On Fri, Feb 05, 2021 at 10:00:12PM +0000, Chris Wilson wrote: > Userspace has discovered the functionality offered by SYS_kcmp and has > started to depend upon it. In particular, Mesa uses SYS_kcmp for > os_same_file_description() in order to identify when two fd (e.g. device > or dmabuf) point to the same struct file. Since they depend on it for > core functionality, lift SYS_kcmp out of the non-default > CONFIG_CHECKPOINT_RESTORE into the selectable syscall category. > > Rasmus Villemoes also pointed out that systemd uses SYS_kcmp to > deduplicate the per-service file descriptor store. > > Note that some distributions such as Ubuntu are already enabling > CHECKPOINT_RESTORE in their configs and so, by extension, SYS_kcmp. > > References: https://gitlab.freedesktop.org/drm/intel/-/issues/3046 > Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> Thanks! Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx> -Kees > Cc: Kees Cook <keescook@xxxxxxxxxxxx> > Cc: Andy Lutomirski <luto@xxxxxxxxxxxxxx> > Cc: Will Drewry <wad@xxxxxxxxxxxx> > Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> > Cc: Dave Airlie <airlied@xxxxxxxxx> > Cc: Daniel Vetter <daniel@xxxxxxxx> > Cc: Lucas Stach <l.stach@xxxxxxxxxxxxxx> > Cc: Rasmus Villemoes <linux@xxxxxxxxxxxxxxxxxx> > Cc: Cyrill Gorcunov <gorcunov@xxxxxxxxx> > Cc: stable@xxxxxxxxxxxxxxx > Acked-by: Daniel Vetter <daniel.vetter@xxxxxxxx> # DRM depends on kcmp > Acked-by: Rasmus Villemoes <linux@xxxxxxxxxxxxxxxxxx> # systemd uses kcmp > > --- > v2: > - Default n. > - Borrrow help message from man kcmp. > - Export get_epoll_tfile_raw_ptr() for CONFIG_KCMP > v3: > - Select KCMP for CONFIG_DRM > --- > drivers/gpu/drm/Kconfig | 3 +++ > fs/eventpoll.c | 4 ++-- > include/linux/eventpoll.h | 2 +- > init/Kconfig | 11 +++++++++++ > kernel/Makefile | 2 +- > tools/testing/selftests/seccomp/seccomp_bpf.c | 2 +- > 6 files changed, 19 insertions(+), 5 deletions(-) > > diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig > index 0973f408d75f..af6c6d214d91 100644 > --- a/drivers/gpu/drm/Kconfig > +++ b/drivers/gpu/drm/Kconfig > @@ -15,6 +15,9 @@ menuconfig DRM > select I2C_ALGOBIT > select DMA_SHARED_BUFFER > select SYNC_FILE > +# gallium uses SYS_kcmp for os_same_file_description() to de-duplicate > +# device and dmabuf fd. Let's make sure that is available for our userspace. > + select KCMP > help > Kernel-level support for the Direct Rendering Infrastructure (DRI) > introduced in XFree86 4.0. If you say Y here, you need to select > diff --git a/fs/eventpoll.c b/fs/eventpoll.c > index a829af074eb5..3196474cbe24 100644 > --- a/fs/eventpoll.c > +++ b/fs/eventpoll.c > @@ -979,7 +979,7 @@ static struct epitem *ep_find(struct eventpoll *ep, struct file *file, int fd) > return epir; > } > > -#ifdef CONFIG_CHECKPOINT_RESTORE > +#ifdef CONFIG_KCMP > static struct epitem *ep_find_tfd(struct eventpoll *ep, int tfd, unsigned long toff) > { > struct rb_node *rbp; > @@ -1021,7 +1021,7 @@ struct file *get_epoll_tfile_raw_ptr(struct file *file, int tfd, > > return file_raw; > } > -#endif /* CONFIG_CHECKPOINT_RESTORE */ > +#endif /* CONFIG_KCMP */ > > /** > * Adds a new entry to the tail of the list in a lockless way, i.e. > diff --git a/include/linux/eventpoll.h b/include/linux/eventpoll.h > index 0350393465d4..593322c946e6 100644 > --- a/include/linux/eventpoll.h > +++ b/include/linux/eventpoll.h > @@ -18,7 +18,7 @@ struct file; > > #ifdef CONFIG_EPOLL > > -#ifdef CONFIG_CHECKPOINT_RESTORE > +#ifdef CONFIG_KCMP > struct file *get_epoll_tfile_raw_ptr(struct file *file, int tfd, unsigned long toff); > #endif > > diff --git a/init/Kconfig b/init/Kconfig > index b77c60f8b963..9cc7436b2f73 100644 > --- a/init/Kconfig > +++ b/init/Kconfig > @@ -1194,6 +1194,7 @@ endif # NAMESPACES > config CHECKPOINT_RESTORE > bool "Checkpoint/restore support" > select PROC_CHILDREN > + select KCMP > default n > help > Enables additional kernel features in a sake of checkpoint/restore. > @@ -1737,6 +1738,16 @@ config ARCH_HAS_MEMBARRIER_CALLBACKS > config ARCH_HAS_MEMBARRIER_SYNC_CORE > bool > > +config KCMP > + bool "Enable kcmp() system call" if EXPERT > + help > + Enable the kernel resource comparison system call. It provides > + user-space with the ability to compare two processes to see if they > + share a common resource, such as a file descriptor or even virtual > + memory space. > + > + If unsure, say N. > + > config RSEQ > bool "Enable rseq() system call" if EXPERT > default y > diff --git a/kernel/Makefile b/kernel/Makefile > index aa7368c7eabf..320f1f3941b7 100644 > --- a/kernel/Makefile > +++ b/kernel/Makefile > @@ -51,7 +51,7 @@ obj-y += livepatch/ > obj-y += dma/ > obj-y += entry/ > > -obj-$(CONFIG_CHECKPOINT_RESTORE) += kcmp.o > +obj-$(CONFIG_KCMP) += kcmp.o > obj-$(CONFIG_FREEZER) += freezer.o > obj-$(CONFIG_PROFILING) += profile.o > obj-$(CONFIG_STACKTRACE) += stacktrace.o > diff --git a/tools/testing/selftests/seccomp/seccomp_bpf.c b/tools/testing/selftests/seccomp/seccomp_bpf.c > index 26c72f2b61b1..1b6c7d33c4ff 100644 > --- a/tools/testing/selftests/seccomp/seccomp_bpf.c > +++ b/tools/testing/selftests/seccomp/seccomp_bpf.c > @@ -315,7 +315,7 @@ TEST(kcmp) > ret = __filecmp(getpid(), getpid(), 1, 1); > EXPECT_EQ(ret, 0); > if (ret != 0 && errno == ENOSYS) > - SKIP(return, "Kernel does not support kcmp() (missing CONFIG_CHECKPOINT_RESTORE?)"); > + SKIP(return, "Kernel does not support kcmp() (missing CONFIG_KCMP?)"); > } > > TEST(mode_strict_support) > -- > 2.20.1 > -- Kees Cook _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
