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__compute_return_epc() uses CFC1 instruction which might result in a 

coprocessor unusable exception since the process can lose its fpu
context by preemption.

Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
This commit is contained in:
Ralf Baechle 2005-05-09 13:16:07 +00:00
parent d547c5cc21
commit 1d74f6bc85
2 changed files with 14 additions and 5 deletions
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10
arch/mips/kernel/branch.c
View File

@ -12,6 +12,7 @@
#include <asm/branch.h>
#include <asm/cpu.h>
#include <asm/cpu-features.h>
#include <asm/fpu.h>
#include <asm/inst.h>
#include <asm/ptrace.h>
#include <asm/uaccess.h>
@ -161,10 +162,13 @@ int __compute_return_epc(struct pt_regs *regs)
* And now the FPA/cp1 branch instructions.
*/
case cop1_op:
if (!cpu_has_fpu)
fcr31 = current->thread.fpu.soft.fcr31;
else
preempt_disable();
if (is_fpu_owner())
asm volatile("cfc1\t%0,$31" : "=r" (fcr31));
else
fcr31 = current->thread.fpu.hard.fcr31;
preempt_enable();
bit = (insn.i_format.rt >> 2);
bit += (bit != 0);
bit += 23;

9
include/asm-mips/fpu.h
View File

@ -80,9 +80,14 @@ do { \
#define clear_fpu_owner() clear_thread_flag(TIF_USEDFPU)
static inline int __is_fpu_owner(void)
{
return test_thread_flag(TIF_USEDFPU);
}
static inline int is_fpu_owner(void)
{
return cpu_has_fpu && test_thread_flag(TIF_USEDFPU);
return cpu_has_fpu && __is_fpu_owner();
}
static inline void own_fpu(void)
@ -127,7 +132,7 @@ static inline void restore_fp(struct task_struct *tsk)
static inline fpureg_t *get_fpu_regs(struct task_struct *tsk)
{
if (cpu_has_fpu) {
if ((tsk == current) && is_fpu_owner())
if ((tsk == current) && __is_fpu_owner())
_save_fp(current);
return tsk->thread.fpu.hard.fpr;
}