Commit 59765e87 authored by simonmar's avatar simonmar

[project @ 2005-03-10 14:47:33 by simonmar]

x86: For some reason the code for obscure_ccall_ret_code was allocated
dynamically and specified using literal bytes rather than inline
assembly.  Change it to use inline assembly.
parent d3f4e410
......@@ -95,7 +95,30 @@ mallocBytesRWX(int len)
}
#if defined(i386_HOST_ARCH)
static unsigned char *obscure_ccall_ret_code;
/*
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.
*/
__asm__ (
".globl obscure_ccall_ret_code\n"
"obscure_ccall_ret_code:\n\t"
"addl $0x4, %esp\n\t"
"ret"
);
extern void obscure_ccall_ret_code(void);
#endif
#if defined(alpha_HOST_ARCH)
......@@ -906,30 +929,4 @@ freeHaskellFunctionPtr(void* ptr)
void
initAdjustor(void)
{
#if defined(i386_HOST_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 = mallocBytesRWX(4);
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 */
#endif
}
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