1 /* 2 * Copyright (C) 2013 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 #ifndef KERNEL_ARGUMENT_BLOCK_H 18 #define KERNEL_ARGUMENT_BLOCK_H 19 20 #include <elf.h> 21 #include <link.h> 22 #include <stdint.h> 23 #include <sys/auxv.h> 24 25 #include "private/bionic_macros.h" 26 27 struct abort_msg_t; 28 29 // When the kernel starts the dynamic linker, it passes a pointer to a block 30 // of memory containing argc, the argv array, the environment variable array, 31 // and the array of ELF aux vectors. This class breaks that block up into its 32 // constituents for easy access. 33 class KernelArgumentBlock { 34 public: 35 explicit KernelArgumentBlock(void* raw_args) { 36 uintptr_t* args = reinterpret_cast<uintptr_t*>(raw_args); 37 argc = static_cast<int>(*args); 38 argv = reinterpret_cast<char**>(args + 1); 39 envp = argv + argc + 1; 40 41 // Skip over all environment variable definitions to find the aux vector. 42 // The end of the environment block is marked by a NULL pointer. 43 char** p = envp; 44 while (*p != NULL) { 45 ++p; 46 } 47 ++p; // Skip the NULL itself. 48 49 auxv = reinterpret_cast<ElfW(auxv_t)*>(p); 50 } 51 52 // Similar to ::getauxval but doesn't require the libc global variables to be set up, 53 // so it's safe to call this really early on. 54 unsigned long getauxval(unsigned long type) { 55 for (ElfW(auxv_t)* v = auxv; v->a_type != AT_NULL; ++v) { 56 if (v->a_type == type) { 57 return v->a_un.a_val; 58 } 59 } 60 return 0; 61 } 62 63 int argc; 64 char** argv; 65 char** envp; 66 ElfW(auxv_t)* auxv; 67 68 abort_msg_t** abort_message_ptr; 69 70 private: 71 DISALLOW_COPY_AND_ASSIGN(KernelArgumentBlock); 72 }; 73 74 #endif // KERNEL_ARGUMENT_BLOCK_H 75
