From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([209.51.188.92]:50240) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1h2Ece-0007Cf-7N for qemu-devel@nongnu.org; Fri, 08 Mar 2019 07:29:10 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1h2Eca-0003W9-Rk for qemu-devel@nongnu.org; Fri, 08 Mar 2019 07:29:07 -0500 From: Markus Armbruster References: <20190308062455.29755-1-armbru@redhat.com> <481d398a-e26c-6c0a-20b7-7466ae1ebf1f@redhat.com> Date: Fri, 08 Mar 2019 13:28:54 +0100 In-Reply-To: <481d398a-e26c-6c0a-20b7-7466ae1ebf1f@redhat.com> (Laszlo Ersek's message of "Fri, 8 Mar 2019 12:47:52 +0100") Message-ID: <875zsteeih.fsf@dusky.pond.sub.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Subject: Re: [Qemu-devel] [PATCH v7] pflash: Require backend size to match device, improve errors List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Laszlo Ersek Cc: qemu-devel@nongnu.org, kwolf@redhat.com, philmd@redhat.com, alex.bennee@linaro.org, qemu-block@nongnu.org, mreitz@redhat.com Laszlo Ersek writes: > On 03/08/19 07:24, Markus Armbruster wrote: >> From: Alex Benn=C3=A9e >>=20 >> We reject undersized backends with a rather enigmatic "failed to read >> the initial flash content" error. >>=20 >> 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. >>=20 >> 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". >>=20 >> Improve the error for actual read failures to "can't read initial >> flash content from block backend 'NAME'. >>=20 >> 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. >>=20 >> Signed-off-by: Alex Benn=C3=A9e >> Signed-off-by: Markus Armbruster >> --- >> hw/block/pflash_cfi01.c | 31 ++++++++++++++++++++++--------- >> hw/block/pflash_cfi02.c | 31 +++++++++++++++++++++++-------- >> 2 files changed, 45 insertions(+), 17 deletions(-) >>=20 >> 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 =3D sector_len_per_device * blocks_per_device; >>=20=20 >> - /* XXX: to be fixed */ >> -#if 0 >> - if (total_len !=3D (8 * 1024 * 1024) && total_len !=3D (16 * 1024 *= 1024) && >> - total_len !=3D (32 * 1024 * 1024) && total_len !=3D (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) >> } >>=20=20 >> 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. >> + */ >> + int64_t backing_len =3D 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 !=3D 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 =3D 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) >> } >>=20=20 >> chip_len =3D pfl->sector_len * pfl->nb_blocs; >> - /* XXX: to be fixed */ >> -#if 0 >> - if (total_len !=3D (8 * 1024 * 1024) && total_len !=3D (16 * 1024 *= 1024) && >> - total_len !=3D (32 * 1024 * 1024) && total_len !=3D (64 * 1024 = * 1024)) >> - return NULL; >> -#endif >>=20=20 >> 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) >> } >>=20=20 >> 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. >> + */ >> + int64_t backing_len =3D 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 !=3D 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 =3D 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; >> } >> } >>=20 > > This one has got to be one of the longest bike-shedding sessions! :) > > I'm fine with this patch, but I could suggest two improvements. > > (1) When blk_getlength() fails, we could format the negative error code > returned by it into the error message. I can do that. > (2) We could extract the common code to a new function in > "hw/block/block.c". (It says "Common code for block device models" on > the tin.) There's so much common code in these two files even before this patch... > I realize the vmstate_unregister_ram() rollbacks are not identical > between cfi01 and cfi02. However, that difference only draws my > attention to the fact that the unregister calls are not made on the > other error branches in this patch anyway! You're right, that needs fixing. > So we should have a common function like this: > > void pflash_cfi_read_initial_content(BlockBackend *blk, uint64_t size, > void *buf, Error **errp) > { > int64_t backing_len =3D blk_getlength(blk); > int ret; > > if (backing_len < 0) { > error_setg(...); > return; > } > > if (backing_len !=3D size) { > error_setg(...); > return; > } > > ret =3D blk_pread(blk, 0, buf, size); > if (ret < 0) { > error_setg(...); > } > } > > And at the call sites, we can do > > if (pfl->blk) { > Error *local_err =3D NULL; > > pflash_cfi_read_initial_content(pfl->blk, > total_len OR chip_len, > pfl->storage, > &local_err); > if (local_err) { > error_propagate(errp, local_err); > vmstate_unregister_ram(...); // as appropriate for cfiXX > return; > } > } I'll give it a try for v8. Thanks!