Commit 29da4f91 authored by Ravi Bangoria's avatar Ravi Bangoria Committed by Michael Ellerman

powerpc/watchpoint: Don't allow concurrent perf and ptrace events

With Book3s DAWR, ptrace and perf watchpoints on powerpc behaves
differently. Ptrace watchpoint works in one-shot mode and generates
signal before executing instruction. It's ptrace user's job to
single-step the instruction and re-enable the watchpoint. OTOH, in
case of perf watchpoint, kernel emulates/single-steps the instruction
and then generates event. If perf and ptrace creates two events with
same or overlapping address ranges, it's ambiguous to decide who
should single-step the instruction. Because of this issue, don't
allow perf and ptrace watchpoint at the same time if their address
range overlaps.
Signed-off-by: default avatarRavi Bangoria <ravi.bangoria@linux.ibm.com>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
Reviewed-by: default avatarMichael Neuling <mikey@neuling.org>
Link: https://lore.kernel.org/r/20200514111741.97993-15-ravi.bangoria@linux.ibm.com
parent 74c68810
...@@ -70,6 +70,8 @@ extern int hw_breakpoint_exceptions_notify(struct notifier_block *unused, ...@@ -70,6 +70,8 @@ extern int hw_breakpoint_exceptions_notify(struct notifier_block *unused,
unsigned long val, void *data); unsigned long val, void *data);
int arch_install_hw_breakpoint(struct perf_event *bp); int arch_install_hw_breakpoint(struct perf_event *bp);
void arch_uninstall_hw_breakpoint(struct perf_event *bp); void arch_uninstall_hw_breakpoint(struct perf_event *bp);
int arch_reserve_bp_slot(struct perf_event *bp);
void arch_release_bp_slot(struct perf_event *bp);
void arch_unregister_hw_breakpoint(struct perf_event *bp); void arch_unregister_hw_breakpoint(struct perf_event *bp);
void hw_breakpoint_pmu_read(struct perf_event *bp); void hw_breakpoint_pmu_read(struct perf_event *bp);
extern void flush_ptrace_hw_breakpoint(struct task_struct *tsk); extern void flush_ptrace_hw_breakpoint(struct task_struct *tsk);
......
...@@ -124,6 +124,227 @@ static bool is_ptrace_bp(struct perf_event *bp) ...@@ -124,6 +124,227 @@ static bool is_ptrace_bp(struct perf_event *bp)
return bp->overflow_handler == ptrace_triggered; return bp->overflow_handler == ptrace_triggered;
} }
struct breakpoint {
struct list_head list;
struct perf_event *bp;
bool ptrace_bp;
};
static DEFINE_PER_CPU(struct breakpoint *, cpu_bps[HBP_NUM_MAX]);
static LIST_HEAD(task_bps);
static struct breakpoint *alloc_breakpoint(struct perf_event *bp)
{
struct breakpoint *tmp;
tmp = kzalloc(sizeof(*tmp), GFP_KERNEL);
if (!tmp)
return ERR_PTR(-ENOMEM);
tmp->bp = bp;
tmp->ptrace_bp = is_ptrace_bp(bp);
return tmp;
}
static bool bp_addr_range_overlap(struct perf_event *bp1, struct perf_event *bp2)
{
__u64 bp1_saddr, bp1_eaddr, bp2_saddr, bp2_eaddr;
bp1_saddr = ALIGN_DOWN(bp1->attr.bp_addr, HW_BREAKPOINT_SIZE);
bp1_eaddr = ALIGN(bp1->attr.bp_addr + bp1->attr.bp_len, HW_BREAKPOINT_SIZE);
bp2_saddr = ALIGN_DOWN(bp2->attr.bp_addr, HW_BREAKPOINT_SIZE);
bp2_eaddr = ALIGN(bp2->attr.bp_addr + bp2->attr.bp_len, HW_BREAKPOINT_SIZE);
return (bp1_saddr < bp2_eaddr && bp1_eaddr > bp2_saddr);
}
static bool alternate_infra_bp(struct breakpoint *b, struct perf_event *bp)
{
return is_ptrace_bp(bp) ? !b->ptrace_bp : b->ptrace_bp;
}
static bool can_co_exist(struct breakpoint *b, struct perf_event *bp)
{
return !(alternate_infra_bp(b, bp) && bp_addr_range_overlap(b->bp, bp));
}
static int task_bps_add(struct perf_event *bp)
{
struct breakpoint *tmp;
tmp = alloc_breakpoint(bp);
if (IS_ERR(tmp))
return PTR_ERR(tmp);
list_add(&tmp->list, &task_bps);
return 0;
}
static void task_bps_remove(struct perf_event *bp)
{
struct list_head *pos, *q;
list_for_each_safe(pos, q, &task_bps) {
struct breakpoint *tmp = list_entry(pos, struct breakpoint, list);
if (tmp->bp == bp) {
list_del(&tmp->list);
kfree(tmp);
break;
}
}
}
/*
* If any task has breakpoint from alternate infrastructure,
* return true. Otherwise return false.
*/
static bool all_task_bps_check(struct perf_event *bp)
{
struct breakpoint *tmp;
list_for_each_entry(tmp, &task_bps, list) {
if (!can_co_exist(tmp, bp))
return true;
}
return false;
}
/*
* If same task has breakpoint from alternate infrastructure,
* return true. Otherwise return false.
*/
static bool same_task_bps_check(struct perf_event *bp)
{
struct breakpoint *tmp;
list_for_each_entry(tmp, &task_bps, list) {
if (tmp->bp->hw.target == bp->hw.target &&
!can_co_exist(tmp, bp))
return true;
}
return false;
}
static int cpu_bps_add(struct perf_event *bp)
{
struct breakpoint **cpu_bp;
struct breakpoint *tmp;
int i = 0;
tmp = alloc_breakpoint(bp);
if (IS_ERR(tmp))
return PTR_ERR(tmp);
cpu_bp = per_cpu_ptr(cpu_bps, bp->cpu);
for (i = 0; i < nr_wp_slots(); i++) {
if (!cpu_bp[i]) {
cpu_bp[i] = tmp;
break;
}
}
return 0;
}
static void cpu_bps_remove(struct perf_event *bp)
{
struct breakpoint **cpu_bp;
int i = 0;
cpu_bp = per_cpu_ptr(cpu_bps, bp->cpu);
for (i = 0; i < nr_wp_slots(); i++) {
if (!cpu_bp[i])
continue;
if (cpu_bp[i]->bp == bp) {
kfree(cpu_bp[i]);
cpu_bp[i] = NULL;
break;
}
}
}
static bool cpu_bps_check(int cpu, struct perf_event *bp)
{
struct breakpoint **cpu_bp;
int i;
cpu_bp = per_cpu_ptr(cpu_bps, cpu);
for (i = 0; i < nr_wp_slots(); i++) {
if (cpu_bp[i] && !can_co_exist(cpu_bp[i], bp))
return true;
}
return false;
}
static bool all_cpu_bps_check(struct perf_event *bp)
{
int cpu;
for_each_online_cpu(cpu) {
if (cpu_bps_check(cpu, bp))
return true;
}
return false;
}
/*
* We don't use any locks to serialize accesses to cpu_bps or task_bps
* because are already inside nr_bp_mutex.
*/
int arch_reserve_bp_slot(struct perf_event *bp)
{
int ret;
/* ptrace breakpoint */
if (is_ptrace_bp(bp)) {
if (all_cpu_bps_check(bp))
return -ENOSPC;
if (same_task_bps_check(bp))
return -ENOSPC;
return task_bps_add(bp);
}
/* perf breakpoint */
if (is_kernel_addr(bp->attr.bp_addr))
return 0;
if (bp->hw.target && bp->cpu == -1) {
if (same_task_bps_check(bp))
return -ENOSPC;
return task_bps_add(bp);
} else if (!bp->hw.target && bp->cpu != -1) {
if (all_task_bps_check(bp))
return -ENOSPC;
return cpu_bps_add(bp);
}
if (same_task_bps_check(bp))
return -ENOSPC;
ret = cpu_bps_add(bp);
if (ret)
return ret;
ret = task_bps_add(bp);
if (ret)
cpu_bps_remove(bp);
return ret;
}
void arch_release_bp_slot(struct perf_event *bp)
{
if (!is_kernel_addr(bp->attr.bp_addr)) {
if (bp->hw.target)
task_bps_remove(bp);
if (bp->cpu != -1)
cpu_bps_remove(bp);
}
}
/* /*
* Perform cleanup of arch-specific counters during unregistration * Perform cleanup of arch-specific counters during unregistration
* of the perf-event * of the perf-event
......
...@@ -213,6 +213,15 @@ toggle_bp_slot(struct perf_event *bp, bool enable, enum bp_type_idx type, ...@@ -213,6 +213,15 @@ toggle_bp_slot(struct perf_event *bp, bool enable, enum bp_type_idx type,
list_del(&bp->hw.bp_list); list_del(&bp->hw.bp_list);
} }
__weak int arch_reserve_bp_slot(struct perf_event *bp)
{
return 0;
}
__weak void arch_release_bp_slot(struct perf_event *bp)
{
}
/* /*
* Function to perform processor-specific cleanup during unregistration * Function to perform processor-specific cleanup during unregistration
*/ */
...@@ -270,6 +279,7 @@ static int __reserve_bp_slot(struct perf_event *bp, u64 bp_type) ...@@ -270,6 +279,7 @@ static int __reserve_bp_slot(struct perf_event *bp, u64 bp_type)
struct bp_busy_slots slots = {0}; struct bp_busy_slots slots = {0};
enum bp_type_idx type; enum bp_type_idx type;
int weight; int weight;
int ret;
/* We couldn't initialize breakpoint constraints on boot */ /* We couldn't initialize breakpoint constraints on boot */
if (!constraints_initialized) if (!constraints_initialized)
...@@ -294,6 +304,10 @@ static int __reserve_bp_slot(struct perf_event *bp, u64 bp_type) ...@@ -294,6 +304,10 @@ static int __reserve_bp_slot(struct perf_event *bp, u64 bp_type)
if (slots.pinned + (!!slots.flexible) > nr_slots[type]) if (slots.pinned + (!!slots.flexible) > nr_slots[type])
return -ENOSPC; return -ENOSPC;
ret = arch_reserve_bp_slot(bp);
if (ret)
return ret;
toggle_bp_slot(bp, true, type, weight); toggle_bp_slot(bp, true, type, weight);
return 0; return 0;
...@@ -317,6 +331,8 @@ static void __release_bp_slot(struct perf_event *bp, u64 bp_type) ...@@ -317,6 +331,8 @@ static void __release_bp_slot(struct perf_event *bp, u64 bp_type)
enum bp_type_idx type; enum bp_type_idx type;
int weight; int weight;
arch_release_bp_slot(bp);
type = find_slot_idx(bp_type); type = find_slot_idx(bp_type);
weight = hw_breakpoint_weight(bp); weight = hw_breakpoint_weight(bp);
toggle_bp_slot(bp, false, type, weight); toggle_bp_slot(bp, false, type, weight);
......
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