| 1 | //===-- enable_execute_stack.c - Implement __enable_execute_stack ---------===// |
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| 2 | // |
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| 3 | // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
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| 4 | // See https://llvm.org/LICENSE.txt for license information. |
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| 5 | // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
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| 6 | // |
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| 7 | //===----------------------------------------------------------------------===// |
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| 8 | |
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| 9 | #include "int_lib.h" |
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| 10 | |
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| 11 | #ifndef _WIN32 |
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| 12 | #include <sys/mman.h> |
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| 13 | #endif |
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| 14 | |
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| 15 | // #include "config.h" |
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| 16 | // FIXME: CMake - include when cmake system is ready. |
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| 17 | // Remove #define HAVE_SYSCONF 1 line. |
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| 18 | #define HAVE_SYSCONF 1 |
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| 19 | |
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| 20 | #ifdef _WIN32 |
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| 21 | #define WIN32_LEAN_AND_MEAN |
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| 22 | #include <windows.h> |
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| 23 | #else |
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| 24 | #ifndef __APPLE__ |
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| 25 | #include <unistd.h> |
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| 26 | #endif // __APPLE__ |
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| 27 | #endif // _WIN32 |
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| 28 | |
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| 29 | #if __LP64__ |
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| 30 | #define TRAMPOLINE_SIZE 48 |
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| 31 | #else |
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| 32 | #define TRAMPOLINE_SIZE 40 |
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| 33 | #endif |
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| 34 | |
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| 35 | // The compiler generates calls to __enable_execute_stack() when creating |
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| 36 | // trampoline functions on the stack for use with nested functions. |
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| 37 | // It is expected to mark the page(s) containing the address |
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| 38 | // and the next 48 bytes as executable. Since the stack is normally rw- |
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| 39 | // that means changing the protection on those page(s) to rwx. |
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| 40 | |
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| 41 | COMPILER_RT_ABI void __enable_execute_stack(void *addr) { |
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| 42 | |
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| 43 | #if _WIN32 |
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| 44 | MEMORY_BASIC_INFORMATION mbi; |
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| 45 | if (!VirtualQuery(addr, &mbi, sizeof(mbi))) |
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| 46 | return; // We should probably assert here because there is no return value |
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| 47 | VirtualProtect(mbi.BaseAddress, mbi.RegionSize, PAGE_EXECUTE_READWRITE, |
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| 48 | &mbi.Protect); |
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| 49 | #else |
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| 50 | #if __APPLE__ |
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| 51 | // On Darwin, pagesize is always 4096 bytes |
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| 52 | const uintptr_t pageSize = 4096; |
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| 53 | #elif !defined(HAVE_SYSCONF) |
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| 54 | #error "HAVE_SYSCONF not defined! See enable_execute_stack.c" |
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| 55 | #else |
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| 56 | const uintptr_t pageSize = sysconf(_SC_PAGESIZE); |
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| 57 | #endif // __APPLE__ |
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| 58 | |
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| 59 | const uintptr_t pageAlignMask = ~(pageSize - 1); |
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| 60 | uintptr_t p = (uintptr_t)addr; |
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| 61 | unsigned char *startPage = (unsigned char *)(p & pageAlignMask); |
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| 62 | unsigned char *endPage = |
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| 63 | (unsigned char *)((p + TRAMPOLINE_SIZE + pageSize) & pageAlignMask); |
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| 64 | size_t length = endPage - startPage; |
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| 65 | (void)mprotect(addr: (void *)startPage, len: length, PROT_READ | PROT_WRITE | PROT_EXEC); |
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| 66 | #endif |
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| 67 | } |
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| 68 | |
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