From 28c205c5ec498bd8d0e4a79ddabbb87e01df0ba1 Mon Sep 17 00:00:00 2001
From: "A.Olokhtonov" <a.olokhtonov@norsi-trans.ru>
Date: Tue, 20 Jul 2021 23:57:47 +0300
Subject: [PATCH] Disambiguate recursive calls in step over

---
 .gitignore          |  1 +
 command.c           | 27 +++++++++++++++++++++------
 res/003-recursion.c | 15 +++++++++++++++
 res/Makefile        |  1 +
 4 files changed, 38 insertions(+), 6 deletions(-)
 create mode 100644 res/003-recursion.c

diff --git a/.gitignore b/.gitignore
index 733fb82..a92e670 100644
--- a/.gitignore
+++ b/.gitignore
@@ -2,3 +2,4 @@
 build/
 res/001-simple
 res/002-compilation-units
+res/003-recursion
diff --git a/command.c b/command.c
index 56d01be..e142c9a 100644
--- a/command.c
+++ b/command.c
@@ -22,6 +22,7 @@ command_step(struct mi_process proc)
     struct mi_sourcepoint *next_sp;
     
     do {
+        // TODO: step until source line changes (for active file)
         ptrace(PTRACE_SINGLESTEP, proc.pid, 0, 0);
         waitpid(proc.pid, 0, 0);
         regs = get_process_registers(proc);
@@ -51,25 +52,39 @@ command_next(struct mi_process proc)
     struct mi_sourcepoint *next_sp;
     
     do {
+        // TODO: step until source line changes (for active file)
+        
         ptrace(PTRACE_SINGLESTEP, proc.pid, 0, 0);
         waitpid(proc.pid, 0, 0);
         regs = get_process_registers(proc);
         
         long instruction = ptrace(PTRACE_PEEKDATA, proc.pid, regs.rip, NULL);
+        
         if (is_call_instruction(instruction)) {
-            u64 call_at = regs.rip;
+            long base_address = regs.rbp;
             
-            // Do single step, get return address from stack, place breakpoint there, continue
+            // NOTE do single step, get return address from stack, place breakpoint there, continue
             ptrace(PTRACE_SINGLESTEP, proc.pid, 0, 0);
             waitpid(proc.pid, 0, 0);
             regs = get_process_registers(proc);
             
             long return_address = ptrace(PTRACE_PEEKDATA, proc.pid, regs.rsp, NULL);
-            long saved_instruction = place_breakpoint_at(proc, return_address);
-            run_until_breakpoint_and_restore(proc, return_address, saved_instruction);
-            // TODO: disambiguate recursive calls
             
-            regs = get_process_registers(proc);
+            // NOTE: disambiguate recursive calls
+            for (;;) {
+                long saved_instruction = place_breakpoint_at(proc, return_address);
+                run_until_breakpoint_and_restore(proc, return_address, saved_instruction);
+                regs = get_process_registers(proc);
+                long actual_base_address = regs.rbp;
+                
+                if (base_address == actual_base_address) {
+                    break;
+                } else {
+                    // NOTE: step to the next instruction after the return address, so that we can add a  breakpoint there
+                    ptrace(PTRACE_SINGLESTEP, proc.pid, 0, 0);
+                    waitpid(proc.pid, 0, 0);
+                }
+            }
         }
         // TODO: repXXX
         
diff --git a/res/003-recursion.c b/res/003-recursion.c
new file mode 100644
index 0000000..903d181
--- /dev/null
+++ b/res/003-recursion.c
@@ -0,0 +1,15 @@
+static int
+fact(int n)
+{
+	if (n == 0 || n == 1) {
+		return(1);
+	}
+	return(n * fact(n - 1));
+}
+
+int
+main(void)
+{
+	int result = fact(5);
+	return(0);
+}
diff --git a/res/Makefile b/res/Makefile
index 159ef78..fe1d447 100644
--- a/res/Makefile
+++ b/res/Makefile
@@ -1,3 +1,4 @@
 all:
 	gcc -g -o 001-simple 001-simple.c
 	gcc -g -o 002-compilation-units 002-compilation-units.c 002-compilation-units-impl.c
+	gcc -g -o 003-recursion 003-recursion.c