diff options
| author | Maciej W. Rozycki <macro@imgtec.com> | 2016-10-28 08:21:03 +0100 |
|---|---|---|
| committer | Ralf Baechle <ralf@linux-mips.org> | 2016-11-04 01:28:41 +0100 |
| commit | 5a1aca4469fdccd5b74ba0b4e490173b2b447895 (patch) | |
| tree | bdfad3f7a9ce39cc48edd2a1cff8c89a0549c60a /arch/mips/kernel/mips-r2-to-r6-emul.c | |
| parent | c9e5603974573367c4d80964a845237a2297228c (diff) | |
MIPS: Fix FCSR Cause bit handling for correct SIGFPE issue
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>
Diffstat (limited to 'arch/mips/kernel/mips-r2-to-r6-emul.c')
| -rw-r--r-- | arch/mips/kernel/mips-r2-to-r6-emul.c | 10 |
1 files changed, 5 insertions, 5 deletions
diff --git a/arch/mips/kernel/mips-r2-to-r6-emul.c b/arch/mips/kernel/mips-r2-to-r6-emul.c index 22dedd62818a..bd09853aecdf 100644 --- a/arch/mips/kernel/mips-r2-to-r6-emul.c +++ b/arch/mips/kernel/mips-r2-to-r6-emul.c @@ -899,7 +899,7 @@ static inline int mipsr2_find_op_func(struct pt_regs *regs, u32 inst, * mipsr2_decoder: Decode and emulate a MIPS R2 instruction * @regs: Process register set * @inst: Instruction to decode and emulate - * @fcr31: Floating Point Control and Status Register returned + * @fcr31: Floating Point Control and Status Register Cause bits returned */ int mipsr2_decoder(struct pt_regs *regs, u32 inst, unsigned long *fcr31) { @@ -1172,13 +1172,13 @@ fpu_emul: err = fpu_emulator_cop1Handler(regs, ¤t->thread.fpu, 0, &fault_addr); - *fcr31 = current->thread.fpu.fcr31; /* - * We can't allow the emulated instruction to leave any of - * the cause bits set in $fcr31. + * We can't allow the emulated instruction to leave any + * enabled Cause bits set in $fcr31. */ - current->thread.fpu.fcr31 &= ~FPU_CSR_ALL_X; + *fcr31 = res = mask_fcr31_x(current->thread.fpu.fcr31); + current->thread.fpu.fcr31 &= ~res; /* * this is a tricky issue - lose_fpu() uses LL/SC atomics |