This test case uses a BPF program to enforce the following THP allocation
policy:
- Only the current task is permitted to allocate THP.
- All other tasks are denied.
The expected behavior:
- Before the BPF prog is attached
No tasks can allocate THP.
- After the BPF prog is attached
Only the current task can allocate THP.
- Switch to "never" mode after the BPF prog is attached
THP allocation is not allowed even for the current task.
The result is as follows,
$ ./test_progs --name="thp_adjust"
#437 thp_adjust:OK
Summary: 1/0 PASSED, 0 SKIPPED, 0 FAILED
CONFIG_TRANSPARENT_HUGEPAGE=y is required for this test.
Signed-off-by: Yafang Shao <laoar.shao@xxxxxxxxx>
---
tools/testing/selftests/bpf/config | 1 +
.../selftests/bpf/prog_tests/thp_adjust.c | 175 ++++++++++++++++++
.../selftests/bpf/progs/test_thp_adjust.c | 39 ++++
3 files changed, 215 insertions(+)
create mode 100644 tools/testing/selftests/bpf/prog_tests/thp_adjust.c
create mode 100644 tools/testing/selftests/bpf/progs/test_thp_adjust.c
diff --git a/tools/testing/selftests/bpf/config b/tools/testing/selftests/bpf/config
index c378d5d07e02..bb8a8a9d77a2 100644
--- a/tools/testing/selftests/bpf/config
+++ b/tools/testing/selftests/bpf/config
@@ -113,3 +113,4 @@ CONFIG_XDP_SOCKETS=y
CONFIG_XFRM_INTERFACE=y
CONFIG_TCP_CONG_DCTCP=y
CONFIG_TCP_CONG_BBR=y
+CONFIG_TRANSPARENT_HUGEPAGE=y
diff --git a/tools/testing/selftests/bpf/prog_tests/thp_adjust.c b/tools/testing/selftests/bpf/prog_tests/thp_adjust.c
new file mode 100644
index 000000000000..6accd110d8ea
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/thp_adjust.c
@@ -0,0 +1,175 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <sys/mman.h>
+#include <test_progs.h>
+#include "test_thp_adjust.skel.h"
+
+#define LEN (4 * 1024 * 1024) /* 4MB */
+#define THP_ENABLED_PATH "/sys/kernel/mm/transparent_hugepage/enabled"
+#define SMAPS_PATH "/proc/self/smaps"
+#define ANON_HUGE_PAGES "AnonHugePages:"
+
+static char *thp_addr;
+static char old_mode[32];
+
+int thp_mode_save(void)
+{
+ const char *start, *end;
+ char buf[128];
+ int fd, err;
+ size_t len;
+
+ fd = open(THP_ENABLED_PATH, O_RDONLY);
+ if (fd == -1)
+ return -1;
+
+ err = read(fd, buf, sizeof(buf) - 1);
+ if (err == -1)
+ goto close;
+
+ start = strchr(buf, '[');
+ end = start ? strchr(start, ']') : NULL;
+ if (!start || !end || end <= start) {
+ err = -1;
+ goto close;
+ }
+
+ len = end - start - 1;
+ if (len >= sizeof(old_mode))
+ len = sizeof(old_mode) - 1;
+ strncpy(old_mode, start + 1, len);
+ old_mode[len] = '\0';
+
+close:
+ close(fd);
+ return err;
+}
+
+int thp_set(const char *desired_mode)
+{
+ int fd, err;
+
+ fd = open(THP_ENABLED_PATH, O_RDWR);
+ if (fd == -1)
+ return -1;
+
+ err = write(fd, desired_mode, strlen(desired_mode));
+ close(fd);
+ return err;
+}
+
+int thp_reset(void)
+{
+ int fd, err;
+
+ fd = open(THP_ENABLED_PATH, O_WRONLY);
+ if (fd == -1)
+ return -1;
+
+ err = write(fd, old_mode, strlen(old_mode));
+ close(fd);
+ return err;
+}
+
+int thp_alloc(void)
+{
+ int err, i;
+
+ thp_addr = mmap(NULL, LEN, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANON, -1, 0);
+ if (thp_addr == MAP_FAILED)
+ return -1;
+
+ err = madvise(thp_addr, LEN, MADV_HUGEPAGE);
+ if (err == -1)
+ goto unmap;
+
+ for (i = 0; i < LEN; i += 4096)
+ thp_addr[i] = 1;
+ return 0;
+
+unmap:
+ munmap(thp_addr, LEN);
+ return -1;
+}
+
+void thp_free(void)
+{
+ if (!thp_addr)
+ return;
+ munmap(thp_addr, LEN);
+}
+
+void test_thp_adjust(void)
+{
+ struct bpf_link *fentry_link, *ops_link;
+ struct test_thp_adjust *skel;
+ int err, first_calls;
+
+ if (!ASSERT_NEQ(thp_mode_save(), -1, "THP mode save"))
+ return;
+ if (!ASSERT_GE(thp_set("bpf"), 0, "THP mode set"))
+ return;
+
+ skel = test_thp_adjust__open();
+ if (!ASSERT_OK_PTR(skel, "open"))
+ goto thp_reset;
+
+ skel->bss->target_pid = getpid();
+
+ err = test_thp_adjust__load(skel);
+ if (!ASSERT_OK(err, "load"))
+ goto destroy;
+
+ fentry_link = bpf_program__attach_trace(skel->progs.thp_run);
+ if (!ASSERT_OK_PTR(fentry_link, "attach fentry"))
+ goto destroy;
+
+ if (!ASSERT_NEQ(thp_alloc(), -1, "THP alloc"))
+ goto destroy;
+
+ /* Before attaching struct_ops, THP won't be allocated. */
+ if (!ASSERT_EQ(skel->bss->thp_calls, 0, "THP calls"))
+ goto thp_free;
+
+ if (!ASSERT_EQ(skel->bss->thp_wrong_calls, 0, "THP calls"))
+ goto thp_free;
+
+ thp_free();
+
+ ops_link = bpf_map__attach_struct_ops(skel->maps.thp);
+ if (!ASSERT_OK_PTR(ops_link, "attach struct_ops"))
+ goto destroy;
+
+ if (!ASSERT_NEQ(thp_alloc(), -1, "THP alloc"))
+ goto destroy;
+
+ /* After attaching struct_ops, THP will be allocated. */
+ if (!ASSERT_GT(skel->bss->thp_calls, 0, "THP calls"))
+ goto thp_free;
+
+ first_calls = skel->bss->thp_calls;
+
+ if (!ASSERT_EQ(skel->bss->thp_wrong_calls, 0, "THP calls"))
+ goto thp_free;
+
+ thp_free();
+
+ if (!ASSERT_GE(thp_set("never"), 0, "THP set"))
+ goto destroy;
+
+ if (!ASSERT_NEQ(thp_alloc(), -1, "THP alloc"))
+ goto destroy;
+
+ /* In "never" mode, THP won't be allocated even if the prog is attached. */
+ if (!ASSERT_EQ(skel->bss->thp_calls, first_calls, "THP calls"))
+ goto thp_free;
+
+ ASSERT_EQ(skel->bss->thp_wrong_calls, 0, "THP calls");
+
+thp_free:
+ thp_free();
+destroy:
+ test_thp_adjust__destroy(skel);
+thp_reset:
+ ASSERT_GE(thp_reset(), 0, "THP mode reset");
+}
diff --git a/tools/testing/selftests/bpf/progs/test_thp_adjust.c b/tools/testing/selftests/bpf/progs/test_thp_adjust.c
new file mode 100644
index 000000000000..69135380853c
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/test_thp_adjust.c
@@ -0,0 +1,39 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include "vmlinux.h"
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+
+char _license[] SEC("license") = "GPL";
+
+int target_pid;
+int thp_calls;
+int thp_wrong_calls;
+
+SEC("fentry/do_huge_pmd_anonymous_page")
+int BPF_PROG(thp_run)
+{
+ struct task_struct *current = bpf_get_current_task_btf();
+
+ if (current->pid == target_pid)
+ thp_calls++;
+ else
+ thp_wrong_calls++;
+ return 0;
+}
+
+SEC("struct_ops/thp_bpf_allowable")
+bool BPF_PROG(thp_bpf_allowable)
+{
+ struct task_struct *current = bpf_get_current_task_btf();
+
+ /* Permit the current task to allocate memory using THP. */
+ if (current->pid == target_pid)
+ return true;
+ return false;
+}
+
+SEC(".struct_ops.link")
+struct bpf_thp_ops thp = {
+ .thp_bpf_allowable = (void *)thp_bpf_allowable,
+};
--
2.43.5
