| Message ID | 20190222122430.21180-1-vincenzo.frascino@arm.com (mailing list archive) |
|---|---|
| Headers | show |
| Series | Unify vDSOs across more architectures | expand |
On Fri, 22 Feb 2019, Vincenzo Frascino wrote: > This implementation contains the following design choices: > * Every architecture defines the arch specific code in an header in > "asm/vdso/". > * The generic implementation includes the arch specific one and lives > in "lib/vdso". > * The arch specific code for gettimeofday lives in > "<arch path>/vdso/gettimeofday.c" and includes the generic code only. > * This approach allows to consolidate the common code in a single place > with the benefit of avoiding code duplication. This is moving into the right direction. Good job! Thanks, tglx
On Fri, Feb 22, 2019 at 1:25 PM Vincenzo Frascino <vincenzo.frascino@arm.com> wrote: > > vDSO (virtual dynamic shared object) is a mechanism that the Linux > kernel provides as an alternative to system calls to reduce where > possible the costs in terms of cycles. > This is possible because certain syscalls like gettimeofday() do > not write any data and return one or more values that are stored > in the kernel, which makes relatively safe calling them directly > as a library function. I tried applying the series on top of v5.0-rc7, and got a set of build warnings with arm64 defconfig: In file included from /git/arm-soc/arch/arm64/include/asm/thread_info.h:30:0, from /git/arm-soc/include/linux/thread_info.h:38, from /git/arm-soc/arch/arm64/include/asm/preempt.h:5, from /git/arm-soc/include/linux/preempt.h:78, from /git/arm-soc/include/linux/spinlock.h:51, from /git/arm-soc/include/linux/seqlock.h:36, from /git/arm-soc/include/linux/time.h:6, from /git/arm-soc/lib/vdso/gettimeofday.c:7, from <command-line>:0: /git/arm-soc/arch/arm64/include/asm/memory.h: In function ‘kaslr_offset’: /git/arm-soc/arch/arm64/include/asm/memory.h:191:2: warning: left shift count >= width of type [enabled by default] return kimage_vaddr - KIMAGE_VADDR; ^ /git/arm-soc/arch/arm64/include/asm/memory.h: In function ‘virt_to_phys’: /git/arm-soc/arch/arm64/include/asm/memory.h:283:2: warning: left shift count >= width of type [enabled by default] return __virt_to_phys((unsigned long)(x)); ^ /git/arm-soc/arch/arm64/include/asm/memory.h:283:2: warning: left shift count >= width of type [enabled by default] /git/arm-soc/arch/arm64/include/asm/memory.h: In function ‘phys_to_virt’: /git/arm-soc/arch/arm64/include/asm/memory.h:289:2: warning: left shift count >= width of type [enabled by default] return (void *)(__phys_to_virt(x)); ^ In file included from /git/arm-soc/arch/arm64/include/asm/pgtable-hwdef.h:19:0, from /git/arm-soc/arch/arm64/include/asm/processor.h:46, from /git/arm-soc/arch/arm64/include/asm/elf.h:129, from /git/arm-soc/include/linux/elf.h:5, from /git/arm-soc/include/linux/elfnote.h:62, from /git/arm-soc/arch/arm64/kernel/vdso32/note.c:11: /git/arm-soc/arch/arm64/include/asm/memory.h: In function ‘kaslr_offset’: /git/arm-soc/arch/arm64/include/asm/memory.h:191:2: warning: left shift count >= width of type [enabled by default] return kimage_vaddr - KIMAGE_VADDR; ^ /git/arm-soc/arch/arm64/include/asm/memory.h: In function ‘virt_to_phys’: /git/arm-soc/arch/arm64/include/asm/memory.h:283:2: warning: left shift count >= width of type [enabled by default] return __virt_to_phys((unsigned long)(x)); ^ /git/arm-soc/arch/arm64/include/asm/memory.h:283:2: warning: left shift count >= width of type [enabled by default] /git/arm-soc/arch/arm64/include/asm/memory.h: In function ‘phys_to_virt’: /git/arm-soc/arch/arm64/include/asm/memory.h:289:2: warning: left shift count >= width of type [enabled by default] return (void *)(__phys_to_virt(x)); ^ I think this is all harmless, but we need to limit the set of header files that can be included indirectly when compiling the vdso in arm32 mode. Arnd
Hi Arnd, thank you for testing my code. On 28/02/2019 11:40, Arnd Bergmann wrote: > On Fri, Feb 22, 2019 at 1:25 PM Vincenzo Frascino > <vincenzo.frascino@arm.com> wrote: >> >> vDSO (virtual dynamic shared object) is a mechanism that the Linux >> kernel provides as an alternative to system calls to reduce where >> possible the costs in terms of cycles. >> This is possible because certain syscalls like gettimeofday() do >> not write any data and return one or more values that are stored >> in the kernel, which makes relatively safe calling them directly >> as a library function. > > I tried applying the series on top of v5.0-rc7, and got a set of > build warnings with arm64 defconfig: > > In file included from /git/arm-soc/arch/arm64/include/asm/thread_info.h:30:0, > from /git/arm-soc/include/linux/thread_info.h:38, > from /git/arm-soc/arch/arm64/include/asm/preempt.h:5, > from /git/arm-soc/include/linux/preempt.h:78, > from /git/arm-soc/include/linux/spinlock.h:51, > from /git/arm-soc/include/linux/seqlock.h:36, > from /git/arm-soc/include/linux/time.h:6, > from /git/arm-soc/lib/vdso/gettimeofday.c:7, > from <command-line>:0: > /git/arm-soc/arch/arm64/include/asm/memory.h: In function ‘kaslr_offset’: > /git/arm-soc/arch/arm64/include/asm/memory.h:191:2: warning: left > shift count >= width of type [enabled by default] > return kimage_vaddr - KIMAGE_VADDR; > ^ > /git/arm-soc/arch/arm64/include/asm/memory.h: In function ‘virt_to_phys’: > /git/arm-soc/arch/arm64/include/asm/memory.h:283:2: warning: left > shift count >= width of type [enabled by default] > return __virt_to_phys((unsigned long)(x)); > ^ > /git/arm-soc/arch/arm64/include/asm/memory.h:283:2: warning: left > shift count >= width of type [enabled by default] > /git/arm-soc/arch/arm64/include/asm/memory.h: In function ‘phys_to_virt’: > /git/arm-soc/arch/arm64/include/asm/memory.h:289:2: warning: left > shift count >= width of type [enabled by default] > return (void *)(__phys_to_virt(x)); > ^ > In file included from /git/arm-soc/arch/arm64/include/asm/pgtable-hwdef.h:19:0, > from /git/arm-soc/arch/arm64/include/asm/processor.h:46, > from /git/arm-soc/arch/arm64/include/asm/elf.h:129, > from /git/arm-soc/include/linux/elf.h:5, > from /git/arm-soc/include/linux/elfnote.h:62, > from /git/arm-soc/arch/arm64/kernel/vdso32/note.c:11: > /git/arm-soc/arch/arm64/include/asm/memory.h: In function ‘kaslr_offset’: > /git/arm-soc/arch/arm64/include/asm/memory.h:191:2: warning: left > shift count >= width of type [enabled by default] > return kimage_vaddr - KIMAGE_VADDR; > ^ > /git/arm-soc/arch/arm64/include/asm/memory.h: In function ‘virt_to_phys’: > /git/arm-soc/arch/arm64/include/asm/memory.h:283:2: warning: left > shift count >= width of type [enabled by default] > return __virt_to_phys((unsigned long)(x)); > ^ > /git/arm-soc/arch/arm64/include/asm/memory.h:283:2: warning: left > shift count >= width of type [enabled by default] > /git/arm-soc/arch/arm64/include/asm/memory.h: In function ‘phys_to_virt’: > /git/arm-soc/arch/arm64/include/asm/memory.h:289:2: warning: left > shift count >= width of type [enabled by default] > return (void *)(__phys_to_virt(x)); > ^ > > I think this is all harmless, but we need to limit the set of header files > that can be included indirectly when compiling the vdso in arm32 mode. > I agree with you on the principle, but I am unable to replicate the warnings. Did you make any customization to the default defconfig? What is the top commit-id you have on your tree? > Arnd >
On Thu, Feb 28, 2019 at 1:09 PM Vincenzo Frascino <vincenzo.frascino@arm.com> wrote: > > thank you for testing my code. > > On 28/02/2019 11:40, Arnd Bergmann wrote: > > On Fri, Feb 22, 2019 at 1:25 PM Vincenzo Frascino > > <vincenzo.frascino@arm.com> wrote: > > ^ > > > > I think this is all harmless, but we need to limit the set of header files > > that can be included indirectly when compiling the vdso in arm32 mode. > > > > I agree with you on the principle, but I am unable to replicate the warnings. > Did you make any customization to the default defconfig? What is the top > commit-id you have on your tree? I observed this on top of v5.0-rc7 earlier, and have since rebased to today's linux-next, where it still happens with the regular 'make defconfig', on all compiler versions I have (4.8 through 8.1). Arnd
On 28/02/2019 12:38, Arnd Bergmann wrote: > On Thu, Feb 28, 2019 at 1:09 PM Vincenzo Frascino > <vincenzo.frascino@arm.com> wrote: >> >> thank you for testing my code. >> >> On 28/02/2019 11:40, Arnd Bergmann wrote: >>> On Fri, Feb 22, 2019 at 1:25 PM Vincenzo Frascino >>> <vincenzo.frascino@arm.com> wrote: >>> ^ >>> >>> I think this is all harmless, but we need to limit the set of header files >>> that can be included indirectly when compiling the vdso in arm32 mode. >>> >> >> I agree with you on the principle, but I am unable to replicate the warnings. >> Did you make any customization to the default defconfig? What is the top >> commit-id you have on your tree? > > I observed this on top of v5.0-rc7 earlier, and have since rebased to > today's linux-next, where it still happens with the regular 'make defconfig', > on all compiler versions I have (4.8 through 8.1). > Thanks, I will try to rebase my patches on linux-next and see if I can reproduce it. > Arnd >
On Thu, Feb 28, 2019 at 1:42 PM Vincenzo Frascino <vincenzo.frascino@arm.com> wrote: > > On 28/02/2019 12:38, Arnd Bergmann wrote: > > On Thu, Feb 28, 2019 at 1:09 PM Vincenzo Frascino > > <vincenzo.frascino@arm.com> wrote: > >> > >> thank you for testing my code. > >> > >> On 28/02/2019 11:40, Arnd Bergmann wrote: > >>> On Fri, Feb 22, 2019 at 1:25 PM Vincenzo Frascino > >>> <vincenzo.frascino@arm.com> wrote: > >>> ^ > >>> > >>> I think this is all harmless, but we need to limit the set of header files > >>> that can be included indirectly when compiling the vdso in arm32 mode. > >>> > >> > >> I agree with you on the principle, but I am unable to replicate the warnings. > >> Did you make any customization to the default defconfig? What is the top > >> commit-id you have on your tree? > > > > I observed this on top of v5.0-rc7 earlier, and have since rebased to > > today's linux-next, where it still happens with the regular 'make defconfig', > > on all compiler versions I have (4.8 through 8.1). > > > > Thanks, I will try to rebase my patches on linux-next and see if I can reproduce it. I just found a related issue: when CONFIG_CPU_BIG_ENDIAN is set, everything breaks in the compat vdso because of the included arm64 headers in arm32 code. That should be easier to reproduce. For the moment, I'm using this patch: --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -103,7 +103,7 @@ config ARM64 select GENERIC_STRNLEN_USER select GENERIC_TIME_VSYSCALL select GENERIC_GETTIMEOFDAY - select GENERIC_COMPAT_VDSO + select GENERIC_COMPAT_VDSO if !CPU_BIG_ENDIAN select HANDLE_DOMAIN_IRQ select HARDIRQS_SW_RESEND select HAVE_PCI Arnd
Hi Arnd, On 28/02/2019 13:54, Arnd Bergmann wrote: > On Thu, Feb 28, 2019 at 1:42 PM Vincenzo Frascino > <vincenzo.frascino@arm.com> wrote: >> >> On 28/02/2019 12:38, Arnd Bergmann wrote: >>> On Thu, Feb 28, 2019 at 1:09 PM Vincenzo Frascino >>> <vincenzo.frascino@arm.com> wrote: >>>> >>>> thank you for testing my code. >>>> >>>> On 28/02/2019 11:40, Arnd Bergmann wrote: >>>>> On Fri, Feb 22, 2019 at 1:25 PM Vincenzo Frascino >>>>> <vincenzo.frascino@arm.com> wrote: >>>>> ^ >>>>> >>>>> I think this is all harmless, but we need to limit the set of header files >>>>> that can be included indirectly when compiling the vdso in arm32 mode. >>>>> >>>> >>>> I agree with you on the principle, but I am unable to replicate the warnings. >>>> Did you make any customization to the default defconfig? What is the top >>>> commit-id you have on your tree? >>> >>> I observed this on top of v5.0-rc7 earlier, and have since rebased to >>> today's linux-next, where it still happens with the regular 'make defconfig', >>> on all compiler versions I have (4.8 through 8.1). >>> >> >> Thanks, I will try to rebase my patches on linux-next and see if I can reproduce it. > > I just found a related issue: when CONFIG_CPU_BIG_ENDIAN is > set, everything breaks in the compat vdso because of the included > arm64 headers in arm32 code. That should be easier to reproduce. > For the moment, I'm using this patch: > > --- a/arch/arm64/Kconfig > +++ b/arch/arm64/Kconfig > @@ -103,7 +103,7 @@ config ARM64 > select GENERIC_STRNLEN_USER > select GENERIC_TIME_VSYSCALL > select GENERIC_GETTIMEOFDAY > - select GENERIC_COMPAT_VDSO > + select GENERIC_COMPAT_VDSO if !CPU_BIG_ENDIAN > select HANDLE_DOMAIN_IRQ > select HARDIRQS_SW_RESEND > select HAVE_PCI > > Thanks for this, but I can't still reproduce the issue. I rebased my patches on: commit 42fd8df9d1d9c83046226e771a4f5f3d05a706ff (tag: next-20190228, linux-next/master) and enabled CONFIG_CPU_BIG_ENDIAN. > Arnd >
vDSO (virtual dynamic shared object) is a mechanism that the Linux kernel provides as an alternative to system calls to reduce where possible the costs in terms of cycles. This is possible because certain syscalls like gettimeofday() do not write any data and return one or more values that are stored in the kernel, which makes relatively safe calling them directly as a library function. Even if the mechanism is pretty much standard, every architecture in the last few years ended up implementing their own vDSO library in the architectural code. The purpose of this patch-set is to identify the commonalities in between the architectures and try to consolidate the common code paths, starting with gettimeofday(). This implementation contains the following design choices: * Every architecture defines the arch specific code in an header in "asm/vdso/". * The generic implementation includes the arch specific one and lives in "lib/vdso". * The arch specific code for gettimeofday lives in "<arch path>/vdso/gettimeofday.c" and includes the generic code only. * This approach allows to consolidate the common code in a single place with the benefit of avoiding code duplication. This implementation contains the portings to the common library for: arm64, compat mode for arm64, arm, mips, x86_64, compat mode for x86_64 and i386. The mips porting has been tested on qemu for mips32el. A configuration to repeat the tests can be found at [4]. The x86_64 porting has been tested on an Intel Xeon 5120T based machine running Ubuntu 18.04 and using the Ubuntu provided defconfig. The i386 porting has been tested on qemu using the i386_defconfig configuration. Last but not least from this porting arm64, compat arm64, arm and mips gain the support for: * CLOCK_BOOTTIME that can be useful in certain scenarios since it keeps track of the time during sleep as well. * CLOCK_TAI that is like CLOCK_REALTIME, but uses the International Atomic Time (TAI) reference instead of UTC to avoid jumping on leap second updates. for both clock_gettime and clock_getres. The porting has been validated using the vdsotest test-suite [1] extended to cover all the clock ids [2]. A new test has been added to the linux kselftest in order to validate the newly added library. To simplify the testing, a copy of the patchset on top of a recent linux tree can be found at [3] and [4]. [1] https://github.com/nathanlynch/vdsotest [2] https://github.com/fvincenzo/vdsotest [3] git://linux-arm.org/linux-vf.git vdso/v5 [4] git://linux-arm.org/linux-vf.git vdso-mips/v5 Changes: -------- v5: - Rebased on 5.0-rc7. - Added x86_64, compat mode for x86_64 and i386 portings. - Extended vDSO kselftest. - Addressed review comments. v4: - Rebased on 5.0-rc2. - Addressed review comments. - Disabled compat vdso on arm64 when the kernel is compiled with clang. v3: - Ported the latest fixes and optimizations done on the x86 architecture to the generic library. - Addressed review comments. - Improved the documentation of the interfaces. - Changed the HAVE_ARCH_TIMER config option to a more generic HAVE_HW_COUNTER. v2: - Added -ffixed-x18 to arm64 - Repleced occurrences of timeval and timespec - Modified datapage.h to be compliant with y2038 on all the architectures - Removed __u_vdso type 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: Ralf Baechle <ralf@linux-mips.org> Cc: Paul Burton <paul.burton@mips.com> Cc: Daniel Lezcano <daniel.lezcano@linaro.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Mark Salyzyn <salyzyn@android.com> Cc: Peter Collingbourne <pcc@google.com> Cc: Shuah Khan <shuah@kernel.org> Cc: Dmitry Safonov <0x7f454c46@gmail.com> Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk> Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com> Peter Collingbourne (1): arm64: Build vDSO with -ffixed-x18 Vincenzo Frascino (22): kernel: Standardize vdso_datapage kernel: Define gettimeofday vdso common code arm64: Substitute gettimeofday with C implementation arm64: compat: Alloc separate pages for vectors and sigpage arm64: compat: Split kuser32 arm64: compat: Refactor aarch32_alloc_vdso_pages() arm64: compat: Add KUSER_HELPERS config option arm64: compat: Add missing syscall numbers arm64: compat: Expose signal related structures arm64: compat: Generate asm offsets for signals lib: vdso: Add compat support arm64: compat: Add vDSO arm64: Refactor vDSO code arm64: compat: vDSO setup for compat layer arm64: elf: vDSO code page discovery arm64: compat: Get sigreturn trampolines from vDSO arm64: Add vDSO compat support arm64: Enable compat vDSO support arm: Add support for generic vDSO mips: Add support for generic vDSO x86: Add support for generic vDSO kselftest: Extend vDSO selftest arch/arm/Kconfig | 3 + arch/arm/include/asm/vdso/gettimeofday.h | 82 +++ arch/arm/include/asm/vdso_datapage.h | 25 +- arch/arm/kernel/vdso.c | 108 ++-- arch/arm/vdso/Makefile | 13 +- arch/arm/vdso/note.c | 15 + arch/arm/vdso/vdso.lds.S | 1 + arch/arm/vdso/vgettimeofday.c | 267 +-------- arch/arm64/Kconfig | 24 + arch/arm64/Makefile | 23 +- arch/arm64/configs/defconfig | 1 + arch/arm64/include/asm/elf.h | 20 +- arch/arm64/include/asm/processor.h | 4 +- arch/arm64/include/asm/signal32.h | 58 +- arch/arm64/include/asm/unistd.h | 3 + arch/arm64/include/asm/vdso.h | 3 + arch/arm64/include/asm/vdso/compat_barrier.h | 36 ++ .../include/asm/vdso/compat_gettimeofday.h | 119 ++++ arch/arm64/include/asm/vdso/gettimeofday.h | 85 +++ arch/arm64/include/asm/vdso_datapage.h | 47 -- arch/arm64/kernel/Makefile | 7 +- arch/arm64/kernel/asm-offsets.c | 45 +- arch/arm64/kernel/kuser32.S | 65 +-- arch/arm64/kernel/signal32.c | 76 +-- arch/arm64/kernel/sigreturn32.S | 46 ++ arch/arm64/kernel/vdso.c | 506 +++++++++++++----- arch/arm64/kernel/vdso/Makefile | 28 +- arch/arm64/kernel/vdso/gettimeofday.S | 328 ------------ arch/arm64/kernel/vdso/vgettimeofday.c | 28 + arch/arm64/kernel/vdso32/.gitignore | 2 + arch/arm64/kernel/vdso32/Makefile | 184 +++++++ arch/arm64/kernel/vdso32/note.c | 15 + arch/arm64/kernel/vdso32/sigreturn.S | 62 +++ arch/arm64/kernel/vdso32/vdso.S | 19 + arch/arm64/kernel/vdso32/vdso.lds.S | 81 +++ arch/arm64/kernel/vdso32/vgettimeofday.c | 41 ++ arch/mips/Kconfig | 2 + arch/mips/include/asm/vdso.h | 60 +-- arch/mips/include/asm/vdso/gettimeofday.h | 165 ++++++ arch/mips/{ => include/asm}/vdso/vdso.h | 6 +- arch/mips/kernel/vdso.c | 107 +++- arch/mips/vdso/Makefile | 23 +- arch/mips/vdso/elf.S | 2 +- arch/mips/vdso/gettimeofday.c | 273 ---------- arch/mips/vdso/sigreturn.S | 2 +- arch/mips/vdso/vdso.lds.S | 1 + arch/mips/vdso/vgettimeofday.c | 28 + arch/x86/Kconfig | 3 + arch/x86/entry/vdso/Makefile | 9 + arch/x86/entry/vdso/vclock_gettime.c | 239 +-------- arch/x86/entry/vdso/vdso.lds.S | 2 + arch/x86/entry/vdso/vdso32/vdso32.lds.S | 1 + arch/x86/entry/vdso/vdsox32.lds.S | 1 + arch/x86/entry/vsyscall/vsyscall_gtod.c | 110 ++-- arch/x86/include/asm/vdso/gettimeofday.h | 203 +++++++ arch/x86/include/asm/vgtod.h | 73 +-- arch/x86/include/asm/vvar.h | 2 +- include/vdso/datapage.h | 75 +++ include/vdso/helpers.h | 52 ++ include/vdso/types.h | 39 ++ lib/Kconfig | 5 + lib/vdso/Kconfig | 37 ++ lib/vdso/Makefile | 22 + lib/vdso/gettimeofday.c | 179 +++++++ tools/testing/selftests/vDSO/Makefile | 2 + tools/testing/selftests/vDSO/vdso_full_test.c | 246 +++++++++ 66 files changed, 2812 insertions(+), 1627 deletions(-) create mode 100644 arch/arm/include/asm/vdso/gettimeofday.h create mode 100644 arch/arm/vdso/note.c create mode 100644 arch/arm64/include/asm/vdso/compat_barrier.h create mode 100644 arch/arm64/include/asm/vdso/compat_gettimeofday.h create mode 100644 arch/arm64/include/asm/vdso/gettimeofday.h delete mode 100644 arch/arm64/include/asm/vdso_datapage.h create mode 100644 arch/arm64/kernel/sigreturn32.S delete mode 100644 arch/arm64/kernel/vdso/gettimeofday.S create mode 100644 arch/arm64/kernel/vdso/vgettimeofday.c create mode 100644 arch/arm64/kernel/vdso32/.gitignore create mode 100644 arch/arm64/kernel/vdso32/Makefile create mode 100644 arch/arm64/kernel/vdso32/note.c create mode 100644 arch/arm64/kernel/vdso32/sigreturn.S create mode 100644 arch/arm64/kernel/vdso32/vdso.S create mode 100644 arch/arm64/kernel/vdso32/vdso.lds.S create mode 100644 arch/arm64/kernel/vdso32/vgettimeofday.c create mode 100644 arch/mips/include/asm/vdso/gettimeofday.h rename arch/mips/{ => include/asm}/vdso/vdso.h (90%) delete mode 100644 arch/mips/vdso/gettimeofday.c create mode 100644 arch/mips/vdso/vgettimeofday.c create mode 100644 arch/x86/include/asm/vdso/gettimeofday.h create mode 100644 include/vdso/datapage.h create mode 100644 include/vdso/helpers.h create mode 100644 include/vdso/types.h create mode 100644 lib/vdso/Kconfig create mode 100644 lib/vdso/Makefile create mode 100644 lib/vdso/gettimeofday.c create mode 100644 tools/testing/selftests/vDSO/vdso_full_test.c