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i#2350 rseq: Add -disable_rseq option
Adds a new option -disable_rseq, which returns -ENOSYS on any SYS_rseq system call. This is intended as a workaround for applications that do not satisfy DR's limitations for full rseq support. Adds a test that fails unless -disable_rseq is passed. Moves the rseq limitations list to a new section on rseq in the documentation. Issue: #2350
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| Original file line number | Diff line number | Diff line change |
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| /* ********************************************************** | ||
| * Copyright (c) 2019 Google, Inc. All rights reserved. | ||
| * **********************************************************/ | ||
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| /* | ||
| * Redistribution and use in source and binary forms, with or without | ||
| * modification, are permitted provided that the following conditions are met: | ||
| * | ||
| * * Redistributions of source code must retain the above copyright notice, | ||
| * this list of conditions and the following disclaimer. | ||
| * | ||
| * * Redistributions in binary form must reproduce the above copyright notice, | ||
| * this list of conditions and the following disclaimer in the documentation | ||
| * and/or other materials provided with the distribution. | ||
| * | ||
| * * Neither the name of VMware, Inc. nor the names of its contributors may be | ||
| * used to endorse or promote products derived from this software without | ||
| * specific prior written permission. | ||
| * | ||
| * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" | ||
| * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE | ||
| * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE | ||
| * ARE DISCLAIMED. IN NO EVENT SHALL VMWARE, INC. OR CONTRIBUTORS BE LIABLE | ||
| * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL | ||
| * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR | ||
| * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER | ||
| * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT | ||
| * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY | ||
| * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH | ||
| * DAMAGE. | ||
| */ | ||
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| /* This test uses rseq but does not comply with the conventions that DR requires. | ||
| * It shares similar code to the other rseq tests but not enough to try to share | ||
| * the separate bits of code. | ||
| */ | ||
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| #include "tools.h" | ||
| #ifndef LINUX | ||
| # error Only Linux is supported. | ||
| #endif | ||
| /* TODO i#2350: Port this to other platforms and bitwidths. There is a lot of | ||
| * assembly which makes that non-trivial work. | ||
| */ | ||
| #if !defined(X86) || !defined(X64) | ||
| # error Only x86_64 is supported. | ||
| #endif | ||
| #include "../../core/unix/include/syscall.h" | ||
| #ifndef HAVE_RSEQ | ||
| # error The linux/rseq header is required. | ||
| #endif | ||
| #include <linux/rseq.h> | ||
| #include <errno.h> | ||
| #include <assert.h> | ||
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| #define EXPANDSTR(x) #x | ||
| #define STRINGIFY(x) EXPANDSTR(x) | ||
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| #define RSEQ_SIG 0x90909090 /* nops to disasm nicely */ | ||
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| /* This cannot be a stack-local variable, as the kernel will force SIGSEGV on a syscall | ||
| * if it can't read this struct. And for multiple threads it should be in TLS. | ||
| */ | ||
| static __thread volatile struct rseq rseq_tls; | ||
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| #ifdef RSEQ_TEST_ATTACH | ||
| static volatile int exit_requested; | ||
| static void *thread_ready; | ||
| #endif | ||
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| int | ||
| test_rseq(void) | ||
| { | ||
| /* We use static to avoid stack reference issues with our extra frame inside the asm. | ||
| */ | ||
| static __u32 id = RSEQ_CPU_ID_UNINITIALIZED; | ||
| static int restarts = 0; | ||
| __asm__ __volatile__( | ||
| /* We deliberately do NOT put our data into an __rseq_cs section. */ | ||
| ".pushsection .data, \"aw\"\n\t" | ||
| ".balign 32\n\t" | ||
| "1:\n\t" | ||
| ".long 0, 0\n\t" /* version, flags */ | ||
| ".quad 2f, 3f-2f, 4f\n\t" /* start_ip, post_commit_offset, abort_ip */ | ||
| ".popsection\n\t" | ||
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| /* We do NOT structure this as a call. */ | ||
| "6:\n\t" | ||
| /* Store the entry into the ptr. */ | ||
| "leaq 1b(%%rip), %%rax\n\t" | ||
| "movq %%rax, %0\n\t" | ||
| /* Test "falling into" the rseq region. */ | ||
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| /* Restartable sequence. | ||
| * If I pause in gdb in here, often the thread is migrated and the abort | ||
| * handler invoked: a simple way to test a restart natively. | ||
| */ | ||
| "2:\n\t" | ||
| "mov %3, %%rax\n\t" | ||
| "mov %%rax, %1\n\t" | ||
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| /* Post-commit. */ | ||
| "3:\n\t" | ||
| "jmp 5f\n\t" | ||
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| /* Abort handler. */ | ||
| /* clang-format off */ /* (avoid indenting next few lines) */ | ||
| ".long " STRINGIFY(RSEQ_SIG) "\n\t" | ||
| "4:\n\t" | ||
| "addl $1, %2\n\t" | ||
| "jmp 6b\n\t" | ||
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| /* Clear the ptr. */ | ||
| "5:\n\t" | ||
| "leaq 1b(%%rip), %%rax\n\t" | ||
| "movq $0, %0\n\t" | ||
| /* clang-format on */ | ||
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| : "=m"(rseq_tls.rseq_cs), "=m"(id), "=m"(restarts) | ||
| : "m"(rseq_tls.cpu_id) | ||
| : "rax", "memory"); | ||
| assert(id != RSEQ_CPU_ID_UNINITIALIZED); | ||
| return restarts; | ||
| } | ||
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| int | ||
| main() | ||
| { | ||
| int restart_count = 0; | ||
| rseq_tls.cpu_id = RSEQ_CPU_ID_UNINITIALIZED; | ||
| int res = syscall(SYS_rseq, &rseq_tls, sizeof(rseq_tls), 0, RSEQ_SIG); | ||
| if (res == 0) { | ||
| restart_count = test_rseq(); | ||
| } else { | ||
| /* Linux kernel 4.18+ is required. */ | ||
| assert(errno == ENOSYS); | ||
| /* Make the test pass. */ | ||
| restart_count = 1; | ||
| } | ||
| /* We expect 0 restart_count natively (ok, tiny chance of >0), and 1 under DR. */ | ||
| print("Saw %s restarts\n", restart_count > 0 ? "some" : "no"); | ||
| print("All done\n"); | ||
| return 0; | ||
| } |
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| Saw some restarts | ||
| All done |