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In Linux, the set_thread_area system call stores the address of the thread local storage area into a field of the current thread_info structure. Later, to access that value, the program uses the rdhwr instruction to read a "hardware register" with index 29. The 64 bit MIPS manual, volume II, says that index 29 is reserved for a future ABI extension and should cause a "Reserved Instruction Exception". In Linux (and potentially other ISAs) that exception is trapped and emulated to return the value stored by set_thread_area as if that were actually stored by a physical register. The tp_value address (as named in the Linux kernel) is ironically stored as a control register so that it goes with a particular ThreadContext. Syscall emulation will use that to emulate storing to the OS's thread info structure, and rdhwr will emulate faulting and returning that value from software by returning the value itself, as if it was in hardware. In other words, we fake faking the register in SE mode. In an FS mode implementation it should work as specified in the manual.
This is release 2.0_beta6 of the M5 simulator. For detailed information about building the simulator and getting started please refer to http://www.m5sim.org. Specific pages of interest are: http://www.m5sim.org/wiki/index.php/Compiling_M5 http://www.m5sim.org/wiki/index.php/Running_M5 Short version: 1. If you don't have SCons version 0.96.91 or newer, get it from http://wwww.scons.org. 2. If you don't have SWIG version 1.3.28 or newer, get it from http://wwww.swig.org. 3. In this directory, type 'scons build/ALPHA_SE/tests/debug/quick'. This will build the debug version of the m5 binary (m5.debug) for the Alpha syscall emulation target, and run the quick regression tests on it. If you have questions, please send mail to m5-users@m5sim.org WHAT'S INCLUDED (AND NOT) ------------------------- The basic source release includes these subdirectories: - m5: - src: source code of the m5 simulator - tests: regression tests - ext: less-common external packages needed to build m5 To run full-system simulations, you will need compiled console, PALcode, and kernel binaries and one or more disk images. These files are collected in a separate archive, m5_system.tar.bz2. This file can he downloaded separately. M5 supports Linux 2.4/2.6, FreeBSD, and the proprietary Compaq/HP Tru64 version of Unix. We are able to distribute Linux and FreeBSD bootdisks, but we are unable to distribute bootable disk images of Tru64 Unix. If you have a Tru64 license and are interested in obtaining disk images, contact us at m5-users@m5sim.org