diff options
Diffstat (limited to 'sysdeps/unix/sysv/linux/i386/tst-bz21269.c')
| -rw-r--r-- | sysdeps/unix/sysv/linux/i386/tst-bz21269.c | 235 |
1 files changed, 235 insertions, 0 deletions
diff --git a/sysdeps/unix/sysv/linux/i386/tst-bz21269.c b/sysdeps/unix/sysv/linux/i386/tst-bz21269.c new file mode 100644 index 0000000000..6ee3fc62be --- /dev/null +++ b/sysdeps/unix/sysv/linux/i386/tst-bz21269.c @@ -0,0 +1,235 @@ +/* Test for i386 sigaction sa_restorer handling (BZ#21269) + Copyright (C) 2017 Free Software Foundation, Inc. + This file is part of the GNU C Library. + + The GNU C Library is free software; you can redistribute it and/or + modify it under the terms of the GNU Lesser General Public + License as published by the Free Software Foundation; either + version 2.1 of the License, or (at your option) any later version. + + The GNU C Library is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + Lesser General Public License for more details. + + You should have received a copy of the GNU Lesser General Public + License along with the GNU C Library; if not, see + <http://www.gnu.org/licenses/>. */ + +/* This is based on Linux test tools/testing/selftests/x86/ldt_gdt.c, + more specifically in do_multicpu_tests function. The main changes + are: + + - C11 atomics instead of plain access. + - Remove x86_64 support which simplifies the syscall handling + and fallbacks. + - Replicate only the test required to trigger the issue for the + BZ#21269. */ + +#include <stdatomic.h> + +#include <asm/ldt.h> +#include <linux/futex.h> + +#include <setjmp.h> +#include <signal.h> +#include <errno.h> +#include <sys/syscall.h> +#include <sys/mman.h> + +#include <support/xunistd.h> +#include <support/check.h> +#include <support/xthread.h> + +static int +xset_thread_area (struct user_desc *u_info) +{ + long ret = syscall (SYS_set_thread_area, u_info); + TEST_VERIFY_EXIT (ret == 0); + return ret; +} + +static void +xmodify_ldt (int func, const void *ptr, unsigned long bytecount) +{ + TEST_VERIFY_EXIT (syscall (SYS_modify_ldt, 1, ptr, bytecount) == 0); +} + +static int +futex (int *uaddr, int futex_op, int val, void *timeout, int *uaddr2, + int val3) +{ + return syscall (SYS_futex, uaddr, futex_op, val, timeout, uaddr2, val3); +} + +static void +xsethandler (int sig, void (*handler)(int, siginfo_t *, void *), int flags) +{ + struct sigaction sa = { 0 }; + sa.sa_sigaction = handler; + sa.sa_flags = SA_SIGINFO | flags; + TEST_VERIFY_EXIT (sigemptyset (&sa.sa_mask) == 0); + TEST_VERIFY_EXIT (sigaction (sig, &sa, 0) == 0); +} + +static jmp_buf jmpbuf; + +static void +sigsegv_handler (int sig, siginfo_t *info, void *ctx_void) +{ + siglongjmp (jmpbuf, 1); +} + +/* Points to an array of 1024 ints, each holding its own index. */ +static const unsigned int *counter_page; +static struct user_desc *low_user_desc; +static struct user_desc *low_user_desc_clear; /* Used to delete GDT entry. */ +static int gdt_entry_num; + +static void +setup_counter_page (void) +{ + long page_size = sysconf (_SC_PAGE_SIZE); + TEST_VERIFY_EXIT (page_size > 0); + unsigned int *page = xmmap (NULL, page_size, PROT_READ | PROT_WRITE, + MAP_ANONYMOUS | MAP_PRIVATE | MAP_32BIT, -1); + for (int i = 0; i < (page_size / sizeof (unsigned int)); i++) + page[i] = i; + counter_page = page; +} + +static void +setup_low_user_desc (void) +{ + low_user_desc = xmmap (NULL, 2 * sizeof (struct user_desc), + PROT_READ | PROT_WRITE, + MAP_ANONYMOUS | MAP_PRIVATE | MAP_32BIT, -1); + + low_user_desc->entry_number = -1; + low_user_desc->base_addr = (unsigned long) &counter_page[1]; + low_user_desc->limit = 0xffff; + low_user_desc->seg_32bit = 1; + low_user_desc->contents = 0; + low_user_desc->read_exec_only = 0; + low_user_desc->limit_in_pages = 1; + low_user_desc->seg_not_present = 0; + low_user_desc->useable = 0; + + xset_thread_area (low_user_desc); + + low_user_desc_clear = low_user_desc + 1; + low_user_desc_clear->entry_number = gdt_entry_num; + low_user_desc_clear->read_exec_only = 1; + low_user_desc_clear->seg_not_present = 1; +} + +/* Possible values of futex: + 0: thread is idle. + 1: thread armed. + 2: thread should clear LDT entry 0. + 3: thread should exit. */ +static atomic_uint ftx; + +static void * +threadproc (void *ctx) +{ + while (1) + { + futex ((int *) &ftx, FUTEX_WAIT, 1, NULL, NULL, 0); + while (atomic_load (&ftx) != 2) + { + if (atomic_load (&ftx) >= 3) + return NULL; + } + + /* clear LDT entry 0. */ + const struct user_desc desc = { 0 }; + xmodify_ldt (1, &desc, sizeof (desc)); + + /* If ftx == 2, set it to zero, If ftx == 100, quit. */ + if (atomic_fetch_add (&ftx, -2) != 2) + return NULL; + } +} + + +/* As described in testcase, for historical reasons x86_32 Linux (and compat + on x86_64) interprets SA_RESTORER clear with nonzero sa_restorer as a + request for stack switching if the SS segment is 'funny' (this is default + scenario for vDSO system). This means that anything that tries to mix + signal handling with segmentation should explicit clear the sa_restorer. + + This testcase check if sigaction in fact does it by changing the local + descriptor table (LDT) through the modify_ldt syscall and triggering + a synchronous segfault on iret fault by trying to install an invalid + segment. With a correct zeroed sa_restorer it should not trigger an + 'real' SEGSEGV and allows the siglongjmp in signal handler. */ + +static int +do_test (void) +{ + setup_counter_page (); + setup_low_user_desc (); + + pthread_t thread; + unsigned short orig_ss; + + xsethandler (SIGSEGV, sigsegv_handler, 0); + /* 32-bit kernels send SIGILL instead of SIGSEGV on IRET faults. */ + xsethandler (SIGILL, sigsegv_handler, 0); + /* Some kernels send SIGBUS instead. */ + xsethandler (SIGBUS, sigsegv_handler, 0); + + thread = xpthread_create (0, threadproc, 0); + + asm volatile ("mov %%ss, %0" : "=rm" (orig_ss)); + + for (int i = 0; i < 5; i++) + { + if (sigsetjmp (jmpbuf, 1) != 0) + continue; + + /* Make sure the thread is ready after the last test. */ + while (atomic_load (&ftx) != 0) + ; + + struct user_desc desc = { + .entry_number = 0, + .base_addr = 0, + .limit = 0xffff, + .seg_32bit = 1, + .contents = 0, + .read_exec_only = 0, + .limit_in_pages = 1, + .seg_not_present = 0, + .useable = 0 + }; + + xmodify_ldt (0x11, &desc, sizeof (desc)); + + /* Arm the thread. */ + ftx = 1; + futex ((int*) &ftx, FUTEX_WAKE, 0, NULL, NULL, 0); + + asm volatile ("mov %0, %%ss" : : "r" (0x7)); + + /* Fire up thread modify_ldt call. */ + atomic_store (&ftx, 2); + + while (atomic_load (&ftx) != 0) + ; + + /* On success, modify_ldt will segfault us synchronously and we will + escape via siglongjmp. */ + support_record_failure (); + } + + atomic_store (&ftx, 100); + futex ((int*) &ftx, FUTEX_WAKE, 0, NULL, NULL, 0); + + xpthread_join (thread); + + return 0; +} + +#include <support/test-driver.c> |