kc3-lang/libffi/src/x86

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  • Hash : fe203ffb
    Author : mikulas-patocka
    Date : 2025-03-27T01:31:49 

    Fix bugs in the x86-64 and x32 target (#887) (#889)

This commit fixes two bugs in ffi in the x86-64 target. The bugs were
introduced by the commit d21881f55ed4a44d464c9091871e69b0bb47611a ("Fix
x86/ffi64 calls with 6 gp and some sse registers").

The first bug is that when we pass an argument with less than 8 bytes,
ffi will read memory beyond argument end, causing a crash if the argument
is located just before the end of the mapped region.

The second bug is in the x32 ABI - pointers in x32 are 4-byte, but GCC
assumes that the pointer values in the registers are zero-extended. ffi
doesn't respect this assumption, causing crashes in the called library.

For example, when we compile this function for x32:
int fn(int *a)
{
	if (a)
		return *a;
	return -1;
}
we get this code:
fn:
	testq   %rdi, %rdi
	je      .L3
	movl    (%edi), %eax
	ret
.L3:
	movl    $-1, %eax
	ret
When we call this function using ffi with the argument NULL, the function
crashes because top 4 bytes of the RDI register are not cleared.


Fixes: d21881f55ed4 ("Fix x86/ffi64 calls with 6 gp and some sse registers (#848)")

Signed-off-by: Mikulas Patocka <mikulas@twibright.com>

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