* Josh Triplett <josh@xxxxxxxxxxxxxxxx> wrote: > clone has some of the quirkiest syscall handling in the kernel, with > a pile of special cases, historical curiosities, and > architecture-specific calling conventions. In particular, clone > with CLONE_SETTLS accepts a parameter "tls" that the C entry point > completely ignores and some assembly entry points overwrite; > instead, the low-level arch-specific code pulls the tls parameter > out of the arch-specific register captured as part of pt_regs on > entry to the kernel. That's a massive hack, and it makes the > arch-specific code only work when called via the specific existing > syscall entry points; because of this hack, any new clone-like > system call would have to accept an identical tls argument in > exactly the same arch-specific position, rather than providing a > unified system call entry point across architectures. > > The first patch allows architectures to handle the tls argument via > normal C parameter passing, if they opt in by selecting > HAVE_COPY_THREAD_TLS. The second patch makes 32-bit and 64-bit x86 > opt into this. > > These two patches came out of the clone4 series, which isn't ready > for this merge window, but these first two cleanup patches were > entirely uncontroversial and have acks. I'd like to go ahead and > submit these two so that other architectures can begin building on > top of this and opting into HAVE_COPY_THREAD_TLS. However, I'm also > happy to wait and send these through the next merge window (along > with v3 of clone4) if anyone would prefer that. > > v2: Move co-author from signoffs to a note in the commit message, as > required by Ingo Molnar. > > Josh Triplett (2): > clone: Support passing tls argument via C rather than pt_regs magic > x86: Opt into HAVE_COPY_THREAD_TLS, for both 32-bit and 64-bit > > arch/Kconfig | 7 ++++++ > arch/x86/Kconfig | 1 + > arch/x86/ia32/ia32entry.S | 2 +- > arch/x86/kernel/process_32.c | 6 ++--- > arch/x86/kernel/process_64.c | 8 +++---- > include/linux/sched.h | 14 +++++++++++ > include/linux/syscalls.h | 6 ++--- > kernel/fork.c | 55 +++++++++++++++++++++++++++++--------------- > 8 files changed, 69 insertions(+), 30 deletions(-) So I have no objections if Linus doesn't see a cleaner/better approach. Thanks, Ingo -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
