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Some hw breakpoint fixes

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Enable usage of dr1-dr3.  Clear control bits when a breakpoint
is disabled. Use DR_LEN_1 instead of DR_LEN_8 so breakpoint work on
unaligned adresses.

Fixes #51.
This commit is contained in:
Michael Gehring
2015-01-24 02:58:03 +01:00
parent ff789d1df6
commit 2a66ecb10b
1 changed files with 41 additions and 6 deletions
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47
proctl/breakpoints_linux_amd64.go
View File

@ -17,6 +17,7 @@ import "C"
import ( import (
"fmt" "fmt"
"syscall" "syscall"
"unsafe"
) )
// Represents a single breakpoint. Stores information on the break // Represents a single breakpoint. Stores information on the break
@ -50,6 +51,15 @@ func PtracePokeUser(tid int, off, addr uintptr) error {
return nil return nil
} }
func PtracePeekUser(tid int, off uintptr) (uintptr, error) {
var x uintptr // XXX: this should not be necessary
ret, _, err := syscall.Syscall6(syscall.SYS_PTRACE, syscall.PTRACE_PEEKUSR, uintptr(tid), uintptr(off), uintptr(unsafe.Pointer(&x)), 0, 0)
if err != syscall.Errno(0) {
return 0, err
}
return ret, nil
}
func (dbp *DebuggedProcess) BreakpointExists(addr uint64) bool { func (dbp *DebuggedProcess) BreakpointExists(addr uint64) bool {
for _, bp := range dbp.HWBreakPoints { for _, bp := range dbp.HWBreakPoints {
if bp != nil && bp.Addr == addr { if bp != nil && bp.Addr == addr {
@ -133,24 +143,49 @@ func (dbp *DebuggedProcess) newBreakpoint(fn, f string, l int, addr uint64, data
// that we want to break at. There are only 4 debug registers // that we want to break at. There are only 4 debug registers
// DR0-DR3. Debug register 7 is the control register. // DR0-DR3. Debug register 7 is the control register.
func setHardwareBreakpoint(reg, tid int, addr uint64) error { func setHardwareBreakpoint(reg, tid int, addr uint64) error {
if reg < 0 || reg > 7 { if reg < 0 || reg > 3 {
return fmt.Errorf("invalid register value") return fmt.Errorf("invalid register value")
} }
var ( var (
off = uintptr(C.offset(C.int(reg))) dr7off = uintptr(C.offset(C.DR_CONTROL))
dr7 = uintptr(0x1 | C.DR_RW_EXECUTE | C.DR_LEN_8) drxoff = uintptr(C.offset(C.int(reg)))
dr7addr = uintptr(C.offset(C.DR_CONTROL)) drxmask = uintptr((((1 << C.DR_CONTROL_SIZE) - 1) << uintptr(reg*C.DR_CONTROL_SIZE)) | (((1 << C.DR_ENABLE_SIZE) - 1) << uintptr(reg*C.DR_ENABLE_SIZE)))
drxenable = uintptr(0x1) << uintptr(reg*C.DR_ENABLE_SIZE)
drxctl = uintptr(C.DR_RW_EXECUTE|C.DR_LEN_1) << uintptr(reg*C.DR_CONTROL_SIZE)
) )
// Get current state
dr7, err := PtracePeekUser(tid, dr7off)
if err != nil {
return err
}
// If addr == 0 we are expected to disable the breakpoint
if addr == 0 {
dr7 &= ^drxmask
return PtracePokeUser(tid, dr7off, dr7)
}
// Error out if dr`reg` is already used
if dr7&(0x3<<uint(reg*C.DR_ENABLE_SIZE)) != 0 {
return fmt.Errorf("dr%d already enabled", reg)
}
// Set the debug register `reg` with the address of the // Set the debug register `reg` with the address of the
// instruction we want to trigger a debug exception. // instruction we want to trigger a debug exception.
if err := PtracePokeUser(tid, off, uintptr(addr)); err != nil { if err := PtracePokeUser(tid, drxoff, uintptr(addr)); err != nil {
return err return err
} }
// Clear dr`reg` flags
dr7 &= ^drxmask
// Enable dr`reg`
dr7 |= (drxctl<<C.DR_CONTROL_SHIFT) | drxenable
// Set the debug control register. This // Set the debug control register. This
// instructs the cpu to raise a debug // instructs the cpu to raise a debug
// exception when hitting the address of // exception when hitting the address of
// an instruction stored in dr0-dr3. // an instruction stored in dr0-dr3.
return PtracePokeUser(tid, dr7addr, dr7) return PtracePokeUser(tid, dr7off, dr7)
} }