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Commit 57c7ea51 authored by Alex Smith's avatar Alex Smith Committed by Ralf Baechle
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MIPS: ptrace: Avoid smp_processor_id() in preemptible code 



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: default avatarAlex Smith <alex.smith@imgtec.com>
Reviewed-by: default avatarPaul Burton <paul.burton@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/6879/


Signed-off-by: default avatarRalf Baechle <ralf@linux-mips.org>
parent f02ffb19

arch/mips/kernel/ptrace.c

+7 −7
Original line number Original line Diff line number Diff line
@@ -163,7 +163,7 @@ int ptrace_get_watch_regs(struct task_struct *child, 
	enum pt_watch_style style;

	enum pt_watch_style style;

	int i;

	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;

		return -EIO;

	if (!access_ok(VERIFY_WRITE, addr, sizeof(struct pt_watch_regs)))

	if (!access_ok(VERIFY_WRITE, addr, sizeof(struct pt_watch_regs)))

		return -EIO;

		return -EIO;
@@ -177,14 +177,14 @@ int ptrace_get_watch_regs(struct task_struct *child, 
#endif

#endif





	__put_user(style, &addr->style);

	__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);

		   &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],

		__put_user(child->thread.watch.mips3264.watchlo[i],

			   &addr->WATCH_STYLE.watchlo[i]);

			   &addr->WATCH_STYLE.watchlo[i]);

		__put_user(child->thread.watch.mips3264.watchhi[i] & 0xfff,

		__put_user(child->thread.watch.mips3264.watchhi[i] & 0xfff,

			   &addr->WATCH_STYLE.watchhi[i]);

			   &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]);

			   &addr->WATCH_STYLE.watch_masks[i]);

	}

	}

	for (; i < 8; i++) {

	for (; i < 8; i++) {
@@ -204,12 +204,12 @@ int ptrace_set_watch_regs(struct task_struct *child, 
	unsigned long lt[NUM_WATCH_REGS];

	unsigned long lt[NUM_WATCH_REGS];

	u16 ht[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;

		return -EIO;

	if (!access_ok(VERIFY_READ, addr, sizeof(struct pt_watch_regs)))

	if (!access_ok(VERIFY_READ, addr, sizeof(struct pt_watch_regs)))

		return -EIO;

		return -EIO;

	/* Check the values. */

	/* 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]);

		__get_user(lt[i], &addr->WATCH_STYLE.watchlo[i]);

#ifdef CONFIG_32BIT

#ifdef CONFIG_32BIT

		if (lt[i] & __UA_LIMIT)

		if (lt[i] & __UA_LIMIT)
@@ -228,7 +228,7 @@ int ptrace_set_watch_regs(struct task_struct *child, 
			return -EINVAL;

			return -EINVAL;

	}

	}

	/* Install them. */

	/* 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)

		if (lt[i] & 7)

			watch_active = 1;

			watch_active = 1;

		child->thread.watch.mips3264.watchlo[i] = lt[i];

		child->thread.watch.mips3264.watchlo[i] = lt[i];