platform_bionic/libc/private/KernelArgumentBlock.h
Elliott Hughes 5e62b34c0d Clean up bionic_macros.h a bit.
Use <android-base/macros.h> instead where possible, and move the bionic
macros out of the way of the libbase ones. Yes, there are folks who manage
to end up with both included at once (thanks OpenGL!), and cleaning that
up doesn't seem nearly as practical as just making this change.

Bug: N/A
Test: builds
Change-Id: I23fc544f39d5addf81dc61471771a5438778895b
2018-10-25 11:00:00 -07:00

74 lines
2.2 KiB
C++

/*
* 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.
*/
#pragma once
#include <elf.h>
#include <link.h>
#include <stdint.h>
#include <sys/auxv.h>
#include "private/bionic_macros.h"
struct abort_msg_t;
struct libc_shared_globals;
// 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:
explicit 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 the aux vector.
// The end of the environment block is marked by a NULL pointer.
char** p = envp;
while (*p != nullptr) {
++p;
}
++p; // Skip the NULL itself.
auxv = reinterpret_cast<ElfW(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.
unsigned long getauxval(unsigned long type) {
for (ElfW(auxv_t)* v = auxv; v->a_type != AT_NULL; ++v) {
if (v->a_type == type) {
return v->a_un.a_val;
}
}
return 0;
}
int argc;
char** argv;
char** envp;
ElfW(auxv_t)* auxv;
// Other data that we want to pass from the dynamic linker to libc.so.
abort_msg_t** abort_message_ptr;
libc_shared_globals* shared_globals;
private:
BIONIC_DISALLOW_COPY_AND_ASSIGN(KernelArgumentBlock);
};