Re: Syscall changes registers beyond %eax, on linux-i386

[Mikael Pettersson]

Daniel Jacobowitz writes:
 > That's not going to help.  As Richard said, the memory in question
 > belongs to the called function.  GCC knows this.  It can freely modify
 > it.  The fact that the value of the parameter is const is a
 > language-level, semantic thing.  It doesn't say anything about the
 > const-ness of that memory.  Only the ABI does.

Does Linux/x86 even have a proper ABI document? I've never seen one.
The closest I've seen would be the SVR4 i386 psABI, but it
deliberately doesn't define the raw syscall interface, only the
each-syscall-is-a-C-function one implemented by the C library,
and that interface doesn't suffer from the current issue.

IOW, the kernel may not be at fault if user-space code invokes int
$0x80 directly and then sees clobbered registers.

/Mikael