本文为看雪论坛优秀文章
看雪论坛作者ID：有毒
一、简述
ptrace(PTRACE_foom, pid, ...) // pid为linux中对应的线程ID
二、函数原型及初步使用
1. 函数原型
long ptrace(enum __ptrace_request request, pid_t pid, void *addr, void *data);
2. 函数定义
SYSCALL_DEFINE4(ptrace, long, request, long, pid, unsigned long, addr,unsigned long, data){struct task_struct *child;long ret;if (request == PTRACE_TRACEME) {ret = ptrace_traceme();if (!ret)arch_ptrace_attach(current);goto out;}child = find_get_task_by_vpid(pid);if (!child) {ret = -ESRCH;goto out;}if (request == PTRACE_ATTACH || request == PTRACE_SEIZE) {ret = ptrace_attach(child, request, addr, data);/** Some architectures need to do book-keeping after* a ptrace attach.*/if (!ret)arch_ptrace_attach(child);goto out_put_task_struct;}ret = ptrace_check_attach(child, request == PTRACE_KILL ||request == PTRACE_INTERRUPT);if (ret < 0)goto out_put_task_struct;ret = arch_ptrace(child, request, addr, data);if (ret || request != PTRACE_DETACH)ptrace_unfreeze_traced(child);out_put_task_struct:put_task_struct(child);out:return ret;}
define SYSCALL_DEFINE1(name, ...) SYSCALL_DEFINEx(1, _##name, __VA_ARGS__)define SYSCALL_DEFINE2(name, ...) SYSCALL_DEFINEx(2, _##name, __VA_ARGS__)define SYSCALL_DEFINE3(name, ...) SYSCALL_DEFINEx(3, _##name, __VA_ARGS__)define SYSCALL_DEFINE4(name, ...) SYSCALL_DEFINEx(4, _##name, __VA_ARGS__)define SYSCALL_DEFINE5(name, ...) SYSCALL_DEFINEx(5, _##name, __VA_ARGS__)define SYSCALL_DEFINE6(name, ...) SYSCALL_DEFINEx(6, _##name, __VA_ARGS__)
SYSCALL_METADATA(sname, x, __VA_ARGS__)__SYSCALL_DEFINEx(x, sname, __VA_ARGS__)/** The asmlinkage stub is aliased to a function named __se_sys_*() which* sign-extends 32-bit ints to longs whenever needed. The actual work is* done within __do_sys_*().*/__diag_push();__diag_ignore(GCC, 8, "-Wattribute-alias","Type aliasing is used to sanitize syscall arguments");asmlinkage long sys__attribute__((alias(__stringify(__se_sysALLOW_ERROR_INJECTION(sysstatic inline long __do_sysasmlinkage long __se_sysasmlinkage long __se_sys{long ret = __do_sys__MAP(x,__SC_TEST,__VA_ARGS__);__PROTECT(x, ret,__MAP(x,__SC_ARGS,__VA_ARGS__));return ret;}__diag_pop();static inline long __do_sys
/* kernel/ptrace.c */asmlinkage long sys_ptrace(long request, long pid, unsigned long addr,unsigned long data);
SYSCALL_DEFINE4(ptrace, long, request, long, pid, unsigned long, addr, unsigned long, data)--> SYSCALL_DEFINEx(4, _ptrace, __VA_ARGS__)--> __SYSCALL_DEFINEx(4, __ptrace, __VA_ARGS__)asmlinkage long sys--> asmlinkage long sys_ptrace(__MAP(4,__SC_DECL,__VA_ARGS__))
/** __MAP - apply a macro to syscall arguments* __MAP(n, m, t1, a1, t2, a2, ..., tn, an) will expand to* m(t1, a1), m(t2, a2), ..., m(tn, an)* The first argument must be equal to the amount of type/name* pairs given. Note that this list of pairs (i.e. the arguments* of __MAP starting at the third one) is in the same format as* for SYSCALL_DEFINE<n>/COMPAT_SYSCALL_DEFINE<n>*/#define __MAP0(m,...)#define __MAP1(m,t,a,...) m(t,a)#define __MAP2(m,t,a,...) m(t,a), __MAP1(m,__VA_ARGS__)#define __MAP3(m,t,a,...) m(t,a), __MAP2(m,__VA_ARGS__)#define __MAP4(m,t,a,...) m(t,a), __MAP3(m,__VA_ARGS__)#define __MAP5(m,t,a,...) m(t,a), __MAP4(m,__VA_ARGS__)#define __MAP6(m,t,a,...) m(t,a), __MAP5(m,__VA_ARGS__)#define __MAP(n,...) __MAP##n(__VA_ARGS__)#define __SC_DECL(t, a) t a
__MAP(4,__SC_DECL, long request, long pid, unsigned long addr,unsigned long data)--> __MAP4(__SC_DECL, long, request, long, pid, unsigned long, addr,unsigned long, data)--> __SC_DECL(long, request), __MAP3(__SC_DECL, __VA_ARGS__)__MAP3(__SC_DECL, long, pid, unsigned long, addr, unsigned long, data)--> __SC_DECL(long, pid), __MAP2(__SC_DECL, unsigned long, addr, unsigned long, data)-->__SC_DECL(unsigned long, addr), __MAP1(__SC_DECL, __VA_ARGS__)unsigned long addr, __SC_DECL(unsigned long, data)--> unsigned long datalong pid, __SC_DECL(unsigned long, addr), __MAP1(__SC_DECL, __VA_ARGS__)--> long pid, unsigned long addr, unsigned long data--> long request, __SC_DECL(long, pid), __MAP2(__SC_DECL, __VA_ARGS__)--> long request, long pid, unsigned long addr, unsigned long data
asmlinkage long __se_sys##name(__MAP(x,__SC_LONG,__VA_ARGS__)){long ret = __do_sys##name(__MAP(x,__SC_CAST,__VA_ARGS__));__MAP(x,__SC_TEST,__VA_ARGS__);__PROTECT(x, ret,__MAP(x,__SC_ARGS,__VA_ARGS__));return ret;}define __TYPE_AS(t, v) __same_type((__force t)0, v) /*判断t和v是否是同一个类型*/define __TYPE_IS_L(t) (__TYPE_AS(t, 0L)) /*判断t是否是long 类型,是返回1*/define __TYPE_IS_UL(t) (__TYPE_AS(t, 0UL)) /*判断t是否是unsigned long 类型,是返回1*/define __TYPE_IS_LL(t) (__TYPE_AS(t, 0LL) || __TYPE_AS(t, 0ULL)) /*是long类型就返回1*/define __SC_LONG(t, a) __typeof(__builtin_choose_expr(__TYPE_IS_LL(t), 0LL, 0L)) a /*将参数转换成long类型*/define __SC_CAST(t, a) (__force t) a /*转成成原来的类型*/define __force __attribute__((force)) /*表示所定义的变量类型可以做强制类型转换*/
3. 初步使用
（1）最简单的ls跟踪
int main(int argc, char *argv[]){pid_t child;long orig_rax;child = fork();if(child == 0){ptrace(PTRACE_TRACEME, 0, NULL, NULL); // Tell kernel, trace meexecl("/bin/ls", "ls", NULL);}else{/*Receive certification after child process stopped*/wait(NULL);/*Read child process's rax*/orig_rax = ptrace(PTRACE_PEEKUSER, child, 8*ORIG_RAX, NULL);printf("[+] The child made a system call %ld.n", orig_rax);/*Continue*/ptrace(PTRACE_CONT, child, NULL, NULL);}return 0;}
（2）系统调用查看参数
int main(int argc, char *argv[]){pid_t child;long orig_rax, rax;long params[3];int status;int insyscall = 0;child = fork();if(child == 0){ptrace(PTRACE_TRACEME, 0, NULL, NULL);execl("/bin/ls", "ls", NULL);}else{while(1){wait(&status);if(WIFEXITED(status))break;orig_rax = ptrace(PTRACE_PEEKUSER, child, 8 * ORIG_RAX, NULL);if(orig_rax == SYS_write){if(insyscall == 0){insyscall = 1;params[0] = ptrace(PTRACE_PEEKUSER, child, 8 * RBX, NULL);params[1] = ptrace(PTRACE_PEEKUSER, child, 8 * RCX, NULL);params[2] = ptrace(PTRACE_PEEKUSER, child, 8 * RDX, NULL);printf("Write called with %ld, %ld, %ldn", params[0], params[1], params[2]);}else{rax = ptrace(PTRACE_PEEKUSER, child, 8 * RAX, NULL);printf("Write returned with %ldn", rax);insyscall = 0;}}ptrace(PTRACE_SYSCALL, child, NULL, NULL);}}return 0;}
（3）系统调用参数-改进版
int main(int argc, char *argv[]){pid_t child;long orig_rax, rax;long params[3];int status;int insyscall = 0;struct user_regs_struct regs;child = fork();if(child == 0){ptrace(PTRACE_TRACEME, child, 8 * ORIG_RAX, NULL);execl("/bin/ls", "ls", NULL);}else{while(1){wait(&status);if(WIFEXITED(status))break;orig_rax = ptrace(PTRACE_PEEKUSER, child, 8*ORIG_RAX, NULL);if(orig_rax == SYS_write){if(insyscall == 0){insyscall == 1;ptrace(PTRACE_GETREGS, child, NULL, ®s);printf("Write called with %lld, %lld, %lldn", regs.rbx, regs.rcx, regs.rdx);}else{rax = ptrace(PTRACE_PEEKUSER, child, 8*rax, NULL);printf("Write returned with %ldn", rax);insyscall = 0;}}ptrace(PTRACE_SYSCALL, child, NULL, NULL);}}return 0;}
参考文献
看雪ID：有毒
https://bbs.pediy.com/user-home-7797730.htm
# 往期推荐
球分享
球点赞
球在看
点击“阅读原文”，了解更多！
本文始发于微信公众号（看雪学院）：Linux ptrace详细分析系列（一）
- 左青龙
- 微信扫一扫
-
- 右白虎
- 微信扫一扫
-
评论