On 27 June 2017 at 19:05, Richard Henderson <r...@twiddle.net> wrote: > On 06/27/2017 09:49 AM, Peter Maydell wrote: >> >> The 32-bit PPC auxv is a bit complicated because in the >> mists of time it used to be 16-aligned rather than directly >> after the environment. Older glibc versions had code to >> try to probe for whether it needed alignment or not: >> >> https://sourceware.org/git/?p=glibc.git;a=blob;f=sysdeps/unix/sysv/linux/powerpc/dl-sysdep.c;hb=e84eabb3871c9b39e59323bf3f6b98c2ca9d1cd0 >> and the kernel has code which puts some magic entries at >> the bottom to ensure that the alignment probe fails: >> >> http://elixir.free-electrons.com/linux/latest/source/arch/powerpc/include/asm/elf.h#L158 >> >> QEMU has similar code too, but it was broken by commit >> 7c4ee5bcc82e64, which changed elfload.c from filling in >> the auxv starting at the highest address and working down >> to starting at the lowest address and working up. This >> means that the ARCH_DLINFO hook must now be invoked first >> rather than last, and the entries in it for PPC must >> be reversed so that the magic AT_IGNOREPPC entries come >> at the lowest address in the auxv as they should. >> >> The effect of this was that if running a guest binary that >> used an old glibc with the alignment probing the guest ld.so >> code would segfault if the size of the guest environment and >> argv happened to put the auxv at an address that triggered >> the alignment code in the guest glibc. >> >> Signed-off-by: Peter Maydell<peter.mayd...@linaro.org> >> --- >> linux-user/elfload.c | 23 ++++++++++++----------- >> 1 file changed, 12 insertions(+), 11 deletions(-) > > > Reviewed-by: Richard Henderson <r...@twiddle.net> > Tested-by: Richard Henderson <r...@twiddle.net>
Thanks; applied directly to master since this has been causing my mergebuild tests to fail (some recent environment change result in it triggering this week...) thanks -- PMM
