diff mbox series

[v10,13/36] function_graph: Use a simple LRU for fgraph_array index number

Message ID 171509103267.162236.6885097397289135378.stgit@devnote2 (mailing list archive)
State Not Applicable
Headers show
Series tracing: fprobe: function_graph: Multi-function graph and fprobe on fgraph | expand

Checks

Context Check Description
netdev/tree_selection success Guessing tree name failed - patch did not apply
bpf/vmtest-bpf-PR success PR summary
bpf/vmtest-bpf-VM_Test-2 success Logs for Unittests
bpf/vmtest-bpf-VM_Test-3 success Logs for Validate matrix.py
bpf/vmtest-bpf-VM_Test-0 success Logs for Lint
bpf/vmtest-bpf-VM_Test-4 success Logs for aarch64-gcc / build / build for aarch64 with gcc
bpf/vmtest-bpf-VM_Test-1 success Logs for ShellCheck
bpf/vmtest-bpf-VM_Test-5 success Logs for aarch64-gcc / build-release
bpf/vmtest-bpf-VM_Test-6 success Logs for aarch64-gcc / test (test_maps, false, 360) / test_maps on aarch64 with gcc
bpf/vmtest-bpf-VM_Test-7 success Logs for aarch64-gcc / test (test_progs, false, 360) / test_progs on aarch64 with gcc
bpf/vmtest-bpf-VM_Test-8 success Logs for aarch64-gcc / test (test_progs_no_alu32, false, 360) / test_progs_no_alu32 on aarch64 with gcc
bpf/vmtest-bpf-VM_Test-9 success Logs for aarch64-gcc / test (test_verifier, false, 360) / test_verifier on aarch64 with gcc
bpf/vmtest-bpf-VM_Test-10 success Logs for aarch64-gcc / veristat
bpf/vmtest-bpf-VM_Test-11 success Logs for s390x-gcc / build / build for s390x with gcc
bpf/vmtest-bpf-VM_Test-12 success Logs for s390x-gcc / build-release
bpf/vmtest-bpf-VM_Test-13 success Logs for s390x-gcc / test (test_maps, false, 360) / test_maps on s390x with gcc
bpf/vmtest-bpf-VM_Test-14 success Logs for s390x-gcc / test (test_progs, false, 360) / test_progs on s390x with gcc
bpf/vmtest-bpf-VM_Test-15 success Logs for s390x-gcc / test (test_progs_no_alu32, false, 360) / test_progs_no_alu32 on s390x with gcc
bpf/vmtest-bpf-VM_Test-16 success Logs for s390x-gcc / test (test_verifier, false, 360) / test_verifier on s390x with gcc
bpf/vmtest-bpf-VM_Test-17 success Logs for s390x-gcc / veristat
bpf/vmtest-bpf-VM_Test-18 success Logs for set-matrix
bpf/vmtest-bpf-VM_Test-19 success Logs for x86_64-gcc / build / build for x86_64 with gcc
bpf/vmtest-bpf-VM_Test-20 success Logs for x86_64-gcc / build-release
bpf/vmtest-bpf-VM_Test-21 success Logs for x86_64-gcc / test (test_maps, false, 360) / test_maps on x86_64 with gcc
bpf/vmtest-bpf-VM_Test-22 success Logs for x86_64-gcc / test (test_progs, false, 360) / test_progs on x86_64 with gcc
bpf/vmtest-bpf-VM_Test-23 success Logs for x86_64-gcc / test (test_progs_no_alu32, false, 360) / test_progs_no_alu32 on x86_64 with gcc
bpf/vmtest-bpf-VM_Test-24 success Logs for x86_64-gcc / test (test_progs_no_alu32_parallel, true, 30) / test_progs_no_alu32_parallel on x86_64 with gcc
bpf/vmtest-bpf-VM_Test-25 success Logs for x86_64-gcc / test (test_progs_parallel, true, 30) / test_progs_parallel on x86_64 with gcc
bpf/vmtest-bpf-VM_Test-26 success Logs for x86_64-gcc / test (test_verifier, false, 360) / test_verifier on x86_64 with gcc
bpf/vmtest-bpf-VM_Test-27 success Logs for x86_64-gcc / veristat / veristat on x86_64 with gcc
bpf/vmtest-bpf-VM_Test-28 success Logs for x86_64-llvm-17 / build / build for x86_64 with llvm-17
bpf/vmtest-bpf-VM_Test-29 success Logs for x86_64-llvm-17 / build-release / build for x86_64 with llvm-17 and -O2 optimization
bpf/vmtest-bpf-VM_Test-30 success Logs for x86_64-llvm-17 / test (test_maps, false, 360) / test_maps on x86_64 with llvm-17
bpf/vmtest-bpf-VM_Test-31 success Logs for x86_64-llvm-17 / test (test_progs, false, 360) / test_progs on x86_64 with llvm-17
bpf/vmtest-bpf-VM_Test-32 success Logs for x86_64-llvm-17 / test (test_progs_no_alu32, false, 360) / test_progs_no_alu32 on x86_64 with llvm-17
bpf/vmtest-bpf-VM_Test-33 success Logs for x86_64-llvm-17 / test (test_verifier, false, 360) / test_verifier on x86_64 with llvm-17
bpf/vmtest-bpf-VM_Test-34 success Logs for x86_64-llvm-17 / veristat
bpf/vmtest-bpf-VM_Test-35 success Logs for x86_64-llvm-18 / build / build for x86_64 with llvm-18
bpf/vmtest-bpf-VM_Test-36 success Logs for x86_64-llvm-18 / build-release / build for x86_64 with llvm-18 and -O2 optimization
bpf/vmtest-bpf-VM_Test-37 success Logs for x86_64-llvm-18 / test (test_maps, false, 360) / test_maps on x86_64 with llvm-18
bpf/vmtest-bpf-VM_Test-38 success Logs for x86_64-llvm-18 / test (test_progs, false, 360) / test_progs on x86_64 with llvm-18
bpf/vmtest-bpf-VM_Test-39 success Logs for x86_64-llvm-18 / test (test_progs_cpuv4, false, 360) / test_progs_cpuv4 on x86_64 with llvm-18
bpf/vmtest-bpf-VM_Test-40 success Logs for x86_64-llvm-18 / test (test_progs_no_alu32, false, 360) / test_progs_no_alu32 on x86_64 with llvm-18
bpf/vmtest-bpf-VM_Test-41 success Logs for x86_64-llvm-18 / test (test_verifier, false, 360) / test_verifier on x86_64 with llvm-18
bpf/vmtest-bpf-VM_Test-42 success Logs for x86_64-llvm-18 / veristat

Commit Message

Masami Hiramatsu (Google) May 7, 2024, 2:10 p.m. UTC 
From: Masami Hiramatsu (Google) <mhiramat@kernel.org>

Since the fgraph_array index is used for the bitmap on the shadow
stack, it may leave some entries after a function_graph instance is
removed. Thus if another instance reuses the fgraph_array index soon
after releasing it, the fgraph may confuse to call the newer callback
for the entries which are pushed by the older instance.
To avoid reusing the fgraph_array index soon after releasing, introduce
a simple LRU table for managing the index number. This will reduce the
possibility of this confusion.

Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
---
 Changes in v8:
  - Add a WARN_ON_ONCE() if fgraph_lru_table[] is broken when releasing
    index, and remove WARN_ON_ONCE() from unregister_ftrace_graph()
  - Fix to release allocated index if register_ftrace_graph() fails.
  - Add comments and code cleanup.
 Changes in v5:
  - Fix the underflow bug in fgraph_lru_release_index() and return 0
    if the release is succeded.
 Changes in v4:
  - Newly added.
---
 kernel/trace/fgraph.c |   71 +++++++++++++++++++++++++++++++++++--------------
 1 file changed, 50 insertions(+), 21 deletions(-)
diff mbox series

Patch

diff --git a/kernel/trace/fgraph.c b/kernel/trace/fgraph.c
index b6949e4fda79..c00a299decb1 100644
--- a/kernel/trace/fgraph.c
+++ b/kernel/trace/fgraph.c
@@ -97,10 +97,48 @@  enum {
 DEFINE_STATIC_KEY_FALSE(kill_ftrace_graph);
 int ftrace_graph_active;
 
-static int fgraph_array_cnt;
-
 static struct fgraph_ops *fgraph_array[FGRAPH_ARRAY_SIZE];
 
+/* LRU index table for fgraph_array */
+static int fgraph_lru_table[FGRAPH_ARRAY_SIZE];
+static int fgraph_lru_next;
+static int fgraph_lru_last;
+
+/* Initialize fgraph_lru_table with unused index */
+static void fgraph_lru_init(void)
+{
+	int i;
+
+	for (i = 0; i < FGRAPH_ARRAY_SIZE; i++)
+		fgraph_lru_table[i] = i;
+}
+
+/* Release the used index to the LRU table */
+static int fgraph_lru_release_index(int idx)
+{
+	if (idx < 0 || idx >= FGRAPH_ARRAY_SIZE ||
+	    WARN_ON_ONCE(fgraph_lru_table[fgraph_lru_last] != -1))
+		return -1;
+
+	fgraph_lru_table[fgraph_lru_last] = idx;
+	fgraph_lru_last = (fgraph_lru_last + 1) % FGRAPH_ARRAY_SIZE;
+	return 0;
+}
+
+/* Allocate a new index from LRU table */
+static int fgraph_lru_alloc_index(void)
+{
+	int idx = fgraph_lru_table[fgraph_lru_next];
+
+	/* No id is available */
+	if (idx == -1)
+		return -1;
+
+	fgraph_lru_table[fgraph_lru_next] = -1;
+	fgraph_lru_next = (fgraph_lru_next + 1) % FGRAPH_ARRAY_SIZE;
+	return idx;
+}
+
 static inline int get_frame_offset(struct task_struct *t, int offset)
 {
 	return t->ret_stack[offset] & FGRAPH_FRAME_OFFSET_MASK;
@@ -365,7 +403,7 @@  int function_graph_enter(unsigned long ret, unsigned long func,
 	if (offset < 0)
 		goto out;
 
-	for (i = 0; i < fgraph_array_cnt; i++) {
+	for (i = 0; i < FGRAPH_ARRAY_SIZE; i++) {
 		struct fgraph_ops *gops = fgraph_array[i];
 
 		if (gops == &fgraph_stub)
@@ -917,7 +955,7 @@  int register_ftrace_graph(struct fgraph_ops *gops)
 {
 	int command = 0;
 	int ret = 0;
-	int i;
+	int i = -1;
 
 	mutex_lock(&ftrace_lock);
 
@@ -933,21 +971,16 @@  int register_ftrace_graph(struct fgraph_ops *gops)
 		/* The array must always have real data on it */
 		for (i = 0; i < FGRAPH_ARRAY_SIZE; i++)
 			fgraph_array[i] = &fgraph_stub;
+		fgraph_lru_init();
 	}
 
-	/* Look for an available spot */
-	for (i = 0; i < FGRAPH_ARRAY_SIZE; i++) {
-		if (fgraph_array[i] == &fgraph_stub)
-			break;
-	}
-	if (i >= FGRAPH_ARRAY_SIZE) {
+	i = fgraph_lru_alloc_index();
+	if (i < 0 || WARN_ON_ONCE(fgraph_array[i] != &fgraph_stub)) {
 		ret = -ENOSPC;
 		goto out;
 	}
 
 	fgraph_array[i] = gops;
-	if (i + 1 > fgraph_array_cnt)
-		fgraph_array_cnt = i + 1;
 	gops->idx = i;
 
 	ftrace_graph_active++;
@@ -971,6 +1004,7 @@  int register_ftrace_graph(struct fgraph_ops *gops)
 	if (ret) {
 		fgraph_array[i] = &fgraph_stub;
 		ftrace_graph_active--;
+		fgraph_lru_release_index(i);
 	}
 out:
 	mutex_unlock(&ftrace_lock);
@@ -980,25 +1014,20 @@  int register_ftrace_graph(struct fgraph_ops *gops)
 void unregister_ftrace_graph(struct fgraph_ops *gops)
 {
 	int command = 0;
-	int i;
 
 	mutex_lock(&ftrace_lock);
 
 	if (unlikely(!ftrace_graph_active))
 		goto out;
 
-	if (unlikely(gops->idx < 0 || gops->idx >= fgraph_array_cnt))
+	if (unlikely(gops->idx < 0 || gops->idx >= FGRAPH_ARRAY_SIZE ||
+		     fgraph_array[gops->idx] != gops))
 		goto out;
 
-	WARN_ON_ONCE(fgraph_array[gops->idx] != gops);
+	if (fgraph_lru_release_index(gops->idx) < 0)
+		goto out;
 
 	fgraph_array[gops->idx] = &fgraph_stub;
-	if (gops->idx + 1 == fgraph_array_cnt) {
-		i = gops->idx;
-		while (i >= 0 && fgraph_array[i] == &fgraph_stub)
-			i--;
-		fgraph_array_cnt = i + 1;
-	}
 
 	ftrace_graph_active--;