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ARM: hw_breakpoint: reserve one breakpoint for watchpoint stepping

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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>
This commit is contained in:
Will Deacon 2011-08-02 13:01:17 +01:00
parent b5d5b8f986
commit c512de955f
1 changed files with 24 additions and 39 deletions
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63
arch/arm/kernel/hw_breakpoint.c
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@ -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;
}