Albert Cahalan wrote:
We actually have an ABI problem right now because of this.
Note that i386 and x86_64 use different GDT slots.
As far as I can tell, users need to hard-code the mapping
from TLS slot to segment number. They use 0,1,2 to ask the
kernel to set things up (via set_thread_area), but can't
just pop that into %fs or %gs.
That's not true at all. The program I posted earlier in this thread
uses set_thread_area() to allocate a GDT slot, and it works on both
native 32 bit and 32-under-64. The entry_number field in the struct
user_desc is an actual entry number, so you can easily construct a
selector from it.
Typical hacks that result from this:
call uname() and look for "x86_64"
see of the addresses of local variables exceed 0xbfffffff
examine /proc/1/maps
check for a /lib64 directory
change SSE register 8 in a signal handler frame and see if it sticks
checksum the vdso code
...
Please save us from these foul hacks.
Er, that all looks completely unnecessary.
J
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