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ARM: hw_breakpoint: fix ordering of debug register reset sequence

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The debug register reset sequence for v7 and v7.1 is congruent with
tap-dancing through a minefield.

Rather than wait until we've blown ourselves to pieces, this patch
instead checks the debug_err_mask after each potentially faulting
operation. We also move the enabling of monitor_mode to the end of the
sequence in order to prevent spurious debug events generated by UNKNOWN
register values.

Reported-by: Stephen Boyd <sboyd@codeaurora.org>
Tested-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>
This commit is contained in:
Will Deacon 2012-09-21 15:38:26 +01:00
parent b59a540ca9
commit 614bea500a
1 changed files with 26 additions and 10 deletions
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36
arch/arm/kernel/hw_breakpoint.c
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@ -231,8 +231,6 @@ static int get_num_brps(void)
static int enable_monitor_mode(void)
{
u32 dscr;
int ret = 0;
ARM_DBG_READ(c1, 0, dscr);
/* If monitor mode is already enabled, just return. */
@ -251,17 +249,18 @@ static int enable_monitor_mode(void)
isb();
break;
default:
ret = -ENODEV;
goto out;
return -ENODEV;
}
/* Check that the write made it through. */
ARM_DBG_READ(c1, 0, dscr);
if (!(dscr & ARM_DSCR_MDBGEN))
ret = -EPERM;
if (WARN_ONCE(!(dscr & ARM_DSCR_MDBGEN),
"Failed to enable monitor mode on CPU %d.\n",
smp_processor_id()))
return -EPERM;
out:
return ret;
return 0;
}
int hw_breakpoint_slots(int type)
@ -962,11 +961,16 @@ clear_vcr:
asm volatile("mcr p14, 0, %0, c0, c7, 0" : : "r" (0));
isb();
reset_regs:
if (enable_monitor_mode())
if (cpumask_intersects(&debug_err_mask, cpumask_of(cpu))) {
pr_warning("CPU %d failed to disable vector catch\n", cpu);
return;
}
/* We must also reset any reserved registers. */
reset_regs:
/*
* The control/value register pairs are UNKNOWN out of reset so
* clear them to avoid spurious debug events.
*/
raw_num_brps = get_num_brp_resources();
for (i = 0; i < raw_num_brps; ++i) {
write_wb_reg(ARM_BASE_BCR + i, 0UL);
@ -977,6 +981,18 @@ reset_regs:
write_wb_reg(ARM_BASE_WCR + i, 0UL);
write_wb_reg(ARM_BASE_WVR + i, 0UL);
}
if (cpumask_intersects(&debug_err_mask, cpumask_of(cpu))) {
pr_warning("CPU %d failed to clear debug register pairs\n", cpu);
return;
}
/*
* Have a crack at enabling monitor mode. We don't actually need
* it yet, but reporting an error early is useful if it fails.
*/
if (enable_monitor_mode())
cpumask_or(&debug_err_mask, &debug_err_mask, cpumask_of(cpu));
}
static int __cpuinit dbg_reset_notify(struct notifier_block *self,