[Bug sanitizer/64435] [5 Regression] Bootstrap failure in libsanitizer on AArch64 with Linux kernel <= 3.15

["jakub at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64435

--- Comment #14 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
And the reason why at least in RHEL and Fedora asan doesn't work at all is:
cat /proc/self/maps; ASAN_OPTIONS=verbosity=1 ./null-deref-1.exe
00400000-00410000 r-xp 00000000 fd:00 134631897                         
/usr/bin/cat
00410000-00420000 r--p 00000000 fd:00 134631897                         
/usr/bin/cat
00420000-00430000 rw-p 00010000 fd:00 134631897                         
/usr/bin/cat
142c0000-142f0000 rw-p 00000000 00:00 0                                  [heap]
3ff929d0000-3ff99270000 r--p 00000000 fd:00 4086                        
/usr/lib/locale/locale-archive
3ff99270000-3ff993d0000 r-xp 00000000 fd:00 203072141                   
/usr/lib64/libc-2.17.so
3ff993d0000-3ff993e0000 r--p 00150000 fd:00 203072141                   
/usr/lib64/libc-2.17.so
3ff993e0000-3ff993f0000 rw-p 00160000 fd:00 203072141                   
/usr/lib64/libc-2.17.so
3ff99410000-3ff99420000 r--p 00000000 00:00 0                            [vvar]
3ff99420000-3ff99430000 r-xp 00000000 00:00 0                            [vdso]
3ff99430000-3ff99450000 r-xp 00000000 fd:00 201341988                   
/usr/lib64/ld-2.17.so
3ff99450000-3ff99460000 r--p 00010000 fd:00 201341988                   
/usr/lib64/ld-2.17.so
3ff99460000-3ff99470000 rw-p 00020000 fd:00 201341988                   
/usr/lib64/ld-2.17.so
3fff0680000-3fff06b0000 rw-p 00000000 00:00 0                           
[stack]
==2862==Parsed ASAN_OPTIONS: verbosity=1
==2862==AddressSanitizer: libc interceptors initialized
|| `[0x002000000000, 0x007fffffffff]` || HighMem    ||
|| `[0x001400000000, 0x001fffffffff]` || HighShadow ||
|| `[0x001200000000, 0x0013ffffffff]` || ShadowGap  ||
|| `[0x001000000000, 0x0011ffffffff]` || LowShadow  ||
|| `[0x000000000000, 0x000fffffffff]` || LowMem     ||
MemToShadow(shadow): 0x001200000000 0x00123fffffff 0x001280000000
0x0013ffffffff
redzone=16
max_redzone=2048
quarantine_size=256M
malloc_context_size=30
SHADOW_SCALE: 3
SHADOW_GRANULARITY: 8
SHADOW_OFFSET: 1000000000
==2862==Installed the sigaction for signal 11
==2862==AddressSanitizer CHECK failed:
../../../../libsanitizer/asan/asan_poisoning.cc:24 "((AddrIsInMem(addr))) !=
(0)" (0x0, 0x0)

https://github.com/torvalds/linux/blob/master/arch/arm64/include/asm/memory.h
https://github.com/torvalds/linux/blob/master/arch/arm64/Kconfig
reveals that aarch64 can be on Linux configured to support 39, 42 or 48 bits
virtual address space.  The current libsanitizer/asan/ and
gcc/config/aarch64/aarch64.c (aarch64_asan_shadow_offset) seems to be okay only
for the 39 bits virtual address space, while Fedora/RHEL apparently use 42 bits
VA.  Wonder if aarch64 couldn't use a layout closer to what x86_64 uses for
asan, with shadow offset low 0x7fff8000, which is flexible to different sizes
of the virtual address space.