| Message ID | 20200306133242.26279-1-vincenzo.frascino@arm.com (mailing list archive) |
|---|---|
| Headers | show |
| Series | Introduce common headers | expand |
> On Mar 6, 2020, at 5:32 AM, Vincenzo Frascino <vincenzo.frascino@arm.com> wrote: > > Back in July last year we started having a problem in building compat > vDSOs on arm64 [1] [2] that was not present when the arm64 porting to > the Unified vDSO was done. In particular when the compat vDSO on such > architecture is built with gcc it generates the warning below: > > In file included from ./arch/arm64/include/asm/thread_info.h:17:0, > from ./include/linux/thread_info.h:38, > from ./arch/arm64/include/asm/preempt.h:5, > from ./include/linux/preempt.h:78, > from ./include/linux/spinlock.h:51, > from ./include/linux/seqlock.h:36, > from ./include/linux/time.h:6, > from ./lib/vdso/gettimeofday.c:7, > from <command-line>:0: > ./arch/arm64/include/asm/memory.h: In function ‘__tag_set’: > ./arch/arm64/include/asm/memory.h:233:15: warning: cast from pointer > to integer of different size [-Wpointer-to-int-cast] > u64 __addr = (u64)addr & ~__tag_shifted(0xff); > ^ > In file included from ./arch/arm64/include/asm/pgtable-hwdef.h:8:0, > from ./arch/arm64/include/asm/processor.h:34, > from ./arch/arm64/include/asm/elf.h:118, > from ./include/linux/elf.h:5, > from ./include/linux/elfnote.h:62, > from arch/arm64/kernel/vdso32/note.c:11: > ./arch/arm64/include/asm/memory.h: In function ‘__tag_set’: > ./arch/arm64/include/asm/memory.h:233:15: warning: cast from pointer > to integer of different size [-Wpointer-to-int-cast] > u64 __addr = (u64)addr & ~__tag_shifted(0xff); > > The same porting does not build at all when the selected compiler is > clang. > > I started an investigation to try to understand better the problem and > after various discussions at Plumbers and Recipes last year the > conclusion was that the vDSO library as it stands it is including more > headers that it needs. In particular, being a user-space library, it > should require only the UAPI and a minimal vDSO kernel interface instead > of all the kernel-related inline functions which are not directly used > and in some cases can have side effects. > > To solve the problem, I decided to use the approach below: > * Extract from include/linux/ the vDSO required kernel interface > and place it in include/common/ I really like the approach, but I’m wondering if “common” is the right name. This directory is headers that aren’t stable ABI like uapi but are shared between the kernel and the vDSO. Regular user code should *not* include these, right? Would “vdso” or perhaps “private-abi” be clearer? > * Make sure that where meaningful the kernel includes "common" > * Limit the vDSO library to include headers coming only from UAPI > and "common" (with 2 exceptions compiler.h for barriers and > param.h for HZ). > * Adapt all the architectures that support the unified vDSO library > to use "common" headers. > > According to me this approach allows up to exercise a better control on > what the vDSO library can include and to prevent potential issues in > future. > > This patch series contains the implementation of the described approach. > > The "common" headers have been verified on all the architectures that support > unified vDSO using the vdsotest [3] testsuite for what concerns the vDSO part > and randconfig to verify that they are included in the correct places. > > To simplify the testing, a copy of the patchset on top of a recent linux > tree can be found at [4]. > > [1] https://github.com/ClangBuiltLinux/linux/issues/595 > [2] https://lore.kernel.org/lkml/20190926151704.GH9689@arrakis.emea.arm.com > [3] https://github.com/nathanlynch/vdsotest > [4] git://linux-arm.org/linux-vf.git common-headers/v2 > > Changes: > -------- > v2: > - Addressed review comments for clang support. > - Rebased on 5.6-rc4. > > Cc: Catalin Marinas <catalin.marinas@arm.com> > Cc: Will Deacon <will.deacon@arm.com> > Cc: Arnd Bergmann <arnd@arndb.de> > Cc: Russell King <linux@armlinux.org.uk> > Cc: Paul Burton <paul.burton@mips.com> > Cc: Thomas Gleixner <tglx@linutronix.de> > Cc: Andy Lutomirski <luto@kernel.org> > Cc: Ingo Molnar <mingo@redhat.com> > Cc: Borislav Petkov <bp@alien8.de> > Cc: Stephen Boyd <sboyd@kernel.org> > Cc: Mark Salyzyn <salyzyn@android.com> > Cc: Kees Cook <keescook@chromium.org> > Cc: Peter Collingbourne <pcc@google.com> > Cc: Dmitry Safonov <0x7f454c46@gmail.com> > Cc: Andrei Vagin <avagin@openvz.org> > Cc: Nick Desaulniers <ndesaulniers@google.com> > Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com> > > Vincenzo Frascino (20): > linux/const.h: Extract common header for vDSO > linux/bits.h: Extract common header for vDSO > linux/limits.h: Extract common header for vDSO > linux/math64.h: Extract common header for vDSO > linux/time.h: Extract common header for vDSO > linux/time32.h: Extract common header for vDSO > linux/time64.h: Extract common header for vDSO > linux/jiffies.h: Extract common header for vDSO > linux/ktime.h: Extract common header for vDSO > common: Introduce processor.h > linux/elfnote.h: Replace elf.h with UAPI equivalent > arm64: Introduce asm/common/processor.h > arm64: vdso: Include common headers in the vdso library > arm64: vdso32: Include common headers in the vdso library > arm64: Introduce asm/common/arch_timer.h > mips: vdso: Enable mips to use common headers > x86: vdso: Enable x86 to use common headers > arm: vdso: Enable arm to use common headers > lib: vdso: Enable common headers > arm64: vdso32: Enable Clang Compilation > > arch/arm/include/asm/common/cp15.h | 38 +++++++++++++++++++ > arch/arm/include/asm/common/processor.h | 22 +++++++++++ > arch/arm/include/asm/cp15.h | 20 +--------- > arch/arm/include/asm/processor.h | 11 +----- > arch/arm/include/asm/vdso/gettimeofday.h | 4 +- > arch/arm64/include/asm/arch_timer.h | 29 +++----------- > arch/arm64/include/asm/common/arch_timer.h | 33 ++++++++++++++++ > arch/arm64/include/asm/common/processor.h | 31 +++++++++++++++ > arch/arm64/include/asm/processor.h | 16 +------- > .../include/asm/vdso/compat_gettimeofday.h | 2 +- > arch/arm64/include/asm/vdso/gettimeofday.h | 8 ++-- > arch/arm64/kernel/vdso/vgettimeofday.c | 2 - > arch/arm64/kernel/vdso32/Makefile | 13 ++++++- > arch/arm64/kernel/vdso32/vgettimeofday.c | 3 -- > arch/mips/include/asm/common/processor.h | 27 +++++++++++++ > arch/mips/include/asm/processor.h | 16 +------- > arch/mips/include/asm/vdso/gettimeofday.h | 4 -- > arch/x86/include/asm/common/processor.h | 23 +++++++++++ > arch/x86/include/asm/processor.h | 12 +----- > include/common/bits.h | 9 +++++ > include/common/const.h | 10 +++++ > include/common/jiffies.h | 11 ++++++ > include/common/ktime.h | 16 ++++++++ > include/common/limits.h | 18 +++++++++ > include/common/math64.h | 24 ++++++++++++ > include/common/processor.h | 14 +++++++ > include/common/time.h | 12 ++++++ > include/common/time32.h | 17 +++++++++ > include/common/time64.h | 14 +++++++ > include/linux/bits.h | 2 +- > include/linux/const.h | 5 +-- > include/linux/elfnote.h | 2 +- > include/linux/jiffies.h | 4 +- > include/linux/ktime.h | 9 +---- > include/linux/limits.h | 13 +------ > include/linux/math64.h | 20 +--------- > include/linux/time.h | 5 +-- > include/linux/time32.h | 13 +------ > include/linux/time64.h | 10 +---- > include/vdso/datapage.h | 32 ++++++++++++++-- > lib/vdso/gettimeofday.c | 21 ---------- > 41 files changed, 388 insertions(+), 207 deletions(-) > create mode 100644 arch/arm/include/asm/common/cp15.h > create mode 100644 arch/arm/include/asm/common/processor.h > create mode 100644 arch/arm64/include/asm/common/arch_timer.h > create mode 100644 arch/arm64/include/asm/common/processor.h > create mode 100644 arch/mips/include/asm/common/processor.h > create mode 100644 arch/x86/include/asm/common/processor.h > create mode 100644 include/common/bits.h > create mode 100644 include/common/const.h > create mode 100644 include/common/jiffies.h > create mode 100644 include/common/ktime.h > create mode 100644 include/common/limits.h > create mode 100644 include/common/math64.h > create mode 100644 include/common/processor.h > create mode 100644 include/common/time.h > create mode 100644 include/common/time32.h > create mode 100644 include/common/time64.h > > -- > 2.25.1 >
Hi Andy, On 3/6/20 4:04 PM, Andy Lutomirski wrote: [...] >> >> To solve the problem, I decided to use the approach below: >> * Extract from include/linux/ the vDSO required kernel interface >> and place it in include/common/ > > I really like the approach, but I’m wondering if “common” is the right name. This directory is headers that aren’t stable ABI like uapi but are shared between the kernel and the vDSO. Regular user code should *not* include these, right? > > Would “vdso” or perhaps “private-abi” be clearer? > Thanks! These headers are definitely not "uapi" like and they are meant to evolve in future like any other kernel header. We have just to make sure that the evolution does not break what we are trying to achieve with this series. I have to admit that I spent quite some time in choosing the name and I am not completely satisfied with "common" either. The reason why I ended up with this is that the headers are common in between the kernel and the vdso (userspace) but I agree that it does not make completely self explanatory. Using "vdso" would mean according to me that those are vdso only headers, probably "private-abi" is the best choice here. If there is enough consensus, I am happy to rework my patches accordingly. What do you think? >> * Make sure that where meaningful the kernel includes "common" >> * Limit the vDSO library to include headers coming only from UAPI >> and "common" (with 2 exceptions compiler.h for barriers and >> param.h for HZ). >> * Adapt all the architectures that support the unified vDSO library >> to use "common" headers. > [...]
On Mon, Mar 09, 2020 at 11:07:08AM +0000, Vincenzo Frascino wrote: > Hi Andy, > > On 3/6/20 4:04 PM, Andy Lutomirski wrote: > > [...] > > >> > >> To solve the problem, I decided to use the approach below: > >> * Extract from include/linux/ the vDSO required kernel interface > >> and place it in include/common/ > > > > I really like the approach, but I’m wondering if “common” is the > > right name. This directory is headers that aren’t stable ABI like > > uapi but are shared between the kernel and the vDSO. Regular user > > code should *not* include these, right? > > > > Would “vdso” or perhaps “private-abi” be clearer? > > Thanks! These headers are definitely not "uapi" like and they are meant to > evolve in future like any other kernel header. We have just to make sure that > the evolution does not break what we are trying to achieve with this series. Given we already include uapi/* headers in kernel code, I think placing these in a vdso/* namespace would be fine. I think that more clearly expresses the constraints on the headers than private-abi/* would. Thanks, Mark.
Mark Rutland <mark.rutland@arm.com> writes: > On Mon, Mar 09, 2020 at 11:07:08AM +0000, Vincenzo Frascino wrote: >> On 3/6/20 4:04 PM, Andy Lutomirski wrote: >> >> To solve the problem, I decided to use the approach below: >> >> * Extract from include/linux/ the vDSO required kernel interface >> >> and place it in include/common/ >> > >> > I really like the approach, but I’m wondering if “common” is the >> > right name. This directory is headers that aren’t stable ABI like >> > uapi but are shared between the kernel and the vDSO. Regular user >> > code should *not* include these, right? >> > >> > Would “vdso” or perhaps “private-abi” be clearer? >> >> Thanks! These headers are definitely not "uapi" like and they are meant to >> evolve in future like any other kernel header. We have just to make sure that >> the evolution does not break what we are trying to achieve with this series. > > Given we already include uapi/* headers in kernel code, I think placing > these in a vdso/* namespace would be fine. I think that more clearly > expresses the constraints on the headers than private-abi/* would. Yes, that makes most sense. Thanks, tglx
Back in July last year we started having a problem in building compat vDSOs on arm64 [1] [2] that was not present when the arm64 porting to the Unified vDSO was done. In particular when the compat vDSO on such architecture is built with gcc it generates the warning below: In file included from ./arch/arm64/include/asm/thread_info.h:17:0, from ./include/linux/thread_info.h:38, from ./arch/arm64/include/asm/preempt.h:5, from ./include/linux/preempt.h:78, from ./include/linux/spinlock.h:51, from ./include/linux/seqlock.h:36, from ./include/linux/time.h:6, from ./lib/vdso/gettimeofday.c:7, from <command-line>:0: ./arch/arm64/include/asm/memory.h: In function ‘__tag_set’: ./arch/arm64/include/asm/memory.h:233:15: warning: cast from pointer to integer of different size [-Wpointer-to-int-cast] u64 __addr = (u64)addr & ~__tag_shifted(0xff); ^ In file included from ./arch/arm64/include/asm/pgtable-hwdef.h:8:0, from ./arch/arm64/include/asm/processor.h:34, from ./arch/arm64/include/asm/elf.h:118, from ./include/linux/elf.h:5, from ./include/linux/elfnote.h:62, from arch/arm64/kernel/vdso32/note.c:11: ./arch/arm64/include/asm/memory.h: In function ‘__tag_set’: ./arch/arm64/include/asm/memory.h:233:15: warning: cast from pointer to integer of different size [-Wpointer-to-int-cast] u64 __addr = (u64)addr & ~__tag_shifted(0xff); The same porting does not build at all when the selected compiler is clang. I started an investigation to try to understand better the problem and after various discussions at Plumbers and Recipes last year the conclusion was that the vDSO library as it stands it is including more headers that it needs. In particular, being a user-space library, it should require only the UAPI and a minimal vDSO kernel interface instead of all the kernel-related inline functions which are not directly used and in some cases can have side effects. To solve the problem, I decided to use the approach below: * Extract from include/linux/ the vDSO required kernel interface and place it in include/common/ * Make sure that where meaningful the kernel includes "common" * Limit the vDSO library to include headers coming only from UAPI and "common" (with 2 exceptions compiler.h for barriers and param.h for HZ). * Adapt all the architectures that support the unified vDSO library to use "common" headers. According to me this approach allows up to exercise a better control on what the vDSO library can include and to prevent potential issues in future. This patch series contains the implementation of the described approach. The "common" headers have been verified on all the architectures that support unified vDSO using the vdsotest [3] testsuite for what concerns the vDSO part and randconfig to verify that they are included in the correct places. To simplify the testing, a copy of the patchset on top of a recent linux tree can be found at [4]. [1] https://github.com/ClangBuiltLinux/linux/issues/595 [2] https://lore.kernel.org/lkml/20190926151704.GH9689@arrakis.emea.arm.com [3] https://github.com/nathanlynch/vdsotest [4] git://linux-arm.org/linux-vf.git common-headers/v2 Changes: -------- v2: - Addressed review comments for clang support. - Rebased on 5.6-rc4. Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Will Deacon <will.deacon@arm.com> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Russell King <linux@armlinux.org.uk> Cc: Paul Burton <paul.burton@mips.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Andy Lutomirski <luto@kernel.org> Cc: Ingo Molnar <mingo@redhat.com> Cc: Borislav Petkov <bp@alien8.de> Cc: Stephen Boyd <sboyd@kernel.org> Cc: Mark Salyzyn <salyzyn@android.com> Cc: Kees Cook <keescook@chromium.org> Cc: Peter Collingbourne <pcc@google.com> Cc: Dmitry Safonov <0x7f454c46@gmail.com> Cc: Andrei Vagin <avagin@openvz.org> Cc: Nick Desaulniers <ndesaulniers@google.com> Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com> Vincenzo Frascino (20): linux/const.h: Extract common header for vDSO linux/bits.h: Extract common header for vDSO linux/limits.h: Extract common header for vDSO linux/math64.h: Extract common header for vDSO linux/time.h: Extract common header for vDSO linux/time32.h: Extract common header for vDSO linux/time64.h: Extract common header for vDSO linux/jiffies.h: Extract common header for vDSO linux/ktime.h: Extract common header for vDSO common: Introduce processor.h linux/elfnote.h: Replace elf.h with UAPI equivalent arm64: Introduce asm/common/processor.h arm64: vdso: Include common headers in the vdso library arm64: vdso32: Include common headers in the vdso library arm64: Introduce asm/common/arch_timer.h mips: vdso: Enable mips to use common headers x86: vdso: Enable x86 to use common headers arm: vdso: Enable arm to use common headers lib: vdso: Enable common headers arm64: vdso32: Enable Clang Compilation arch/arm/include/asm/common/cp15.h | 38 +++++++++++++++++++ arch/arm/include/asm/common/processor.h | 22 +++++++++++ arch/arm/include/asm/cp15.h | 20 +--------- arch/arm/include/asm/processor.h | 11 +----- arch/arm/include/asm/vdso/gettimeofday.h | 4 +- arch/arm64/include/asm/arch_timer.h | 29 +++----------- arch/arm64/include/asm/common/arch_timer.h | 33 ++++++++++++++++ arch/arm64/include/asm/common/processor.h | 31 +++++++++++++++ arch/arm64/include/asm/processor.h | 16 +------- .../include/asm/vdso/compat_gettimeofday.h | 2 +- arch/arm64/include/asm/vdso/gettimeofday.h | 8 ++-- arch/arm64/kernel/vdso/vgettimeofday.c | 2 - arch/arm64/kernel/vdso32/Makefile | 13 ++++++- arch/arm64/kernel/vdso32/vgettimeofday.c | 3 -- arch/mips/include/asm/common/processor.h | 27 +++++++++++++ arch/mips/include/asm/processor.h | 16 +------- arch/mips/include/asm/vdso/gettimeofday.h | 4 -- arch/x86/include/asm/common/processor.h | 23 +++++++++++ arch/x86/include/asm/processor.h | 12 +----- include/common/bits.h | 9 +++++ include/common/const.h | 10 +++++ include/common/jiffies.h | 11 ++++++ include/common/ktime.h | 16 ++++++++ include/common/limits.h | 18 +++++++++ include/common/math64.h | 24 ++++++++++++ include/common/processor.h | 14 +++++++ include/common/time.h | 12 ++++++ include/common/time32.h | 17 +++++++++ include/common/time64.h | 14 +++++++ include/linux/bits.h | 2 +- include/linux/const.h | 5 +-- include/linux/elfnote.h | 2 +- include/linux/jiffies.h | 4 +- include/linux/ktime.h | 9 +---- include/linux/limits.h | 13 +------ include/linux/math64.h | 20 +--------- include/linux/time.h | 5 +-- include/linux/time32.h | 13 +------ include/linux/time64.h | 10 +---- include/vdso/datapage.h | 32 ++++++++++++++-- lib/vdso/gettimeofday.c | 21 ---------- 41 files changed, 388 insertions(+), 207 deletions(-) create mode 100644 arch/arm/include/asm/common/cp15.h create mode 100644 arch/arm/include/asm/common/processor.h create mode 100644 arch/arm64/include/asm/common/arch_timer.h create mode 100644 arch/arm64/include/asm/common/processor.h create mode 100644 arch/mips/include/asm/common/processor.h create mode 100644 arch/x86/include/asm/common/processor.h create mode 100644 include/common/bits.h create mode 100644 include/common/const.h create mode 100644 include/common/jiffies.h create mode 100644 include/common/ktime.h create mode 100644 include/common/limits.h create mode 100644 include/common/math64.h create mode 100644 include/common/processor.h create mode 100644 include/common/time.h create mode 100644 include/common/time32.h create mode 100644 include/common/time64.h