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ARM: 6656/1: hw_breakpoint: avoid UNPREDICTABLE behaviour when reading DBGDSCR

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Reading baseline CP14 registers, other than DBGDIDR, when the OS Lock
is set leads to UNPREDICTABLE behaviour.

This patch ensures that we clear the OS lock before accessing anything
other than the DBGDIDR, thereby avoiding this behaviour.

Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
This commit is contained in:
Will Deacon 2011-02-11 15:55:12 +01:00 committed by Russell King
parent 34cd2d38db
commit ed19b739c5
1 changed files with 13 additions and 13 deletions
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26
arch/arm/kernel/hw_breakpoint.c
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@ -834,11 +834,11 @@ static void reset_ctrl_regs(void *unused)
/* /*
* v7 debug contains save and restore registers so that debug state * v7 debug contains save and restore registers so that debug state
* can be maintained across low-power modes without leaving * can be maintained across low-power modes without leaving the debug
* the debug logic powered up. It is IMPLEMENTATION DEFINED whether * logic powered up. It is IMPLEMENTATION DEFINED whether we can access
* we can write to the debug registers out of reset, so we must * the debug registers out of reset, so we must unlock the OS Lock
* unlock the OS Lock Access Register to avoid taking undefined * Access Register to avoid taking undefined instruction exceptions
* instruction exceptions later on. * later on.
*/ */
if (debug_arch >= ARM_DEBUG_ARCH_V7_ECP14) { if (debug_arch >= ARM_DEBUG_ARCH_V7_ECP14) {
/* /*
@ -899,18 +899,18 @@ static int __init arch_hw_breakpoint_init(void)
pr_info("%d breakpoint(s) reserved for watchpoint " pr_info("%d breakpoint(s) reserved for watchpoint "
"single-step.\n", core_num_reserved_brps); "single-step.\n", core_num_reserved_brps);
/*
* Reset the breakpoint resources. We assume that a halting
* debugger will leave the world in a nice state for us.
*/
on_each_cpu(reset_ctrl_regs, NULL, 1);
ARM_DBG_READ(c1, 0, dscr); ARM_DBG_READ(c1, 0, dscr);
if (dscr & ARM_DSCR_HDBGEN) { if (dscr & ARM_DSCR_HDBGEN) {
max_watchpoint_len = 4;
pr_warning("halting debug mode enabled. Assuming maximum " pr_warning("halting debug mode enabled. Assuming maximum "
"watchpoint size of 4 bytes."); "watchpoint size of %u bytes.", max_watchpoint_len);
} else { } else {
/*
* Reset the breakpoint resources. We assume that a halting
* debugger will leave the world in a nice state for us.
*/
smp_call_function(reset_ctrl_regs, NULL, 1);
reset_ctrl_regs(NULL);
/* Work out the maximum supported watchpoint length. */ /* Work out the maximum supported watchpoint length. */
max_watchpoint_len = get_max_wp_len(); max_watchpoint_len = get_max_wp_len();
pr_info("maximum watchpoint size is %u bytes.\n", pr_info("maximum watchpoint size is %u bytes.\n",