| Message ID | 20220830010104.1282-10-kirill.shutemov@linux.intel.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | Linear Address Masking enabling | expand |
On Tue, 2022-08-30 at 04:01 +0300, Kirill A. Shutemov wrote: > From: Weihong Zhang <weihong.zhang@intel.com> > > Add mmap and SYSCALL test cases. > > SYSCALL test cases: > > - LAM supports set metadata in high bits 62:57 (LAM_U57) of a user > pointer, pass > the pointer to SYSCALL, SYSCALL can dereference the pointer and > return correct > result. > > - Disable LAM, pass a pointer with metadata in high bits to SYSCALL, > SYSCALL returns -1 (EFAULT). > > MMAP test cases: > > - Enable LAM_U57, MMAP with low address (below bits 47), set > metadata > in high bits of the address, dereference the address should be > allowed. > > - Enable LAM_U57, MMAP with high address (above bits 47), set > metadata > in high bits of the address, dereference the address should be > allowed. > > Signed-off-by: Weihong Zhang <weihong.zhang@intel.com> > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> > Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> > --- > tools/testing/selftests/x86/lam.c | 135 > +++++++++++++++++++++++++++++- > 1 file changed, 132 insertions(+), 3 deletions(-) > > diff --git a/tools/testing/selftests/x86/lam.c > b/tools/testing/selftests/x86/lam.c > index 900a3a0fb709..b88e007ee0a3 100644 > --- a/tools/testing/selftests/x86/lam.c > +++ b/tools/testing/selftests/x86/lam.c > @@ -7,6 +7,7 @@ > #include <signal.h> > #include <setjmp.h> > #include <sys/mman.h> > +#include <sys/utsname.h> > #include <sys/wait.h> > #include <inttypes.h> > > @@ -29,11 +30,18 @@ > /* Specified test function bits */ > #define FUNC_MALLOC 0x1 > #define FUNC_BITS 0x2 > +#define FUNC_MMAP 0x4 > +#define FUNC_SYSCALL 0x8 > > -#define TEST_MASK 0x3 > +#define TEST_MASK 0xf > + > +#define LOW_ADDR (0x1UL << 30) > +#define HIGH_ADDR (0x3UL << 48) > > #define MALLOC_LEN 32 > > +#define PAGE_SIZE (4 << 10) > + > struct testcases { > unsigned int later; > int expected; /* 2: SIGSEGV Error; 1: other errors */ > @@ -49,6 +57,7 @@ jmp_buf segv_env; > static void segv_handler(int sig) > { > ksft_print_msg("Get segmentation fault(%d).", sig); > + > siglongjmp(segv_env, 1); > } > > @@ -61,6 +70,16 @@ static inline int cpu_has_lam(void) > return (cpuinfo[0] & (1 << 26)); > } > > +/* Check 5-level page table feature in CPUID.(EAX=07H, > ECX=00H):ECX.[bit 16] */ > +static inline int cpu_has_la57(void) > +{ > + unsigned int cpuinfo[4]; > + > + __cpuid_count(0x7, 0, cpuinfo[0], cpuinfo[1], cpuinfo[2], > cpuinfo[3]); > + > + return (cpuinfo[2] & (1 << 16)); > +} > + > /* > * Set tagged address and read back untag mask. > * check if the untagged mask is expected. > @@ -213,6 +232,68 @@ static int handle_malloc(struct testcases *test) > return ret; > } > > +static int handle_mmap(struct testcases *test) > +{ > + void *ptr; > + unsigned int flags = MAP_PRIVATE | MAP_ANONYMOUS | MAP_FIXED; > + int ret = 0; > + > + if (test->later == 0 && test->lam != 0) > + if (set_lam(test->lam) != 0) > + return 1; > + > + ptr = mmap((void *)test->addr, PAGE_SIZE, PROT_READ | > PROT_WRITE, > + flags, -1, 0); > + if (ptr == MAP_FAILED) { > + if (test->addr == HIGH_ADDR) > + if (!cpu_has_la57()) > + return 3; /* unsupport LA57 */ I think here return 3 to indicate skip cases. Perhaps you can enable skip case like this? Just FYI, I'm not familiar with selftests yet. @@ -321,8 +323,10 @@ static int handle_mmap(struct testcases *test) flags, -1, 0); if (ptr == MAP_FAILED) { if (test->addr == HIGH_ADDR) - if (!cpu_has_la57()) + if (!cpu_has_la57()) { + perror("Unsupport LA57. Skip"); return 3; /* unsupport LA57 */ + } return 1; } @@ -746,12 +750,16 @@ static void run_test(struct testcases *test, int count) /* fork a process to run test case */ ret = fork_test(t); + tests_cnt++; + if (ret == 3) { + ksft_test_result_skip(t->msg); + continue; + } if (ret != 0) ret = (t->expected == ret); else ret = !(t->expected); - tests_cnt++; ksft_test_result(ret, t->msg); } } > + return 1; > + } > + > + if (test->later != 0 && test->lam != 0) > + if (set_lam(test->lam) != 0) > + ret = 1; > + > + if (ret == 0) { > + if (sigsetjmp(segv_env, 1) == 0) { > + signal(SIGSEGV, segv_handler); > + ret = handle_lam_test(ptr, test->lam); > + } else { > + ret = 2; > + } > + } > + > + munmap(ptr, PAGE_SIZE); > + return ret; > +} > + > +static int handle_syscall(struct testcases *test) > +{ > + struct utsname unme, *pu; > + int ret = 0; > + > + if (test->later == 0 && test->lam != 0) > + if (set_lam(test->lam) != 0) > + return 1; > + > + if (sigsetjmp(segv_env, 1) == 0) { > + signal(SIGSEGV, segv_handler); > + pu = (struct utsname *)set_metadata((uint64_t)&unme, > test->lam); > + ret = uname(pu); > + if (ret < 0) > + ret = 1; > + } else { > + ret = 2; > + } > + > + if (test->later != 0 && test->lam != 0) > + if (set_lam(test->lam) != -1 && ret == 0) > + ret = 1; > + > + return ret; > +} > + > static int fork_test(struct testcases *test) > { > int ret, child_ret; > @@ -268,7 +349,6 @@ static struct testcases malloc_cases[] = { > }, > }; > > - > static struct testcases bits_cases[] = { > { > .test_func = handle_max_bits, > @@ -276,11 +356,54 @@ static struct testcases bits_cases[] = { > }, > }; > > +static struct testcases syscall_cases[] = { > + { > + .later = 0, > + .lam = LAM_U57_BITS, > + .test_func = handle_syscall, > + .msg = "SYSCALL: LAM_U57. syscall with metadata\n", > + }, > + { > + .later = 1, > + .expected = 1, > + .lam = LAM_U57_BITS, > + .test_func = handle_syscall, > + .msg = "SYSCALL:[Negative] Disable LAM. Dereferencing > pointer with metadata.\n", > + }, > +}; > + > +static struct testcases mmap_cases[] = { > + { > + .later = 1, > + .expected = 0, > + .lam = LAM_U57_BITS, > + .addr = HIGH_ADDR, > + .test_func = handle_mmap, > + .msg = "MMAP: First mmap high address, then set > LAM_U57.\n", > + }, > + { > + .later = 0, > + .expected = 0, > + .lam = LAM_U57_BITS, > + .addr = HIGH_ADDR, > + .test_func = handle_mmap, > + .msg = "MMAP: First LAM_U57, then High address.\n", > + }, > + { > + .later = 0, > + .expected = 0, > + .lam = LAM_U57_BITS, > + .addr = LOW_ADDR, > + .test_func = handle_mmap, > + .msg = "MMAP: First LAM_U57, then Low address.\n", > + }, > +}; > + > static void cmd_help(void) > { > printf("usage: lam [-h] [-t test list]\n"); > printf("\t-t test list: run tests specified in the test list, > default:0x%x\n", TEST_MASK); > - printf("\t\t0x1:malloc; 0x2:max_bits;\n"); > + printf("\t\t0x1:malloc; 0x2:max_bits; 0x4:mmap; > 0x8:syscall.\n"); > printf("\t-h: help\n"); > } > > @@ -320,6 +443,12 @@ int main(int argc, char **argv) > if (tests & FUNC_BITS) > run_test(bits_cases, ARRAY_SIZE(bits_cases)); > > + if (tests & FUNC_MMAP) > + run_test(mmap_cases, ARRAY_SIZE(mmap_cases)); > + > + if (tests & FUNC_SYSCALL) > + run_test(syscall_cases, ARRAY_SIZE(syscall_cases)); > + > ksft_set_plan(tests_cnt); > > return ksft_exit_pass();
> -----Original Message----- > From: Robert Hoo <robert.hu@linux.intel.com> > Sent: Wednesday, September 7, 2022 11:20 AM > To: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>; Dave Hansen > <dave.hansen@linux.intel.com>; Lutomirski, Andy <luto@kernel.org>; Peter > Zijlstra <peterz@infradead.org> > Cc: x86@kernel.org; Kostya Serebryany <kcc@google.com>; Andrey Ryabinin > <ryabinin.a.a@gmail.com>; Andrey Konovalov <andreyknvl@gmail.com>; > Alexander Potapenko <glider@google.com>; Taras Madan > <tarasmadan@google.com>; Dmitry Vyukov <dvyukov@google.com>; H . J . > Lu <hjl.tools@gmail.com>; Andi Kleen <ak@linux.intel.com>; Edgecombe, > Rick P <rick.p.edgecombe@intel.com>; linux-mm@kvack.org; linux- > kernel@vger.kernel.org; Zhang, Weihong <weihong.zhang@intel.com> > Subject: Re: [PATCHv8 09/11] selftests/x86/lam: Add mmap and SYSCALL > test cases for linear-address masking > > On Tue, 2022-08-30 at 04:01 +0300, Kirill A. Shutemov wrote: > > From: Weihong Zhang <weihong.zhang@intel.com> > > > > Add mmap and SYSCALL test cases. > > > > SYSCALL test cases: > > > > - LAM supports set metadata in high bits 62:57 (LAM_U57) of a user > > pointer, pass > > the pointer to SYSCALL, SYSCALL can dereference the pointer and > > return correct > > result. > > > > - Disable LAM, pass a pointer with metadata in high bits to SYSCALL, > > SYSCALL returns -1 (EFAULT). > > > > MMAP test cases: > > > > - Enable LAM_U57, MMAP with low address (below bits 47), set > metadata > > in high bits of the address, dereference the address should be > > allowed. > > > > - Enable LAM_U57, MMAP with high address (above bits 47), set > > metadata > > in high bits of the address, dereference the address should be > > allowed. > > > > Signed-off-by: Weihong Zhang <weihong.zhang@intel.com> > > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> > > Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> > > --- > > tools/testing/selftests/x86/lam.c | 135 > > +++++++++++++++++++++++++++++- > > 1 file changed, 132 insertions(+), 3 deletions(-) > > > > diff --git a/tools/testing/selftests/x86/lam.c > > b/tools/testing/selftests/x86/lam.c > > index 900a3a0fb709..b88e007ee0a3 100644 > > --- a/tools/testing/selftests/x86/lam.c > > +++ b/tools/testing/selftests/x86/lam.c > > @@ -7,6 +7,7 @@ > > #include <signal.h> > > #include <setjmp.h> > > #include <sys/mman.h> > > +#include <sys/utsname.h> > > #include <sys/wait.h> > > #include <inttypes.h> > > > > @@ -29,11 +30,18 @@ > > /* Specified test function bits */ > > #define FUNC_MALLOC 0x1 > > #define FUNC_BITS 0x2 > > +#define FUNC_MMAP 0x4 > > +#define FUNC_SYSCALL 0x8 > > > > -#define TEST_MASK 0x3 > > +#define TEST_MASK 0xf > > + > > +#define LOW_ADDR (0x1UL << 30) > > +#define HIGH_ADDR (0x3UL << 48) > > > > #define MALLOC_LEN 32 > > > > +#define PAGE_SIZE (4 << 10) > > + > > struct testcases { > > unsigned int later; > > int expected; /* 2: SIGSEGV Error; 1: other errors */ @@ -49,6 +57,7 > > @@ jmp_buf segv_env; static void segv_handler(int sig) { > > ksft_print_msg("Get segmentation fault(%d).", sig); > > + > > siglongjmp(segv_env, 1); > > } > > > > @@ -61,6 +70,16 @@ static inline int cpu_has_lam(void) > > return (cpuinfo[0] & (1 << 26)); > > } > > > > +/* Check 5-level page table feature in CPUID.(EAX=07H, > > ECX=00H):ECX.[bit 16] */ > > +static inline int cpu_has_la57(void) > > +{ > > + unsigned int cpuinfo[4]; > > + > > + __cpuid_count(0x7, 0, cpuinfo[0], cpuinfo[1], cpuinfo[2], > > cpuinfo[3]); > > + > > + return (cpuinfo[2] & (1 << 16)); > > +} > > + > > /* > > * Set tagged address and read back untag mask. > > * check if the untagged mask is expected. > > @@ -213,6 +232,68 @@ static int handle_malloc(struct testcases *test) > > return ret; > > } > > > > +static int handle_mmap(struct testcases *test) { > > + void *ptr; > > + unsigned int flags = MAP_PRIVATE | MAP_ANONYMOUS | > MAP_FIXED; > > + int ret = 0; > > + > > + if (test->later == 0 && test->lam != 0) > > + if (set_lam(test->lam) != 0) > > + return 1; > > + > > + ptr = mmap((void *)test->addr, PAGE_SIZE, PROT_READ | > > PROT_WRITE, > > + flags, -1, 0); > > + if (ptr == MAP_FAILED) { > > + if (test->addr == HIGH_ADDR) > > + if (!cpu_has_la57()) > > + return 3; /* unsupport LA57 */ > > I think here return 3 to indicate skip cases. > > Perhaps you can enable skip case like this? Just FYI, I'm not familiar with > selftests yet. > Yes, this case can be regarded as skip case. > @@ -321,8 +323,10 @@ static int handle_mmap(struct testcases *test) > flags, -1, 0); > if (ptr == MAP_FAILED) { > if (test->addr == HIGH_ADDR) > - if (!cpu_has_la57()) > + if (!cpu_has_la57()) { > + perror("Unsupport LA57. Skip"); > return 3; /* unsupport LA57 */ > + } > return 1; > } > > @@ -746,12 +750,16 @@ static void run_test(struct testcases *test, int > count) > > /* fork a process to run test case */ > ret = fork_test(t); > + tests_cnt++; > + if (ret == 3) { > + ksft_test_result_skip(t->msg); > + continue; > + } > if (ret != 0) > ret = (t->expected == ret); > else > ret = !(t->expected); > > - tests_cnt++; > ksft_test_result(ret, t->msg); > } > } > > > + return 1; > > + } > > + > > + if (test->later != 0 && test->lam != 0) > > + if (set_lam(test->lam) != 0) > > + ret = 1; > > + > > + if (ret == 0) { > > + if (sigsetjmp(segv_env, 1) == 0) { > > + signal(SIGSEGV, segv_handler); > > + ret = handle_lam_test(ptr, test->lam); > > + } else { > > + ret = 2; > > + } > > + } > > + > > + munmap(ptr, PAGE_SIZE); > > + return ret; > > +} > > + > > +static int handle_syscall(struct testcases *test) { > > + struct utsname unme, *pu; > > + int ret = 0; > > + > > + if (test->later == 0 && test->lam != 0) > > + if (set_lam(test->lam) != 0) > > + return 1; > > + > > + if (sigsetjmp(segv_env, 1) == 0) { > > + signal(SIGSEGV, segv_handler); > > + pu = (struct utsname *)set_metadata((uint64_t)&unme, > > test->lam); > > + ret = uname(pu); > > + if (ret < 0) > > + ret = 1; > > + } else { > > + ret = 2; > > + } > > + > > + if (test->later != 0 && test->lam != 0) > > + if (set_lam(test->lam) != -1 && ret == 0) > > + ret = 1; > > + > > + return ret; > > +} > > + > > static int fork_test(struct testcases *test) { > > int ret, child_ret; > > @@ -268,7 +349,6 @@ static struct testcases malloc_cases[] = { > > }, > > }; > > > > - > > static struct testcases bits_cases[] = { > > { > > .test_func = handle_max_bits, > > @@ -276,11 +356,54 @@ static struct testcases bits_cases[] = { > > }, > > }; > > > > +static struct testcases syscall_cases[] = { > > + { > > + .later = 0, > > + .lam = LAM_U57_BITS, > > + .test_func = handle_syscall, > > + .msg = "SYSCALL: LAM_U57. syscall with metadata\n", > > + }, > > + { > > + .later = 1, > > + .expected = 1, > > + .lam = LAM_U57_BITS, > > + .test_func = handle_syscall, > > + .msg = "SYSCALL:[Negative] Disable LAM. Dereferencing > > pointer with metadata.\n", > > + }, > > +}; > > + > > +static struct testcases mmap_cases[] = { > > + { > > + .later = 1, > > + .expected = 0, > > + .lam = LAM_U57_BITS, > > + .addr = HIGH_ADDR, > > + .test_func = handle_mmap, > > + .msg = "MMAP: First mmap high address, then set > > LAM_U57.\n", > > + }, > > + { > > + .later = 0, > > + .expected = 0, > > + .lam = LAM_U57_BITS, > > + .addr = HIGH_ADDR, > > + .test_func = handle_mmap, > > + .msg = "MMAP: First LAM_U57, then High address.\n", > > + }, > > + { > > + .later = 0, > > + .expected = 0, > > + .lam = LAM_U57_BITS, > > + .addr = LOW_ADDR, > > + .test_func = handle_mmap, > > + .msg = "MMAP: First LAM_U57, then Low address.\n", > > + }, > > +}; > > + > > static void cmd_help(void) > > { > > printf("usage: lam [-h] [-t test list]\n"); > > printf("\t-t test list: run tests specified in the test list, > > default:0x%x\n", TEST_MASK); > > - printf("\t\t0x1:malloc; 0x2:max_bits;\n"); > > + printf("\t\t0x1:malloc; 0x2:max_bits; 0x4:mmap; > > 0x8:syscall.\n"); > > printf("\t-h: help\n"); > > } > > > > @@ -320,6 +443,12 @@ int main(int argc, char **argv) > > if (tests & FUNC_BITS) > > run_test(bits_cases, ARRAY_SIZE(bits_cases)); > > > > + if (tests & FUNC_MMAP) > > + run_test(mmap_cases, ARRAY_SIZE(mmap_cases)); > > + > > + if (tests & FUNC_SYSCALL) > > + run_test(syscall_cases, ARRAY_SIZE(syscall_cases)); > > + > > ksft_set_plan(tests_cnt); > > > > return ksft_exit_pass();
diff --git a/tools/testing/selftests/x86/lam.c b/tools/testing/selftests/x86/lam.c index 900a3a0fb709..b88e007ee0a3 100644 --- a/tools/testing/selftests/x86/lam.c +++ b/tools/testing/selftests/x86/lam.c @@ -7,6 +7,7 @@ #include <signal.h> #include <setjmp.h> #include <sys/mman.h> +#include <sys/utsname.h> #include <sys/wait.h> #include <inttypes.h> @@ -29,11 +30,18 @@ /* Specified test function bits */ #define FUNC_MALLOC 0x1 #define FUNC_BITS 0x2 +#define FUNC_MMAP 0x4 +#define FUNC_SYSCALL 0x8 -#define TEST_MASK 0x3 +#define TEST_MASK 0xf + +#define LOW_ADDR (0x1UL << 30) +#define HIGH_ADDR (0x3UL << 48) #define MALLOC_LEN 32 +#define PAGE_SIZE (4 << 10) + struct testcases { unsigned int later; int expected; /* 2: SIGSEGV Error; 1: other errors */ @@ -49,6 +57,7 @@ jmp_buf segv_env; static void segv_handler(int sig) { ksft_print_msg("Get segmentation fault(%d).", sig); + siglongjmp(segv_env, 1); } @@ -61,6 +70,16 @@ static inline int cpu_has_lam(void) return (cpuinfo[0] & (1 << 26)); } +/* Check 5-level page table feature in CPUID.(EAX=07H, ECX=00H):ECX.[bit 16] */ +static inline int cpu_has_la57(void) +{ + unsigned int cpuinfo[4]; + + __cpuid_count(0x7, 0, cpuinfo[0], cpuinfo[1], cpuinfo[2], cpuinfo[3]); + + return (cpuinfo[2] & (1 << 16)); +} + /* * Set tagged address and read back untag mask. * check if the untagged mask is expected. @@ -213,6 +232,68 @@ static int handle_malloc(struct testcases *test) return ret; } +static int handle_mmap(struct testcases *test) +{ + void *ptr; + unsigned int flags = MAP_PRIVATE | MAP_ANONYMOUS | MAP_FIXED; + int ret = 0; + + if (test->later == 0 && test->lam != 0) + if (set_lam(test->lam) != 0) + return 1; + + ptr = mmap((void *)test->addr, PAGE_SIZE, PROT_READ | PROT_WRITE, + flags, -1, 0); + if (ptr == MAP_FAILED) { + if (test->addr == HIGH_ADDR) + if (!cpu_has_la57()) + return 3; /* unsupport LA57 */ + return 1; + } + + if (test->later != 0 && test->lam != 0) + if (set_lam(test->lam) != 0) + ret = 1; + + if (ret == 0) { + if (sigsetjmp(segv_env, 1) == 0) { + signal(SIGSEGV, segv_handler); + ret = handle_lam_test(ptr, test->lam); + } else { + ret = 2; + } + } + + munmap(ptr, PAGE_SIZE); + return ret; +} + +static int handle_syscall(struct testcases *test) +{ + struct utsname unme, *pu; + int ret = 0; + + if (test->later == 0 && test->lam != 0) + if (set_lam(test->lam) != 0) + return 1; + + if (sigsetjmp(segv_env, 1) == 0) { + signal(SIGSEGV, segv_handler); + pu = (struct utsname *)set_metadata((uint64_t)&unme, test->lam); + ret = uname(pu); + if (ret < 0) + ret = 1; + } else { + ret = 2; + } + + if (test->later != 0 && test->lam != 0) + if (set_lam(test->lam) != -1 && ret == 0) + ret = 1; + + return ret; +} + static int fork_test(struct testcases *test) { int ret, child_ret; @@ -268,7 +349,6 @@ static struct testcases malloc_cases[] = { }, }; - static struct testcases bits_cases[] = { { .test_func = handle_max_bits, @@ -276,11 +356,54 @@ static struct testcases bits_cases[] = { }, }; +static struct testcases syscall_cases[] = { + { + .later = 0, + .lam = LAM_U57_BITS, + .test_func = handle_syscall, + .msg = "SYSCALL: LAM_U57. syscall with metadata\n", + }, + { + .later = 1, + .expected = 1, + .lam = LAM_U57_BITS, + .test_func = handle_syscall, + .msg = "SYSCALL:[Negative] Disable LAM. Dereferencing pointer with metadata.\n", + }, +}; + +static struct testcases mmap_cases[] = { + { + .later = 1, + .expected = 0, + .lam = LAM_U57_BITS, + .addr = HIGH_ADDR, + .test_func = handle_mmap, + .msg = "MMAP: First mmap high address, then set LAM_U57.\n", + }, + { + .later = 0, + .expected = 0, + .lam = LAM_U57_BITS, + .addr = HIGH_ADDR, + .test_func = handle_mmap, + .msg = "MMAP: First LAM_U57, then High address.\n", + }, + { + .later = 0, + .expected = 0, + .lam = LAM_U57_BITS, + .addr = LOW_ADDR, + .test_func = handle_mmap, + .msg = "MMAP: First LAM_U57, then Low address.\n", + }, +}; + static void cmd_help(void) { printf("usage: lam [-h] [-t test list]\n"); printf("\t-t test list: run tests specified in the test list, default:0x%x\n", TEST_MASK); - printf("\t\t0x1:malloc; 0x2:max_bits;\n"); + printf("\t\t0x1:malloc; 0x2:max_bits; 0x4:mmap; 0x8:syscall.\n"); printf("\t-h: help\n"); } @@ -320,6 +443,12 @@ int main(int argc, char **argv) if (tests & FUNC_BITS) run_test(bits_cases, ARRAY_SIZE(bits_cases)); + if (tests & FUNC_MMAP) + run_test(mmap_cases, ARRAY_SIZE(mmap_cases)); + + if (tests & FUNC_SYSCALL) + run_test(syscall_cases, ARRAY_SIZE(syscall_cases)); + ksft_set_plan(tests_cnt); return ksft_exit_pass();