forked from OSchip/llvm-project
41 lines
1.3 KiB
C
41 lines
1.3 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 distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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#include <stdint.h>
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#include <sys/mman.h>
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#ifndef __APPLE__
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#include <unistd.h>
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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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#else
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// FIXME: We should have a configure check for this.
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const uintptr_t pageSize = getpagesize();
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#endif
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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+48+pageSize) & pageAlignMask);
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mprotect(startPage, endPage-startPage, PROT_READ | PROT_WRITE | PROT_EXEC);
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}
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