Re: [PATCH v2 0/4] Static calls

Steven Rostedt
2018-12-04T23:08:41Z

Where did this end up BTW?

I know that there's controversy about the
CONFIG_HAVE_STATIC_CALL_OPTIMIZED option, but I don't think the
CONFIG_HAVE_STATIC_CALL_UNOPTIMIZED version was controversial. From the
v1 patch 0 description:

There are three separate implementations, depending on what the arch
supports:

1) CONFIG_HAVE_STATIC_CALL_OPTIMIZED: patched call sites - requires
objtool and a small amount of arch code

2) CONFIG_HAVE_STATIC_CALL_UNOPTIMIZED: patched trampolines - requires
a small amount of arch code

3) If no arch support, fall back to regular function pointers

My benchmarks showed the best improvements with the
STATIC_CALL_OPTIMIZED, but it still showed improvement with the
UNOPTIMIZED version as well. Can we at least apply 2 and 3 from the
above (which happen to be the first part of the patch set. 1 comes in
at the end).

I would also just call it CONFIG_STATIC_CALL. If we every agree on the
optimized version, then we can call it CONFIG_STATIC_CALL_OPTIMIZED.
Have an option called UNOPTIMIZED just seems wrong.

-- Steve

On Mon, 26 Nov 2018 07:54:56 -0600
Josh Poimboeuf <jpoimboe@redhat.com> wrote:

> v2:
> - fix STATIC_CALL_TRAMP() macro by using __PASTE() [Ard]
> - rename optimized/unoptimized -> inline/out-of-line [Ard]
> - tweak arch interfaces for PLT and add key->tramp field [Ard]
> - rename 'poison' to 'defuse' and do it after all sites have been patched [Ard]
> - fix .init handling [Ard, Steven]
> - add CONFIG_HAVE_STATIC_CALL [Steven]
> - make interfaces more consistent across configs to allow tracepoints to
> use them [Steven]
> - move __ADDRESSABLE() to static_call() macro [Steven]
> - prevent 2-byte jumps [Steven]
> - add offset to asm-offsets.c instead of hard coding key->func offset
> - add kernel_text_address() sanity check
> - make __ADDRESSABLE() symbols truly unique
>
> TODO:
> - port Ard's arm64 patches to the new arch interfaces
> - tracepoint performance testing
>
> --------------------
>
> These patches are related to two similar patch sets from Ard and Steve:
>
> - https://lkml.kernel.org/r/20181005081333.15018-1-ard.biesheuvel@linaro.org
> - https://lkml.kernel.org/r/20181006015110.653946300@goodmis.org
>
> The code is also heavily inspired by the jump label code, as some of the
> concepts are very similar.
>
> There are three separate implementations, depending on what the arch
> supports:
>
> 1) CONFIG_HAVE_STATIC_CALL_INLINE: patched call sites - requires
> objtool and a small amount of arch code
>
> 2) CONFIG_HAVE_STATIC_CALL_OUTLINE: patched trampolines - requires
> a small amount of arch code
>
> 3) If no arch support, fall back to regular function pointers
>
>
> Josh Poimboeuf (4):
> compiler.h: Make __ADDRESSABLE() symbol truly unique
> static_call: Add static call infrastructure
> x86/static_call: Add out-of-line static call implementation
> x86/static_call: Add inline static call implementation for x86-64
>
> arch/Kconfig | 10 +
> arch/x86/Kconfig | 4 +-
> arch/x86/include/asm/static_call.h | 52 +++
> arch/x86/kernel/Makefile | 1 +
> arch/x86/kernel/asm-offsets.c | 6 +
> arch/x86/kernel/static_call.c | 78 ++++
> include/asm-generic/vmlinux.lds.h | 11 +
> include/linux/compiler.h | 2 +-
> include/linux/module.h | 10 +
> include/linux/static_call.h | 202 ++++++++++
> include/linux/static_call_types.h | 19 +
> kernel/Makefile | 1 +
> kernel/module.c | 5 +
> kernel/static_call.c | 350 ++++++++++++++++++
> tools/objtool/Makefile | 3 +-
> tools/objtool/check.c | 126 ++++++-
> tools/objtool/check.h | 2 +
> tools/objtool/elf.h | 1 +
> .../objtool/include/linux/static_call_types.h | 19 +
> tools/objtool/sync-check.sh | 1 +
> 20 files changed, 899 insertions(+), 4 deletions(-)
> create mode 100644 arch/x86/include/asm/static_call.h
> create mode 100644 arch/x86/kernel/static_call.c
> create mode 100644 include/linux/static_call.h
> create mode 100644 include/linux/static_call_types.h
> create mode 100644 kernel/static_call.c
> create mode 100644 tools/objtool/include/linux/static_call_types.h
>