620a72252e
Talking futher to the person doing the glibc risc-v ifunc work, they clarified that glibc _is_ passing hwcap as the first argument, and the null pointer is actually the second argument. https://sourceware.org/pipermail/libc-alpha/2023-August/150967.html So since our whole purpose here was source compatibility, let's do what they're actually doing, and let's add some tests. I've also added a test that __riscv_hwprobe() works from an ifunc resolver because that's one place where it might well be used. That said, one other thing that came out of the discussion is that I actually went away and looked at a sample of top apps to see how many are using ifuncs currently. The result? Zero. So although this _might_ be interesting long term (especially if clang gets riscv64 FMV), I think we've done more than we need to with riscv64 ifuncs for now! Test: ran locally, both dynamic and static tests Change-Id: Ie2044d9f4e47c32c00ad381f045c537f4df38b08
71 lines
3 KiB
C++
71 lines
3 KiB
C++
/*
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* Copyright (C) 2019 The Android Open Source Project
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* * Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* * Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in
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* the documentation and/or other materials provided with the
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* distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
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* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
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* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#include "private/bionic_call_ifunc_resolver.h"
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#include <sys/auxv.h>
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#include <sys/ifunc.h>
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#include "private/bionic_auxv.h"
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// This code is called in the linker before it has been relocated, so minimize calls into other
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// parts of Bionic. In particular, we won't ever have two ifunc resolvers called concurrently, so
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// initializing the ifunc resolver argument doesn't need to be thread-safe.
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ElfW(Addr) __bionic_call_ifunc_resolver(ElfW(Addr) resolver_addr) {
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#if defined(__aarch64__)
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typedef ElfW(Addr) (*ifunc_resolver_t)(uint64_t, __ifunc_arg_t*);
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static __ifunc_arg_t arg;
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static bool initialized = false;
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if (!initialized) {
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initialized = true;
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arg._size = sizeof(__ifunc_arg_t);
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arg._hwcap = getauxval(AT_HWCAP);
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arg._hwcap2 = getauxval(AT_HWCAP2);
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}
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return reinterpret_cast<ifunc_resolver_t>(resolver_addr)(arg._hwcap | _IFUNC_ARG_HWCAP, &arg);
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#elif defined(__arm__)
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typedef ElfW(Addr) (*ifunc_resolver_t)(unsigned long);
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static unsigned long hwcap;
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static bool initialized = false;
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if (!initialized) {
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initialized = true;
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hwcap = getauxval(AT_HWCAP);
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}
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return reinterpret_cast<ifunc_resolver_t>(resolver_addr)(hwcap);
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#elif defined(__riscv)
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// The pointer argument is currently unused, but reserved for future
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// expansion. If we pass nullptr from the beginning, it'll be easier
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// to recognize if/when we pass actual data (and matches glibc).
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typedef ElfW(Addr) (*ifunc_resolver_t)(uint64_t, void*);
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static uint64_t hwcap = getauxval(AT_HWCAP);
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return reinterpret_cast<ifunc_resolver_t>(resolver_addr)(hwcap, nullptr);
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#else
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typedef ElfW(Addr) (*ifunc_resolver_t)(void);
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return reinterpret_cast<ifunc_resolver_t>(resolver_addr)();
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#endif
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}
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