60 lines
1.7 KiB
C
60 lines
1.7 KiB
C
/* ===-- enable_execute_stack.c - Implement __enable_execute_stack ---------===
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*
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* The LLVM Compiler Infrastructure
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*
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* This file is dual licensed under the MIT and the University of Illinois Open
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* Source Licenses. See LICENSE.TXT for details.
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*
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* ===----------------------------------------------------------------------===
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*/
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#include "int_lib.h"
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#include <sys/mman.h>
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/* #include "config.h"
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* FIXME: CMake - include when cmake system is ready.
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* Remove #define HAVE_SYSCONF 1 line.
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*/
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#define HAVE_SYSCONF 1
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#ifndef __APPLE__
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#include <unistd.h>
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#endif /* __APPLE__ */
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#if __LP64__
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#define TRAMPOLINE_SIZE 48
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#else
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#define TRAMPOLINE_SIZE 40
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#endif
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/*
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* The compiler generates calls to __enable_execute_stack() when creating
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* trampoline functions on the stack for use with nested functions.
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* It is expected to mark the page(s) containing the address
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* and the next 48 bytes as executable. Since the stack is normally rw-
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* that means changing the protection on those page(s) to rwx.
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*/
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void __enable_execute_stack(void* addr)
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{
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#if __APPLE__
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/* On Darwin, pagesize is always 4096 bytes */
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const uintptr_t pageSize = 4096;
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#elif !defined(HAVE_SYSCONF)
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#error "HAVE_SYSCONF not defined! See enable_execute_stack.c"
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#else
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const uintptr_t pageSize = sysconf(_SC_PAGESIZE);
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#endif /* __APPLE__ */
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const uintptr_t pageAlignMask = ~(pageSize-1);
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uintptr_t p = (uintptr_t)addr;
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unsigned char* startPage = (unsigned char*)(p & pageAlignMask);
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unsigned char* endPage = (unsigned char*)((p+TRAMPOLINE_SIZE+pageSize) & pageAlignMask);
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size_t length = endPage - startPage;
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(void) mprotect((void *)startPage, length, PROT_READ | PROT_WRITE | PROT_EXEC);
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}
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