On Sat, Jul 02, 2016 at 09:12:09PM +0100, Peter Maydell wrote: > On 2 July 2016 at 17:41, Laurent Vivier <laur...@vivier.eu> wrote: > > Sadly, this can't work: > > > > sparc/sparc64/cris use sys_select for NR_select AND NR_newselect. > > > Not sure all is correct, but it's what I've found: > > > > | __NR_select | __NR__newselect > > ------------+----------------+-----------------+ > > arm | sys_old_select | sys_select | > > ------------+----------------+-----------------+ > > aarch64 | sys_select | - | > > ------------+----------------+-----------------+ > > alpha | sys_select | - | > > ------------+----------------+-----------------+ > > cris | sys_select | sys_select | > > ------------+----------------+-----------------+ > > m68k | sys_old_select | sys_select | > > ------------+----------------+-----------------+ > > microblaze | sys_old_select | sys_select | > > ------------+----------------+-----------------+ > > mips | sys_old_select | sys_select | > > ------------+----------------+-----------------+ > > mips64 | sys_select | - | > > ------------+----------------+-----------------+ > > openrisc | sys_select | - | > > ------------+----------------+-----------------+ > > ppc | sys_old_select | sys_select | > > ------------+----------------+-----------------+ > > s390x | sys_select | - | > > ------------+----------------+-----------------+ > > sh4 | sys_old_select | sys_select | > > ------------+----------------+-----------------+ > > sparc | sys_select | sys_select | > > ------------+----------------+-----------------+ > > sparc64 | sys_select | sys_select | > > ------------+----------------+-----------------+ > > tilegx | sys_select | - | > > ------------+----------------+-----------------+ > > unicore32 | sys_select | - | > > ------------+----------------+-----------------+ > > x86_64 | sys_select | - | > > ------------+----------------+-----------------+ > > i386 | sys_old_select | sys_select | > > ------------+----------------+-----------------+ > > Hmm. Looking at current Linux git master, I get > slightly different results. The only architectures which > define __ARCH_WANT_SYS_OLD_SELECT are: > arm, m68k, mn10300, x86 > and no others use sys_old_select. > > So I think we have the following behaviours: > > (1) Define neither NR_select nor NR__newselect > (and use pselect6 syscall for select): > aarch64, openrisc, tilegx, unicore32, presumably any future arch > > (2) only define NR__newselect, it is new select: > mips, mips64, sh, s390 > > (3) Only define NR_select, want that to be new select: > alpha, x86_64, s390x > > (4) NR__newselect is new select, NR_select is old_select: > i386, m68k, arm if kernel is not CONFIG_AEABI > > (5) NR__newselect is new select, NR_select is defined but > if called returns ENOSYS: > microblaze, arm if CONFIG_AEABI, ppc64 > > (6) NR__newselect is new select, NR_select is a bonkers custom > thing that tries to autodetect the calling convention: > http://lxr.free-electrons.com/source/arch/powerpc/kernel/syscalls.c#L86 > ppc32 (but only native 32-bit; 32-bit compat support > on a ppc64 kernel is category 5, so I vote for ignoring > this weirdness and calling ppc category 5) > > (7) NR_select and NR__newselect are different numbers > but both are new select: > cris, sparc, sparc64 > > which is a pretty confusing mess, but I think it equates to: > (0) if defined, NR__newselect is always new select > (1) if NR_select is defined, the choices are: > (a) NR_select is old_select: > i386, m68k, arm > (b) NR_select is defined but should ENOSYS: > microblaze, ppc > (c) NR_select defined and is new select: > everything else (alpha, x86-64, s390x, cris, sparc, sparc64) > > and I think we should handle that by having the code in syscall.c > be something like: > > #ifdef TARGET_NR_select > case TARGET_NR_select: > #if defined(TARGET_WANT_NI_OLD_SELECT) > /* some architectures used to have old_select here > * but now ENOSYS it. > */ > ret = -TARGET_ENOSYS; > break; > #elif defined(TARGET_WANT_OLD_SYS_SELECT) > /* code for old select here; maybe factored out to > * its own function: ret = do_old_select() ? > */ > #else > /* select is new style select */ > ret = do_select(...); > #endif > #endif
I agree, this seems to be the best way to fix select properly. > where TARGET_WANT_NI_OLD_SELECT and > TARGET_WANT_OLD_SYS_SELECT are #defined in > linux-user/$(ARCH)/target_syscall.h by those > architectures that need that behaviour > (microblaze, ppc for the first; i386, m68k, arm > for the second). > > We could just not define TARGET_NR_select for > microblaze and ppc, of course, but that might > be confusing and easily accidentally reverted. > > For openrisc, sh and tilegx we incorrectly define > a TARGET_NR_select which the kernel doesn't, so > we should delete that from our headers. > > I think overall that produces a reasonable separation > of "what behaviour does my architecture want" from > the implementation of the various behaviours, and > means the default will be correct for any architectures > we add later (only the oddball legacy cases need > to request special behaviour). > > thanks > -- PMM
