Handle signals

debugus.c

@@ -1,3 +1,4 @@
+#define _XOPEN_SOURCE 600
 #include <stdio.h>
 #include <stdlib.h>
 #include <stddef.h>
@@ -9,6 +10,7 @@
 #include <errno.h>
 #include <libelf.h>
 #include <gelf.h>
+#include <signal.h>
 #include <sys/types.h>
 #include <sys/wait.h>
 #include <sys/ptrace.h>
@@ -164,10 +166,46 @@ typedef struct {
     HashTable js_descs;
 } Dbg;
 
+siginfo_t dbg_get_siginfo(Dbg *dbg)
+{
+    siginfo_t i;
+    ptrace(PTRACE_GETSIGINFO, dbg->pid, NULL, &i);
+    return i;
+}
+
+void dbg_handle_sigsegv(Dbg *dbg, siginfo_t info)
+{
+    unused(dbg);
+    LOG_ERR("Caught a segfault %d. SKILL ISSUE BRO\n", info.si_code);
+}
+
+void dbg_handle_sigtrap(Dbg *dbg, siginfo_t info)
+{
+    void dbg_set_rip(Dbg *dbg, uint64_t v);
+    uint64_t dbg_get_rip(Dbg *dbg);
+
+    switch (info.si_code) {
+        case SI_KERNEL:
+        case TRAP_BRKPT:
+            dbg_set_rip(dbg, dbg_get_rip(dbg) - 1);
+            LOG_INF("Hit breakpoint at 0x%"PRIxPTR"\n", dbg_get_rip(dbg));
+            return;
+        case TRAP_TRACE:
+            return;
+    }
+}
+
 void dbg_wait(Dbg *dbg)
 {
     int status, options = 0;
     waitpid(dbg->pid, &status, options);
+
+    siginfo_t info = dbg_get_siginfo(dbg);
+    switch (info.si_signo) {
+        case SIGTRAP: dbg_handle_sigtrap(dbg, info); break;
+        case SIGSEGV: dbg_handle_sigsegv(dbg, info); break;
+        default:      LOG_INF("Signal %d\n!!", info.si_signo); break;
+    }
 }
 
 // Memory
@@ -238,13 +276,11 @@ void dbg_set_rip(Dbg *dbg, uint64_t v)
 
 void dbg_step_brk(Dbg *dbg)
 {
-    uint64_t loc = dbg_get_rip(dbg) - 1;
+    uint64_t loc = dbg_get_rip(dbg);
     char key[20];
     snprintf(key, sizeof(key), "0x%"PRIxPTR, (uintptr_t)loc);
     Brk *brk = hashtable_get(&dbg->brks, key);
     if ((brk != NULL  && brk->enabled)) {
-        uint64_t prev_instr = loc;
-        dbg_set_rip(dbg, prev_instr);
         brk_disable(brk);
         ptrace(PTRACE_SINGLESTEP, brk->pid, NULL, NULL);
         dbg_wait(dbg);