42b2c6a5ee
There's now only one place where we deal with this stuff, it only needs to be parsed once by the dynamic linker (rather than by each recipient), and it's now easier for us to get hold of auxv data early on. Change-Id: I6314224257c736547aac2e2a650e66f2ea53bef5
77 lines
2.4 KiB
C++
77 lines
2.4 KiB
C++
/*
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* Copyright (C) 2013 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#ifndef KERNEL_ARGUMENT_BLOCK_H
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#define KERNEL_ARGUMENT_BLOCK_H
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#include <elf.h>
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#include <stdint.h>
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#include <sys/auxv.h>
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// When the kernel starts the dynamic linker, it passes a pointer to a block
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// of memory containing argc, the argv array, the environment variable array,
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// and the array of ELF aux vectors. This class breaks that block up into its
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// constituents for easy access.
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class KernelArgumentBlock {
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public:
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KernelArgumentBlock(void* raw_args) {
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uint32_t* args = reinterpret_cast<uint32_t*>(raw_args);
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argc = static_cast<int>(*args);
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argv = reinterpret_cast<char**>(args + 1);
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envp = argv + argc + 1;
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// Skip over all environment variable definitions to find aux vector.
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// The end of the environment block is marked by two NULL pointers.
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char** p = envp;
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while (*p != NULL) {
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++p;
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}
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++p; // Skip second NULL;
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auxv = reinterpret_cast<Elf32_auxv_t*>(p);
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}
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// Similar to ::getauxval but doesn't require the libc global variables to be set up,
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// so it's safe to call this really early on. This function also lets you distinguish
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// between the inability to find the given type and its value just happening to be 0.
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unsigned long getauxval(unsigned long type, bool* found_match = NULL) {
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for (Elf32_auxv_t* v = auxv; v->a_type != AT_NULL; ++v) {
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if (v->a_type == type) {
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if (found_match != NULL) {
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*found_match = true;
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}
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return v->a_un.a_val;
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}
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}
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if (found_match != NULL) {
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*found_match = false;
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}
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return 0;
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}
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int argc;
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char** argv;
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char** envp;
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Elf32_auxv_t* auxv;
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private:
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// Disallow copy and assignment.
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KernelArgumentBlock(const KernelArgumentBlock&);
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void operator=(const KernelArgumentBlock&);
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};
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#endif // KERNEL_ARGUMENT_BLOCK_H
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