From: Fangrui Song <maskray@google.com>
To: Jarmo Tiitto <jarmo.tiitto@gmail.com>
Cc: Kees Cook <keescook@chromium.org>,
Sami Tolvanen <samitolvanen@google.com>,
Bill Wendling <wcw@google.com>,
Nathan Chancellor <nathan@kernel.org>,
Nick Desaulniers <ndesaulniers@google.com>,
clang-built-linux@googlegroups.com, linux-kernel@vger.kernel.org,
morbo@google.com
Subject: Re: [PATCH v3 1/1] pgo: Fix allocate_node() v2
Date: Sat, 5 Jun 2021 16:45:51 -0700 [thread overview]
Message-ID: <20210605234551.k25j232kvsuzodxd@google.com> (raw)
In-Reply-To: <2268220.EOMg9uvDZY@hyperiorarchmachine>
On 2021-06-05, Jarmo Tiitto wrote:
>> Kees Cook wrote perjantaina 4. kesäkuuta 2021 21.06.37 EEST:
>> >
>> > I grep -R'd where the memory_contains() can be found and it is only
>> > found in #include <asm-generic/sections.h>
>>
>> That's true, but the way to use "asm-generic" is to include the
>> top-level "asm" file, so that architectures can override things as
>> needed.
>>
>Thanks, I didn't know that.
>
>> > I cross my fingers and await if this is my first accepted patch. :-)
>>
>> I tweaked it a bit and applied it (see the separate email).
>>
>> Thank you!
>>
>> -Kees
>>
>> --
>> Kees Cook
>>
>
>Whoa!
>Thanks, I'm glad it worked out. :-)
>
>Btw. I have almost forgotten that I once wrote code
>(that I didn't send) for the GCC gcov subsystem that also enabled
>-fprofile-generate/use for the kernel.
>However the Clang PGO looks much more approachable and
>easier to hack on since the profile data format is simpler.
>
>So starting to work on this felt just natural to me. :-)
>
>-Jarmo
Right, __llvm_prf_vnodes reserves space for static allocation.
There is no relocation referencing __llvm_prf_vnodes so there is
no straightforward way using the space for the kernel.
In userspace shared objects, the scheme works by linking
libclang_rt.profile-*.a into every shared object. The
__start___llvm_prf_vnodes/__stop___llvm_prf_vnodes symbols are
delieberately hidden in compiler-rt InstrProfilingPlatformLinux.c.
The GCC gcov format is definitely simpler than the LLVM format:)
prev parent reply other threads:[~2021-06-05 23:46 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-04 16:58 [PATCH v3 1/1] pgo: Fix allocate_node() v2 Jarmo Tiitto
2021-06-04 17:04 ` Nathan Chancellor
2021-06-04 17:28 ` Nick Desaulniers
2021-06-04 17:58 ` Kees Cook
2021-06-04 18:06 ` Kees Cook
2021-06-05 17:15 ` Jarmo Tiitto
2021-06-05 23:45 ` Fangrui Song [this message]
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