Date: Thu, 30 Aug 2007 14:20:33 -0700 From: Jin Guojun <jin@george.lbl.gov> To: threads@freebsd.org Cc: hackers@freebsd.org Subject: How TLS is used in Kernel thread Message-ID: <46D734A1.2090700@george.lbl.gov> In-Reply-To: <20070803090530.GH2738@deviant.kiev.zoral.com.ua> References: <46B245D5.1050606@george.lbl.gov> <20070803090530.GH2738@deviant.kiev.zoral.com.ua>
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By looking through _pthread_create() code and find it uses a magic
cookie -- TLS -- created
by rtld_allocate_tls(), and passed into kernel by sysarch() via
_tcb_set() / _kcb_set().
The information seems to be set by rtld (ld-elf.so.1) in digest_phdr()
under tag PT_TLS.
But it is very magic for where the TLS object is created and how it is
passed to digest_phdr().
The whole object passed into kernel (as sd.gsbase) looks like this:
TCB: ______________________________
| TLS | TCB |
|______________|_______________|
Can someone give some basic exaplain on following questions?
1) What TLS stand for?
2) Where TLS object is created? (below is the tls assigned, but I couls
not find where ph is from)
case PT_TLS:
obj->tlsindex = 1;
obj->tlssize = ph->p_memsz;
obj->tlsalign = ph->p_align;
obj->tlsinitsize = ph->p_filesz;
obj->tlsinit = (void*) ph->p_vaddr;
3) Where in kernel the TLS is used for thread operation?
Thanks in advance,
-Jin
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