debugger: added breakpoints

Info.plist

@@ -0,0 +1,11 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+<plist version="1.0">
+<dict>
+    <key>SecTaskAccess</key>
+    <array>
+        <string>allowed</string>
+        <string>debug</string>
+    </array>
+</dict>
+</plist>

Makefile

@@ -3,12 +3,13 @@ BUILDDIR=bin/
 PREFIX=/usr/local/bin/
 SOURCES=$(wildcard src/*.c)
 MAIN=main.c
-override CFLAGS+=-Werror -Wall -g -fPIC -O2 -DNDEBUG -ftrapv -Wfloat-equal -Wundef -Wwrite-strings -Wuninitialized -pedantic -std=c11
+OSX_BS=-sectcreate __TEXT __info_plist Info.plist
+override CFLAGS+=-Werror -Wall -g -fPIC -O2 -DNDEBUG -ftrapv -Wfloat-equal -Wundef -Wwrite-strings -Wuninitialized -pedantic -std=gnu11
 override LDFLAGS+=-ledit
 
 all: main.c
 	mkdir -p $(BUILDDIR)
-	$(CC) $(MAIN) $(SOURCES) -o $(BUILDDIR)$(TARGET) $(CFLAGS) $(LDFLAGS)
+	$(CC) $(MAIN) $(SOURCES) -o $(BUILDDIR)$(TARGET) $(CFLAGS) $(LDFLAGS) $(OSX_BS)
 
 install: all
 	install $(BUILDDIR)$(TARGET) $(PREFIX)$(TARGET)

src/debugger.c

@@ -1,5 +1,55 @@
 #include "debugger.h"
 
+debugger* new_debugger(pid_t pid) {
+  debugger* d = malloc(sizeof(debugger));
+  d->breakpoints = NULL;
+  d->n_breakpoints = 0;
+  d->pid = pid;
+  return d;
+}
+
+breakpoint* new_breakpoint(pid_t pid, void* addr) {
+  breakpoint* b = malloc(sizeof(breakpoint));
+  b->pid = pid;
+  b->addr = addr;
+  b->enabled = 0;
+  b->data = 0;
+  return b;
+}
+
+void free_debugger(debugger* d) {
+  int i;
+  for (i = 0; i < d->n_breakpoints; i++) free(d->breakpoints[i]);
+  free(d);
+}
+
+void enable(breakpoint* b) {
+    long data = ptrace(PTRACE_PEEKDATA, b->pid, b->addr, 0);
+    b->data = data & 0xff;
+    uint64_t int3 = 0xcc;
+    uint64_t data_with_int3 = ((data & ~0xff) | int3);
+    ptrace(PTRACE_POKEDATA, b->pid, b->addr, data_with_int3);
+
+    b->enabled = 1;
+}
+
+void disable(breakpoint* b) {
+    long data = ptrace(PTRACE_PEEKDATA, b->pid, b->addr, 0);
+    long restored = ((data & ~0xff) | b->data);
+    ptrace(PTRACE_POKEDATA, b->pid, b->addr, restored);
+
+    b->enabled = 0;
+}
+
+void set_breakpoint(debugger* d, void* addr) {
+  printf("Setting breakpoint at addres %p\n", addr);
+  breakpoint* b = new_breakpoint(d->pid, addr);
+  enable(b);
+  d->breakpoints = realloc(d->breakpoints,
+                           (++d->n_breakpoints)*sizeof(breakpoint*));
+  d->breakpoints[d->n_breakpoints-1] = b;
+}
+
 void run_target(char* program) {
   if (ptrace(PTRACE_TRACEME, 0, 0, 0) < 0) perror("Error while creating child: ptrace failed");
   else execl(program, program, NULL);
@@ -12,25 +62,42 @@ void debug_continue(pid_t pid) {
   waitpid(pid, &status, 0);
 }
 
-void debug_loop(char* command, pid_t pid) {
+short debug_loop(char* command, debugger* d) {
+  int quit = 0;
+  int i = 0;
+  char** args = split(command, ' ');
+  command = args[0];
+
   if (!strcmp(command, "c")) {
-    debug_continue(pid);
+    debug_continue(d->pid);
+  } else if (!strcmp(command, "b")) {
+    if (!args[1]) puts("'b' needs an argument");
+    else set_breakpoint(d, (void*)strtol(args[1], NULL, 16));
+  } else if ((!strcmp(command, "e")) || (!strcmp(command, "q"))) {
+    puts("Moriturus te saluto.");
+    quit = 1;
   } else {
     printf("%s: Unknown command\n", command);
   }
+  while(args[i]) free(args[i++]);
+  free(args);
+  return quit;
 }
 
 void run_debugger(pid_t pid) {
   int status;
   char* line = NULL;
+  debugger* d = new_debugger(pid);
+  short quit = 0;
 
   waitpid(pid, &status, 0);
 
-  while((line = readline("minidbg> ")) != NULL) {
-    debug_loop(line, pid);
+  while(!quit && (line = readline("minidbg> "))) {
+    quit = debug_loop(line, d);
     add_history(line);
     free(line);
   }
+  free_debugger(d);
 }
 
 void debug(char* program) {

src/debugger.h

@@ -1,17 +1,31 @@
-#include <stdlib.h>
-#include <string.h>
+#include <stdint.h>
 #include <unistd.h>
 
 #include <editline/readline.h>
 #include <sys/ptrace.h>
 #include <sys/wait.h>
 
+#include "util.h"
+
 #ifdef __APPLE__
 #define PTRACE_TRACEME PT_TRACE_ME
 #define PTRACE_CONT PT_CONTINUE
-#define DATA 0
+#define PTRACE_PEEKDATA PT_READ_D
+#define PTRACE_POKEDATA PT_WRITE_D
 #else
-#define DATA NULL
 #endif
 
+typedef struct {
+  short enabled;
+  uint8_t data;
+  pid_t pid;
+  void* addr;
+} breakpoint;
+
+typedef struct {
+  breakpoint** breakpoints;
+  int n_breakpoints;
+  pid_t pid;
+} debugger;
+
 void debug(char*);

src/util.c

@@ -0,0 +1,37 @@
+#include "util.h"
+
+char** split(char* inpt, char d) {
+  char** res = NULL;
+  size_t count = 0;
+  char* tmp = inpt;
+  char* last_comma = NULL;
+  size_t idx = 0;
+  char delim[2];
+  delim[0] = d;
+  delim[1] = '\0';
+  char* tok;
+
+  while (*tmp) {
+    if (d == *tmp) {
+      count++;
+      last_comma = tmp;
+    }
+    tmp++;
+  }
+
+  count += last_comma < (inpt+strlen(inpt)-1);
+
+  res = malloc((++count)*sizeof(char*));
+
+  if (res) {
+    tok = strsep(&inpt, delim);
+
+    while (tok) {
+        res[idx++] = strdup(tok);
+        tok = strsep(&inpt, delim);
+    }
+    res[idx] = NULL;
+  }
+
+  return res;
+}

src/util.h

@@ -0,0 +1,4 @@
+#include <string.h>
+#include <stdlib.h>
+
+char** split(char*, char);