asmsh/asm_env.h

/* Copyright Yann Weber <asmsh@yannweb.net>
   This file is part of asmsh.

   asmsh is free software: you can redistribute it and/or modify it under the
   terms of the GNU General Public License as published by the Free Software
   Foundation, either version 3 of the License, or any later version.
   
   asmsh is distributed in the hope that it will be useful, but WITHOUT ANY
   WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
   FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
   details.
   
   You should have received a copy of the GNU General Public License along
   with asmsh. If not, see <https://www.gnu.org/licenses/>.
*/
#ifndef ASMSH_ASM_ENV_H
#define ASMSH_ASM_ENV_H
#include "config.h"

#include <errno.h>
#include <stdlib.h>
#include <stdio.h>
#include <sys/ptrace.h>
#include <sys/types.h>
#include <sys/user.h>
#include <sys/wait.h>

#include "mmap_parse.h"
#include "compile.h"

///! Initial size of the child's memory map with PROT_EXEC permission
#define ASMSH_CHILD_TEXT_MAP_SZ 0x1000 // defined in child.s

#define ASMSH_CHILD_PATH_DEFAULT "./child"

typedef struct asmsh_env_s asmsh_env_t;

struct asmsh_env_s
{
	///! Path on wich the child will execve
	char *childpath;
	///! Child process pid
	pid_t pid;
	///! Last status fetched from child using waitpid
	int status;
	///! Child process registers value
	struct user_regs_struct regs;
	///! Child's memory map
	child_mmap_l mmap;

	/**Pointer, in child memory, of the mmap with PROT_EXEC
	 * perm allowing use to write code to be executed by the
	 * child
	 */
	void *txt_map_addr;
	/** child's map size */
	size_t txt_map_sz;
	/** Pointer on current write addr in child's map */
	void *txt_map_ptr;

	/** Pointer on the next addr where we should write some
	 *  compiled bytecode */
	void *code_write_ptr;

	/** Pointer, in child memory, of the stack */
	void *stack_addr;
	size_t stack_sz;

};

/** Run a new asm child and return the environment
 * @param const char* the path of the executable to execve in child
 * @return NULL if error or a pointer on a newly allocated env
 */
asmsh_env_t* asmsh_env(const char *childpath);
/** Free an env returned by @ref asmsh_env() */
void asmsh_env_free(asmsh_env_t *asmenv);

/** Write a buffer in tracee memory
 *
 * Handle un-alligned addr by reading tracee memory before writing if
 * needed.
 * @param asmsh_env_t* 
 * @param void* The address in tracee memory
 * @param const unsigned char* The buffer to write
 * @param size_t number of bytes to write
 * @return 0 if no errors else -1 with errno set
 */
int asmsh_env_write_mem(asmsh_env_t *env, void *addr, const unsigned char *buf, size_t buf_sz);

/** Write bytecode at the next location available in the text map
 * @param asmsh_env_t* The run environment
 * @param asmsh_bytecode_t* The bytecode to copy
 * @return 0 if no error occured 1 if child finished in unexpected state or -1
 * 	   on other errror
 */
int asmsh_env_write_code(asmsh_env_t *env, asmsh_bytecode_t *bcode);

/** Run the next instruction
 * @param asmsh_env_t* The run environment
 * @param int* If not null will be set to the status of the child PID (error cases)
 * @return 0 if no error from the child pid else -1 and wstatus is set to the child status
 */
int asmsh_env_step(asmsh_env_t *env, int *status);

/** Update both registers and memory maps */
int asmsh_env_update(asmsh_env_t *asmenv);
/** Update env registers from child */
int asmsh_env_update_regs(asmsh_env_t *asmenv);
/** Update child's memory map in env */
int asmsh_env_update_maps(asmsh_env_t *asmenv);

/** Convert a child's memory address into a "txt" addr
 *
 * The local address is calculated as an offset from the start of the child's
 * "txt" map (the one with PROT_READ | PROT_EXEC perm)
 *
 * @param asmsh_env_t*
 * @param void* the address to convert
 * @param void** the converted txt offset
 * @return 0 if no error else -1
 */
int asmsh_env_txt_addr(asmsh_env_t *asmenv, void *addr, void **loc);

#endif