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MIPS: ptrace: Avoid smp_processor_id() in preemptible code

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ptrace_{get,set}_watch_regs access current_cpu_data to get the watch
register count/masks, which calls smp_processor_id(). However they are
run in preemptible context and therefore trigger warnings like so:

[ 6340.092000] BUG: using smp_processor_id() in preemptible [00000000] code: gdb/367
[ 6340.092000] caller is ptrace_get_watch_regs+0x44/0x220

Since the watch register count/masks should be the same across all
CPUs, use boot_cpu_data instead. Note that this may need to change in
future should a heterogenous system be supported where the count/masks
are not the same across all CPUs (the current code is also incorrect
for this scenario - current_cpu_data here would not necessarily be
correct for the CPU that the target task will execute on).

Signed-off-by: Alex Smith <alex.smith@imgtec.com>
Reviewed-by: Paul Burton <paul.burton@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/6879/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
This commit is contained in:
Alex Smith 2014-05-01 12:51:19 +01:00 committed by Ralf Baechle
parent f02ffb199d
commit 57c7ea513f
1 changed files with 7 additions and 7 deletions
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14
arch/mips/kernel/ptrace.c
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@ -163,7 +163,7 @@ int ptrace_get_watch_regs(struct task_struct *child,
enum pt_watch_style style;
int i;
if (!cpu_has_watch || current_cpu_data.watch_reg_use_cnt == 0)
if (!cpu_has_watch || boot_cpu_data.watch_reg_use_cnt == 0)
return -EIO;
if (!access_ok(VERIFY_WRITE, addr, sizeof(struct pt_watch_regs)))
return -EIO;
@ -177,14 +177,14 @@ int ptrace_get_watch_regs(struct task_struct *child,
#endif
__put_user(style, &addr->style);
__put_user(current_cpu_data.watch_reg_use_cnt,
__put_user(boot_cpu_data.watch_reg_use_cnt,
&addr->WATCH_STYLE.num_valid);
for (i = 0; i < current_cpu_data.watch_reg_use_cnt; i++) {
for (i = 0; i < boot_cpu_data.watch_reg_use_cnt; i++) {
__put_user(child->thread.watch.mips3264.watchlo[i],
&addr->WATCH_STYLE.watchlo[i]);
__put_user(child->thread.watch.mips3264.watchhi[i] & 0xfff,
&addr->WATCH_STYLE.watchhi[i]);
__put_user(current_cpu_data.watch_reg_masks[i],
__put_user(boot_cpu_data.watch_reg_masks[i],
&addr->WATCH_STYLE.watch_masks[i]);
}
for (; i < 8; i++) {
@ -204,12 +204,12 @@ int ptrace_set_watch_regs(struct task_struct *child,
unsigned long lt[NUM_WATCH_REGS];
u16 ht[NUM_WATCH_REGS];
if (!cpu_has_watch || current_cpu_data.watch_reg_use_cnt == 0)
if (!cpu_has_watch || boot_cpu_data.watch_reg_use_cnt == 0)
return -EIO;
if (!access_ok(VERIFY_READ, addr, sizeof(struct pt_watch_regs)))
return -EIO;
/* Check the values. */
for (i = 0; i < current_cpu_data.watch_reg_use_cnt; i++) {
for (i = 0; i < boot_cpu_data.watch_reg_use_cnt; i++) {
__get_user(lt[i], &addr->WATCH_STYLE.watchlo[i]);
#ifdef CONFIG_32BIT
if (lt[i] & __UA_LIMIT)
@ -228,7 +228,7 @@ int ptrace_set_watch_regs(struct task_struct *child,
return -EINVAL;
}
/* Install them. */
for (i = 0; i < current_cpu_data.watch_reg_use_cnt; i++) {
for (i = 0; i < boot_cpu_data.watch_reg_use_cnt; i++) {
if (lt[i] & 7)
watch_active = 1;
child->thread.watch.mips3264.watchlo[i] = lt[i];