On Fri, Apr 06, 2018 at 11:20:46AM +0200, Ingo Molnar wrote: > > * Dominik Brodowski <li...@dominikbrodowski.net> wrote: > > > On Fri, Apr 06, 2018 at 10:23:22AM +0200, Ingo Molnar wrote: > > > > > > * Dominik Brodowski <li...@dominikbrodowski.net> wrote: > > > > > > > On Thu, Apr 05, 2018 at 05:19:33PM +0200, Ingo Molnar wrote: > > > > > Ok, this series looks mostly good to me, but AFAICS this breaks the > > > > > UML build: > > > > > > > > > > make: *** No rule to make target 'archheaders'. Stop. > > > > > arch/um/Makefile:119: recipe for target 'archheaders' failed > > > > > make: *** [archheaders] Error 2 > > > > > make: *** Waiting for unfinished jobs.... > > > > > > > > Ah, that's caused by patch 8/8 which I did and do not like all that much > > > > anyway: UML re-uses syscall_64.tbl which now has x86-specific entries > > > > like > > > > __sys_x86_pread64, but expects the generic syscall stub sys_pread64 > > > > referenced there. Fixup patch below; could be folded with patch 8/8. Or > > > > patch 8/8 could simply be dropped from the series altogether... > > > > > > I still like the 'truth in advertising' aspect. For example if I see this > > > in the > > > syscall table: > > > > > > 10 common mprotect __sys_x86_mprotect > > > > > > I can immediately find the _real_ syscall entry point: > > > > > > ffffffff81180a10 <__sys_x86_mprotect>: > > > ffffffff81180a10: 48 8b 57 60 mov 0x60(%rdi),%rdx > > > ffffffff81180a14: 48 8b 77 68 mov 0x68(%rdi),%rsi > > > ffffffff81180a18: b9 ff ff ff ff mov $0xffffffff,%ecx > > > ffffffff81180a1d: 48 8b 7f 70 mov 0x70(%rdi),%rdi > > > ffffffff81180a21: e8 fa fc ff ff callq ffffffff81180720 > > > <do_mprotect_pkey> > > > ffffffff81180a26: 48 98 cltq > > > ffffffff81180a28: c3 retq > > > ffffffff81180a29: 0f 1f 80 00 00 00 00 nopl 0x0(%rax) > > > > > > If, on the other hand, I see this entry: > > > > > > 10 common mprotect sys_mprotect > > > > > > Then, as a first step, no symbol anywhere matches with this: > > > > > > triton:~/tip> grep sys_mprotect System.map > > > triton:~/tip> > > > > > > "sys_mprotect" does not exist in any easily discoverable sense. You have > > > to *know* > > > to replace the sys_ prefix with __sys_x86_ to find it. > > > > > > Now arguably we could use a __sys_ prefix instead of the grep-barrier > > > __sys_x86 > > > prefix - but that too would be somewhat confusing I think. > > > > Well, if looking at the ARCH="um" kernel, you won't find the > > __sys_x86_mprotect > > there in its System.map -- so we either have to disentangle um and plain > > x86, or > > live with some cause for confusion. > > I'm primarily concerned about everything making sense on x86 - UML is an > entirely > separate architecture with heavy tradeoffs and kludges.
Agreed. > > __sys_mprotect as prefix won't work by the way, as the double-underscore > > __sys_ > > variant is already used in net/* for internal syscall helpers. > > Ok - then triple underscore - but overall I think it's more confusing. > > Btw., what was the problem with calling the x86 ptregs wrapper sys_mprotect? > > The only reason I suggested the __sys_x86_ prefix was because you originally > suggested that there's symbol name overlap, but I don't think that's the case > within the same kernel build, as the regular non-ptregs prototype: Indeed, there's no symbol name overlap within the same kernel build, but technically different stubs named the same. If that's fine, just drop patch 8/8 (including the UML fixup) and things should be fine, with the stub and the entry in the syscall table both named sys_mprotect. For IA32_EMULATION, we have __sys_ia32_mprotect as stub for the same syscall, including this name as entry in syscall_32.tbl. More problematic is the naming for the compat stubs for IA32_EMAULATION and X32, where we have __compat_sys_ia32_waitid __compat_sys_x32_waitid for example. We *could* rename one of those to compat_sys_waitid() and levae the other as-is, but actually I prefer it now how it is. Thanks, Dominik