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[Jeremy Kerr <jk@xxxxxxxxxx>]

Looks like I can trip this with any glibc version, using the attached
testcase.

Basically, this does an anoymous mmap, then a cacheflush on the address
returned from the mmap. We get an oops from the cacheflush on the actual
coprocessor instruction:

        mcr     p15, 0, r0, c7, c11, 1

- r0 is the start address given to cacheflush, and will be the address
which we see the invalid paging operation on.

I'm unsure why this instruction is generating an access to this address.

** Attachment added: "Testcase to trigger oops"
   https://bugs.launchpad.net/ubuntu/+source/eglibc/+bug/605042/+attachment/1848731/+files/test.c

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https://bugs.launchpad.net/bugs/605042

Title:
  [armel] java fails to start with eglibc-2.12-0ubuntu4

Status in Linaro Toolchain Miscellanies:
  Confirmed
Status in Release Notes for Ubuntu:
  New
Status in “eglibc” package in Ubuntu:
  Triaged
Status in “linux-fsl-imx51” package in Ubuntu:
  Invalid
Status in “openjdk-6” package in Ubuntu:
  Invalid
Status in “eglibc” source package in Lucid:
  Invalid
Status in “linux-fsl-imx51” source package in Lucid:
  Confirmed
Status in “openjdk-6” source package in Lucid:
  Invalid
Status in “eglibc” source package in Maverick:
  Triaged
Status in “linux-fsl-imx51” source package in Maverick:
  Invalid
Status in “openjdk-6” source package in Maverick:
  Invalid
Status in “eglibc” source package in Natty:
  Triaged
Status in “linux-fsl-imx51” source package in Natty:
  Invalid
Status in “openjdk-6” source package in Natty:
  Invalid
Status in “eglibc” package in Debian:
  Unknown

Bug description:
  reverting back to eglibc-2.12-0ubuntu3 works around the problem

  $ strace java -version
  [...]
  access("/etc/ld.so.nohwcap", F_OK)      = -1 ENOENT (No such file or directory)
  open("/lib/libm.so.6", O_RDONLY)        = 3
  read(3, "\177ELF\1\1\1\0\0\0\0\0\0\0\0\0\3\0(\0\1\0\0\0\3701\0\0004\0\0\0"..., 512) = 512
  fstat64(3, {st_mode=S_IFREG|0644, st_size=407156, ...}) = 0
  mmap2(NULL, 438440, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x40424000
  mprotect(0x40487000, 28672, PROT_NONE)  = 0
  mmap2(0x4048e000, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x62) = 0x4048e000
  close(3)                                = 0
  mprotect(0x4048e000, 4096, PROT_READ)   = 0
  mprotect(0x40169000, 2572288, PROT_READ|PROT_WRITE) = 0
  mprotect(0x40169000, 2572288, PROT_READ|PROT_EXEC) = 0
  cacheflush(0x40169000, 0x403dd000, 0, 0x40169000, 0x19448 <unfinished ...>
  +++ killed by SIGSEGV +++
  Segmentation fault

  Unable to handle kernel paging request at virtual address 401a1000
  pgd = cd108000
  [401a1000] *pgd=99a5b031, *pte=00000000, *ppte=00000000
  Internal error: Oops: 817 [#4455]
  Modules linked in: ov3640_camera v4l2_int_device uio_pdrv_genirq joydev uio
  CPU: 0    Tainted: G      D     (2.6.31-608-imx51 #14-Ubuntu)
  PC is at v7_coherent_kern_range+0x18/0x44
  LR is at arm_syscall+0x2a8/0x2c4
  pc : [<c003e1e8>]    lr : [<c003a858>]    psr: 80000013
  sp : cc81be80  ip : dc172bb0  fp : cc81bfa4
  r10: 4001e568  r9 : cc81a000  r8 : 00000000
  r7 : 000f0002  r6 : 00000000  r5 : 40169000  r4 : 403dd000
  r3 : 0000003f  r2 : 00000040  r1 : 403dd000  r0 : 401a1000
  Flags: Nzcv  IRQs on  FIQs on  Mode SVC_32  ISA ARM  Segment user
  Control: 10c5387d  Table: 9d108019  DAC: 00000015
  Process java (pid: 6558, stack limit = 0xcc81a2f0)
  Stack: (0xcc81be80 to 0xcc81c000)
  be80: cc81bed4 cc81be90 c047edc0 c005d290 c047edc0 c006e6dc c060d26c c006e6dc 
  bea0: c060d288 c060d270 cc81befc 00000005 cc81a000 00000005 cc81bee8 c0036ae4 
  bec0: cc81a000 00000005 cc81bee4 cc81bed8 c006e724 c006bd04 cc81bf84 cc81bee8 
  bee0: c006e7e0 c006e64c 00000005 00000000 00000005 0000199e 000009db 00000000 
  bf00: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 
  bf20: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 
  bf40: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 
  bf60: 00000000 00000000 cc81a000 cc81bfb0 000f0002 000f0002 cc81bfa4 cc81bf88 
  bf80: c0037a50 c006e76c 40169000 00019448 be970fa8 00000050 00000000 cc81bfa8 
  bfa0: c0036ac0 c003a5bc 00019448 be970fa8 40169000 403dd000 00000000 40169000 
  bfc0: 00019448 be970fa8 00000050 000f0002 40169000 00000cc0 4001e568 4001e8b8 
  bfe0: 000f0002 be970f90 400093cd 4000fd96 00000030 40169000 696c4075 2e737473 
  Backtrace: 
  [<c003a5b0>] (arm_syscall+0x0/0x2c4) from [<c0036ac0>] (__sys_trace_return+0x0/0x20)
   r6:00000050 r5:be970fa8 r4:00019448
  Code: e3a02010 e1a02312 e2423001 e1c00003 (ee070f3b) 
  mxc_ipu mxc_ipu: Channel already disabled 9
  mxc_ipu mxc_ipu: Channel already uninitialized 9
  DMFC high resolution has set, will not change
  ---[ end trace b707ea3bd34d5698 ]---