Merge branch 'bpf-maximum-combined-stack-depth'

Paul Chaignon says:

====================
bpf: Maximum combined stack depth

This patchset dumps the maximum combined stack depth in verifier logs
and parses it in veristat.

Changes in v3:
  - Increment spec_cnt field in veristat for new MAX_STACK id (AI bot).
Changes in v2:
  - Remove unnecessary max_stack_depth assignment (Eduard).
  - Fix and test incorrect handling of private stacks.
  - Add veristat metric (Eduard).
====================

Link: https://patch.msgid.link/cover.1778700777.git.paul.chaignon@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

5 files changed, 32 insertions, 7 deletions

diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h
index 6f12fc40b682..20c421b43849 100644
--- a/include/linux/bpf_verifier.h
+++ b/include/linux/bpf_verifier.h
@@ -989,6 +989,8 @@ struct bpf_verifier_env {
 	u32 prev_insn_processed, insn_processed;
 	/* number of jmps, calls, exits analyzed so far */
 	u32 prev_jmps_processed, jmps_processed;
+	/* maximum combined stack depth */
+	u32 max_stack_depth;
 	/* total verification time */
 	u64 verification_time;
 	/* maximum number of verifier states kept in 'branching' instructions */
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 82b9531f87f6..76a07f09ab64 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -5177,6 +5177,8 @@ process_func:
 	}
 
 	if (subprog[idx].priv_stack_mode == PRIV_STACK_ADAPTIVE) {
+		if (subprog_depth > env->max_stack_depth)
+			env->max_stack_depth = subprog_depth;
 		if (subprog_depth > MAX_BPF_STACK) {
 			verbose(env, "stack size of subprog %d is %d. Too large\n",
 				idx, subprog_depth);
@@ -5184,6 +5186,8 @@ process_func:
 		}
 	} else {
 		depth += subprog_depth;
+		if (depth > env->max_stack_depth)
+			env->max_stack_depth = depth;
 		if (depth > MAX_BPF_STACK) {
 			total = 0;
 			for (tmp = idx; tmp >= 0; tmp = dinfo[tmp].caller)
@@ -18555,7 +18559,7 @@ static void print_verification_stats(struct bpf_verifier_env *env)
 		verbose(env, "stack depth %d", env->subprog_info[0].stack_depth);
 		for (i = 1; i < subprog_cnt; i++)
 			verbose(env, "+%d", env->subprog_info[i].stack_depth);
-		verbose(env, "\n");
+		verbose(env, " max %d\n", env->max_stack_depth);
 		verbose(env, "insns processed %d", env->subprog_info[0].insn_processed);
 		for (i = 1; i < subprog_cnt; i++)
 			if (bpf_subprog_is_global(env, i))
diff --git a/tools/testing/selftests/bpf/progs/verifier_bpf_fastcall.c b/tools/testing/selftests/bpf/progs/verifier_bpf_fastcall.c
index 0d9e167555b5..8d7ff38e4c06 100644
--- a/tools/testing/selftests/bpf/progs/verifier_bpf_fastcall.c
+++ b/tools/testing/selftests/bpf/progs/verifier_bpf_fastcall.c
@@ -799,8 +799,7 @@ __naked int bpf_loop_interaction2(void)
 
 SEC("raw_tp")
 __arch_x86_64
-__log_level(4)
-__msg("stack depth 512+0")
+__log_level(4) __msg("stack depth 512+0 max 512")
 /* just to print xlated version when debugging */
 __xlated("r0 = &(void __percpu *)(r0)")
 __success
diff --git a/tools/testing/selftests/bpf/progs/verifier_private_stack.c b/tools/testing/selftests/bpf/progs/verifier_private_stack.c
index c5078face38d..046f7445a458 100644
--- a/tools/testing/selftests/bpf/progs/verifier_private_stack.c
+++ b/tools/testing/selftests/bpf/progs/verifier_private_stack.c
@@ -86,6 +86,7 @@ __naked static void cumulative_stack_depth_subprog(void)
 SEC("kprobe")
 __description("Private stack, subtree > MAX_BPF_STACK")
 __success
+__log_level(4) __msg("stack depth 512+32 max 512")
 __arch_x86_64
 /* private stack fp for the main prog */
 __jited("	movabsq	$0x{{.*}}, %r9")
@@ -324,6 +325,8 @@ int private_stack_async_callback_1(void)
 SEC("fentry/bpf_fentry_test9")
 __description("Private stack, async callback, potential nesting")
 __success __retval(0)
+__load_if_JITed()
+__log_level(4) __msg("stack depth 8+0+256+0 max 272")
 __arch_x86_64
 __jited("	subq	$0x100, %rsp")
 __arch_arm64
@@ -344,6 +347,18 @@ int private_stack_async_callback_2(void)
 	return 0;
 }
 
+SEC("fentry/bpf_fentry_test9")
+__description("private stack, max stack depth is private stack")
+__success
+__log_level(4) __msg("stack depth 8+256+0 max 256")
+int private_stack_max_depth(void)
+{
+	int x = 0;
+
+	subprog1(&x);
+	return 0;
+}
+
 #else
 
 SEC("kprobe")
diff --git a/tools/testing/selftests/bpf/veristat.c b/tools/testing/selftests/bpf/veristat.c
index 5c82950e6978..a7db6f04f7e1 100644
--- a/tools/testing/selftests/bpf/veristat.c
+++ b/tools/testing/selftests/bpf/veristat.c
@@ -48,6 +48,7 @@ enum stat_id {
 	SIZE,
 	JITED_SIZE,
 	STACK,
+	MAX_STACK,
 	PROG_TYPE,
 	ATTACH_TYPE,
 	MEMORY_PEAK,
@@ -789,13 +790,13 @@ cleanup:
 }
 
 static const struct stat_specs default_csv_output_spec = {
-	.spec_cnt = 15,
+	.spec_cnt = 16,
 	.ids = {
 		FILE_NAME, PROG_NAME, VERDICT, DURATION,
 		TOTAL_INSNS, TOTAL_STATES, PEAK_STATES,
 		MAX_STATES_PER_INSN, MARK_READ_MAX_LEN,
 		SIZE, JITED_SIZE, PROG_TYPE, ATTACH_TYPE,
-		STACK, MEMORY_PEAK,
+		STACK, MAX_STACK, MEMORY_PEAK,
 	},
 };
 
@@ -834,6 +835,7 @@ static struct stat_def {
 	[SIZE] = { "Program size", {"prog_size"}, },
 	[JITED_SIZE] = { "Jited size", {"prog_size_jited"}, },
 	[STACK] = {"Stack depth", {"stack_depth", "stack"}, },
+	[MAX_STACK] = {"Max stack depth", {"max_stack_depth"}, },
 	[PROG_TYPE] = { "Program type", {"prog_type"}, },
 	[ATTACH_TYPE] = { "Attach type", {"attach_type", }, },
 	[MEMORY_PEAK] = { "Peak memory (MiB)", {"mem_peak", }, },
@@ -1023,7 +1025,7 @@ static int parse_verif_log(char * const buf, size_t buf_sz, struct verif_stats *
 				&s->stats[MARK_READ_MAX_LEN]))
 			continue;
 
-		if (1 == sscanf(cur, "stack depth %511s", stack))
+		if (2 == sscanf(cur, "stack depth %511s max %ld", stack, &s->stats[MAX_STACK]))
 			continue;
 	}
 	while ((token = strtok_r(cnt++ ? NULL : stack, "+", &state))) {
@@ -2278,6 +2280,7 @@ static int cmp_stat(const struct verif_stats *s1, const struct verif_stats *s2,
 	case SIZE:
 	case JITED_SIZE:
 	case STACK:
+	case MAX_STACK:
 	case VERDICT:
 	case DURATION:
 	case TOTAL_INSNS:
@@ -2512,6 +2515,7 @@ static void prepare_value(const struct verif_stats *s, enum stat_id id,
 	case MAX_STATES_PER_INSN:
 	case MARK_READ_MAX_LEN:
 	case STACK:
+	case MAX_STACK:
 	case SIZE:
 	case JITED_SIZE:
 	case MEMORY_PEAK:
@@ -2602,7 +2606,8 @@ static int parse_stat_value(const char *str, enum stat_id id, struct verif_stats
 	case SIZE:
 	case JITED_SIZE:
 	case MEMORY_PEAK:
-	case STACK: {
+	case STACK:
+	case MAX_STACK: {
 		long val;
 		int err, n;