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On Tue, 17 Dec 2002, Ulrich Drepper wrote: > > The problem with the current solution is the instruction set of the x86. > In your test code you simply use call 0xfffff000 and it magically work. > But this is only the case because your program is linked statically. Yeah, it's not very convenient. I didn't find any real alternatives, though, and you can always just put 0xfffff000 in memory or registers and jump to that. In fact, I suspect that if you actually want to use it in glibc, then at least in the short term that's what you need to do anyway, sinc eyou probably don't want to have a glibc that only works with very recent kernels. So I was actually assuming that the glibc code would look more like something like this: old_fashioned: int $0x80 ret unsigned long system_call_ptr = old_fashioned; /* .. startup .. */ if (kernel_version > xxx) system_call_ptr = 0xfffff000; /* ... usage ... */ call *system_call_ptr; since you cannot depend on the 0xfffff000 on older kernels anyway.. > Instead I've changed the syscall handling to effectve do > > pushl %ebp > movl $0xfffff000, %ebp > call *%ebp > popl %ebp The above will work, but then you'd have limited yourself to a binary that _only_ works on new kernels. So I'd suggest the memory indirection instead. Linus - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ | |||||||||
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