[PATCH openEuler-22.09 v2] bpf:programmable: Fix build error of 'stack exceeds 512 bytes'

21 Sep 2022

From: Hui Tang tanghui20@huawei.com
hulk inclusion
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I5RMFU
CVE: NA
--------------------------------
1.Change arg type of 'bpf_get_cpumask_info' to avoid
  bpf program stack exceeds 512 bytes.
2.Fix back-edge error in sample 'sched_select_core'
3.Fix loop too complex in sample 'sached_select_core'
Changes in v2:
  Move cpu initialization out of the for loop.
Fixes: 1bf0417b95a9 ("sched: programmable: Add helper function for cpu topo...")
Fixes: 2c1189e32bf9 ("samples:bpf: Add samples for cfs select core")
Signed-off-by: Hui Tang tanghui20@huawei.com
---
 include/uapi/linux/bpf.h             |  2 +-
 kernel/sched/bpf_topology.c          |  9 ++-
 samples/bpf/sched_select_core_kern.c | 32 ++++++++---
 tools/include/uapi/linux/bpf.h       |  2 +-
 tools/lib/bpf/libbpf_sched.h         | 86 +++++++++++++++++++++-------
 5 files changed, 96 insertions(+), 35 deletions(-)

diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index db585d960d64..7e474c6fc4a7 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -3903,7 +3903,7 @@ union bpf_attr {
  *	Return
  *		0 on success, or a negative error in case of failure.
  *
- * int bpf_get_cpumask_info(struct bpf_cpumask_info *cpus, int len)
+ * int bpf_get_cpumask_info(struct bpf_map *map, struct bpf_cpumask_info *cpus)
  *	Description
  *		Get system cpus returned in *cpus*.
  *	Return
diff --git a/kernel/sched/bpf_topology.c b/kernel/sched/bpf_topology.c
index 9c2eda139e2a..843b6092a64f 100644
--- a/kernel/sched/bpf_topology.c
+++ b/kernel/sched/bpf_topology.c
@@ -70,10 +70,9 @@ const struct bpf_func_proto bpf_init_cpu_topology_proto = {
    .arg2_type	= ARG_ANYTHING,
 };
-BPF_CALL_2(bpf_get_cpumask_info, struct bpf_cpumask_info *, cpus,
-	   int, len)
+BPF_CALL_2(bpf_get_cpumask_info, struct bpf_map *, map, struct bpf_cpumask_info *, cpus)
 {
-	if (len != sizeof(*cpus))
+	if (!cpus)
    	return -EINVAL;
cpumask_copy(&cpus->cpu_possible_cpumask, cpu_possible_mask);
@@ -92,6 +91,6 @@ const struct bpf_func_proto bpf_get_cpumask_info_proto = {
    .func		= bpf_get_cpumask_info,
    .gpl_only	= false,
    .ret_type	= RET_INTEGER,
-	.arg1_type	= ARG_PTR_TO_UNINIT_MEM,
-	.arg2_type	= ARG_CONST_SIZE,
+	.arg1_type	= ARG_CONST_MAP_PTR,
+	.arg2_type	= ARG_PTR_TO_MAP_VALUE_OR_NULL,
 };
diff --git a/samples/bpf/sched_select_core_kern.c b/samples/bpf/sched_select_core_kern.c
index 18617e89b395..30765ae65f85 100644
--- a/samples/bpf/sched_select_core_kern.c
+++ b/samples/bpf/sched_select_core_kern.c
@@ -62,7 +62,7 @@ struct tag_info {
struct tag_info tag_tbl[] = {
    {TAG_NONE, ""},
-	{TAG_ID(1), "0-3"},
+	{TAG_ID(1), "0-1"},
    {TAG_ID(2), "4-7"},
    {TAG_MAX, ""},
 };
@@ -94,13 +94,17 @@ static struct cpumask *select_better_cpus(struct task_struct *p,
    long min_util = INT_MIN;
    struct task_group *tg;
    long spare;
-	int cpu;
+	int cpu, i;
if (!prefer_cpus_valid(prefer_cpus, (void *)getVal(p->cpus_ptr)))
    	return (void *)getVal(p->cpus_ptr);
tg = p->sched_task_group;
-	libbpf_for_each_cpu(cpu, prefer_cpus) {
+	for (i = 0, cpu = -1; i < BPF_SCHED_LOOP_MAX; i++) {
+		cpu = libbpf_cpumask_next(cpu, (void *)getVal(prefer_cpus));
+		if (cpu >= libbpf_nr_cpus_ids())
+			break;
+
    	if (idlest_cpu && libbpf_available_idle_cpu(cpu)) {
    		*idlest_cpu = cpu;
    	} else if (idlest_cpu) {
@@ -159,9 +163,14 @@ int BPF_PROG(cfs_select_cpu_range, struct sched_migrate_ctx *h_ctx)
 SEC("sched/cfs_select_rq_exit")
 int BPF_PROG(cfs_select_cpu_range_exit, struct sched_migrate_ctx *h_ctx)
 {
+	struct task_struct *p = getVal(h_ctx->task);
+	long tag = getVal(p->tag);
    int *idlest_cpu;
    int key = 0;
+	if (tag <= TAG_NONE || tag >= TAG_MAX)
+		return SELECT_RQ_EXIT_CPU_VALID;
+
    idlest_cpu = bpf_map_lookup_elem(&map_idlest_cpu, &key);
    if (!idlest_cpu) {
    	libbpf_sched_set_task_cpus_ptr(h_ctx, (void *)getVal(h_ctx->cpus_allowed));
@@ -186,7 +195,7 @@ static int find_idlest_cpu(struct task_struct *p, int parent)
    int cpu;
    int i;
-	for (i = 0, cpu = -1; i < NR_CPUS; i++) {
+	for (i = 0, cpu = -1; i < BPF_SCHED_LOOP_MAX; i++) {
    	cpu = libbpf_cpumask_next(cpu, (void *)getVal(p->cpus_ptr));
    	if (cpu >= libbpf_nr_cpus_ids())
    		break;
@@ -203,17 +212,26 @@ static int find_idlest_cpu(struct task_struct *p, int parent)
static int select_idle_cpu(struct task_struct *p, int parent, int prev_cpu)
 {
-	int cpu;
+	int cpu, i;
if (libbpf_available_idle_cpu(prev_cpu))
    	return prev_cpu;
if (libbpf_available_idle_cpu(parent))
-		return prev_cpu;
+		return parent;
+
+	cpu = libbpf_cpumask_next_wrap(prev_cpu - 1,
+				       (void *)getVal(p->cpus_ptr),
+				       prev_cpu, false);
+	for (i = 0; i < BPF_SCHED_LOOP_MAX; i++) {
+		if (cpu >= libbpf_nr_cpumask_bits())
+			break;
-	libbpf_for_each_cpu_wrap(cpu, (void *)getVal(p->cpus_ptr), prev_cpu) {
    	if (libbpf_available_idle_cpu(cpu))
    		return cpu;
+
+		cpu = libbpf_cpumask_next_wrap(cpu, (void *)getVal(p->cpus_ptr),
+					       prev_cpu, true);
    }
return prev_cpu;
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 57b927e99092..22f7880a0bb6 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -4613,7 +4613,7 @@ union bpf_attr {
  *	Return
  *		0 on success, or a negative error in case of failure.
  *
- * int bpf_get_cpumask_info(struct bpf_cpumask_info *cpus, int len)
+ * int bpf_get_cpumask_info(struct bpf_map *map, struct bpf_cpumask_info *cpus)
  *	Description
  *		Get system cpus returned in *cpus*.
  *	Return
diff --git a/tools/lib/bpf/libbpf_sched.h b/tools/lib/bpf/libbpf_sched.h
index 6cb30e8e81f8..187e854b99b3 100644
--- a/tools/lib/bpf/libbpf_sched.h
+++ b/tools/lib/bpf/libbpf_sched.h
@@ -21,6 +21,8 @@
 #include <bpf/bpf_helpers.h>
 #include <bpf/bpf_tracing.h>
+/* set bigger value may lead verifier failed */
+#define BPF_SCHED_LOOP_MAX	1024
 #define INVALID_PTR		((void *)(0UL))
 #define getVal(P)							\
    ({								\
@@ -69,6 +71,13 @@ static __always_inline int libbpf_nr_cpumask_bits(void);
#endif
+struct {
+	__uint(type, BPF_MAP_TYPE_PERCPU_ARRAY);
+	__type(key, u32);
+	__type(value, struct bpf_cpumask_info);
+	__uint(max_entries, 1);
+} map_cpumask_info SEC(".maps");
+
 static __always_inline long libbpf_cpumask_copy(struct cpumask *dst,
    					struct cpumask *src)
 {
@@ -228,58 +237,93 @@ static __always_inline long libbpf_cpumask_cpulist_parse(char *src1,
static __always_inline int libbpf_num_active_cpus(void)
 {
-	struct bpf_cpumask_info cpus;
+	struct bpf_cpumask_info *cpus;
+	int key = 0;
+
+	cpus = bpf_map_lookup_elem(&map_cpumask_info, &key);
+	if (!cpus)
+		return -1;
-	bpf_get_cpumask_info(&cpus, sizeof(cpus));
-	return getVal(cpus.nums_active_cpus);
+	bpf_get_cpumask_info(&map_cpumask_info, cpus);
+	return getVal(cpus->nums_active_cpus);
 }
static __always_inline int libbpf_num_possible_cpus(void)
 {
-	struct bpf_cpumask_info cpus;
+	struct bpf_cpumask_info *cpus;
+	int key = 0;
-	bpf_get_cpumask_info(&cpus, sizeof(cpus));
-	return getVal(cpus.nums_possible_cpus);
+	cpus = bpf_map_lookup_elem(&map_cpumask_info, &key);
+	if (!cpus)
+		return -1;
+
+	bpf_get_cpumask_info(&map_cpumask_info, cpus);
+	return getVal(cpus->nums_possible_cpus);
 }
static __always_inline void libbpf_possible_cpus_mask(struct cpumask *mask)
 {
-	struct bpf_cpumask_info cpus;
+	struct bpf_cpumask_info *cpus;
+	int key = 0;
+
+	cpus = bpf_map_lookup_elem(&map_cpumask_info, &key);
+	if (!cpus)
+		return;
-	bpf_get_cpumask_info(&cpus, sizeof(cpus));
-	libbpf_cpumask_copy(mask, &cpus.cpu_possible_cpumask);
+	bpf_get_cpumask_info(&map_cpumask_info, cpus);
+	libbpf_cpumask_copy(mask, &cpus->cpu_possible_cpumask);
 }
static __always_inline void libbpf_active_cpus_mask(struct cpumask *mask)
 {
-	struct bpf_cpumask_info cpus;
+	struct bpf_cpumask_info *cpus;
+	int key = 0;
-	bpf_get_cpumask_info(&cpus, sizeof(cpus));
-	libbpf_cpumask_copy(mask, &cpus.cpu_active_cpumask);
+	cpus = bpf_map_lookup_elem(&map_cpumask_info, &key);
+	if (!cpus)
+		return;
+
+	bpf_get_cpumask_info(&map_cpumask_info, cpus);
+	libbpf_cpumask_copy(mask, &cpus->cpu_active_cpumask);
 }
static __always_inline void libbpf_isolate_cpus_mask(struct cpumask *mask)
 {
-	struct bpf_cpumask_info cpus;
+	struct bpf_cpumask_info *cpus;
+	int key = 0;
+
+	cpus = bpf_map_lookup_elem(&map_cpumask_info, &key);
+	if (!cpus)
+		return;
-	bpf_get_cpumask_info(&cpus, sizeof(cpus));
-	libbpf_cpumask_copy(mask, &cpus.cpu_isolate_cpumask);
+	bpf_get_cpumask_info(&map_cpumask_info, cpus);
+	libbpf_cpumask_copy(mask, &cpus->cpu_isolate_cpumask);
 }
static __always_inline int libbpf_nr_cpus_ids(void)
 {
-	struct bpf_cpumask_info cpus;
+	struct bpf_cpumask_info *cpus;
+	int key = 0;
-	bpf_get_cpumask_info(&cpus, sizeof(cpus));
-	return getVal(cpus.nr_cpu_ids);
+	cpus = bpf_map_lookup_elem(&map_cpumask_info, &key);
+	if (!cpus)
+		return -1;
+
+	bpf_get_cpumask_info(&map_cpumask_info, cpus);
+	return getVal(cpus->nr_cpu_ids);
 }
static __always_inline int libbpf_nr_cpumask_bits(void)
 {
-	struct bpf_cpumask_info cpus;
+	struct bpf_cpumask_info *cpus;
+	int key = 0;
+
+	cpus = bpf_map_lookup_elem(&map_cpumask_info, &key);
+	if (!cpus)
+		return -1;
-	bpf_get_cpumask_info(&cpus, sizeof(cpus));
-	return getVal(cpus.bpf_nr_cpumask_bits);
+	bpf_get_cpumask_info(&map_cpumask_info, cpus);
+	return getVal(cpus->bpf_nr_cpumask_bits);
 }
static __always_inline unsigned long libbpf_cfs_load_avg_of(int cpu)
-- 
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[PATCH openEuler-22.09 v2] bpf:programmable: Fix build error of 'stack exceeds 512 bytes'