Messages in this thread | | | From | "H. Peter Anvin" <> | Subject | Re: [PATCH -mm] i386 syscall opcode reordering (pipelining) | Date | Tue, 13 Jun 2006 15:21:27 -0700 (PDT) |
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Followup to: <e6nd68$4sq$1@terminus.zytor.com> By author: "H. Peter Anvin" <hpa@zytor.com> In newsgroup: linux.dev.kernel > > Probably not. The _syscallN() macros are broken for the general case > on any 32-bit architecture, since they can't handle multiregister > arguments. > > Similarly, a general syscall() function is broken (in the sense that > one would have to have syscall-specific code to mangle the arguments) > on *some*, but not all, 32-bit architectures, since some architectures > have alignment constraints on multiregister arguments, and the syscall > number argument throws off that alignment. >
I should probably add that it is possible to write _syscallN() macros that handle multiregister arguments correctly; just the current ones aren't done correctly. The complexity gets pretty staggering for the higher argument counts, though, as for each _syscallN() you have to support 2^N possible cases, just to deal with 32- and 64-bit arguments (which is all we support at this point, so it'd be okay.)
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