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https://github.com/LuaJIT/LuaJIT.git
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261 lines
6.4 KiB
C
261 lines
6.4 KiB
C
/*
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** Machine code management.
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** Copyright (C) 2005-2010 Mike Pall. See Copyright Notice in luajit.h
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*/
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#define lj_mcode_c
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#define LUA_CORE
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#include "lj_obj.h"
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#if LJ_HASJIT
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#include "lj_gc.h"
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#include "lj_jit.h"
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#include "lj_mcode.h"
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#include "lj_trace.h"
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#include "lj_dispatch.h"
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/* -- OS-specific functions ----------------------------------------------- */
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#if defined(LUA_USE_WIN)
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#define WIN32_LEAN_AND_MEAN
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#include <windows.h>
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#define MCPROT_RW PAGE_READWRITE
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#define MCPROT_RX PAGE_EXECUTE_READ
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#define MCPROT_RWX PAGE_EXECUTE_READWRITE
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static LJ_AINLINE void *mcode_alloc(jit_State *J, size_t sz, DWORD prot)
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{
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void *p = VirtualAlloc(NULL, sz, MEM_RESERVE|MEM_COMMIT|MEM_TOP_DOWN, prot);
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if (!p)
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lj_trace_err(J, LJ_TRERR_MCODEAL);
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return p;
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}
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static LJ_AINLINE void mcode_free(jit_State *J, void *p, size_t sz)
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{
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UNUSED(J); UNUSED(sz);
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VirtualFree(p, 0, MEM_RELEASE);
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}
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static LJ_AINLINE void mcode_setprot(void *p, size_t sz, DWORD prot)
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{
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DWORD oprot;
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VirtualProtect(p, sz, prot, &oprot);
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}
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#elif defined(LUA_USE_POSIX)
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#include <sys/mman.h>
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#ifndef MAP_ANONYMOUS
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#define MAP_ANONYMOUS MAP_ANON
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#endif
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#define MCPROT_RW (PROT_READ|PROT_WRITE)
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#define MCPROT_RX (PROT_READ|PROT_EXEC)
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#define MCPROT_RWX (PROT_READ|PROT_WRITE|PROT_EXEC)
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static LJ_AINLINE void *mcode_alloc(jit_State *J, size_t sz, int prot)
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{
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void *p = mmap(NULL, sz, prot, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0);
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if (p == MAP_FAILED)
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lj_trace_err(J, LJ_TRERR_MCODEAL);
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return p;
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}
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static LJ_AINLINE void mcode_free(jit_State *J, void *p, size_t sz)
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{
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UNUSED(J);
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munmap(p, sz);
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}
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static LJ_AINLINE void mcode_setprot(void *p, size_t sz, int prot)
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{
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mprotect(p, sz, prot);
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}
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#else
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/* Fallback allocator. This will fail if memory is not executable by default. */
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#define LUAJIT_UNPROTECT_MCODE
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#define MCPROT_RW 0
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#define MCPROT_RX 0
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#define MCPROT_RWX 0
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static LJ_AINLINE void *mcode_alloc(jit_State *J, size_t sz, int prot)
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{
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UNUSED(prot);
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return lj_mem_new(J->L, sz);
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}
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static LJ_AINLINE void mcode_free(jit_State *J, void *p, size_t sz)
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{
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lj_mem_free(J2G(J), p, sz);
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}
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#define mcode_setprot(p, sz, prot) UNUSED(p)
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#endif
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/* -- MCode area management ----------------------------------------------- */
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/* Define this ONLY if the page protection twiddling becomes a bottleneck. */
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#ifdef LUAJIT_UNPROTECT_MCODE
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/* It's generally considered to be a potential security risk to have
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** pages with simultaneous write *and* execute access in a process.
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**
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** Do not even think about using this mode for server processes or
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** apps handling untrusted external data (such as a browser).
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**
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** The security risk is not in LuaJIT itself -- but if an adversary finds
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** any *other* flaw in your C application logic, then any RWX memory page
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** simplifies writing an exploit considerably.
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*/
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#define MCPROT_GEN MCPROT_RWX
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#define MCPROT_RUN MCPROT_RWX
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#else
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/* This is the default behaviour and much safer:
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**
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** Most of the time the memory pages holding machine code are executable,
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** but NONE of them is writable.
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**
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** The current memory area is marked read-write (but NOT executable) only
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** during the short time window while the assembler generates machine code.
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*/
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#define MCPROT_GEN MCPROT_RW
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#define MCPROT_RUN MCPROT_RX
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#endif
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/* Change protection of MCode area. */
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static void mcode_protect(jit_State *J, int prot)
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{
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#ifdef LUAJIT_UNPROTECT_MCODE
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UNUSED(J); UNUSED(prot);
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#else
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if (J->mcprot != prot) {
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mcode_setprot(J->mcarea, J->szmcarea, prot);
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J->mcprot = prot;
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}
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#endif
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}
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/* Linked list of MCode areas. */
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typedef struct MCLink {
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MCode *next; /* Next area. */
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size_t size; /* Size of current area. */
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} MCLink;
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/* Allocate a new MCode area. */
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static void mcode_allocarea(jit_State *J)
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{
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MCode *oldarea = J->mcarea;
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size_t sz = (size_t)J->param[JIT_P_sizemcode] << 10;
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sz = (sz + LJ_PAGESIZE-1) & ~(size_t)(LJ_PAGESIZE - 1);
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J->mcarea = (MCode *)mcode_alloc(J, sz, MCPROT_GEN);
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J->szmcarea = sz;
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J->mcprot = MCPROT_GEN;
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J->mctop = (MCode *)((char *)J->mcarea + J->szmcarea);
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J->mcbot = (MCode *)((char *)J->mcarea + sizeof(MCLink));
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((MCLink *)J->mcarea)->next = oldarea;
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((MCLink *)J->mcarea)->size = sz;
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J->szallmcarea += sz;
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}
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/* Free all MCode areas. */
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void lj_mcode_free(jit_State *J)
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{
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MCode *mc = J->mcarea;
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J->mcarea = NULL;
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J->szallmcarea = 0;
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while (mc) {
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MCode *next = ((MCLink *)mc)->next;
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mcode_free(J, mc, ((MCLink *)mc)->size);
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mc = next;
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}
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}
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/* -- MCode transactions -------------------------------------------------- */
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/* Reserve the remainder of the current MCode area. */
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MCode *lj_mcode_reserve(jit_State *J, MCode **lim)
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{
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if (!J->mcarea)
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mcode_allocarea(J);
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else
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mcode_protect(J, MCPROT_GEN);
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*lim = J->mcbot;
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return J->mctop;
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}
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/* Commit the top part of the current MCode area. */
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void lj_mcode_commit(jit_State *J, MCode *top)
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{
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J->mctop = top;
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mcode_protect(J, MCPROT_RUN);
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}
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/* Abort the reservation. */
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void lj_mcode_abort(jit_State *J)
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{
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mcode_protect(J, MCPROT_RUN);
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}
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/* Set/reset protection to allow patching of MCode areas. */
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MCode *lj_mcode_patch(jit_State *J, MCode *ptr, int finish)
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{
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#ifdef LUAJIT_UNPROTECT_MCODE
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UNUSED(J); UNUSED(ptr); UNUSED(finish);
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return NULL;
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#else
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if (finish) {
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if (J->mcarea == ptr)
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mcode_protect(J, MCPROT_RUN);
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else
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mcode_setprot(ptr, ((MCLink *)ptr)->size, MCPROT_RUN);
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return NULL;
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} else {
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MCode *mc = J->mcarea;
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/* Try current area first to use the protection cache. */
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if (ptr >= mc && ptr < mc + J->szmcarea) {
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mcode_protect(J, MCPROT_GEN);
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return mc;
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}
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/* Otherwise search through the list of MCode areas. */
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for (;;) {
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mc = ((MCLink *)mc)->next;
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lua_assert(mc != NULL);
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if (ptr >= mc && ptr < mc + ((MCLink *)mc)->size) {
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mcode_setprot(mc, ((MCLink *)mc)->size, MCPROT_GEN);
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return mc;
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}
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}
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}
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#endif
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}
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/* Limit of MCode reservation reached. */
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void lj_mcode_limiterr(jit_State *J, size_t need)
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{
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size_t sizemcode, maxmcode;
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lj_mcode_abort(J);
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sizemcode = (size_t)J->param[JIT_P_sizemcode] << 10;
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sizemcode = (sizemcode + LJ_PAGESIZE-1) & ~(size_t)(LJ_PAGESIZE - 1);
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maxmcode = (size_t)J->param[JIT_P_maxmcode] << 10;
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if ((size_t)need > sizemcode)
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lj_trace_err(J, LJ_TRERR_MCODEOV); /* Too long for any area. */
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if (J->szallmcarea + sizemcode > maxmcode)
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lj_trace_err(J, LJ_TRERR_MCODEAL);
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mcode_allocarea(J);
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lj_trace_err(J, LJ_TRERR_MCODELM); /* Retry with new area. */
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}
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#endif
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