linux-user: Put PPC AT_IGNOREPPC auxv entries in the right place
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 7c4ee5bc, 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: NPeter Maydell <peter.maydell@linaro.org> Reviewed-by: NRichard Henderson <rth@twiddle.net> Tested-by: NRichard Henderson <rth@twiddle.net> Message-id: 1498582198-6649-1-git-send-email-peter.maydell@linaro.org
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