From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from out30-44.freemail.mail.aliyun.com (out30-44.freemail.mail.aliyun.com [115.124.30.44]) by sourceware.org (Postfix) with ESMTPS id A92E5385800E for ; Fri, 10 Dec 2021 02:34:32 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org A92E5385800E X-Alimail-AntiSpam: AC=PASS; BC=-1|-1; BR=01201311R171e4; CH=green; DM=||false|; DS=||; FP=0|-1|-1|-1|0|-1|-1|-1; HT=e01e04407; MF=rongwei.wang@linux.alibaba.com; NM=1; PH=DS; RN=5; SR=0; TI=SMTPD_---0V-6vx.G_1639103669; Received: from 30.240.97.30(mailfrom:rongwei.wang@linux.alibaba.com fp:SMTPD_---0V-6vx.G_1639103669) by smtp.aliyun-inc.com(127.0.0.1); Fri, 10 Dec 2021 10:34:29 +0800 Message-ID: <089187bb-37d0-e518-5856-e0ede3412eba@linux.alibaba.com> Date: Fri, 10 Dec 2021 10:34:26 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:95.0) Gecko/20100101 Thunderbird/95.0 Subject: Re: [PATCH v4] elf: Properly align PT_LOAD segments [BZ #28676] Content-Language: en-US To: "H.J. Lu" Cc: GNU C Library , Florian Weimer , xuyu@linux.alibaba.com, gavin.dg@linux.alibaba.com References: <20211209055719.56245-1-rongwei.wang@linux.alibaba.com> <20211209055719.56245-2-rongwei.wang@linux.alibaba.com> <969ebb3d-a960-9dde-fd2a-e157cccb5b1b@linux.alibaba.com> From: Rongwei Wang In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Spam-Status: No, score=-21.7 required=5.0 tests=BAYES_00, ENV_AND_HDR_SPF_MATCH, GIT_PATCH_0, KAM_DMARC_STATUS, NICE_REPLY_A, RCVD_IN_DNSWL_NONE, SPF_HELO_NONE, SPF_PASS, TXREP, UNPARSEABLE_RELAY, USER_IN_DEF_SPF_WL autolearn=ham autolearn_force=no version=3.4.4 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on server2.sourceware.org X-BeenThere: libc-alpha@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Libc-alpha mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 10 Dec 2021 02:34:35 -0000 On 12/10/21 10:24 AM, H.J. Lu wrote: > On Thu, Dec 9, 2021 at 5:58 PM Rongwei Wang > wrote: >> >> >> Hi, lhj >> >> Thanks for your help! It's much better than my version. >> And I find a small bug. you can check it again if available. >> >> On 12/10/21 3:29 AM, H.J. Lu wrote: >>> On Thu, Dec 09, 2021 at 10:04:32AM -0800, H.J. Lu wrote: >>>> On Thu, Dec 09, 2021 at 07:14:10AM -0800, H.J. Lu wrote: >>>> >>>> Hi, >>>> >>>> I updated your patch. Please take a look. >>>> >>>> >>>> H.J. >>>> -- >>>> When PT_LOAD segment alignment > the page size, allocate enough space >>>> to ensure that the segment can be properly aligned. >>>> >>>> This fixes [BZ #28676]. >>> >>> >>> H.J. >>> --- >>> Changes in v4: >>> >>> 1. Call unmap when the second mmap fails. >>> >>> When PT_LOAD segment alignment > the page size, allocate enough space >>> to ensure that the segment can be properly aligned. >>> >>> This fixes [BZ #28676]. >>> --- >>> elf/dl-load.c | 1 + >>> elf/dl-load.h | 2 +- >>> elf/dl-map-segments.h | 49 +++++++++++++++++++++++++++++++++++++++---- >>> 3 files changed, 47 insertions(+), 5 deletions(-) >>> >>> diff --git a/elf/dl-load.c b/elf/dl-load.c >>> index bf8957e73c..9a23590bf4 100644 >>> --- a/elf/dl-load.c >>> +++ b/elf/dl-load.c >>> @@ -1150,6 +1150,7 @@ _dl_map_object_from_fd (const char *name, const char *origname, int fd, >>> c->mapend = ALIGN_UP (ph->p_vaddr + ph->p_filesz, GLRO(dl_pagesize)); >>> c->dataend = ph->p_vaddr + ph->p_filesz; >>> c->allocend = ph->p_vaddr + ph->p_memsz; >>> + c->mapalign = ph->p_align; >>> c->mapoff = ALIGN_DOWN (ph->p_offset, GLRO(dl_pagesize)); >>> >>> /* Determine whether there is a gap between the last segment >>> diff --git a/elf/dl-load.h b/elf/dl-load.h >>> index e329d49a81..c121e3456c 100644 >>> --- a/elf/dl-load.h >>> +++ b/elf/dl-load.h >>> @@ -74,7 +74,7 @@ ELF_PREFERRED_ADDRESS_DATA; >>> Its details have been expanded out and converted. */ >>> struct loadcmd >>> { >>> - ElfW(Addr) mapstart, mapend, dataend, allocend; >>> + ElfW(Addr) mapstart, mapend, dataend, allocend, mapalign; >>> ElfW(Off) mapoff; >>> int prot; /* PROT_* bits. */ >>> }; >>> diff --git a/elf/dl-map-segments.h b/elf/dl-map-segments.h >>> index f9fb110ee3..f710cf2e48 100644 >>> --- a/elf/dl-map-segments.h >>> +++ b/elf/dl-map-segments.h >>> @@ -18,6 +18,50 @@ >>> >>> #include >>> >>> +/* Map a segment and align it properly. */ >>> + >>> +static __always_inline ElfW(Addr) >>> +_dl_map_segment (const struct loadcmd *c, ElfW(Addr) mappref, >>> + const size_t maplength, int fd) >>> +{ >>> + if (__glibc_likely (c->mapalign <= GLRO(dl_pagesize))) >>> + return (ElfW(Addr)) __mmap ((void *) mappref, maplength, c->prot, >>> + MAP_COPY|MAP_FILE, fd, c->mapoff); >>> + >>> + /* If the segment alignment > the page size, allocate enough space to >>> + ensure that the segment can be properly aligned. */ >>> + ElfW(Addr) maplen = (maplength >= c->mapalign >>> + ? (maplength + c->mapalign) >>> + : (2 * c->mapalign)); >>> + ElfW(Addr) map_start = (ElfW(Addr)) __mmap ((void *) mappref, maplen, >>> + PROT_NONE, >>> + MAP_ANONYMOUS|MAP_PRIVATE, >>> + -1, 0); >>> + if (__glibc_unlikely ((void *) map_start == MAP_FAILED)) >>> + return map_start; >>> + >>> + ElfW(Addr) map_start_aligned = ALIGN_UP (map_start, c->mapalign); >>> + map_start_aligned = (ElfW(Addr)) __mmap ((void *) map_start_aligned, >>> + maplength, c->prot, >>> + MAP_COPY|MAP_FILE|MAP_FIXED, >>> + fd, c->mapoff); >>> + if (__glibc_unlikely ((void *) map_start == MAP_FAILED)) >> Is map_start_aligned here? >> >>> + __munmap ((void *) map_start, maplen); >>> + else >>> + { >>> + /* Unmap the unused regions. */ >>> + ElfW(Addr) delta = map_start_aligned - map_start; >>> + if (delta) >>> + __munmap ((void *) map_start, delta); >>> + ElfW(Addr) map_end = map_start_aligned + maplength; >>> + delta = map_start + maplen - map_end; >>> + if (delta) >>> + __munmap ((void *) map_end, delta); >>> + } >>> + >>> + return map_start_aligned; >>> +} >>> + >>> /* This implementation assumes (as does the corresponding implementation >>> of _dl_unmap_segments, in dl-unmap-segments.h) that shared objects >>> are always laid out with all segments contiguous (or with gaps >>> @@ -53,10 +97,7 @@ _dl_map_segments (struct link_map *l, int fd, >>> - MAP_BASE_ADDR (l)); >>> >>> /* Remember which part of the address space this object uses. */ >>> - l->l_map_start = (ElfW(Addr)) __mmap ((void *) mappref, maplength, >>> - c->prot, >>> - MAP_COPY|MAP_FILE, >>> - fd, c->mapoff); >>> + l->l_map_start = _dl_map_segment (c, mappref, maplength, fd); >>> if (__glibc_unlikely ((void *) l->l_map_start == MAP_FAILED)) >>> return DL_MAP_SEGMENTS_ERROR_MAP_SEGMENT; >>> >>> >> All is OK for me. >> >> And I am not sure whether I need to add a testcase in one new patch, >> because I saw you had submitted the testcase: >> https://gitlab.com/x86-glibc/glibc/-/commit/ba63c1cb2ea1b0ae421f66756771ff4c89d4a470 > > No, I didn't submit it. > >> I will test it again, and send out PATCH v5. > > Please include my testcase in your v5 patch. Ok Thanks. > > Thanks. > > > -- > H.J. >