From patchwork Wed Feb 26 21:41:23 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Florian Weimer X-Patchwork-Id: 38334 Received: (qmail 81187 invoked by alias); 26 Feb 2020 21:43:05 -0000 Mailing-List: contact libc-alpha-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Unsubscribe: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: libc-alpha-owner@sourceware.org Delivered-To: mailing list libc-alpha@sourceware.org Received: (qmail 80102 invoked by uid 89); 26 Feb 2020 21:43:04 -0000 Authentication-Results: sourceware.org; auth=none X-Spam-SWARE-Status: No, score=-16.4 required=5.0 tests=AWL, BAYES_00, GIT_PATCH_0, GIT_PATCH_1, GIT_PATCH_2, GIT_PATCH_3, SPF_PASS autolearn=ham version=3.3.1 spammy=H*r:TLS1.2 X-HELO: albireo.enyo.de From: Florian Weimer To: Joseph Myers Cc: Florian Weimer , , , Patsy Griffin Subject: Re: [PATCH] elf: Apply attribute_relro to pointers in elf/dl-minimal.c References: <87tv3d2x91.fsf@oldenburg2.str.redhat.com> Date: Wed, 26 Feb 2020 22:41:23 +0100 In-Reply-To: (Joseph Myers's message of "Wed, 26 Feb 2020 21:23:49 +0000") Message-ID: <87a75558n0.fsf@mid.deneb.enyo.de> MIME-Version: 1.0 * Joseph Myers: > This change (commit 758599bc9dcc5764e862bd9e1613c5d1e6efc5d3) breaks the > build for alpha-linux-gnu with GCC and binutils mainline. I get a series > of errors of the form (this is in the "compilers" glibc build): > > /scratch/jmyers/glibc/many10/build/compilers/alpha-linux-gnu/glibc/alpha-linux-gnu/elf/librtld.os: > in function `calloc': > /scratch/jmyers/glibc/many10/src/glibc/elf/../include/rtld-malloc.h:44:(.text+0xd98): > relocation truncated to fit: GPREL16 against symbol `__rtld_calloc' > defined in .data.rel.ro section in > /scratch/jmyers/glibc/many10/build/compilers/alpha-linux-gnu/glibc/alpha-linux-gnu/elf/librtld.os > /scratch/jmyers/glibc/many10/build/compilers/alpha-linux-gnu/glibc/alpha-linux-gnu/elf/librtld.os: > in function `malloc': > /scratch/jmyers/glibc/many10/src/glibc/elf/../include/rtld-malloc.h:56:(.text+0x2978): > relocation truncated to fit: GPREL16 against symbol `__rtld_malloc' > defined in .data.rel.ro section in > /scratch/jmyers/glibc/many10/build/compilers/alpha-linux-gnu/glibc/alpha-linux-gnu/elf/librtld.os I don't know much about alpha unfortunately. Running this $ objdump -d --reloc /lib/ld-linux.so.2 | grep -E 'lda\s.*gp,' on a default build (not mainline, so successful) gives me what I assume are GP-relative load instructions ranging from 9ff4: 40 80 bd 23 lda gp,-32704(gp) to a040: f4 7f bd 23 lda gp,32756(gp) That seems to be rather close to the 64 KiB displacement that alpha apparently supports. This suggests me that we aren't hitting a bug as such, but that we were already rather near the limit before, and the additional PLT avoidance that the patch brought finally moved us across the limit. Would it be acceptable to switch from -fpic to -fPIC to fix this (if it addresses the issue)? diff --git a/sysdeps/alpha/Makefile b/sysdeps/alpha/Makefile index da52c1d4d1..baf5d480e5 100644 --- a/sysdeps/alpha/Makefile +++ b/sysdeps/alpha/Makefile @@ -57,10 +57,6 @@ endif # "current" rounding mode, and it's easiest to set this with all of them. sysdep-CFLAGS += -mieee -mfp-rounding-mode=d -# libc.so requires about 16k for the small data area, which is well -# below the 64k maximum. -pic-ccflag = -fpic - # Software floating-point emulation. ifeq ($(subdir),soft-fp)