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authorWill Deacon <will.deacon@arm.com>2011-08-02 13:01:17 +0100
committerWill Deacon <will.deacon@arm.com>2011-08-31 10:42:48 +0100
commitc512de955f0982aafa49d3f00d5643052a6790e5 (patch)
tree5bf3d463211f174ccf724e82be07cdf800b3168d /arch/arm/kernel/hw_breakpoint.c
parentb5d5b8f98641edac6641af9e19e933083ade603b (diff)
ARM: hw_breakpoint: reserve one breakpoint for watchpoint stepping
The current hw_breakpoint code on ARM reserves 1 breakpoint for each watchpoint that is available. Since debug architectures prior to 7.1 are restricted to 1 watchpoint anyway, only one breakpoint was ever reserved. This patch changes the reservation strategy so that a single breakpoint is reserved, regardless of the number of watchpoints. This is in preparation for multiple-watchpoint support on debug architectures from 7.1 onwards. Signed-off-by: Will Deacon <will.deacon@arm.com>
Diffstat (limited to 'arch/arm/kernel/hw_breakpoint.c')
-rw-r--r--arch/arm/kernel/hw_breakpoint.c63
1 files changed, 24 insertions, 39 deletions
diff --git a/arch/arm/kernel/hw_breakpoint.c b/arch/arm/kernel/hw_breakpoint.c
index b6ddbfaae52..156b8af1357 100644
--- a/arch/arm/kernel/hw_breakpoint.c
+++ b/arch/arm/kernel/hw_breakpoint.c
@@ -45,7 +45,6 @@ static DEFINE_PER_CPU(struct perf_event *, wp_on_reg[ARM_MAX_WRP]);
/* Number of BRP/WRP registers on this CPU. */
static int core_num_brps;
-static int core_num_reserved_brps;
static int core_num_wrps;
/* Debug architecture version. */
@@ -160,7 +159,15 @@ static int debug_arch_supported(void)
arch >= ARM_DEBUG_ARCH_V7_1;
}
-/* Determine number of BRP register available. */
+/* Determine number of WRP registers available. */
+static int get_num_wrp_resources(void)
+{
+ u32 didr;
+ ARM_DBG_READ(c0, 0, didr);
+ return ((didr >> 28) & 0xf) + 1;
+}
+
+/* Determine number of BRP registers available. */
static int get_num_brp_resources(void)
{
u32 didr;
@@ -179,9 +186,10 @@ static int core_has_mismatch_brps(void)
static int get_num_wrps(void)
{
/*
- * FIXME: When a watchpoint fires, the only way to work out which
- * watchpoint it was is by disassembling the faulting instruction
- * and working out the address of the memory access.
+ * On debug architectures prior to 7.1, when a watchpoint fires, the
+ * only way to work out which watchpoint it was is by disassembling
+ * the faulting instruction and working out the address of the memory
+ * access.
*
* Furthermore, we can only do this if the watchpoint was precise
* since imprecise watchpoints prevent us from calculating register
@@ -195,36 +203,17 @@ static int get_num_wrps(void)
* [the ARM ARM states that the DFAR is UNKNOWN, but experience shows
* that it is set on some implementations].
*/
+ if (get_debug_arch() < ARM_DEBUG_ARCH_V7_1)
+ return 1;
-#if 0
- int wrps;
- u32 didr;
- ARM_DBG_READ(c0, 0, didr);
- wrps = ((didr >> 28) & 0xf) + 1;
-#endif
- int wrps = 1;
-
- if (core_has_mismatch_brps() && wrps >= get_num_brp_resources())
- wrps = get_num_brp_resources() - 1;
-
- return wrps;
-}
-
-/* We reserve one breakpoint for each watchpoint. */
-static int get_num_reserved_brps(void)
-{
- if (core_has_mismatch_brps())
- return get_num_wrps();
- return 0;
+ return get_num_wrp_resources();
}
/* Determine number of usable BRPs available. */
static int get_num_brps(void)
{
int brps = get_num_brp_resources();
- if (core_has_mismatch_brps())
- brps -= get_num_reserved_brps();
- return brps;
+ return core_has_mismatch_brps() ? brps - 1 : brps;
}
/*
@@ -721,7 +710,7 @@ static void watchpoint_single_step_handler(unsigned long pc)
slots = (struct perf_event **)__get_cpu_var(wp_on_reg);
- for (i = 0; i < core_num_reserved_brps; ++i) {
+ for (i = 0; i < core_num_wrps; ++i) {
rcu_read_lock();
wp = slots[i];
@@ -840,7 +829,7 @@ static int hw_breakpoint_pending(unsigned long addr, unsigned int fsr,
*/
static void reset_ctrl_regs(void *info)
{
- int i, err = 0, cpu = smp_processor_id();
+ int i, raw_num_brps, err = 0, cpu = smp_processor_id();
u32 dbg_power;
cpumask_t *cpumask = info;
@@ -896,7 +885,8 @@ static void reset_ctrl_regs(void *info)
return;
/* We must also reset any reserved registers. */
- for (i = 0; i < core_num_brps + core_num_reserved_brps; ++i) {
+ raw_num_brps = get_num_brp_resources();
+ for (i = 0; i < raw_num_brps; ++i) {
write_wb_reg(ARM_BASE_BCR + i, 0UL);
write_wb_reg(ARM_BASE_BVR + i, 0UL);
}
@@ -933,15 +923,11 @@ static int __init arch_hw_breakpoint_init(void)
/* Determine how many BRPs/WRPs are available. */
core_num_brps = get_num_brps();
- core_num_reserved_brps = get_num_reserved_brps();
core_num_wrps = get_num_wrps();
- pr_info("found %d breakpoint and %d watchpoint registers.\n",
- core_num_brps + core_num_reserved_brps, core_num_wrps);
-
- if (core_num_reserved_brps)
- pr_info("%d breakpoint(s) reserved for watchpoint "
- "single-step.\n", core_num_reserved_brps);
+ pr_info("found %d " "%s" "breakpoint and %d watchpoint registers.\n",
+ core_num_brps, core_has_mismatch_brps() ? "(+1 reserved) " :
+ "", core_num_wrps);
/*
* Reset the breakpoint resources. We assume that a halting
@@ -950,7 +936,6 @@ static int __init arch_hw_breakpoint_init(void)
on_each_cpu(reset_ctrl_regs, &cpumask, 1);
if (!cpumask_empty(&cpumask)) {
core_num_brps = 0;
- core_num_reserved_brps = 0;
core_num_wrps = 0;
return 0;
}