X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Frts%2FAdjustor.c;h=44fbcf2c53816ab8db41abecdd3f5677f30548ab;hb=aa47e9aaabf6b11875749923c2e2726a30235e0a;hp=bf9e02b3d7100d2f65c09ccd4e88577a137928a0;hpb=10a5b31160c92f84f7d945c701df22347da7f6b0;p=ghc-hetmet.git diff --git a/ghc/rts/Adjustor.c b/ghc/rts/Adjustor.c index bf9e02b..44fbcf2 100644 --- a/ghc/rts/Adjustor.c +++ b/ghc/rts/Adjustor.c @@ -61,7 +61,7 @@ typedef enum { * TODO: Can the code span more than one page? If yes, we need to make two * pages executable! */ -static rtsBool +static void execPage (void* addr, pageMode mode) { #if defined(i386_TARGET_ARCH) && defined(_WIN32) && 0 @@ -75,47 +75,16 @@ execPage (void* addr, pageMode mode) sInfo.dwPageSize, ( mode == pageExecuteReadWrite ? PAGE_EXECUTE_READWRITE : PAGE_EXECUTE_READ), &dwOldProtect) == 0 ) { -# if 1 DWORD rc = GetLastError(); - prog_belch("execPage: failed to protect 0x%p; error=%lu; old protection: %lu\n", addr, rc, dwOldProtect); -# endif - return rtsFalse; + barf("execPage: failed to protect 0x%p; error=%lu; old protection: %lu\n", addr, rc, dwOldProtect); } - return rtsTrue; #else (void)addr; (void)mode; /* keep gcc -Wall happy */ - return rtsTrue; #endif } - -static unsigned char __obscure_ccall_ret_code [] = #if defined(i386_TARGET_ARCH) -/* Now here's something obscure for you: - - When generating an adjustor thunk that uses the C calling - convention, we have to make sure that the thunk kicks off - the process of jumping into Haskell with a tail jump. Why? - Because as a result of jumping in into Haskell we may end - up freeing the very adjustor thunk we came from using - freeHaskellFunctionPtr(). Hence, we better not return to - the adjustor code on our way out, since it could by then - point to junk. - - The fix is readily at hand, just include the opcodes - for the C stack fixup code that we need to perform when - returning in some static piece of memory and arrange - to return to it before tail jumping from the adjustor thunk. - - For this to work we make the assumption that bytes in .data - are considered executable. -*/ - { 0x83, 0xc4, 0x04 /* addl $0x4, %esp */ - , 0xc3 /* ret */ - }; -#else -/* No such mind-twisters on non-Intel platforms */ - { }; +static unsigned char *obscure_ccall_ret_code; #endif #if defined(alpha_TARGET_ARCH) @@ -179,7 +148,8 @@ createAdjustor(int cconv, StgStablePtr hptr, StgFunPtr wptr) : ff e0 jmp %eax # and jump to it. # the callee cleans up the stack */ - if ((adjustor = stgMallocBytes(14, "createAdjustor")) != NULL) { + adjustor = stgMallocBytes(14, "createAdjustor"); + { unsigned char *const adj_code = (unsigned char *)adjustor; adj_code[0x00] = (unsigned char)0x58; /* popl %eax */ @@ -208,7 +178,7 @@ createAdjustor(int cconv, StgStablePtr hptr, StgFunPtr wptr) <00>: 68 ef be ad de pushl $0xdeadbeef # constant is large enough to # hold a StgStablePtr <05>: b8 fa ef ff 00 movl $0x00ffeffa, %eax # load up wptr - <0a>: 68 ef be ad de pushl $__obscure_ccall_ret_code # push the return address + <0a>: 68 ef be ad de pushl $obscure_ccall_ret_code # push the return address <0f>: ff e0 jmp *%eax # jump to wptr The ccall'ing version is a tad different, passing in the return @@ -216,7 +186,7 @@ createAdjustor(int cconv, StgStablePtr hptr, StgFunPtr wptr) via the stable pointer.) (The auto-generated C stub is in on this game, don't worry :-) - See the comment next to __obscure_ccall_ret_code why we need to + See the comment next to obscure_ccall_ret_code why we need to perform a tail jump instead of a call, followed by some C stack fixup. @@ -225,7 +195,8 @@ createAdjustor(int cconv, StgStablePtr hptr, StgFunPtr wptr) That's (thankfully) the case here with the restricted set of return types that we support. */ - if ((adjustor = stgMallocBytes(17, "createAdjustor")) != NULL) { + adjustor = stgMallocBytes(17, "createAdjustor"); + { unsigned char *const adj_code = (unsigned char *)adjustor; adj_code[0x00] = (unsigned char)0x68; /* pushl hptr (which is a dword immediate ) */ @@ -234,8 +205,8 @@ createAdjustor(int cconv, StgStablePtr hptr, StgFunPtr wptr) adj_code[0x05] = (unsigned char)0xb8; /* movl $wptr, %eax */ *((StgFunPtr*)(adj_code + 0x06)) = (StgFunPtr)wptr; - adj_code[0x0a] = (unsigned char)0x68; /* pushl __obscure_ccall_ret_code */ - *((StgFunPtr*)(adj_code + 0x0b)) = (StgFunPtr)__obscure_ccall_ret_code; + adj_code[0x0a] = (unsigned char)0x68; /* pushl obscure_ccall_ret_code */ + *((StgFunPtr*)(adj_code + 0x0b)) = (StgFunPtr)obscure_ccall_ret_code; adj_code[0x0f] = (unsigned char)0xff; /* jmp *%eax */ adj_code[0x10] = (unsigned char)0xe0; @@ -272,7 +243,8 @@ createAdjustor(int cconv, StgStablePtr hptr, StgFunPtr wptr) similarly, and local variables should be accessed via %fp, not %sp. In a nutshell: This should work! (Famous last words! :-) */ - if ((adjustor = stgMallocBytes(4*(11+1), "createAdjustor")) != NULL) { + adjustor = stgMallocBytes(4*(11+1), "createAdjustor"); + { unsigned long *const adj_code = (unsigned long *)adjustor; adj_code[ 0] = 0x9C23A008UL; /* sub %sp, 8, %sp */ @@ -348,7 +320,8 @@ TODO: Depending on how much allocation overhead stgMallocBytes uses for 4 bytes (getting rid of the nop), hence saving memory. [ccshan] */ ASSERT(((StgWord64)wptr & 3) == 0); - if ((adjustor = stgMallocBytes(48, "createAdjustor")) != NULL) { + adjustor = stgMallocBytes(48, "createAdjustor"); + { StgWord64 *const code = (StgWord64 *)adjustor; code[0] = 0x4610041246520414L; @@ -385,7 +358,8 @@ TODO: Depending on how much allocation overhead stgMallocBytes uses for this code, it only works for up to 6 arguments (when floating point arguments are involved, this may be more or less, depending on the exact situation). */ - if ((adjustor = stgMallocBytes(4*13, "createAdjustor")) != NULL) { + adjustor = stgMallocBytes(4*13, "createAdjustor"); + { unsigned long *const adj_code = (unsigned long *)adjustor; // make room for extra arguments @@ -584,8 +558,35 @@ freeHaskellFunctionPtr(void* ptr) * * Perform initialisation of adjustor thunk layer (if needed.) */ -rtsBool +void initAdjustor(void) { - return execPage(__obscure_ccall_ret_code, pageExecuteRead); +#if defined(i386_TARGET_ARCH) + /* Now here's something obscure for you: + + When generating an adjustor thunk that uses the C calling + convention, we have to make sure that the thunk kicks off + the process of jumping into Haskell with a tail jump. Why? + Because as a result of jumping in into Haskell we may end + up freeing the very adjustor thunk we came from using + freeHaskellFunctionPtr(). Hence, we better not return to + the adjustor code on our way out, since it could by then + point to junk. + + The fix is readily at hand, just include the opcodes + for the C stack fixup code that we need to perform when + returning in some static piece of memory and arrange + to return to it before tail jumping from the adjustor thunk. + */ + + obscure_ccall_ret_code = stgMallocBytes(4, "initAdjustor"); + + obscure_ccall_ret_code[0x00] = (unsigned char)0x83; /* addl $0x4, %esp */ + obscure_ccall_ret_code[0x01] = (unsigned char)0xc4; + obscure_ccall_ret_code[0x02] = (unsigned char)0x04; + + obscure_ccall_ret_code[0x03] = (unsigned char)0xc3; /* ret */ + + execPage(obscure_ccall_ret_code, pageExecuteRead); +#endif }