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When CONFIG_MIPS_FP_SUPPORT=n we don't support floating point, so we
don't need to worry about floating point exceptions pending in the
Floating point Control & Status Register (FCSR) during switch_to(). Stub
out the __sanitize_fcr31() macro in this case.
Signed-off-by: Paul Burton <paul.burton@mips.com>
Patchwork: https://patchwork.linux-mips.org/patch/21010/
Cc: linux-mips@linux-mips.org
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Commit 7c151d3d5d7a ("MIPS: Make use of the ERETNC instruction on MIPS
R6") began clearing LLBit during context switches, but did so on all
systems where it is writable for unclear reasons & did so from a macro
with "software_ll_bit" in its name, which is intended to operate on the
ll_bit variable used by ll/sc emulation for old CPUs.
We do now need to clear LLBit on MIPSr6 systems where we'll use eretnc
to return to userland, but we don't need to do so on MIPSr5 systems with
a writable LLBit.
Move the clear to its own appropriately named macro, do it only for
MIPSr6 systems & comment about why.
Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/14409/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
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Sanitize FCSR Cause bit handling, following a trail of past attempts:
* commit 4249548454f7 ("MIPS: ptrace: Fix FP context restoration FCSR
regression"),
* commit 443c44032a54 ("MIPS: Always clear FCSR cause bits after
emulation"),
* commit 64bedffe4968 ("MIPS: Clear [MSA]FPE CSR.Cause after
notify_die()"),
* commit b1442d39fac2 ("MIPS: Prevent user from setting FCSR cause
bits"),
* commit b54d2901517d ("Properly handle branch delay slots in connection
with signals.").
Specifically do not mask these bits out in ptrace(2) processing and send
a SIGFPE signal instead whenever a matching pair of an FCSR Cause and
Enable bit is seen as execution of an affected context is about to
resume. Only then clear Cause bits, and even then do not clear any bits
that are set but masked with the respective Enable bits. Adjust Cause
bit clearing throughout code likewise, except within the FPU emulator
proper where they are set according to IEEE 754 exceptions raised as the
operation emulated executed. Do so so that any IEEE 754 exceptions
subject to their default handling are recorded like with operations
executed by FPU hardware.
Signed-off-by: Maciej W. Rozycki <macro@imgtec.com>
Cc: Paul Burton <paul.burton@imgtec.com>
Cc: James Hogan <james.hogan@imgtec.com>
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/14460/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
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Commit f51246efee2b ("MIPS: Get rid of finish_arch_switch().") moved the
__restore_watch() call from finish_arch_switch() (i.e. after resume()
returns) to before the resume() call in switch_to(). This results in
watchpoints only being restored when a task is descheduled, preventing
the watchpoints from being effective most of the time, except due to
chance before the watchpoints are lazily removed.
Fix the call sequence from switch_to() through to
mips_install_watch_registers() to pass the task_struct pointer of the
next task, instead of using current. This allows the watchpoints for the
next (non-current) task to be restored without reintroducing
finish_arch_switch().
Fixes: f51246efee2b ("MIPS: Get rid of finish_arch_switch().")
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Paul Burton <paul.burton@imgtec.com>
Cc: linux-mips@linux-mips.org
Cc: <stable@vger.kernel.org> # 4.3.x-
Patchwork: https://patchwork.linux-mips.org/patch/12726/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
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Rather than saving the scalar FP or vector context in the assembly
resume function, reuse the existing C code we have in fpu.h to do
exactly that. This reduces duplication, results in a much easier to read
resume function & should allow the compiler to optimise out more MSA
code due to is_msa_enabled()/cpu_has_msa being known-zero at compile
time for kernels without MSA support.
Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Cc: linux-mips@linux-mips.org
Cc: Leonid Yegoshin <Leonid.Yegoshin@imgtec.com>
Cc: Maciej W. Rozycki <macro@linux-mips.org>
Cc: linux-kernel@vger.kernel.org
Cc: James Hogan <james.hogan@imgtec.com>
Cc: Markos Chandras <markos.chandras@imgtec.com>
Cc: Manuel Lauss <manuel.lauss@gmail.com>
Patchwork: https://patchwork.linux-mips.org/patch/10830/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
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MIPS was using finish_arch_switch() as a hook to restore and initialize
CPU context for all threads, even newly created kernel and user threads.
This is however entirely solvable within switch_to() so get rid of
finish_arch_switch() which is in the way of scheduler cleanups.
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
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Due to the slightly odd way that new threads and processes start execution
when scheduled for the very first time they were bypassing the required
disable_msa call.
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
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The ERETNC instruction, introduced in MIPS R5, is similar to the ERET
one, except it does not clear the LLB bit in the LLADDR register.
This feature is necessary to safely emulate R2 LL/SC instructions.
However, on context switches, we need to clear the LLAddr/LLB bit
in order to make sure that an SC instruction from the new thread
will never succeed if it happens to interrupt an LL operation on the
same address from the previous thread.
Signed-off-by: Markos Chandras <markos.chandras@imgtec.com>
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- Don't pass things to macros that couldn't be dereferences if that
macro was actually a function.
- Don't use empty function-like macros.
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
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This patch adds support for context switching the MSA vector registers.
These 128 bit vector registers are aliased with the FP registers - an
FP register accesses the least significant bits of the vector register
with which it is aliased (ie. the register with the same index). Due to
both this & the requirement that the scalar FPU must be 64-bit (FR=1) if
enabled at the same time as MSA the kernel will enable MSA & scalar FP
at the same time for tasks which use MSA. If we restore the MSA vector
context then we might as well enable the scalar FPU since the reason it
was left disabled was to allow for lazy FP context restoring - but we
just restored the FP context as it's a subset of the vector context. If
we restore the FP context and have previously used MSA then we have to
restore the whole vector context anyway (see comment in
enable_restore_fp_context for details) so similarly we might as well
enable MSA.
Thus if a task does not use MSA then it will continue to behave as
without this patch - the scalar FP context will be saved & restored as
usual. But if a task executes an MSA instruction then it will save &
restore the vector context forever more.
Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/6431/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
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This patch cleans up the declaration of the resume function by replacing
void pointers with their correct types. The irrelevant & incorrect
comment preceeding the resume function is replaced by one documenting
its function.
Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Reviewed-by: Qais Yousef <qais.yousef@imgtec.com>
Signed-off-by: John Crispin <blogic@openwrt.org>
Patchwork: http://patchwork.linux-mips.org/patch/6146/
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Move the common code for saving and restoring platform specific COP2
registers to switch_to(). This will make supporting new platforms (like
Netlogic XLP) easier.
The platform specific COP2 definitions are to be specified in
asm/processor.h and in asm/cop2.h.
Signed-off-by: Jayachandran C <jchandra@broadcom.com>
Cc: linux-mips@linux-mips.org
Cc: ddaney.cavm@gmail.com
Patchwork: https://patchwork.linux-mips.org/patch/5411/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
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Having received another series of whitespace patches I decided to do this
once and for all rather than dealing with this kind of patches trickling
in forever.
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
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[ralf@linux-mips.org: Cosmetic changes; also fixed up r2300_switch.S and
octeon_switch.S which needed similar modifications.]
Signed-off-by: Leonid Yegoshin <yegoshin@mips.com>
Signed-off-by: Steven J. Hill <sjhill@mips.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/3784/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
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Disintegrate asm/system.h for MIPS.
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Ralf Baechle <ralf@linux-mips.org>
cc: linux-mips@linux-mips.org
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