_realize(DeviceState *dev, 
> Error **errp)
>      }
>
>      if (pfl->blk) {
> +        /*
> +         * Validate the backing store is the right size for pflash
> +         * devices. If the user supplies a larger file we ignore the
> +         * tail.
> +         */

We need to drop the last sentence...

> +        int64_t backing_len = blk_getlength(pfl->blk);
> +
> +        if (backing_len < 0) {
> +            error_setg(errp, "can't get size of block backend '%s'",
> +                       blk_name(pfl->blk));
> +            return;
> +        }
> +        if (backing_len != total_len) {
> +            error_setg(errp, "device requires %" PRIu64 " bytes, "
> +                       "block backend '%s' provides %" PRIu64 " bytes",
> +                       total_len, blk_name(pfl->blk), backing_len);
> +            return;
> +        }
> +
>          /* read the initial flash content */
>          ret = blk_pread(pfl->blk, 0, pfl->storage, total_len);
> -
>          if (ret < 0) {
>              vmstate_unregister_ram(&pfl->mem, DEVICE(pfl));
> -            error_setg(errp, "failed to read the initial flash content");
> +            error_setg(errp, "can't read initial flash content"
> +                       " from block backend '%s'",
> +                       blk_name(pfl->blk));
>              return;
>          }
>      }
> diff --git a/hw/block/pflash_cfi02.c b/hw/block/pflash_cfi02.c
> index 33779ce807..45b88d65d8 100644
> --- a/hw/block/pflash_cfi02.c
> +++ b/hw/block/pflash_cfi02.c
> @@ -550,12 +550,6 @@ static void pflash_cfi02_realize(DeviceState *dev, Error 
> **errp)
>      }
>
>      chip_len = pfl->sector_len * pfl->nb_blocs;
> -    /* XXX: to be fixed */
> -#if 0
> -    if (total_len != (8 * 1024 * 1024) && total_len != (16 * 1024 * 1024) &&
> -        total_len != (32 * 1024 * 1024) && total_len != (64 * 1024 * 1024))
> -        return NULL;
> -#endif
>
>      memory_region_init_rom_device(&pfl->orig_mem, OBJECT(pfl), pfl->be ?
>                                    &pflash_cfi02_ops_be : 
> &pflash_cfi02_ops_le,
> @@ -581,11 +575,32 @@ static void pflash_cfi02_realize(DeviceState *dev, 
> Error **errp)
>      }
>
>      if (pfl->blk) {
> +        /*
> +         * Validate the backing store is the right size for pflash
> +         * devices. If the user supplies a larger file we ignore the
> +         * tail.
> +         */

And here.

> +        int64_t backing_len = blk_getlength(pfl->blk);
> +
> +        if (backing_len < 0) {
> +            error_setg(errp, "can't get size of block backend '%s'",
> +                       blk_name(pfl->blk));
> +            return;
> +        }
> +        if (backing_len != chip_len) {
> +            error_setg(errp, "device requires %" PRIu32 " bytes, "
> +                       "block backend '%s' provides %" PRIu64 " bytes",
> +                       chip_len, blk_name(pfl->blk), backing_len);
> +            return;
> +        }
> +
>          /* read the initial flash content */
>          ret = blk_pread(pfl->blk, 0, pfl->storage, chip_len);
>          if (ret < 0) {
> -            vmstate_unregister_ram(&pfl->orig_mem, DEVICE(pfl));
> -            error_setg(errp, "failed to read the initial flash content");
> +            vmstate_unregister_ram(&pfl->mem, DEVICE(pfl));
> +            error_setg(errp, "can't read initial flash content"
> +                       " from block backend '%s'",
> +                       blk_name(pfl->blk));
>              return;
>          }
>      }

Otherwise all good... not that a r-b means anything from me ;-)

--
Alex Bennée