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