Re: [Qemu-devel] [PATCH v2 00/28] linux-user: fix race between signals and syscalls
On Thu, May 12, 2016 at 06:47:24PM +0100, Peter Maydell wrote: > This patch series is an updated version of the original series > sent by Timothy Baldwin in autumn of last year > (https://lists.gnu.org/archive/html/qemu-devel/2015-09/msg01388.html). > I have attempted to address various code review comments made on that > original patchset. Thanks, applied to linux-user > Changes v1->v2: > * more description in comments and commit messages of what is going on > * implement restarting for all guest architectures (tilegx wasn't >in the tree when v1 was sent out) > * reordered the patches in the series a bit; in particular we add >support for restarting syscalls to all targets and so we don't >need the TARGET_USE_ERESTARTSYS define > * fixed a bug in the Alpha restart code where we were incorrectly >treating env->ir[IR_PV] as the PC, not env->pc > * restrict scope of patchset to just providing and using the >safe_syscall mechanism. (I plan to upstream the other race fixes >in the second half of Timothy's patchset separately once this lot >are in.) > * avoid per-architecture if-ladders in configure and C code by >creating a linux-user/host/$(HOSTARCH) type directory structure >so the makefiles can pull in the right files for the host >automatically > * added patches to use safe_syscall for futex, select and pselect >(in particular fixing futex() allows binaries that use the Boehm >garbage collector, like the Mono runtime, to work) > * include a patch which sets r14 on exit from microblaze syscalls, >which I think clarifies how that architecture does things >(though it is not ABI-wise strictly required) > * fixed bug in wrapping of waitid syscall -- it has five args, not four > * switched safe_syscall() to use a "return -1 and set errno" >convention for failure; this matches syscall(), and seemed to >me to be more intuitive for switching code around and for when >there's a mix of code paths using safe_syscall() and directly >calling libc functions (though it does mean that we push error >numbers into errno and then fish them out again later) > * added the magic GNU-stack rune that avoids incorrectly tainting >our whole binary as "needs an executable stack" when an asm >file is linked into it > > Notes: > * safe_syscall is supported for all guest architectures, but >only the x86_64 host architecture; adding the asm fragment >for our other hosts should be straightforward > * there are a fair number of other system calls that should be >using safe_syscall too > In both cases I thought it was better to avoid making this patchset > any larger or later; we can easily do these in later patches if > the general concept and mechanism has made it into master. > > > I've tested mostly by running the LTP test suite for 32-bit ARM > guests; this patchset neither improves nor worsens our pass rate. > > I think the fixing of select/pselect ought to deal with hangs when > running cmake (https://bugs.launchpad.net/qemu/+bug/955379), but > I have no reliable reproducer for that bug so can't say for sure. > The "Mono hangs due to it using Boehm GC" bug is > https://bugs.launchpad.net/ubuntu/+source/qemu-kvm/+bug/53 > and that is definitely fixed by this patchset. > > > thanks > -- PMM > > Peter Maydell (5): > linux-user: Consistently return host errnos from do_openat() > linux-user: Support for restarting system calls for tilegx targets > linux-user: Set r14 on exit from microblaze syscall > linux-user: Use safe_syscall for pselect, select syscalls > linux-user: Use safe_syscall for futex syscall > > Timothy E Baldwin (23): > linux-user: Check array bounds in errno conversion > linux-user: Reindent signal handling > linux-user: Define TARGET_ERESTART* errno values > linux-user: Renumber TARGET_QEMU_ESIGRETURN, make it not arch-specific > linux-user: Support for restarting system calls for x86 targets > linux-user: Support for restarting system calls for ARM targets > linux-user: Support for restarting system calls for MIPS targets > linux-user: Support for restarting system calls for PPC targets > linux-user: Support for restarting system calls for SPARC targets > linux-user: Support for restarting system calls for SH4 targets > linux-user: Support for restarting system calls for Alpha targets > linux-user: Support for restarting system calls for UniCore32 targets > linux-user: Support for restarting system calls for OpenRISC targets > linux-user: Support for restarting system calls for M68K targets > linux-user: Support for restarting system calls for S390 targets > linux-user: Support for restarting system calls for CRIS targets > linux-user: Support for restarting system calls for Microblaze targets > linux-user: Add debug code to exercise restarting system calls > linux-user: Provide safe_syscall for fixing races between signals and > syscalls >
Re: [Qemu-devel] [PATCH v2 00/28] linux-user: fix race between signals and syscalls
Ping? I have a second series based on top of this which is shaping up nicely and it would be good to get this lot into master before posting the second set... thanks -- PMM On 12 May 2016 at 18:47, Peter Maydellwrote: > This patch series is an updated version of the original series > sent by Timothy Baldwin in autumn of last year > (https://lists.gnu.org/archive/html/qemu-devel/2015-09/msg01388.html). > I have attempted to address various code review comments made on that > original patchset. > > Changes v1->v2: > * more description in comments and commit messages of what is going on > * implement restarting for all guest architectures (tilegx wasn't >in the tree when v1 was sent out) > * reordered the patches in the series a bit; in particular we add >support for restarting syscalls to all targets and so we don't >need the TARGET_USE_ERESTARTSYS define > * fixed a bug in the Alpha restart code where we were incorrectly >treating env->ir[IR_PV] as the PC, not env->pc > * restrict scope of patchset to just providing and using the >safe_syscall mechanism. (I plan to upstream the other race fixes >in the second half of Timothy's patchset separately once this lot >are in.) > * avoid per-architecture if-ladders in configure and C code by >creating a linux-user/host/$(HOSTARCH) type directory structure >so the makefiles can pull in the right files for the host >automatically > * added patches to use safe_syscall for futex, select and pselect >(in particular fixing futex() allows binaries that use the Boehm >garbage collector, like the Mono runtime, to work) > * include a patch which sets r14 on exit from microblaze syscalls, >which I think clarifies how that architecture does things >(though it is not ABI-wise strictly required) > * fixed bug in wrapping of waitid syscall -- it has five args, not four > * switched safe_syscall() to use a "return -1 and set errno" >convention for failure; this matches syscall(), and seemed to >me to be more intuitive for switching code around and for when >there's a mix of code paths using safe_syscall() and directly >calling libc functions (though it does mean that we push error >numbers into errno and then fish them out again later) > * added the magic GNU-stack rune that avoids incorrectly tainting >our whole binary as "needs an executable stack" when an asm >file is linked into it > > Notes: > * safe_syscall is supported for all guest architectures, but >only the x86_64 host architecture; adding the asm fragment >for our other hosts should be straightforward > * there are a fair number of other system calls that should be >using safe_syscall too > In both cases I thought it was better to avoid making this patchset > any larger or later; we can easily do these in later patches if > the general concept and mechanism has made it into master. > > > I've tested mostly by running the LTP test suite for 32-bit ARM > guests; this patchset neither improves nor worsens our pass rate. > > I think the fixing of select/pselect ought to deal with hangs when > running cmake (https://bugs.launchpad.net/qemu/+bug/955379), but > I have no reliable reproducer for that bug so can't say for sure. > The "Mono hangs due to it using Boehm GC" bug is > https://bugs.launchpad.net/ubuntu/+source/qemu-kvm/+bug/53 > and that is definitely fixed by this patchset. > > > thanks > -- PMM > > Peter Maydell (5): > linux-user: Consistently return host errnos from do_openat() > linux-user: Support for restarting system calls for tilegx targets > linux-user: Set r14 on exit from microblaze syscall > linux-user: Use safe_syscall for pselect, select syscalls > linux-user: Use safe_syscall for futex syscall > > Timothy E Baldwin (23): > linux-user: Check array bounds in errno conversion > linux-user: Reindent signal handling > linux-user: Define TARGET_ERESTART* errno values > linux-user: Renumber TARGET_QEMU_ESIGRETURN, make it not arch-specific > linux-user: Support for restarting system calls for x86 targets > linux-user: Support for restarting system calls for ARM targets > linux-user: Support for restarting system calls for MIPS targets > linux-user: Support for restarting system calls for PPC targets > linux-user: Support for restarting system calls for SPARC targets > linux-user: Support for restarting system calls for SH4 targets > linux-user: Support for restarting system calls for Alpha targets > linux-user: Support for restarting system calls for UniCore32 targets > linux-user: Support for restarting system calls for OpenRISC targets > linux-user: Support for restarting system calls for M68K targets > linux-user: Support for restarting system calls for S390 targets > linux-user: Support for restarting system calls for CRIS targets > linux-user: Support for restarting system calls for Microblaze targets > linux-user: