On Tuesday 09 October 2007 02:48:51 Mihai Donțu wrote: > I have *one* more question: maybe I don't fully understand the hole > BASE thing, but since the FreeBSD kernel does not preserve %gs and > %fs, what is the purpose of amd64_set_XXbase()?
The %fs, %gs registers and fsbase and gsbase MSRs are separate registers. When you write %gs:offset, you actually get (gsbase+offset), so the actual value of %gs doesn't matter. There are two ways to set gsbase. One is by using the privileged instruction wrmsr to set gsbase directly (full 64bit base address), which is what amd64_set_gsbase() exposes to userland. The other is by loading a descriptor selector in %gs in which case gsbase will be set to the base address (only 32bit base address) of a descriptor entry in either the GDT or LDT. To get back to what you are trying to do, because %gs isn't preserved, I think you should avoid writing to it and instead strictly use amd64_set_gsbase(). But from what you've written, I'm guessing you're already doing this, so the next thing to try is to create threads with PTHREAD_SCOPE_SYSTEM or use libthr instead of libpthread, because if I'm not mistaken, PTHREAD_SCOPE_PROCESS in libpthread doesn't preserve gsbase either. _______________________________________________ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "[EMAIL PROTECTED]"
