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MIPS: Read watch registers with interrupts disabled. 

If a context switch occurred between the watch exception and reading the
watch registers, it would be possible for the new process to corrupt their
state.  Enabling interrupts only after the watch registers are read avoids
this race.

Signed-off-by: David Daney <ddaney@caviumnetworks.com>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
This commit is contained in:
David Daney 2009-01-05 15:29:58 -08:00 committed by Ralf Baechle
parent 7adbedaf44
commit 8bc6d05b48
2 changed files with 12 additions and 2 deletions
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6
arch/mips/kernel/genex.S
View File

@ -458,7 +458,11 @@ NESTED(nmi_handler, PT_SIZE, sp)
BUILD_HANDLER fpe fpe fpe silent /* #15 */
BUILD_HANDLER mdmx mdmx sti silent /* #22 */
#ifdef CONFIG_HARDWARE_WATCHPOINTS
BUILD_HANDLER watch watch sti silent /* #23 */
/*
* For watch, interrupts will be enabled after the watch
* registers are read.
*/
BUILD_HANDLER watch watch cli silent /* #23 */
#else
BUILD_HANDLER watch watch sti verbose /* #23 */
#endif

8
arch/mips/kernel/traps.c
View File

@ -944,6 +944,9 @@ asmlinkage void do_mdmx(struct pt_regs *regs)
force_sig(SIGILL, current);
}
/*
* Called with interrupts disabled.
*/
asmlinkage void do_watch(struct pt_regs *regs)
{
u32 cause;
@ -963,9 +966,12 @@ asmlinkage void do_watch(struct pt_regs *regs)
*/
if (test_tsk_thread_flag(current, TIF_LOAD_WATCH)) {
mips_read_watch_registers();
local_irq_enable();
force_sig(SIGTRAP, current);
} else
} else {
mips_clear_watch_registers();
local_irq_enable();
}
}
asmlinkage void do_mcheck(struct pt_regs *regs)