From: Marco Elver elver@google.com
[ Upstream commit f95e5a3d59011eec1257d0e76de1e1f8969d426f ]
Internal data structures (cpu_bps, task_bps) of powerpc's hw_breakpoint implementation have relied on nr_bp_mutex serializing access to them.
Before overhauling synchronization of kernel/events/hw_breakpoint.c, introduce 2 spinlocks to synchronize cpu_bps and task_bps respectively, thus avoiding reliance on callers synchronizing powerpc's hw_breakpoint.
Reported-by: Dmitry Vyukov dvyukov@google.com Signed-off-by: Marco Elver elver@google.com Signed-off-by: Peter Zijlstra (Intel) peterz@infradead.org Acked-by: Dmitry Vyukov dvyukov@google.com Acked-by: Ian Rogers irogers@google.com Link: https://lore.kernel.org/r/20220829124719.675715-10-elver@google.com Signed-off-by: Sasha Levin sashal@kernel.org --- arch/powerpc/kernel/hw_breakpoint.c | 53 ++++++++++++++++++++++------- 1 file changed, 40 insertions(+), 13 deletions(-)
diff --git a/arch/powerpc/kernel/hw_breakpoint.c b/arch/powerpc/kernel/hw_breakpoint.c index f4e8f21046f5..b081e60ecc6a 100644 --- a/arch/powerpc/kernel/hw_breakpoint.c +++ b/arch/powerpc/kernel/hw_breakpoint.c @@ -15,6 +15,7 @@ #include <linux/kernel.h> #include <linux/sched.h> #include <linux/smp.h> +#include <linux/spinlock.h> #include <linux/debugfs.h> #include <linux/init.h>
@@ -130,7 +131,14 @@ struct breakpoint { bool ptrace_bp; };
+/* + * While kernel/events/hw_breakpoint.c does its own synchronization, we cannot + * rely on it safely synchronizing internals here; however, we can rely on it + * not requesting more breakpoints than available. + */ +static DEFINE_SPINLOCK(cpu_bps_lock); static DEFINE_PER_CPU(struct breakpoint *, cpu_bps[HBP_NUM_MAX]); +static DEFINE_SPINLOCK(task_bps_lock); static LIST_HEAD(task_bps);
static struct breakpoint *alloc_breakpoint(struct perf_event *bp) @@ -175,7 +183,9 @@ static int task_bps_add(struct perf_event *bp) if (IS_ERR(tmp)) return PTR_ERR(tmp);
+ spin_lock(&task_bps_lock); list_add(&tmp->list, &task_bps); + spin_unlock(&task_bps_lock); return 0; }
@@ -183,6 +193,7 @@ static void task_bps_remove(struct perf_event *bp) { struct list_head *pos, *q;
+ spin_lock(&task_bps_lock); list_for_each_safe(pos, q, &task_bps) { struct breakpoint *tmp = list_entry(pos, struct breakpoint, list);
@@ -192,6 +203,7 @@ static void task_bps_remove(struct perf_event *bp) break; } } + spin_unlock(&task_bps_lock); }
/* @@ -201,12 +213,17 @@ static void task_bps_remove(struct perf_event *bp) static bool all_task_bps_check(struct perf_event *bp) { struct breakpoint *tmp; + bool ret = false;
+ spin_lock(&task_bps_lock); list_for_each_entry(tmp, &task_bps, list) { - if (!can_co_exist(tmp, bp)) - return true; + if (!can_co_exist(tmp, bp)) { + ret = true; + break; + } } - return false; + spin_unlock(&task_bps_lock); + return ret; }
/* @@ -216,13 +233,18 @@ static bool all_task_bps_check(struct perf_event *bp) static bool same_task_bps_check(struct perf_event *bp) { struct breakpoint *tmp; + bool ret = false;
+ spin_lock(&task_bps_lock); list_for_each_entry(tmp, &task_bps, list) { if (tmp->bp->hw.target == bp->hw.target && - !can_co_exist(tmp, bp)) - return true; + !can_co_exist(tmp, bp)) { + ret = true; + break; + } } - return false; + spin_unlock(&task_bps_lock); + return ret; }
static int cpu_bps_add(struct perf_event *bp) @@ -235,6 +257,7 @@ static int cpu_bps_add(struct perf_event *bp) if (IS_ERR(tmp)) return PTR_ERR(tmp);
+ spin_lock(&cpu_bps_lock); cpu_bp = per_cpu_ptr(cpu_bps, bp->cpu); for (i = 0; i < nr_wp_slots(); i++) { if (!cpu_bp[i]) { @@ -242,6 +265,7 @@ static int cpu_bps_add(struct perf_event *bp) break; } } + spin_unlock(&cpu_bps_lock); return 0; }
@@ -250,6 +274,7 @@ static void cpu_bps_remove(struct perf_event *bp) struct breakpoint **cpu_bp; int i = 0;
+ spin_lock(&cpu_bps_lock); cpu_bp = per_cpu_ptr(cpu_bps, bp->cpu); for (i = 0; i < nr_wp_slots(); i++) { if (!cpu_bp[i]) @@ -261,19 +286,25 @@ static void cpu_bps_remove(struct perf_event *bp) break; } } + spin_unlock(&cpu_bps_lock); }
static bool cpu_bps_check(int cpu, struct perf_event *bp) { struct breakpoint **cpu_bp; + bool ret = false; int i;
+ spin_lock(&cpu_bps_lock); 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; + if (cpu_bp[i] && !can_co_exist(cpu_bp[i], bp)) { + ret = true; + break; + } } - return false; + spin_unlock(&cpu_bps_lock); + return ret; }
static bool all_cpu_bps_check(struct perf_event *bp) @@ -287,10 +318,6 @@ static bool all_cpu_bps_check(struct perf_event *bp) 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;