Add function redirection API based on Kprobes.
Suggested-by: Masami Hiramatsu mhiramat@kernel.org Signed-off-by: Tzung-Bi Shih tzungbi@kernel.org --- include/kunit/kprobes_stub.h | 19 ++++++ lib/kunit/Kconfig | 7 +++ lib/kunit/Makefile | 4 ++ lib/kunit/kprobes_stub.c | 113 +++++++++++++++++++++++++++++++++++ 4 files changed, 143 insertions(+) create mode 100644 include/kunit/kprobes_stub.h create mode 100644 lib/kunit/kprobes_stub.c
diff --git a/include/kunit/kprobes_stub.h b/include/kunit/kprobes_stub.h new file mode 100644 index 000000000000..af77c86fe48e --- /dev/null +++ b/include/kunit/kprobes_stub.h @@ -0,0 +1,19 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef _KUNIT_KPROBES_STUB_H +#define _KUNIT_KPROBES_STUB_H + +struct kunit; + +#define kunit_activate_kprobes_stub(test, func, replacement) do { \ + typecheck_fn(typeof(&func), replacement); \ + __kunit_activate_kprobes_stub(test, #func, func, replacement); \ +} while (0) + +void __kunit_activate_kprobes_stub(struct kunit *test, + const char *name, + void *real_fn_addr, + void *replacement_addr); + +void kunit_deactivate_kprobes_stub(struct kunit *test, void *real_fn_addr); + +#endif /* _KUNIT_KPROBES_STUB_H */ diff --git a/lib/kunit/Kconfig b/lib/kunit/Kconfig index 933fda1df5c3..13fdd3471060 100644 --- a/lib/kunit/Kconfig +++ b/lib/kunit/Kconfig @@ -104,4 +104,11 @@ config KUNIT_FTRACE_STUBS NOTE: this does not work on all architectures (like UML, arm64) and relies on a lot of magic (see the dependencies list).
+config KUNIT_KPROBES_STUBS + bool "Support for stubbing out functions in KUnit tests with kprobes" + depends on KPROBES + help + Builds support for stubbing out functions for the duration of KUnit + test cases or suites using kprobes. + endif # KUNIT diff --git a/lib/kunit/Makefile b/lib/kunit/Makefile index 0ecb255576e2..727ce86eb61f 100644 --- a/lib/kunit/Makefile +++ b/lib/kunit/Makefile @@ -33,3 +33,7 @@ obj-$(CONFIG_KUNIT_EXAMPLE_TEST) += kunit-example-test.o ifeq ($(CONFIG_KUNIT_FTRACE_STUBS),y) kunit-objs += ftrace_stub.o endif + +ifeq ($(CONFIG_KUNIT_KPROBES_STUBS),y) +kunit-objs += kprobes_stub.o +endif diff --git a/lib/kunit/kprobes_stub.c b/lib/kunit/kprobes_stub.c new file mode 100644 index 000000000000..95f1dcba346b --- /dev/null +++ b/lib/kunit/kprobes_stub.c @@ -0,0 +1,113 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * KUnit function redirection (kprobes stubbing) API. + */ + +#include <kunit/test.h> +#include <kunit/kprobes_stub.h> + +#include <linux/kprobes.h> + +struct kunit_kprobes_stub_ctx { + unsigned long real_fn_addr; + unsigned long replacement_addr; + struct kprobe kp; +}; + +static void __kunit_kprobes_stub_resource_free(struct kunit_resource *res) +{ + struct kunit_kprobes_stub_ctx *ctx = res->data; + + unregister_kprobe(&ctx->kp); + kfree(ctx); +} + +static int kprobe_handler(struct kprobe *kp, struct pt_regs *regs) +{ + struct kunit_kprobes_stub_ctx *ctx = container_of(kp, struct kunit_kprobes_stub_ctx, kp); + + instruction_pointer_set(regs, ctx->replacement_addr); + return 1; +} + +/* Matching function for kunit_find_resource(). match_data is real_fn_addr. */ +static bool __kunit_kprobes_stub_resource_match(struct kunit *test, + struct kunit_resource *res, + void *match_real_fn_addr) +{ + struct kunit_kprobes_stub_ctx *ctx = res->data; + + /* Make sure the resource is a kprobes stub resource. */ + if (res->free != &__kunit_kprobes_stub_resource_free) + return false; + + return ctx->real_fn_addr == (unsigned long)match_real_fn_addr; +} + +void __kunit_activate_kprobes_stub(struct kunit *test, + const char *name, + void *real_fn_addr, + void *replacement_addr) +{ + struct kunit_kprobes_stub_ctx *ctx; + struct kunit_resource *res; + + KUNIT_ASSERT_PTR_NE_MSG(test, real_fn_addr, NULL, + "Tried to activate a stub for function NULL"); + + /* If the replacement address is NULL, deactivate the stub. */ + if (!replacement_addr) { + kunit_deactivate_kprobes_stub(test, real_fn_addr); + return; + } + + /* Look up any existing stubs for this function, and replace them. */ + res = kunit_find_resource(test, + __kunit_kprobes_stub_resource_match, + real_fn_addr); + if (res) { + ctx = res->data; + ctx->replacement_addr = (unsigned long)replacement_addr; + + /* We got an extra reference from find_resource(), so put it. */ + kunit_put_resource(res); + } else { + ctx = kzalloc(sizeof(*ctx), GFP_KERNEL); + KUNIT_ASSERT_NOT_ERR_OR_NULL_MSG(test, ctx, "Failed to allocate kunit stub for %s", + name); + + ctx->real_fn_addr = (unsigned long)real_fn_addr; + ctx->replacement_addr = (unsigned long)replacement_addr; + + ctx->kp.addr = real_fn_addr; + ctx->kp.pre_handler = kprobe_handler; + KUNIT_ASSERT_EQ_MSG(test, register_kprobe(&ctx->kp), 0, + "Failed to allocate kunit stub for %s", name); + + kunit_alloc_resource(test, NULL, + __kunit_kprobes_stub_resource_free, + GFP_KERNEL, ctx); + } +} +EXPORT_SYMBOL_GPL(__kunit_activate_kprobes_stub); + +void kunit_deactivate_kprobes_stub(struct kunit *test, void *real_fn_addr) +{ + struct kunit_resource *res; + + KUNIT_ASSERT_PTR_NE_MSG(test, real_fn_addr, NULL, "Tried to deactivate a NULL stub."); + + res = kunit_find_resource(test, + __kunit_kprobes_stub_resource_match, + real_fn_addr); + KUNIT_ASSERT_PTR_NE_MSG(test, res, NULL, + "Tried to deactivate a nonexistent stub."); + + /* + * Free the stub. We 'put' twice, as we got a reference + * from kunit_find_resource() + */ + kunit_remove_resource(test, res); + kunit_put_resource(res); +} +EXPORT_SYMBOL_GPL(kunit_deactivate_kprobes_stub);