subscribe 526961 r...@ringlet.net reassign 526961 gcc-4.3 retitle 526961 -fPIE -pie generates corrupt executable on mips/mipsel severity 526961 normal thanks
Okay, as promised, I was able to isolate the problem to a minimal C program that exhibits the weird behavior. It turns out the problem is with gcc, not with the hardening wrapper; the wrapper simply runs the compiler with PIE options, triggering the failure. In short, for the gcc-4.3 team: if you compile the following short program on mipsel/unstable with -fPIE -pie and then try to run the resulting executable, it will segfault before even reaching the entry point of main(). This showed up as a FTBFS for the confget package on the mips and mipsel architectures; it was later confirmed by Jakub Wilk on a QEMU virtual machine in http://lists.debian.org/debian-mentors/2009/08/msg00163.html and today I managed to set up a QEMU virtual machine of my own and spent some time cutting up the confget code to the absolute minimum that segfaults upon execution. Here's the short program; see below for Debian package versions in my QEMU mipsel virtual machine. Note the "#if 1"; if you change that into "#if 0" and do not initialize the array element, everything will be fine, the program will run. With the "#if 1", compile the program with "cc -fPIE -pie -o cminimal cminimal.c"; running it will cause a segfault. #include <stdio.h> #include <string.h> typedef struct { const char *name; } confget_backend; confget_backend confget_ini_backend = { "ini", }; static confget_backend *backends[] = { #if 1 &confget_ini_backend, #else NULL, #endif }; /*** * Main routine */ int main(void) { printf("Hell world, backends is %p!\n", (void *)backends); return (0); } Here's the information that "reportbug gcc-4.3" would've included: Package: gcc-4.3 Version: 4.3.4-1 Severity: normal -- System Information: Debian Release: squeeze/sid APT prefers unstable APT policy: (990, 'unstable'), (300, 'testing') Architecture: mipsel (mips) Kernel: Linux 2.6.30-1-4kc-malta Locale: LANG=en_GB.UTF-8, LC_CTYPE=en_GB.UTF-8 (charmap=UTF-8) Shell: /bin/sh linked to /bin/dash Versions of packages gcc-4.3 depends on: ii binutils 2.19.51.20090805-1 The GNU assembler, linker and bina ii cpp-4.3 4.3.4-1 The GNU C preprocessor ii gcc-4.3-base 4.3.4-1 The GNU Compiler Collection (base ii libc6 2.9-24 GNU C Library: Shared libraries ii libgcc1 1:4.4.1-2 GCC support library ii libgomp1 4.4.1-2 GCC OpenMP (GOMP) support library Versions of packages gcc-4.3 recommends: ii libc6-dev 2.9-24 GNU C Library: Development Librari Versions of packages gcc-4.3 suggests: pn gcc-4.3-doc <none> (no description available) pn gcc-4.3-locales <none> (no description available) pn gcc-4.3-multilib <none> (no description available) pn libgcc1-dbg <none> (no description available) pn libgomp1-dbg <none> (no description available) pn libmudflap0-4.3-dev <none> (no description available) pn libmudflap0-dbg <none> (no description available) -- no debconf information Hope that helps! G'luck, Peter -- Peter Pentchev r...@ringlet.net r...@space.bg r...@freebsd.org PGP key: http://people.FreeBSD.org/~roam/roam.key.asc Key fingerprint FDBA FD79 C26F 3C51 C95E DF9E ED18 B68D 1619 4553 The rest of this sentence is written in Thailand, on
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