[Bug pch/45979] precompiled headers breakage on 2.6.36-rc Linux/ARM kernels

["mikpe at it dot uu.se" <gcc-bugzilla@gcc.gnu.org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45979

--- Comment #5 from Mikael Pettersson <mikpe at it dot uu.se> 2010-10-13 13:57:28 UTC ---
(In reply to comment #1)
> Most likely when the linux arm kernel decided to randomize the heap.

Confirmed.  Bisection of the kernel identified:

From: Nicolas Pitre <nico@fluxnic.net>
Date: Tue, 15 Jun 2010 01:16:19 +0000 (-0400)
Subject: [ARM] add address randomization to mmap()
X-Git-Tag: v2.6.36-rc1~591^2^2~6^2~2
X-Git-Url:
http://git.kernel.org/?p=linux%2Fkernel%2Fgit%2Ftorvalds%2Flinux-2.6.git;a=commitdiff_plain;h=cc92c28b2db5b406657ecc05235d4ca4e222ae34

[ARM] add address randomization to mmap()

Signed-off-by: Nicolas Pitre <nicolas.pitre@linaro.org>
---

diff --git a/arch/arm/mm/mmap.c b/arch/arm/mm/mmap.c
index f5abc51..4f5b396 100644
--- a/arch/arm/mm/mmap.c
+++ b/arch/arm/mm/mmap.c
@@ -7,6 +7,7 @@
 #include <linux/shm.h>
 #include <linux/sched.h>
 #include <linux/io.h>
+#include <linux/random.h>
 #include <asm/cputype.h>
 #include <asm/system.h>

@@ -80,6 +81,9 @@ arch_get_unmapped_area(struct file *filp, unsigned long addr,
                start_addr = addr = TASK_UNMAPPED_BASE;
                mm->cached_hole_size = 0;
        }
+       /* 8 bits of randomness in 20 address space bits */
+       if (current->flags & PF_RANDOMIZE)
+               addr += (get_random_int() % (1 << 8)) << PAGE_SHIFT;

 full_search:
        if (do_align)

as the cause of this regression.  Still, I think the kernel is Ok and it's
really gcc's pch implementation which is broken.