From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([209.51.188.92]:58054) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1h2Gfh-0004H7-9c for qemu-devel@nongnu.org; Fri, 08 Mar 2019 09:40:27 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1h2Gfd-0003sr-Cf for qemu-devel@nongnu.org; Fri, 08 Mar 2019 09:40:25 -0500 Received: from mail-wm1-f66.google.com ([209.85.128.66]:39392) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1h2Gfb-0003aw-AT for qemu-devel@nongnu.org; Fri, 08 Mar 2019 09:40:19 -0500 Received: by mail-wm1-f66.google.com with SMTP id z84so12617370wmg.4 for ; Fri, 08 Mar 2019 06:40:17 -0800 (PST) References: <20190308062455.29755-1-armbru@redhat.com> <481d398a-e26c-6c0a-20b7-7466ae1ebf1f@redhat.com> From: =?UTF-8?Q?Philippe_Mathieu-Daud=c3=a9?= Message-ID: <026c2176-66a1-5818-15d4-23b1ab4a004b@redhat.com> Date: Fri, 8 Mar 2019 15:40:15 +0100 MIME-Version: 1.0 In-Reply-To: <481d398a-e26c-6c0a-20b7-7466ae1ebf1f@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit 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 , Markus Armbruster , qemu-devel@nongnu.org Cc: alex.bennee@linaro.org, kwolf@redhat.com, mreitz@redhat.com, qemu-block@nongnu.org On 3/8/19 12:47 PM, Laszlo Ersek wrote: > On 03/08/19 07:24, Markus Armbruster wrote: >> From: Alex Bennée >> >> 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 >> Signed-off-by: Markus Armbruster >> --- >> 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. >> + */ >> + 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. >> + */ >> + 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; >> } >> } >> > > 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. This one is a worthwhile a v8. > (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.) Good idea, but I'd postpone that for the next dev cycle. > 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! > > 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 = blk_getlength(blk); > int ret; > > if (backing_len < 0) { > error_setg(...); > return; > } > > if (backing_len != size) { > error_setg(...); > return; > } > > ret = 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 = 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; > } > } > > Thanks > Laszlo >