From a323aec6d03620a9de09e5c9bc7ad6871a2a5cbf Mon Sep 17 00:00:00 2001
From: Ryan Fleury <ryan.j.fleury@gmail.com>
Date: Thu, 31 Jul 2025 15:10:25 -0700
Subject: [PATCH] demon/linux: x64 trap writing

---
 src/demon/linux/demon_core_linux.c | 72 ++++++++++++++++++++++++++++++
 1 file changed, 72 insertions(+)

diff --git a/src/demon/linux/demon_core_linux.c b/src/demon/linux/demon_core_linux.c
index 8047cf76..feb3c6c5 100644
--- a/src/demon/linux/demon_core_linux.c
+++ b/src/demon/linux/demon_core_linux.c
@@ -1195,6 +1195,29 @@ dmn_ctrl_run(Arena *arena, DMN_CtrlCtx *ctx, DMN_RunCtrls *ctrls)
     //
     B32 need_wait_on_events = (evts.count == 0);
     
+    ////////////////////////////
+    //- rjf: write all traps into memory
+    //
+    U8 *trap_swap_bytes = push_array_no_zero(scratch.arena, U8, ctrls->traps.trap_count);
+    ProfScope("write all traps into memory")
+    {
+      U64 trap_idx = 0;
+      for(DMN_TrapChunkNode *n = ctrls->traps.first; n != 0; n = n->next)
+      {
+        for(U64 n_idx = 0; n_idx < n->count; n_idx += 1, trap_idx += 1)
+        {
+          DMN_Trap *trap = n->v+n_idx;
+          if(trap->flags == 0)
+          {
+            trap_swap_bytes[trap_idx] = 0xCC;
+            dmn_process_read(trap->process, r1u64(trap->vaddr, trap->vaddr+1), trap_swap_bytes+trap_idx);
+            U8 int3 = 0xCC;
+            dmn_process_write(trap->process, r1u64(trap->vaddr, trap->vaddr+1), &int3);
+          }
+        }
+      }
+    }
+    
     ////////////////////////////
     //- rjf: gather all threads which we should run
     //
@@ -1306,6 +1329,32 @@ dmn_ctrl_run(Arena *arena, DMN_CtrlCtx *ctx, DMN_RunCtrls *ctrls)
       final_wait_pid = wait_id;
       done = 1;
       
+      // NOTE(rjf): siginfo hint from old code:
+#if 0
+      {
+        switch(siginfo.si_code)
+        {
+          // SI_KERNEL (hit int3; 0xCC)
+          case 0x80:
+          {
+            // TODO(rjf): breakpoint event
+          }break;
+          //                            +----------------------"breakpoint"
+          //                            | 
+          //                 v----------v----------------------"hardware breakpoint"
+          // TRAP_UNK, TRAP_HWBKPT, TRAP_BRKPT, TRAP_TRACE
+          case 0x5: case 0x4: case 0x1: case 0x2:
+          {
+            // TODO(rjf): breakpoint event (?)
+          }break;
+          case 0x3: case 0x0:
+          {
+            // TODO(rjf): do nothing(?)
+          }break;
+        }
+      }
+#endif
+      
       //- rjf: unpack event
       int wifexited         = WIFEXITED(status);
       int wifsignaled       = WIFSIGNALED(status);
@@ -1501,6 +1550,29 @@ dmn_ctrl_run(Arena *arena, DMN_CtrlCtx *ctx, DMN_RunCtrls *ctrls)
       }
     }
     
+    //////////////////////////
+    //- rjf: restore original memory at trap locations
+    //
+    ProfScope("restore original memory at trap locations")
+    {
+      U64 trap_idx = 0;
+      for(DMN_TrapChunkNode *n = ctrls->traps.first; n != 0; n = n->next)
+      {
+        for(U64 n_idx = 0; n_idx < n->count; n_idx += 1, trap_idx += 1)
+        {
+          DMN_Trap *trap = n->v+n_idx;
+          if(trap->flags == 0)
+          {
+            U8 og_byte = trap_swap_bytes[trap_idx];
+            if(og_byte != 0xCC)
+            {
+              dmn_process_write(trap->process, r1u64(trap->vaddr, trap->vaddr+1), &og_byte);
+            }
+          }
+        }
+      }
+    }
+    
     scratch_end(scratch);
   }
   return evts;