Messages in this thread | | | Date | Fri, 20 Dec 2002 10:48:29 -0500 | From | Daniel Jacobowitz <> | Subject | Re: PTRACE_GET_THREAD_AREA |
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On Fri, Dec 20, 2002 at 12:32:41AM -0800, Roland McGrath wrote: > This patch vs 2.5.51 (should apply fine to 2.5.52) adds two new ptrace > requests for i386, PTRACE_GET_THREAD_AREA and PTRACE_SET_THREAD_AREA. > These let another process using ptrace do the equivalent of performing > get_thread_area and set_thread_area system calls for another thread. > > We are working on gdb support for the new threading code in the kernel > using the new NPTL library, and use PTRACE_GET_THREAD_AREA for that. > This patch has been working fine for that. > > I added PTRACE_SET_THREAD_AREA just for completeness, so that you can > change all the state via ptrace that you can read via ptrace as has > previously been the case. It doesn't have an equivalent of set_thread_area > with .entry_number = -1, but is otherwise the same. > > Both requests use the ptrace `addr' argument for the entry number rather > than the entry_number field in the struct. The `data' parameter gives the > address of a struct user_desc as used by the set/get_thread_area syscalls. > > The code is quite simple, and doesn't need any special synchronization > because in the ptrace context the thread must be stopped already. > > I chose the new request numbers arbitrarily from ones not used on i386. > I have no opinion on what values should be used. > > People I talked to preferred adding this interface over putting an array of > struct user_desc in struct user as accessed by PTRACE_PEEKUSR/POKEUSR > (which would be a bit unnatural since those calls access one word at a time).
In general, I like this. However, I have to ask one question: how much of the i386-centrism of this patch is actually necessary? What information does GDB _use_ from this, and is there some way we can expose it that will be useful in other places?
Eventually most or all targets will have thread-specific data implemented; I don't want to have to redo this for each one.
Your choice of numbers is fine if this remains i386-centric; if we expect there to be a common interface then it should go in <linux/ptrace.h> and the 0x4200 range instead.
-- Daniel Jacobowitz MontaVista Software Debian GNU/Linux Developer - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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