linux.git/arch/xtensa/kernel/entry.S, branch v3.17

xtensa: deprecate fast_xtensa and fast_spill_registers syscalls

2014-08-14T07:59:33+00:00

These syscalls are not used by userspace tools for some time now, and
they have issues when called with invalid arguments. It's not worth
changing signal delivery mechanism as we don't expect any new users for
these syscalls. Let's keep them for backwards compatibility under #ifdef,
disabled by default.

Signed-off-by: Max Filippov

xtensa: fix a6 and a7 handling in fast_syscall_xtensa

2014-08-14T07:59:31+00:00

Remove restoring a6 on some return paths and instead modify and restore
it in a single place, using symbolic name.
Correctly restore a7 from PT_AREG7 in case of illegal a6 value.

Cc: stable@vger.kernel.org
Signed-off-by: Max Filippov

xtensa: fix TLBTEMP_BASE_2 region handling in fast_second_level_miss

2014-08-14T07:59:19+00:00

Current definition of TLBTEMP_BASE_2 is always 32K above the
TLBTEMP_BASE_1, whereas fast_second_level_miss handler for the TLBTEMP
region analyzes virtual address bit (PAGE_SHIFT + DCACHE_ALIAS_ORDER)
to determine TLBTEMP region where the fault happened. The size of the
TLBTEMP region is also checked incorrectly: not 64K, but twice data
cache way size (whicht may as well be less than the instruction cache
way size).

Fix TLBTEMP_BASE_2 to be TLBTEMP_BASE_1 + data cache way size.
Provide TLBTEMP_SIZE that is a greater of doubled data cache way size or
the instruction cache way size, and use it to determine if the second
level TLB miss occured in the TLBTEMP region.

Practical occurence of page faults in the TLBTEMP area is extremely
rare, this code can be tested by deletion of all w[di]tlb instructions
in the tlbtemp_mapping region.

Cc: stable@vger.kernel.org
Signed-off-by: Max Filippov

xtensa: fix access to THREAD_RA/THREAD_SP/THREAD_DS

2014-08-14T07:59:16+00:00

With SMP and a lot of debug options enabled task_struct::thread gets out
of reach of s32i/l32i instructions with base pointing at task_struct,
breaking build with the following messages:

  arch/xtensa/kernel/entry.S: Assembler messages:
  arch/xtensa/kernel/entry.S:1002: Error: operand 3 of 'l32i.n' has invalid value '1048'
  arch/xtensa/kernel/entry.S:1831: Error: operand 3 of 's32i.n' has invalid value '1040'
  arch/xtensa/kernel/entry.S:1832: Error: operand 3 of 's32i.n' has invalid value '1044'

Change base to point to task_struct::thread in such cases.
Don't use a10 in _switch_to to save/restore prev pointer as a2 is not
clobbered.

Cc: stable@vger.kernel.org
Signed-off-by: Max Filippov

xtensa: fix fast_syscall_spill_registers

2014-01-29T06:09:51+00:00

The original implementation could clobber registers under certain conditions.

The Xtensa processor architecture uses windowed registers and the original
implementation was using a4 as a temporary register, which under certain
conditions could be register a0 of the oldest window frame, and didn't always
restore the content correctly.

By moving the _spill_registers routine inside the fast system call, it frees
up one more register (the return address is not required anymore) for the
spill routine.

Signed-off-by: Chris Zankel

xtensa: save current register frame in fast_syscall_spill_registers_fixup

2014-01-25T19:24:38+00:00

We need it saved because it contains a3 where we track which register
windows we still need to spill, and fixup handler may call C exception
handlers. Also fix comments.

Cc: stable@vger.kernel.org
Signed-off-by: Max Filippov

xtensa: introduce spill_registers_kernel macro

2014-01-25T19:20:09+00:00

Most in-kernel users want registers spilled on the kernel stack and
don't require PS.EXCM to be set. That means that they don't need fixup
routine and could reuse regular window overflow mechanism for that,
which makes spill routine very simple.

Cc: stable@vger.kernel.org
Suggested-by: Chris Zankel 
Signed-off-by: Max Filippov

xtensa: fix fast_syscall_spill_registers_fixup

2013-10-15T20:39:06+00:00

fast_syscall_spill_registers_fixup was not correctly updated by the
'keep a3 and excsave1 on entry to exception handlers' patch: it doesn't
preserve a3 that it gets on entry, breaking _spill_registers in case of
page fault on stack during register spilling, leading to unhandled
exception in kernel mode.

Preserve a3 by saving it in the original _spill_registers stack frame's
a3 during exception handling and restoring it afterwards.

Also fix comments and function bounds annotations.

Reported-by: Baruch Siach 
Signed-off-by: Max Filippov 
Tested-by: Baruch Siach 
Signed-off-by: Chris Zankel

xtensa: new fast_alloca handler

2013-09-06T16:48:12+00:00

Instead of emulating movsp instruction in the kernel use window
underflow handler to load missing register window and retry failed
movsp.

Signed-off-by: Max Filippov 
Signed-off-by: Chris Zankel

xtensa: keep a3 and excsave1 on entry to exception handlers

2013-09-06T16:47:41+00:00

Based on the SMP patch by Joe Taylor and subsequent fixes.
Preserve exception table pointer (normally stored in excsave1 SR) as it
cannot be easily restored in SMP environment.

Signed-off-by: Max Filippov 
Signed-off-by: Chris Zankel