On Tue, 2017-07-04 at 16:31 -0700, Linus Torvalds wrote: > On Tue, Jul 4, 2017 at 4:01 PM, Ben Hutchings <b...@decadent.org.uk> > wrote: > > > > We have: > > > > bottom = 0xff803fff > > sp = 0xffffb178 > > > > The relevant mappings are: > > > > ff7fc000-ff7fd000 rwxp 00000000 00:00 0 > > fffdd000-ffffe000 rw-p 00000000 00:00 > > 0 [stack] > > Ugh. So that stack is actually 8MB in size, but the alloca() is about > to use up almost all of it, and there's only about 28kB left between > "bottom" and that 'rwx' mapping. > > Still, that rwx mapping is interesting: it is a single page, and it > really is almost exactly 8MB below the stack. > > In fact, the top of stack (at 0xffffe000) is *exactly* 8MB+4kB from > the top of that odd one-page allocation (0xff7fd000). > > Can you find out where that is allocated? Perhaps a breakpoint on > mmap, with a condition to catch that particular one? [...]
Found it, and it's now clear why only i386 is affected: http://hg.openjdk.java.net/jdk8/jdk8/hotspot/file/tip/src/os/linux/vm/os_linux.cpp#l4852 http://hg.openjdk.java.net/jdk8/jdk8/hotspot/file/tip/src/os_cpu/linux_x86/vm/os_linux_x86.cpp#l881 Ben. -- Ben Hutchings Anthony's Law of Force: Don't force it, get a larger hammer.
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