This patch add three testcases to verify the proper management of return_instance data by uretprobes:
- uretprobe_longjmp() verifies that longjmp() bypasses the uretprobe BPF program attached to the exit of instrumented function. - uretprobe_cleanup_return_instance() verifies that uretprobe reclaim the return_instances data created before a longjmp(), which leads to kernel recount the nested depth of instrumented function. - uretprobe_reach_nestedness_limit() confirms that the uretprobe doesn't reclaim the return_instances data created before longjmp() and hijack the return address of instrumented function upon the nestedness depth reache the limits (64). Signed-off-by: Liao Chang <[email protected]> --- .../bpf/prog_tests/uretprobe_depth.c | 150 ++++++++++++++++++ .../selftests/bpf/progs/uretprobe_depth.c | 19 +++ 2 files changed, 169 insertions(+) create mode 100644 tools/testing/selftests/bpf/prog_tests/uretprobe_depth.c create mode 100644 tools/testing/selftests/bpf/progs/uretprobe_depth.c diff --git a/tools/testing/selftests/bpf/prog_tests/uretprobe_depth.c b/tools/testing/selftests/bpf/prog_tests/uretprobe_depth.c new file mode 100644 index 000000000000..ba03b1868e37 --- /dev/null +++ b/tools/testing/selftests/bpf/prog_tests/uretprobe_depth.c @@ -0,0 +1,150 @@ +// SPDX-License-Identifier: GPL-2.0 + +#include <test_progs.h> + +#include <unistd.h> +#include <setjmp.h> +#include <asm/ptrace.h> +#include <linux/compiler.h> +#include <linux/stringify.h> +#include "uretprobe_depth.skel.h" + +#define RETVAL 0xFFFF +#define JMPVAL 0x4B1D +#define MAX_URETPROBE_DEPTH 64 // See include/linux/uprobes.h +#define NR_OMITTED_URETPROBE 16 +static jmp_buf jmp; + +unsigned long __uretprobe_longjmp(int nest, int jmpval, int retval) +{ + if (nest) { + nest = ++retval < MAX_URETPROBE_DEPTH + NR_OMITTED_URETPROBE; + return __uretprobe_longjmp(nest, jmpval, retval); + } + + if (jmpval == JMPVAL) { + longjmp(jmp, jmpval); + return 0; + } else + return retval; +} + +static void uretprobe_longjmp(void) +{ + if (setjmp(jmp) == JMPVAL) { + __uretprobe_longjmp(0, 0, JMPVAL); + return; + } + + __uretprobe_longjmp(0, JMPVAL, RETVAL); +} + +static void uretprobe_cleanup_return_instances(void) +{ + if (setjmp(jmp) == JMPVAL) { + /* + * Cleanup these return instance data created before longjmp + * firstly. Then create 16 new return_instance data from here. + */ + __uretprobe_longjmp(1, 0, MAX_URETPROBE_DEPTH); + return; + } + + /* Create 8 return_instance data from here. */ + __uretprobe_longjmp(1, JMPVAL, + MAX_URETPROBE_DEPTH + NR_OMITTED_URETPROBE / 2); +} + +static void uretprobe_reach_nestedness_limit(void) +{ + if (setjmp(jmp) == JMPVAL) { + /* + * Due to uretprobe reach to the nestedness limit, it doesn't + * cleanup the return instance created before longjmp. + */ + __uretprobe_longjmp(1, 0, MAX_URETPROBE_DEPTH); + return; + } + + /* Create 64 return_instance from here. */ + __uretprobe_longjmp(1, JMPVAL, 0); +} + +static void test_uretprobe_longjmp(void) +{ + struct uretprobe_depth *skel = NULL; + int err; + + skel = uretprobe_depth__open_and_load(); + if (!ASSERT_OK_PTR(skel, "uretprobe_depth__open_and_load")) + goto cleanup; + + err = uretprobe_depth__attach(skel); + if (!ASSERT_OK(err, "uretprobe_depth__attach")) + goto cleanup; + + skel->bss->retval = -1; + + uretprobe_longjmp(); + + ASSERT_EQ(skel->bss->retval, JMPVAL, "return value"); + +cleanup: + uretprobe_depth__destroy(skel); +} + +static void test_uretprobe_reach_nestedness_limit(void) +{ + struct uretprobe_depth *skel = NULL; + int err; + + skel = uretprobe_depth__open_and_load(); + if (!ASSERT_OK_PTR(skel, "uretprobe_depth__open_and_load")) + goto cleanup; + + err = uretprobe_depth__attach(skel); + if (!ASSERT_OK(err, "uretprobe_depth__attach")) + goto cleanup; + + skel->bss->depth = 0; + + uretprobe_reach_nestedness_limit(); + + ASSERT_EQ(skel->bss->depth, 0, "nest depth"); + +cleanup: + uretprobe_depth__destroy(skel); +} + +static void test_uretprobe_cleanup_return_instances(void) +{ + struct uretprobe_depth *skel = NULL; + int err; + + skel = uretprobe_depth__open_and_load(); + if (!ASSERT_OK_PTR(skel, "uretprobe_depth__open_and_load")) + goto cleanup; + + err = uretprobe_depth__attach(skel); + if (!ASSERT_OK(err, "uretprobe_depth__attach")) + goto cleanup; + + skel->bss->depth = 0; + + uretprobe_cleanup_return_instances(); + + ASSERT_EQ(skel->bss->depth, NR_OMITTED_URETPROBE + 1, "nest depth"); + +cleanup: + uretprobe_depth__destroy(skel); +} + +void test_uretprobe_return_instance(void) +{ + if (test__start_subtest("uretprobe_longjmp")) + test_uretprobe_longjmp(); + if (test__start_subtest("uretprobe_cleanup_return_instances")) + test_uretprobe_cleanup_return_instances(); + if (test__start_subtest("uretprobe_reach_nestedness_limit")) + test_uretprobe_reach_nestedness_limit(); +} diff --git a/tools/testing/selftests/bpf/progs/uretprobe_depth.c b/tools/testing/selftests/bpf/progs/uretprobe_depth.c new file mode 100644 index 000000000000..b71f2de52b5e --- /dev/null +++ b/tools/testing/selftests/bpf/progs/uretprobe_depth.c @@ -0,0 +1,19 @@ +// SPDX-License-Identifier: GPL-2.0 +#include "vmlinux.h" +#include <bpf/bpf_helpers.h> +#include <string.h> + +int depth; +unsigned long retval; + +char _license[] SEC("license") = "GPL"; + +SEC("uretprobe//proc/self/exe:__uretprobe_longjmp") +int uretprobe(struct pt_regs *ctx) +{ + depth++; +#if defined(__TARGET_ARCH_arm64) || defined(__aarch64__) + retval = ctx->regs[0]; +#endif + return 0; +} -- 2.34.1
