diff options
Diffstat (limited to 'tools/testing/selftests/x86')
| -rw-r--r-- | tools/testing/selftests/x86/Makefile | 2 | ||||
| -rw-r--r-- | tools/testing/selftests/x86/fsgsbase.c | 28 | ||||
| -rw-r--r-- | tools/testing/selftests/x86/fsgsbase_restore.c | 245 | ||||
| -rw-r--r-- | tools/testing/selftests/x86/syscall_arg_fault.c | 26 |
4 files changed, 295 insertions, 6 deletions
diff --git a/tools/testing/selftests/x86/Makefile b/tools/testing/selftests/x86/Makefile index d2796ea98c5a..6703c7906b71 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_vdso test_vsyscall mov_ss_trap \ - syscall_arg_fault + syscall_arg_fault fsgsbase_restore 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/fsgsbase.c b/tools/testing/selftests/x86/fsgsbase.c index 15a329da59fa..998319553523 100644 --- a/tools/testing/selftests/x86/fsgsbase.c +++ b/tools/testing/selftests/x86/fsgsbase.c @@ -285,7 +285,8 @@ static unsigned short load_gs(void) /* 32-bit set_thread_area */ long ret; asm volatile ("int $0x80" - : "=a" (ret) : "a" (243), "b" (low_desc) + : "=a" (ret), "+m" (*low_desc) + : "a" (243), "b" (low_desc) : "r8", "r9", "r10", "r11"); memcpy(&desc, low_desc, sizeof(desc)); munmap(low_desc, sizeof(desc)); @@ -489,11 +490,28 @@ static void test_ptrace_write_gsbase(void) * selector value is changed or not by the GSBASE write in * a ptracer. */ - if (gs == 0 && base == 0xFF) { - printf("[OK]\tGS was reset as expected\n"); - } else { + if (gs != *shared_scratch) { nerrs++; - printf("[FAIL]\tGS=0x%lx, GSBASE=0x%lx (should be 0, 0xFF)\n", gs, base); + printf("[FAIL]\tGS changed to %lx\n", gs); + + /* + * On older kernels, poking a nonzero value into the + * base would zero the selector. On newer kernels, + * this behavior has changed -- poking the base + * changes only the base and, if FSGSBASE is not + * available, this may have no effect once the tracee + * is resumed. + */ + if (gs == 0) + printf("\tNote: this is expected behavior on older kernels.\n"); + } else if (have_fsgsbase && (base != 0xFF)) { + nerrs++; + printf("[FAIL]\tGSBASE changed to %lx\n", base); + } else { + printf("[OK]\tGS remained 0x%hx", *shared_scratch); + if (have_fsgsbase) + printf(" and GSBASE changed to 0xFF"); + printf("\n"); } } diff --git a/tools/testing/selftests/x86/fsgsbase_restore.c b/tools/testing/selftests/x86/fsgsbase_restore.c new file mode 100644 index 000000000000..6fffadc51579 --- /dev/null +++ b/tools/testing/selftests/x86/fsgsbase_restore.c @@ -0,0 +1,245 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * fsgsbase_restore.c, test ptrace vs fsgsbase + * Copyright (c) 2020 Andy Lutomirski + * + * This test case simulates a tracer redirecting tracee execution to + * a function and then restoring tracee state using PTRACE_GETREGS and + * PTRACE_SETREGS. This is similar to what gdb does when doing + * 'p func()'. The catch is that this test has the called function + * modify a segment register. This makes sure that ptrace correctly + * restores segment state when using PTRACE_SETREGS. + * + * This is not part of fsgsbase.c, because that test is 64-bit only. + */ + +#define _GNU_SOURCE +#include <stdio.h> +#include <stdlib.h> +#include <stdbool.h> +#include <string.h> +#include <sys/syscall.h> +#include <unistd.h> +#include <err.h> +#include <sys/user.h> +#include <asm/prctl.h> +#include <sys/prctl.h> +#include <asm/ldt.h> +#include <sys/mman.h> +#include <stddef.h> +#include <sys/ptrace.h> +#include <sys/wait.h> +#include <stdint.h> + +#define EXPECTED_VALUE 0x1337f00d + +#ifdef __x86_64__ +# define SEG "%gs" +#else +# define SEG "%fs" +#endif + +static unsigned int dereference_seg_base(void) +{ + int ret; + asm volatile ("mov %" SEG ":(0), %0" : "=rm" (ret)); + return ret; +} + +static void init_seg(void) +{ + unsigned int *target = mmap( + NULL, sizeof(unsigned int), + PROT_READ | PROT_WRITE, + MAP_PRIVATE | MAP_ANONYMOUS | MAP_32BIT, -1, 0); + if (target == MAP_FAILED) + err(1, "mmap"); + + *target = EXPECTED_VALUE; + + printf("\tsegment base address = 0x%lx\n", (unsigned long)target); + + struct user_desc desc = { + .entry_number = 0, + .base_addr = (unsigned int)(uintptr_t)target, + .limit = sizeof(unsigned int) - 1, + .seg_32bit = 1, + .contents = 0, /* Data, grow-up */ + .read_exec_only = 0, + .limit_in_pages = 0, + .seg_not_present = 0, + .useable = 0 + }; + if (syscall(SYS_modify_ldt, 1, &desc, sizeof(desc)) == 0) { + printf("\tusing LDT slot 0\n"); + asm volatile ("mov %0, %" SEG :: "rm" ((unsigned short)0x7)); + } else { + /* No modify_ldt for us (configured out, perhaps) */ + + struct user_desc *low_desc = mmap( + NULL, sizeof(desc), + PROT_READ | PROT_WRITE, + MAP_PRIVATE | MAP_ANONYMOUS | MAP_32BIT, -1, 0); + memcpy(low_desc, &desc, sizeof(desc)); + + low_desc->entry_number = -1; + + /* 32-bit set_thread_area */ + long ret; + asm volatile ("int $0x80" + : "=a" (ret), "+m" (*low_desc) + : "a" (243), "b" (low_desc) +#ifdef __x86_64__ + : "r8", "r9", "r10", "r11" +#endif + ); + memcpy(&desc, low_desc, sizeof(desc)); + munmap(low_desc, sizeof(desc)); + + if (ret != 0) { + printf("[NOTE]\tcould not create a segment -- can't test anything\n"); + exit(0); + } + printf("\tusing GDT slot %d\n", desc.entry_number); + + unsigned short sel = (unsigned short)((desc.entry_number << 3) | 0x3); + asm volatile ("mov %0, %" SEG :: "rm" (sel)); + } +} + +static void tracee_zap_segment(void) +{ + /* + * The tracer will redirect execution here. This is meant to + * work like gdb's 'p func()' feature. The tricky bit is that + * we modify a segment register in order to make sure that ptrace + * can correctly restore segment registers. + */ + printf("\tTracee: in tracee_zap_segment()\n"); + + /* + * Write a nonzero selector with base zero to the segment register. + * Using a null selector would defeat the test on AMD pre-Zen2 + * CPUs, as such CPUs don't clear the base when loading a null + * selector. + */ + unsigned short sel; + asm volatile ("mov %%ss, %0\n\t" + "mov %0, %" SEG + : "=rm" (sel)); + + pid_t pid = getpid(), tid = syscall(SYS_gettid); + + printf("\tTracee is going back to sleep\n"); + syscall(SYS_tgkill, pid, tid, SIGSTOP); + + /* Should not get here. */ + while (true) { + printf("[FAIL]\tTracee hit unreachable code\n"); + pause(); + } +} + +int main() +{ + printf("\tSetting up a segment\n"); + init_seg(); + + unsigned int val = dereference_seg_base(); + if (val != EXPECTED_VALUE) { + printf("[FAIL]\tseg[0] == %x; should be %x\n", val, EXPECTED_VALUE); + return 1; + } + printf("[OK]\tThe segment points to the right place.\n"); + + pid_t chld = fork(); + if (chld < 0) + err(1, "fork"); + + if (chld == 0) { + prctl(PR_SET_PDEATHSIG, SIGKILL, 0, 0, 0, 0); + + if (ptrace(PTRACE_TRACEME, 0, 0, 0) != 0) + err(1, "PTRACE_TRACEME"); + + pid_t pid = getpid(), tid = syscall(SYS_gettid); + + printf("\tTracee will take a nap until signaled\n"); + syscall(SYS_tgkill, pid, tid, SIGSTOP); + + printf("\tTracee was resumed. Will re-check segment.\n"); + + val = dereference_seg_base(); + if (val != EXPECTED_VALUE) { + printf("[FAIL]\tseg[0] == %x; should be %x\n", val, EXPECTED_VALUE); + exit(1); + } + + printf("[OK]\tThe segment points to the right place.\n"); + exit(0); + } + + int status; + + /* Wait for SIGSTOP. */ + if (waitpid(chld, &status, 0) != chld || !WIFSTOPPED(status)) + err(1, "waitpid"); + + struct user_regs_struct regs; + + if (ptrace(PTRACE_GETREGS, chld, NULL, ®s) != 0) + err(1, "PTRACE_GETREGS"); + +#ifdef __x86_64__ + printf("\tChild GS=0x%lx, GSBASE=0x%lx\n", (unsigned long)regs.gs, (unsigned long)regs.gs_base); +#else + printf("\tChild FS=0x%lx\n", (unsigned long)regs.xfs); +#endif + + struct user_regs_struct regs2 = regs; +#ifdef __x86_64__ + regs2.rip = (unsigned long)tracee_zap_segment; + regs2.rsp -= 128; /* Don't clobber the redzone. */ +#else + regs2.eip = (unsigned long)tracee_zap_segment; +#endif + + printf("\tTracer: redirecting tracee to tracee_zap_segment()\n"); + if (ptrace(PTRACE_SETREGS, chld, NULL, ®s2) != 0) + err(1, "PTRACE_GETREGS"); + if (ptrace(PTRACE_CONT, chld, NULL, NULL) != 0) + err(1, "PTRACE_GETREGS"); + + /* Wait for SIGSTOP. */ + if (waitpid(chld, &status, 0) != chld || !WIFSTOPPED(status)) + err(1, "waitpid"); + + printf("\tTracer: restoring tracee state\n"); + if (ptrace(PTRACE_SETREGS, chld, NULL, ®s) != 0) + err(1, "PTRACE_GETREGS"); + if (ptrace(PTRACE_DETACH, chld, NULL, NULL) != 0) + err(1, "PTRACE_GETREGS"); + + /* Wait for SIGSTOP. */ + if (waitpid(chld, &status, 0) != chld) + err(1, "waitpid"); + + if (WIFSIGNALED(status)) { + printf("[FAIL]\tTracee crashed\n"); + return 1; + } + + if (!WIFEXITED(status)) { + printf("[FAIL]\tTracee stopped for an unexpected reason: %d\n", status); + return 1; + } + + int exitcode = WEXITSTATUS(status); + if (exitcode != 0) { + printf("[FAIL]\tTracee reported failure\n"); + return 1; + } + + printf("[OK]\tAll is well.\n"); + return 0; +} diff --git a/tools/testing/selftests/x86/syscall_arg_fault.c b/tools/testing/selftests/x86/syscall_arg_fault.c index 5b7abebbcbb9..bff474b5efc6 100644 --- a/tools/testing/selftests/x86/syscall_arg_fault.c +++ b/tools/testing/selftests/x86/syscall_arg_fault.c @@ -53,6 +53,7 @@ static void sigsegv_or_sigbus(int sig, siginfo_t *info, void *ctx_void) if (ax != -EFAULT && ax != -ENOSYS) { printf("[FAIL]\tAX had the wrong value: 0x%lx\n", (unsigned long)ax); + printf("\tIP = 0x%lx\n", (unsigned long)ctx->uc_mcontext.gregs[REG_IP]); n_errs++; } else { printf("[OK]\tSeems okay\n"); @@ -207,5 +208,30 @@ int main() } set_eflags(get_eflags() & ~X86_EFLAGS_TF); +#ifdef __x86_64__ + printf("[RUN]\tSYSENTER with TF, invalid state, and GSBASE < 0\n"); + + if (sigsetjmp(jmpbuf, 1) == 0) { + sigtrap_consecutive_syscalls = 0; + + asm volatile ("wrgsbase %%rax\n\t" + :: "a" (0xffffffffffff0000UL)); + + set_eflags(get_eflags() | X86_EFLAGS_TF); + asm volatile ( + "movl $-1, %%eax\n\t" + "movl $-1, %%ebx\n\t" + "movl $-1, %%ecx\n\t" + "movl $-1, %%edx\n\t" + "movl $-1, %%esi\n\t" + "movl $-1, %%edi\n\t" + "movl $-1, %%ebp\n\t" + "movl $-1, %%esp\n\t" + "sysenter" + : : : "memory", "flags"); + } + set_eflags(get_eflags() & ~X86_EFLAGS_TF); +#endif + return 0; } |