github.com/criyle/go-sandbox@v0.10.3/ptracer/context_linux.go (about)

     1  package ptracer
     2  
     3  import (
     4  	"os"
     5  	"syscall"
     6  )
     7  
     8  // Context is the context for current syscall trap
     9  // used to retrive syscall number and arguments
    10  type Context struct {
    11  	// Pid is current context process pid
    12  	Pid int
    13  	// current reg context (platform dependent)
    14  	regs syscall.PtraceRegs
    15  }
    16  
    17  var (
    18  	// UseVMReadv determine whether use ProcessVMReadv syscall to read str
    19  	// initial true and becomes false if tried and failed with ENOSYS
    20  	UseVMReadv = true
    21  	pageSize   = 4 << 10
    22  )
    23  
    24  func init() {
    25  	pageSize = os.Getpagesize()
    26  }
    27  
    28  func getTrapContext(pid int) (*Context, error) {
    29  	var regs syscall.PtraceRegs
    30  	//err := syscall.PtraceGetRegs(pid, &regs)
    31  	err := ptraceGetRegSet(pid, &regs)
    32  	if err != nil {
    33  		return nil, err
    34  	}
    35  	return &Context{
    36  		Pid:  pid,
    37  		regs: regs,
    38  	}, nil
    39  }
    40  
    41  // GetString get the string from process data segment
    42  func (c *Context) GetString(addr uintptr) string {
    43  	buff := make([]byte, syscall.PathMax)
    44  	if UseVMReadv {
    45  		if err := vmReadStr(c.Pid, addr, buff); err != nil {
    46  			// if ENOSYS, then disable this function
    47  			if no, ok := err.(syscall.Errno); ok {
    48  				if no == syscall.ENOSYS {
    49  					UseVMReadv = false
    50  				}
    51  			}
    52  		} else {
    53  			return string(buff[:clen(buff)])
    54  		}
    55  	}
    56  	syscall.PtracePeekData(c.Pid, addr, buff)
    57  	return string(buff[:clen(buff)])
    58  }