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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] [tip:x86/asm] selftests/x86, x86/ldt: Add a selftest for modify_ldt()
Commit-ID: 014dc90b66c8d0b5f5a9400440727c134ee5e5a3 Gitweb: http://git.kernel.org/tip/014dc90b66c8d0b5f5a9400440727c134ee5e5a3 Author: Andy Lutomirski <luto@xxxxxxxxxx> AuthorDate: Thu, 30 Jul 2015 14:31:33 -0700 Committer: Ingo Molnar <mingo@xxxxxxxxxx> CommitDate: Fri, 31 Jul 2015 10:24:37 +0200 selftests/x86, x86/ldt: Add a selftest for modify_ldt() This tests general modify_ldt() behavior (only writes, so far) as well as synchronous updates via IPI. It fails on old kernels. I called this ldt_gdt because I'll add set_thread_area() tests to it at some point. Signed-off-by: Andy Lutomirski <luto@xxxxxxxxxx> Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx> Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx> Cc: Andy Lutomirski <luto@xxxxxxxxxxxxxx> Cc: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx> Cc: Borislav Petkov <bp@xxxxxxxxx> Cc: Brian Gerst <brgerst@xxxxxxxxx> Cc: Denys Vlasenko <dvlasenk@xxxxxxxxxx> Cc: H. Peter Anvin <hpa@xxxxxxxxx> Cc: Jan Beulich <jbeulich@xxxxxxxx> Cc: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx> Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> Cc: Sasha Levin <sasha.levin@xxxxxxxxxx> Cc: Steven Rostedt <rostedt@xxxxxxxxxxx> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Cc: security@xxxxxxxxxx <security@xxxxxxxxxx> Cc: xen-devel <xen-devel@xxxxxxxxxxxxx> Link: http://lkml.kernel.org/r/dcfda65dad07ff5a3ea97a9172b5963bf8031b2e.1438291540.git.luto@xxxxxxxxxx Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx> --- tools/testing/selftests/x86/Makefile | 2 +- tools/testing/selftests/x86/ldt_gdt.c | 576 ++++++++++++++++++++++++++++++++++ 2 files changed, 577 insertions(+), 1 deletion(-) diff --git a/tools/testing/selftests/x86/Makefile b/tools/testing/selftests/x86/Makefile index e8df47e..b70da4a 100644 --- a/tools/testing/selftests/x86/Makefile +++ b/tools/testing/selftests/x86/Makefile @@ -4,7 +4,7 @@ include ../lib.mk .PHONY: all all_32 all_64 warn_32bit_failure clean -TARGETS_C_BOTHBITS := sigreturn single_step_syscall sysret_ss_attrs +TARGETS_C_BOTHBITS := sigreturn single_step_syscall sysret_ss_attrs ldt_gdt TARGETS_C_32BIT_ONLY := entry_from_vm86 syscall_arg_fault TARGETS_C_32BIT_ALL := $(TARGETS_C_BOTHBITS) $(TARGETS_C_32BIT_ONLY) diff --git a/tools/testing/selftests/x86/ldt_gdt.c b/tools/testing/selftests/x86/ldt_gdt.c new file mode 100644 index 0000000..31a3035 --- /dev/null +++ b/tools/testing/selftests/x86/ldt_gdt.c @@ -0,0 +1,576 @@ +/* + * ldt_gdt.c - Test cases for LDT and GDT access + * Copyright (c) 2015 Andrew Lutomirski + */ + +#define _GNU_SOURCE +#include <err.h> +#include <stdio.h> +#include <stdint.h> +#include <signal.h> +#include <setjmp.h> +#include <stdlib.h> +#include <string.h> +#include <errno.h> +#include <unistd.h> +#include <sys/syscall.h> +#include <asm/ldt.h> +#include <sys/types.h> +#include <sys/wait.h> +#include <stdbool.h> +#include <pthread.h> +#include <sched.h> +#include <linux/futex.h> + +#define AR_ACCESSED (1<<8) + +#define AR_TYPE_RODATA (0 * (1<<9)) +#define AR_TYPE_RWDATA (1 * (1<<9)) +#define AR_TYPE_RODATA_EXPDOWN (2 * (1<<9)) +#define AR_TYPE_RWDATA_EXPDOWN (3 * (1<<9)) +#define AR_TYPE_XOCODE (4 * (1<<9)) +#define AR_TYPE_XRCODE (5 * (1<<9)) +#define AR_TYPE_XOCODE_CONF (6 * (1<<9)) +#define AR_TYPE_XRCODE_CONF (7 * (1<<9)) + +#define AR_DPL3 (3 * (1<<13)) + +#define AR_S (1 << 12) +#define AR_P (1 << 15) +#define AR_AVL (1 << 20) +#define AR_L (1 << 21) +#define AR_DB (1 << 22) +#define AR_G (1 << 23) + +static int nerrs; + +static void check_invalid_segment(uint16_t index, int ldt) +{ + uint32_t has_limit = 0, has_ar = 0, limit, ar; + uint32_t selector = (index << 3) | (ldt << 2) | 3; + + asm ("lsl %[selector], %[limit]\n\t" + "jnz 1f\n\t" + "movl $1, %[has_limit]\n\t" + "1:" + : [limit] "=r" (limit), [has_limit] "+rm" (has_limit) + : [selector] "r" (selector)); + asm ("larl %[selector], %[ar]\n\t" + "jnz 1f\n\t" + "movl $1, %[has_ar]\n\t" + "1:" + : [ar] "=r" (ar), [has_ar] "+rm" (has_ar) + : [selector] "r" (selector)); + + if (has_limit || has_ar) { + printf("[FAIL]\t%s entry %hu is valid but should be invalid\n", + (ldt ? "LDT" : "GDT"), index); + nerrs++; + } else { + printf("[OK]\t%s entry %hu is invalid\n", + (ldt ? "LDT" : "GDT"), index); + } +} + +static void check_valid_segment(uint16_t index, int ldt, + uint32_t expected_ar, uint32_t expected_limit, + bool verbose) +{ + uint32_t has_limit = 0, has_ar = 0, limit, ar; + uint32_t selector = (index << 3) | (ldt << 2) | 3; + + asm ("lsl %[selector], %[limit]\n\t" + "jnz 1f\n\t" + "movl $1, %[has_limit]\n\t" + "1:" + : [limit] "=r" (limit), [has_limit] "+rm" (has_limit) + : [selector] "r" (selector)); + asm ("larl %[selector], %[ar]\n\t" + "jnz 1f\n\t" + "movl $1, %[has_ar]\n\t" + "1:" + : [ar] "=r" (ar), [has_ar] "+rm" (has_ar) + : [selector] "r" (selector)); + + if (!has_limit || !has_ar) { + printf("[FAIL]\t%s entry %hu is invalid but should be valid\n", + (ldt ? "LDT" : "GDT"), index); + nerrs++; + return; + } + + if (ar != expected_ar) { + printf("[FAIL]\t%s entry %hu has AR 0x%08X but expected 0x%08X\n", + (ldt ? "LDT" : "GDT"), index, ar, expected_ar); + nerrs++; + } else if (limit != expected_limit) { + printf("[FAIL]\t%s entry %hu has limit 0x%08X but expected 0x%08X\n", + (ldt ? "LDT" : "GDT"), index, limit, expected_limit); + nerrs++; + } else if (verbose) { + printf("[OK]\t%s entry %hu has AR 0x%08X and limit 0x%08X\n", + (ldt ? "LDT" : "GDT"), index, ar, limit); + } +} + +static bool install_valid_mode(const struct user_desc *desc, uint32_t ar, + bool oldmode) +{ + int ret = syscall(SYS_modify_ldt, oldmode ? 1 : 0x11, + desc, sizeof(*desc)); + if (ret < -1) + errno = -ret; + if (ret == 0) { + uint32_t limit = desc->limit; + if (desc->limit_in_pages) + limit = (limit << 12) + 4095; + check_valid_segment(desc->entry_number, 1, ar, limit, true); + return true; + } else if (errno == ENOSYS) { + printf("[OK]\tmodify_ldt returned -ENOSYS\n"); + return false; + } else { + if (desc->seg_32bit) { + printf("[FAIL]\tUnexpected modify_ldt failure %d\n", + errno); + nerrs++; + return false; + } else { + printf("[OK]\tmodify_ldt rejected 16 bit segment\n"); + return false; + } + } +} + +static bool install_valid(const struct user_desc *desc, uint32_t ar) +{ + return install_valid_mode(desc, ar, false); +} + +static void install_invalid(const struct user_desc *desc, bool oldmode) +{ + int ret = syscall(SYS_modify_ldt, oldmode ? 1 : 0x11, + desc, sizeof(*desc)); + if (ret < -1) + errno = -ret; + if (ret == 0) { + check_invalid_segment(desc->entry_number, 1); + } else if (errno == ENOSYS) { + printf("[OK]\tmodify_ldt returned -ENOSYS\n"); + } else { + if (desc->seg_32bit) { + printf("[FAIL]\tUnexpected modify_ldt failure %d\n", + errno); + nerrs++; + } else { + printf("[OK]\tmodify_ldt rejected 16 bit segment\n"); + } + } +} + +static int safe_modify_ldt(int func, struct user_desc *ptr, + unsigned long bytecount) +{ + int ret = syscall(SYS_modify_ldt, 0x11, ptr, bytecount); + if (ret < -1) + errno = -ret; + return ret; +} + +static void fail_install(struct user_desc *desc) +{ + if (safe_modify_ldt(0x11, desc, sizeof(*desc)) == 0) { + printf("[FAIL]\tmodify_ldt accepted a bad descriptor\n"); + nerrs++; + } else if (errno == ENOSYS) { + printf("[OK]\tmodify_ldt returned -ENOSYS\n"); + } else { + printf("[OK]\tmodify_ldt failure %d\n", errno); + } +} + +static void do_simple_tests(void) +{ + struct user_desc desc = { + .entry_number = 0, + .base_addr = 0, + .limit = 10, + .seg_32bit = 1, + .contents = 2, /* Code, not conforming */ + .read_exec_only = 0, + .limit_in_pages = 0, + .seg_not_present = 0, + .useable = 0 + }; + install_valid(&desc, AR_DPL3 | AR_TYPE_XRCODE | AR_S | AR_P | AR_DB); + + desc.limit_in_pages = 1; + install_valid(&desc, AR_DPL3 | AR_TYPE_XRCODE | + AR_S | AR_P | AR_DB | AR_G); + + check_invalid_segment(1, 1); + + desc.entry_number = 2; + install_valid(&desc, AR_DPL3 | AR_TYPE_XRCODE | + AR_S | AR_P | AR_DB | AR_G); + + check_invalid_segment(1, 1); + + desc.base_addr = 0xf0000000; + install_valid(&desc, AR_DPL3 | AR_TYPE_XRCODE | + AR_S | AR_P | AR_DB | AR_G); + + desc.useable = 1; + install_valid(&desc, AR_DPL3 | AR_TYPE_XRCODE | + AR_S | AR_P | AR_DB | AR_G | AR_AVL); + + desc.seg_not_present = 1; + install_valid(&desc, AR_DPL3 | AR_TYPE_XRCODE | + AR_S | AR_DB | AR_G | AR_AVL); + + desc.seg_32bit = 0; + install_valid(&desc, AR_DPL3 | AR_TYPE_XRCODE | + AR_S | AR_G | AR_AVL); + + desc.seg_32bit = 1; + desc.contents = 0; + install_valid(&desc, AR_DPL3 | AR_TYPE_RWDATA | + AR_S | AR_DB | AR_G | AR_AVL); + + desc.read_exec_only = 1; + install_valid(&desc, AR_DPL3 | AR_TYPE_RODATA | + AR_S | AR_DB | AR_G | AR_AVL); + + desc.contents = 1; + install_valid(&desc, AR_DPL3 | AR_TYPE_RODATA_EXPDOWN | + AR_S | AR_DB | AR_G | AR_AVL); + + desc.read_exec_only = 0; + desc.limit_in_pages = 0; + install_valid(&desc, AR_DPL3 | AR_TYPE_RWDATA_EXPDOWN | + AR_S | AR_DB | AR_AVL); + + desc.contents = 3; + install_valid(&desc, AR_DPL3 | AR_TYPE_XRCODE_CONF | + AR_S | AR_DB | AR_AVL); + + desc.read_exec_only = 1; + install_valid(&desc, AR_DPL3 | AR_TYPE_XOCODE_CONF | + AR_S | AR_DB | AR_AVL); + + desc.read_exec_only = 0; + desc.contents = 2; + install_valid(&desc, AR_DPL3 | AR_TYPE_XRCODE | + AR_S | AR_DB | AR_AVL); + + desc.read_exec_only = 1; + +#ifdef __x86_64__ + desc.lm = 1; + install_valid(&desc, AR_DPL3 | AR_TYPE_XOCODE | + AR_S | AR_DB | AR_AVL); + desc.lm = 0; +#endif + + bool entry1_okay = install_valid(&desc, AR_DPL3 | AR_TYPE_XOCODE | + AR_S | AR_DB | AR_AVL); + + if (entry1_okay) { + printf("[RUN]\tTest fork\n"); + pid_t child = fork(); + if (child == 0) { + nerrs = 0; + check_valid_segment(desc.entry_number, 1, + AR_DPL3 | AR_TYPE_XOCODE | + AR_S | AR_DB | AR_AVL, desc.limit, + true); + check_invalid_segment(1, 1); + exit(nerrs ? 1 : 0); + } else { + int status; + if (waitpid(child, &status, 0) != child || + !WIFEXITED(status)) { + printf("[FAIL]\tChild died\n"); + nerrs++; + } else if (WEXITSTATUS(status) != 0) { + printf("[FAIL]\tChild failed\n"); + nerrs++; + } else { + printf("[OK]\tChild succeeded\n"); + } + } + + printf("[RUN]\tTest size\n"); + int i; + for (i = 0; i < 8192; i++) { + desc.entry_number = i; + desc.limit = i; + if (safe_modify_ldt(0x11, &desc, sizeof(desc)) != 0) { + printf("[FAIL]\tFailed to install entry %d\n", i); + nerrs++; + break; + } + } + for (int j = 0; j < i; j++) { + check_valid_segment(j, 1, AR_DPL3 | AR_TYPE_XOCODE | + AR_S | AR_DB | AR_AVL, j, false); + } + printf("[DONE]\tSize test\n"); + } else { + printf("[SKIP]\tSkipping fork and size tests because we have no LDT\n"); + } + + /* Test entry_number too high. */ + desc.entry_number = 8192; + fail_install(&desc); + + /* Test deletion and actions mistakeable for deletion. */ + memset(&desc, 0, sizeof(desc)); + install_valid(&desc, AR_DPL3 | AR_TYPE_RWDATA | AR_S | AR_P); + + desc.seg_not_present = 1; + install_valid(&desc, AR_DPL3 | AR_TYPE_RWDATA | AR_S); + + desc.seg_not_present = 0; + desc.read_exec_only = 1; + install_valid(&desc, AR_DPL3 | AR_TYPE_RODATA | AR_S | AR_P); + + desc.read_exec_only = 0; + desc.seg_not_present = 1; + install_valid(&desc, AR_DPL3 | AR_TYPE_RWDATA | AR_S); + + desc.read_exec_only = 1; + desc.limit = 1; + install_valid(&desc, AR_DPL3 | AR_TYPE_RODATA | AR_S); + + desc.limit = 0; + desc.base_addr = 1; + install_valid(&desc, AR_DPL3 | AR_TYPE_RODATA | AR_S); + + desc.base_addr = 0; + install_invalid(&desc, false); + + desc.seg_not_present = 0; + desc.read_exec_only = 0; + desc.seg_32bit = 1; + install_valid(&desc, AR_DPL3 | AR_TYPE_RWDATA | AR_S | AR_P | AR_DB); + install_invalid(&desc, true); +} + +/* + * 0: thread is idle + * 1: thread armed + * 2: thread should clear LDT entry 0 + * 3: thread should exit + */ +static volatile unsigned int ftx; + +static void *threadproc(void *ctx) +{ + cpu_set_t cpuset; + CPU_ZERO(&cpuset); + CPU_SET(1, &cpuset); + if (sched_setaffinity(0, sizeof(cpuset), &cpuset) != 0) + err(1, "sched_setaffinity to CPU 1"); /* should never fail */ + + while (1) { + syscall(SYS_futex, &ftx, FUTEX_WAIT, 0, NULL, NULL, 0); + while (ftx != 2) { + if (ftx >= 3) + return NULL; + } + + /* clear LDT entry 0 */ + const struct user_desc desc = {}; + if (syscall(SYS_modify_ldt, 1, &desc, sizeof(desc)) != 0) + err(1, "modify_ldt"); + + /* If ftx == 2, set it to zero. If ftx == 100, quit. */ + unsigned int x = -2; + asm volatile ("lock xaddl %[x], %[ftx]" : + [x] "+r" (x), [ftx] "+m" (ftx)); + if (x != 2) + return NULL; + } +} + +static void sethandler(int sig, void (*handler)(int, siginfo_t *, void *), + int flags) +{ + struct sigaction sa; + memset(&sa, 0, sizeof(sa)); + sa.sa_sigaction = handler; + sa.sa_flags = SA_SIGINFO | flags; + sigemptyset(&sa.sa_mask); + if (sigaction(sig, &sa, 0)) + err(1, "sigaction"); + +} + +static jmp_buf jmpbuf; + +static void sigsegv(int sig, siginfo_t *info, void *ctx_void) +{ + siglongjmp(jmpbuf, 1); +} + +static void do_multicpu_tests(void) +{ + cpu_set_t cpuset; + pthread_t thread; + int failures = 0, iters = 5, i; + unsigned short orig_ss; + + CPU_ZERO(&cpuset); + CPU_SET(1, &cpuset); + if (sched_setaffinity(0, sizeof(cpuset), &cpuset) != 0) { + printf("[SKIP]\tCannot set affinity to CPU 1\n"); + return; + } + + CPU_ZERO(&cpuset); + CPU_SET(0, &cpuset); + if (sched_setaffinity(0, sizeof(cpuset), &cpuset) != 0) { + printf("[SKIP]\tCannot set affinity to CPU 0\n"); + return; + } + + sethandler(SIGSEGV, sigsegv, 0); +#ifdef __i386__ + /* True 32-bit kernels send SIGILL instead of SIGSEGV on IRET faults. */ + sethandler(SIGILL, sigsegv, 0); +#endif + + printf("[RUN]\tCross-CPU LDT invalidation\n"); + + if (pthread_create(&thread, 0, threadproc, 0) != 0) + err(1, "pthread_create"); + + asm volatile ("mov %%ss, %0" : "=rm" (orig_ss)); + + for (i = 0; i < 5; i++) { + if (sigsetjmp(jmpbuf, 1) != 0) + continue; + + /* Make sure the thread is ready after the last test. */ + while (ftx != 0) + ; + + struct user_desc desc = { + .entry_number = 0, + .base_addr = 0, + .limit = 0xfffff, + .seg_32bit = 1, + .contents = 0, /* Data */ + .read_exec_only = 0, + .limit_in_pages = 1, + .seg_not_present = 0, + .useable = 0 + }; + + if (safe_modify_ldt(0x11, &desc, sizeof(desc)) != 0) { + if (errno != ENOSYS) + err(1, "modify_ldt"); + printf("[SKIP]\tmodify_ldt unavailable\n"); + break; + } + + /* Arm the thread. */ + ftx = 1; + syscall(SYS_futex, &ftx, FUTEX_WAKE, 0, NULL, NULL, 0); + + asm volatile ("mov %0, %%ss" : : "r" (0x7)); + + /* Go! */ + ftx = 2; + + while (ftx != 0) + ; + + /* + * On success, modify_ldt will segfault us synchronously, + * and we'll escape via siglongjmp. + */ + + failures++; + asm volatile ("mov %0, %%ss" : : "rm" (orig_ss)); + }; + + ftx = 100; /* Kill the thread. */ + syscall(SYS_futex, &ftx, FUTEX_WAKE, 0, NULL, NULL, 0); + + if (pthread_join(thread, NULL) != 0) + err(1, "pthread_join"); + + if (failures) { + printf("[FAIL]\t%d of %d iterations failed\n", failures, iters); + nerrs++; + } else { + printf("[OK]\tAll %d iterations succeeded\n", iters); + } +} + +static int finish_exec_test(void) +{ + /* + * In a sensible world, this would be check_invalid_segment(0, 1); + * For better or for worse, though, the LDT is inherited across exec. + * We can probably change this safely, but for now we test it. + */ + check_valid_segment(0, 1, + AR_DPL3 | AR_TYPE_XRCODE | AR_S | AR_P | AR_DB, + 42, true); + + return nerrs ? 1 : 0; +} + +static void do_exec_test(void) +{ + printf("[RUN]\tTest exec\n"); + + struct user_desc desc = { + .entry_number = 0, + .base_addr = 0, + .limit = 42, + .seg_32bit = 1, + .contents = 2, /* Code, not conforming */ + .read_exec_only = 0, + .limit_in_pages = 0, + .seg_not_present = 0, + .useable = 0 + }; + install_valid(&desc, AR_DPL3 | AR_TYPE_XRCODE | AR_S | AR_P | AR_DB); + + pid_t child = fork(); + if (child == 0) { + execl("/proc/self/exe", "ldt_gdt_test_exec", NULL); + printf("[FAIL]\tCould not exec self\n"); + exit(1); /* exec failed */ + } else { + int status; + if (waitpid(child, &status, 0) != child || + !WIFEXITED(status)) { + printf("[FAIL]\tChild died\n"); + nerrs++; + } else if (WEXITSTATUS(status) != 0) { + printf("[FAIL]\tChild failed\n"); + nerrs++; + } else { + printf("[OK]\tChild succeeded\n"); + } + } +} + +int main(int argc, char **argv) +{ + if (argc == 1 && !strcmp(argv[0], "ldt_gdt_test_exec")) + return finish_exec_test(); + + do_simple_tests(); + + do_multicpu_tests(); + + do_exec_test(); + + return nerrs ? 1 : 0; +} _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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