petrbalvin/gasm-sdk
0
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases 36 Wiki Activity

docs: document watchpoint slot tracking and update debugger commands

Browse Source
This commit is contained in:
petrbalvin
2026-08-07 22:27:49 +02:00
parent d7ee1b78d4
commit cde7d0f96a
7 changed files with 154 additions and 34 deletions
Download Patch File Download Diff File Expand all files Collapse all files
debug/debug_test.go
+50
View File
@@ -271,3 +271,53 @@ func TestBreakpointInfo(t *testing.T) {
t.Errorf("Info %q does not contain label", info)
}
}
func TestWatchpointSlotTracking(t *testing.T) {
s := &Session{}
// All four slots are free initially.
for i := 0; i < 4; i++ {
if s.IsWatchpointSlotUsed(i) {
t.Errorf("slot %d should be free initially", i)
}
}
if got := s.FindFreeWatchpointSlot(); got != 0 {
t.Errorf("FindFreeWatchpointSlot() = %d, want 0", got)
}
// Manually mark slots 0 and 2 as used (simulating successful SetWatchpoint).
s.wpSlots[0] = true
s.wpSlots[2] = true
if !s.IsWatchpointSlotUsed(0) {
t.Error("slot 0 should be in use")
}
if s.IsWatchpointSlotUsed(1) {
t.Error("slot 1 should be free")
}
if !s.IsWatchpointSlotUsed(2) {
t.Error("slot 2 should be in use")
}
if s.IsWatchpointSlotUsed(3) {
t.Error("slot 3 should be free")
}
if got := s.FindFreeWatchpointSlot(); got != 1 {
t.Errorf("FindFreeWatchpointSlot() = %d, want 1", got)
}
// Out-of-range slot queries return false.
if s.IsWatchpointSlotUsed(-1) {
t.Error("slot -1 should be reported as free (out of range)")
}
if s.IsWatchpointSlotUsed(4) {
t.Error("slot 4 should be reported as free (out of range)")
}
// Mark all slots used: FindFreeWatchpointSlot returns -1.
for i := 0; i < 4; i++ {
s.wpSlots[i] = true
}
if got := s.FindFreeWatchpointSlot(); got != -1 {
t.Errorf("FindFreeWatchpointSlot() with all slots used = %d, want -1", got)
}
}
debug/ptrace_linux_amd64.go
+2 -1
View File
@@ -25,7 +25,8 @@ type Session struct {
cmd *exec.Cmd
stopped bool
exited bool
codeBase uint64 // base address of the JIT code in the debuggee
codeBase uint64 // base address of the JIT code in the debuggee
wpSlots [4]bool // watchpoint slot occupancy (DR0-DR3)
}
// Launch starts the debuggee subprocess (gasm debug --target ...) and
debug/repl.go
+25 -14
View File
@@ -384,8 +384,8 @@ func REPL(s *Session, bm *Breakpoints, codeBase uint64, funcOffset, funcSize, ar
fmt.Println(` break <label|addr> [if <reg> <op> <val>] set a breakpoint
delete <label|addr> remove a breakpoint
info break list all breakpoints
watch <addr> [r|w] set a hardware watchpoint (write by default)
unwatch clear all watchpoints
watch <addr> [r|w] [size] set a hardware watchpoint (write by default)
unwatch [<slot>] clear one or all watchpoints
step [n], s single-step n instructions
next, n step over CALL
continue, c run until breakpoint or exit
@@ -457,28 +457,39 @@ func REPL(s *Session, bm *Breakpoints, codeBase uint64, funcOffset, funcSize, ar
if len(parts) > 3 {
size, _ = strconv.Atoi(parts[3])
}
// Find a free slot (0-3).
slot := -1
for i := 0; i < 4; i++ {
// Simple: use slot 0 for now.
slot = i
break
}
slot := s.FindFreeWatchpointSlot()
if slot < 0 {
fmt.Println("no free watchpoint slots")
fmt.Println("no free watchpoint slots (use 'unwatch <slot>' to clear one)")
continue
}
if err := s.SetWatchpoint(slot, addr, typ, size); err != nil {
fmt.Printf("watch: %v\n", err)
} else {
fmt.Printf("watchpoint %d set: %#x (%s, %d bytes)\n", slot, addr, parts[2], size)
typStr := "w"
if typ == WatchRead {
typStr = "r"
}
fmt.Printf("watchpoint %d set: %#x (%s, %d bytes)\n", slot, addr, typStr, size)
}
case "unwatch":
if err := s.ClearAllWatchpoints(); err != nil {
fmt.Printf("unwatch: %v\n", err)
if len(parts) >= 2 {
slot, err := strconv.Atoi(parts[1])
if err != nil || slot < 0 || slot > 3 {
fmt.Println("usage: unwatch [<slot>]")
continue
}
if err := s.ClearWatchpoint(slot); err != nil {
fmt.Printf("unwatch: %v\n", err)
} else {
fmt.Printf("watchpoint %d cleared\n", slot)
}
} else {
fmt.Println("all watchpoints cleared")
if err := s.ClearAllWatchpoints(); err != nil {
fmt.Printf("unwatch: %v\n", err)
} else {
fmt.Println("all watchpoints cleared")
}
}
default:
debug/watchpoint_linux_amd64.go
+36 -4
View File
@@ -25,12 +25,34 @@ const (
WatchRead WatchpointType = 3 // trigger on read or write
)
// FindFreeWatchpointSlot returns the index of the first free watchpoint slot
// (0-3), or -1 if all four hardware watchpoints are in use.
func (s *Session) FindFreeWatchpointSlot() int {
for i := 0; i < 4; i++ {
if !s.wpSlots[i] {
return i
}
}
return -1
}
// IsWatchpointSlotUsed reports whether slot (0-3) currently holds a watchpoint.
func (s *Session) IsWatchpointSlotUsed(slot int) bool {
if slot < 0 || slot > 3 {
return false
}
return s.wpSlots[slot]
}
// SetWatchpoint installs a hardware watchpoint on the given address.
// slot is 0-3 (four hardware watchpoints available).
// slot is 0-3 (four hardware watchpoints available); the slot must be free.
func (s *Session) SetWatchpoint(slot int, addr uint64, typ WatchpointType, size int) error {
if slot < 0 || slot > 3 {
return fmt.Errorf("debug: watchpoint slot must be 0-3")
}
if s.wpSlots[slot] {
return fmt.Errorf("debug: watchpoint slot %d already in use", slot)
}
// Determine the length encoding.
var lenBits uint64
@@ -82,6 +104,7 @@ func (s *Session) SetWatchpoint(slot int, addr uint64, typ WatchpointType, size
if err := ptracePokeUser(s.pid, 0x38, dr7); err != nil {
return fmt.Errorf("debug: set DR7: %w", err)
}
s.wpSlots[slot] = true
return nil
}
@@ -90,20 +113,29 @@ func (s *Session) ClearWatchpoint(slot int) error {
if slot < 0 || slot > 3 {
return fmt.Errorf("debug: watchpoint slot must be 0-3")
}
if !s.wpSlots[slot] {
return fmt.Errorf("debug: watchpoint slot %d is not in use", slot)
}
// Read DR7, clear the enable bit for this slot.
dr7, err := ptracePeekUser(s.pid, 0x38)
if err != nil {
return err
}
dr7 &^= uint64(1) << (2 * slot) // disable
return ptracePokeUser(s.pid, 0x38, dr7)
if err := ptracePokeUser(s.pid, 0x38, dr7); err != nil {
return err
}
s.wpSlots[slot] = false
return nil
}
// ClearAllWatchpoints removes all hardware watchpoints.
func (s *Session) ClearAllWatchpoints() error {
for slot := 0; slot < 4; slot++ {
if err := s.ClearWatchpoint(slot); err != nil {
return err
if s.wpSlots[slot] {
if err := s.ClearWatchpoint(slot); err != nil {
return err
}
}
}
return nil