linux-toradex.git/arch/mips/kernel/unaligned.c, branch v4.4.106

MIPS: Fix MSA ld unaligned failure cases

2016-04-20T06:42:08+00:00

commit fa8ff601d72bad3078ddf5ef17a5547700d06908 upstream.

Copying the content of an MSA vector from user memory may involve TLB
faults & mapping in pages. This will fail when preemption is disabled
due to an inability to acquire mmap_sem from do_page_fault, which meant
such vector loads to unmapped pages would always fail to be emulated.
Fix this by disabling preemption later only around the updating of
vector register state.

This change does however introduce a race between performing the load
into thread context & the thread being preempted, saving its current
live context & clobbering the loaded value. This should be a rare
occureence, so optimise for the fast path by simply repeating the load if
we are preempted.

Additionally if the copy failed then the failure path was taken with
preemption left disabled, leading to the kernel typically encountering
further issues around sleeping whilst atomic. The change to where
preemption is disabled avoids this issue.

Fixes: e4aa1f153add "MIPS: MSA unaligned memory access support"
Reported-by: James Hogan 
Signed-off-by: Paul Burton 
Reviewed-by: James Hogan 
Cc: Leonid Yegoshin 
Cc: Maciej W. Rozycki 
Cc: James Cowgill 
Cc: Markos Chandras 
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/12345/
Signed-off-by: Ralf Baechle 
Signed-off-by: Greg Kroah-Hartman

MIPS: Declare mips_debugfs_dir in a header

2015-10-26T08:49:42+00:00

We have many extern declarations of mips_debugfs_dir through arch/mips/
in various C files. Unify them by declaring mips_debugfs_dir in a
header, including it in each affected C file & removing the duplicate
declarations.

Signed-off-by: Paul Burton 
Cc: linux-mips@linux-mips.org
Cc: Steven J. Hill 
Cc: Alexander Sverdlin 
Cc: Masahiro Yamada 
Cc: Leonid Yegoshin 
Cc: Maciej W. Rozycki 
Cc: linux-kernel@vger.kernel.org
Cc: Joe Perches 
Cc: Jaedon Shin 
Cc: James Hogan 
Cc: David Daney 
Cc: Zubair Lutfullah Kakakhel 
Cc: Markos Chandras 
Cc: James Cowgill 
Patchwork: https://patchwork.linux-mips.org/patch/11181/
Signed-off-by: Ralf Baechle

MIPS: unaligned: Move from deprecated __initcall to arch_initcall.

2015-09-03T10:07:49+00:00

Signed-off-by: Ralf Baechle

MIPS: MSA unaligned memory access support

2015-09-03T10:07:40+00:00

The MSA architecture specification allows for hardware to not implement
unaligned vector memory accesses in some or all cases. A typical example
of this is the I6400 core which does not implement unaligned vector
memory access when the memory crosses a page boundary. The architecture
also requires that such memory accesses complete successfully as far as
userland is concerned, so the kernel is required to emulate them.

This patch implements support for emulating unaligned MSA ld & st
instructions by copying between the user memory & the tasks FP context
in struct thread_struct, updating hardware registers from there as
appropriate in order to avoid saving & restoring the entire vector
context for each unaligned memory access.

Tested both using an I6400 CPU and with a QEMU build hacked to produce
AdEL exceptions for unaligned vector memory accesses.

[paul.burton@imgtec.com:
  - Remove #ifdef's
  - Move msa_op into enum major_op rather than #define
  - Replace msa_{to,from}_wd with {read,write}_msa_wr_{b,h,w,l} and the
    format-agnostic wrappers, removing the custom endian mangling for
    big endian systems.
  - Restructure the msa_op case in emulate_load_store_insn to share
    more code between the load & store cases.
  - Avoid the need for a temporary union fpureg on the stack by simply
    reusing the already suitably aligned context in struct
    thread_struct.
  - Use sizeof(*fpr) rather than hardcoding 16 as the size for user
    memory checks & copies.
  - Stop recalculating the address of the unaligned vector memory access
    and rely upon the value read from BadVAddr as we do for other
    unaligned memory access instructions.
  - Drop the now unused val8 & val16 fields in union fpureg.
  - Rewrite commit message.
  - General formatting cleanups.]

Signed-off-by: Paul Burton 
Cc: linux-mips@linux-mips.org
Cc: Leonid Yegoshin 
Cc: Huacai Chen 
Cc: Maciej W. Rozycki 
Cc: linux-kernel@vger.kernel.org
Cc: Jie Chen 
Cc: Markos Chandras 
Patchwork: https://patchwork.linux-mips.org/patch/10573/
Signed-off-by: Ralf Baechle

MIPS: unaligned: Fix build error on big endian R6 kernels

2015-08-03T07:25:05+00:00

Commit eeb538950367 ("MIPS: unaligned: Prevent EVA instructions on kernel
unaligned accesses") renamed the Load* and Store* defines in unaligned.c
to _Load* and _Store* as part of its fix. One define was missed out which
causes big endian R6 kernels to fail to build.

arch/mips/kernel/unaligned.c:880:35:
error: implicit declaration of function '_StoreDW'
 #define StoreDW(addr, value, res) _StoreDW(addr, value, res)
                                   ^

Signed-off-by: James Cowgill 
Fixes: eeb538950367 ("MIPS: unaligned: Prevent EVA instructions on kernel unaligned accesses")
Cc: Markos Chandras 
Cc:  # 4.0+
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/10575/
Signed-off-by: Ralf Baechle

Merge branch '4.0-fixes' into mips-for-linux-next

2015-04-13T14:03:32+00:00

MIPS: unaligned: Fix regular load/store instruction emulation for EVA

2015-04-10T13:41:45+00:00

When emulating a regular lh/lw/lhu/sh/sw we need to use the appropriate
instruction if we are in EVA mode. This is necessary for userspace
applications which trigger alignment exceptions. In such case, the
userspace load/store instruction needs to be emulated with the correct
eva/non-eva instruction by the kernel emulator.

Signed-off-by: Markos Chandras 
Fixes: c1771216ab48 ("MIPS: kernel: unaligned: Handle unaligned accesses for EVA")
Cc:  # v3.15+
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/9503/
Signed-off-by: Ralf Baechle

MIPS: unaligned: Surround load/store macros in do {} while statements

2015-04-10T13:41:44+00:00

It's best to surround such complex macros with do {} while statements
so they can appear as independent logical blocks when used within other
control blocks.

Signed-off-by: Markos Chandras 
Cc:  # v3.15+
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/9502/
Signed-off-by: Ralf Baechle

MIPS: unaligned: Prevent EVA instructions on kernel unaligned accesses

2015-04-10T13:41:44+00:00

Commit c1771216ab48 ("MIPS: kernel: unaligned: Handle unaligned
accesses for EVA") allowed unaligned accesses to be emulated for
EVA. However, when emulating regular load/store unaligned accesses,
we need to use the appropriate "address space" instructions for that.
Previously, an unaligned load/store instruction in kernel space would
have used the corresponding EVA instructions to emulate it which led to
segmentation faults because of the address translation that happens
with EVA instructions. This is now fixed by using the EVA instruction
only when emulating EVA unaligned accesses.

Signed-off-by: Markos Chandras 
Fixes: c1771216ab48 ("MIPS: kernel: unaligned: Handle unaligned accesses for EVA")
Cc:  # v3.15+
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/9501/
Signed-off-by: Ralf Baechle

MIPS: Fix double inclusion of headers in misalignment emulator.

2015-04-07T23:10:49+00:00

Introduced in 34c2f668d0f6b2ca1c076d8170d6cd4f2235a9d4 (MIPS: microMIPS:
Add unaligned access support.)

Signed-off-by: Ralf Baechle