[PATCH] [ASan] Fix stack-overflow.cc test on PowerPC64 Linux

[Jay Foad]

In http://reviews.llvm.org/D6777#105104, @foad wrote:

> Here's my current theory about what's going wrong with /proc/maps:
>
> 1. Whenever the kernel allocates some stack memory, it also tries to allocate an extra guard page just before the stack. But this can fail, e.g. if you have already reached RLIMIT_STACK. See mm/memory.c:check_stack_guard_page(), which calls mm/mmap.c:expand_downwards(), which calls acct_stack_growth() to check the rlimits.
> 2. /proc/maps adjusts the start address of a stack mapping so as not to include the guard page, but it does this unconditionally, even if the attempt to allocate a guard page failed. See fs/proc/task_mmu.c:show_map_vma().


I've reported this to the kernel people here: http://lkml.iu.edu//hypermail/linux/kernel/1501.0/01025.html


http://reviews.llvm.org/D6777

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