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Tue, 19 Aug 2025 10:56:35 +0000 (UTC) Received: from redhat.com (unknown [10.42.28.237]) by mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id E8EBF195419F; Tue, 19 Aug 2025 10:56:32 +0000 (UTC) Date: Tue, 19 Aug 2025 11:56:29 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= Cc: Markus Armbruster , qemu-devel@nongnu.org, odaki@rsg.ci.i.u-tokyo.ac.jp, marcandre.lureau@redhat.com, Richard Henderson Subject: Re: [PATCH 02/12] tcg: Fix error reporting on mprotect() failure in tcg_region_init() Message-ID: References: <20250808080823.2638861-1-armbru@redhat.com> <20250808080823.2638861-3-armbru@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/2.2.14 (2025-02-20) X-Scanned-By: MIMEDefang 3.0 on 10.30.177.17 Received-SPF: pass client-ip=170.10.133.124; envelope-from=berrange@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.001, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Fri, Aug 08, 2025 at 04:00:42PM +0200, Philippe Mathieu-Daudé wrote: > Hi Markus, > > On 8/8/25 10:08, Markus Armbruster wrote: > > tcg_region_init() calls one of qemu_mprotect_rwx(), > > qemu_mprotect_rw(), and mprotect(), then reports failure with > > error_setg_errno(&error_fatal, errno, ...). > > > > The use of &error_fatal is undesirable. qapi/error.h advises: > > > > * Please don't error_setg(&error_fatal, ...), use error_report() and > > * exit(), because that's more obvious. > > > > The use of errno is wrong. qemu_mprotect_rwx() and qemu_mprotect_rw() > > wrap around qemu_mprotect__osdep(). qemu_mprotect__osdep() calls > > mprotect() on POSIX, VirtualProtect() on Windows, and reports failure > > with error_report(). VirtualProtect() doesn't set errno. mprotect() > > does, but error_report() may clobber it. > > > > Fix tcg_region_init() to report errors only when it calls mprotect(), > > and rely on qemu_mprotect_rwx()'s and qemu_mprotect_rw()'s error > > reporting otherwise. Use error_report(), not error_setg(). > > > > Fixes: 22c6a9938f75 (tcg: Merge buffer protection and guard page protection) > > Fixes: 6bc144237a85 (tcg: Use Error with alloc_code_gen_buffer) > > Cc: Richard Henderson > > Signed-off-by: Markus Armbruster > > --- > > tcg/region.c | 8 ++++++-- > > 1 file changed, 6 insertions(+), 2 deletions(-) > > > > diff --git a/tcg/region.c b/tcg/region.c > > index 7ea0b37a84..74e3b4b774 100644 > > --- a/tcg/region.c > > +++ b/tcg/region.c > > @@ -832,13 +832,17 @@ void tcg_region_init(size_t tb_size, int splitwx, unsigned max_threads) > > } else { > > #ifdef CONFIG_POSIX > > rc = mprotect(start, end - start, need_prot); > > + if (rc) { > > + error_report("mprotect of jit buffer: %s", > > + strerror(errno)); > > + } > > + > > #else > > g_assert_not_reached(); > > #endif > > } > > if (rc) { > > - error_setg_errno(&error_fatal, errno, > > - "mprotect of jit buffer"); > > + exit(1); > > - Before: > > Error displayed when qemu_mprotect_rwx/qemu_mprotect_rw/mprotect fail, > then exit. > > - After: > > Error only displayed when mprotect() fails, then exit. > Nothing displayed when qemu_mprotect_rwx() or qemu_mprotect_rw() failed, > and exit. Check the impl in qemu_mprotect__osdep - it calls error_report already, so those code paths didn't need to be changedin this patch. With regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|