We can print a value of an integer variable!!!

command.c

@@ -143,7 +143,19 @@ command_backtrace(struct mi_process proc)
 }
 
 static void
-command_print(struct mi_process proc, char *command, int command_length)
+command_print(struct mi_process proc, char *name, int name_length)
 {
-    
+    struct mi_registers regs = get_process_registers(proc);
+    u64 pc = regs.rip - proc.base_address;
+    u64 cfa = get_cfa_at_pc(proc, pc);
+    struct mi_variable *variable = get_variable(proc, name, name_length, pc);
+    
+    if (variable) {
+        u64 address = cfa + variable->location;
+        long value = ptrace(PTRACE_PEEKDATA, proc.pid, address, NULL);
+        int val4 = value & 0x00000000FFFFFFFF;
+        printf("%.*s = %d\n", name_length, name, val4);
+    } else {
+        printf("variable %.*s not found\n", name_length, name);
+    }
 }

dwarf.c

@@ -59,7 +59,7 @@ decode_leb128(u8 *at, u32 *dest)
     u64 result = 0;
     u64 shift = 0;
     
-    while (1) {
+    for (;;) {
         u8 byte = at[offset++];
         
         result |= ((byte & 127) << shift);
@@ -88,7 +88,7 @@ decode_leb128s(u8 *at, s32 *dest)
     u32 size = 32;
     u8 byte;
     
-    while (1) {
+    for (;;) {
         byte = at[offset++];
         result |= ((byte & 127) << shift);
         shift += 7;

eh_frame.c

@@ -1,5 +1,6 @@
 static u64
-iterate_call_frame_instructions(u8 *data, u64 to_read)
+iterate_call_frame_instructions(struct dwarf_cie *cie, u8 *data, u64 to_read, 
+                                struct mi_registers *regs, struct dwarf_regset *regset, u64 location)
 {
     u64 read = 0;
     
@@ -12,13 +13,15 @@ iterate_call_frame_instructions(u8 *data, u64 to_read)
         
         if (high_two == DW_CFA_advance_loc) {
             u8 delta = low_six;
+            if (regset) {
+                regset->loc += delta * cie->code_alignment;
+            }
         } else if (high_two == DW_CFA_offset) {
             u8 reg = low_six;
             u32 factored_offset;
             increment += decode_leb128(data, &factored_offset);
         } else if (high_two == DW_CFA_restore) {
             u8 reg = low_six;
-            
         } else if (high_two == 0) {
             switch (low_six) {
                 case DW_CFA_nop: {
@@ -29,6 +32,9 @@ iterate_call_frame_instructions(u8 *data, u64 to_read)
                     u64 address;
                     memcpy(&address, data, 8);
                     increment = 8;
+                    if (regset) {
+                        regset->loc = address; // TODO: encoding??
+                    }
                     break;
                 }
                 
@@ -36,6 +42,9 @@ iterate_call_frame_instructions(u8 *data, u64 to_read)
                     u8 advance;
                     memcpy(&advance, data, 1);
                     increment = 1;
+                    if (regset) {
+                        regset->loc += advance * cie->code_alignment;
+                    }
                     break;
                 }
                 
@@ -43,6 +52,9 @@ iterate_call_frame_instructions(u8 *data, u64 to_read)
                     u16 advance;
                     memcpy(&advance, data, 2);
                     increment = 2;
+                    if (regset) {
+                        regset->loc += advance * cie->code_alignment;
+                    }
                     break;
                 }
                 
@@ -50,6 +62,9 @@ iterate_call_frame_instructions(u8 *data, u64 to_read)
                     u32 advance;
                     memcpy(&advance, data, 4);
                     increment = 4;
+                    if (regset) {
+                        regset->loc += advance * cie->code_alignment;
+                    }
                     break;
                 }
                 
@@ -98,20 +113,35 @@ iterate_call_frame_instructions(u8 *data, u64 to_read)
                 case DW_CFA_def_cfa: {
                     u32 reg;
                     u32 nonfactored_offset;
+                    
                     increment += decode_leb128(data, &reg);
-                    increment += decode_leb128(data, &nonfactored_offset);
+                    increment += decode_leb128(data + increment, &nonfactored_offset);
+                    
+                    if (regset) {
+                        regset->cfa_offset = nonfactored_offset;
+                        regset->cfa_register = reg;
+                    }
+                    
                     break;
                 }
                 
                 case DW_CFA_def_cfa_register: {
                     u32 reg;
                     increment += decode_leb128(data, &reg);
+                    
+                    if (regset) {
+                        regset->cfa_register = reg;
+                    }
+                    
                     break;
                 }
                 
                 case DW_CFA_def_cfa_offset: {
                     u32 offset;
                     increment += decode_leb128(data, &offset);
+                    if (regset) {
+                        regset->cfa_offset = offset;
+                    }
                     break;
                 }
                 
@@ -188,6 +218,11 @@ iterate_call_frame_instructions(u8 *data, u64 to_read)
             }
         }
         
+        if (location && regset->loc > location) {
+            regset->cfa = regset->system[regset->cfa_register] + regset->cfa_offset;
+            break;
+        }
+        
         data += increment;
         read += increment + 1;
         
@@ -236,8 +271,10 @@ read_one_cie(struct dwarf_cie *header, u64 length, u8 *data, u8 *original_data)
     }
     
     header->has_z = has_z;
+    header->instructions = data;
+    header->instructions_length = header->length - (data - original_data - 4);
     
-    data += iterate_call_frame_instructions(data, header->length - (data - original_data - 4));
+    data += iterate_call_frame_instructions(header, data, header->instructions_length, 0, 0, 0);
     
     if (has_R) {
         // NOTE(aolo2): this shit is undocumented. Best sources I could find:
@@ -372,14 +409,13 @@ read_encoded_pointer(struct mi_process proc, struct dwarf_cie *cie, u8 *data, u6
 }
 
 static u64
-read_one_fde(struct mi_process proc, struct dwarf_cie *cie, u64 length, u32 cie_offset, u8 *data, u8 *original_data)
+read_one_fde(struct mi_process proc, struct dwarf_cie *cie, u64 length, u8 *data, u8 *original_data,
+             struct dwarf_fde *header)
 {
-    struct dwarf_fde header = { 0 };
+    header->length = length;
-    
+    header->cie = *cie;
-    header.length = length;
-    header.cie = (struct dwarf_cie *) (data - 4 - cie_offset);
     
-    u32 pointer_size = read_encoded_pointer(proc, cie, data, &header.low_pc);
+    u32 pointer_size = read_encoded_pointer(proc, cie, data, &header->low_pc);
     data += pointer_size;
     
     u64 fde_length = 0;
@@ -394,21 +430,24 @@ read_one_fde(struct mi_process proc, struct dwarf_cie *cie, u64 length, u32 cie_
         data += 8;
     }
     
-    header.high_pc = header.low_pc + fde_length;
+    header->high_pc = header->low_pc + fde_length;
     
     if (cie->has_z) {
-        data += decode_leb128(data, &header.augmentation_data_length);
+        data += decode_leb128(data, &header->augmentation_data_length);
-        header.augmentation_data = data;
+        header->augmentation_data = data;
-        data += header.augmentation_data_length;
+        data += header->augmentation_data_length;
     }
     
-    data += iterate_call_frame_instructions(data, header.length - (data - original_data - 4));
+    header->instructions = data;
+    header->instructions_length = header->length - (data - original_data - 4);
+    
+    data += iterate_call_frame_instructions(cie, data, header->instructions_length, 0, 0, 0);
     
     return(data - original_data);
 }
 
 static u64
-read_one_call_frame_record(struct mi_process proc, struct dwarf_cie *last_cie, u8 *data)
+read_one_call_frame_record(struct mi_process proc, struct dwarf_cie *last_cie, struct dwarf_fde *last_fde, int *is_cie, u8 *data)
 {
     u8 *original_data = data;
     u64 length;
@@ -436,49 +475,76 @@ read_one_call_frame_record(struct mi_process proc, struct dwarf_cie *last_cie, u
     
     if (cie_id == 0) {
         result = read_one_cie(last_cie, length, data, original_data);
+        *is_cie = 1;
     } else {
-        result = read_one_fde(proc, last_cie, length, cie_id, data, original_data);
+        result = read_one_fde(proc, last_cie, length, data, original_data, last_fde);
+        *is_cie = 0;
     }
     
     return(result);
 }
 
-static void
+static struct dwarf_fde
-parse_eh_frame(struct mi_process proc)
+eh_frame_find_fde(struct mi_process proc, u64 pc)
 {
     struct elf_section_table_entry_x64 eh_frame = get_section_entry(proc.elf, ".eh_frame");
     struct dwarf_cie last_cie = { 0 };
+    struct dwarf_fde last_fde = { 0 };
+    int is_cie = 0;
     
     u64 read = 0;
     
     for (;;) {
-        u64 size = read_one_call_frame_record(proc, &last_cie, proc.elf + eh_frame.offset_in_file + read);
+        u64 size = read_one_call_frame_record(proc, &last_cie, &last_fde, &is_cie, proc.elf + eh_frame.offset_in_file + read);
+        
+        if (!is_cie) {
+            if (last_fde.low_pc <= pc && pc < last_fde.high_pc) {
+                return(last_fde);
+            }
+        }
+        
         read += size;
         if (read >= eh_frame.size) {
             break;
         }
     }
-}
     
-static struct dwarf_fde *
+    last_fde.length = 0;
-eh_frame_find_fde(struct mi_process proc, u64 pc)
-{
     
+    return(last_fde);
 }
 
 static struct dwarf_regset
-eh_frame_init_registers(struct mi_process proc, struct dwarf_cie *cie)
+eh_frame_init_registers(struct mi_process proc, struct mi_registers regs, struct dwarf_cie cie)
 {
-    
+    struct dwarf_regset regset = { 0 };
+    
+    regset.system[0]  = regs._sys.rax;
+    regset.system[1]  = regs._sys.rdx;
+    regset.system[2]  = regs._sys.rcx;
+    regset.system[3]  = regs._sys.rbx;
+    regset.system[4]  = regs._sys.rsi;
+    regset.system[5]  = regs._sys.rdi;
+    regset.system[6]  = regs._sys.rbp;
+    regset.system[7]  = regs._sys.rsp;
+    regset.system[8]  = regs._sys.r8;
+    regset.system[9]  = regs._sys.r9;
+    regset.system[10] = regs._sys.r10;
+    regset.system[11] = regs._sys.r11;
+    regset.system[12] = regs._sys.r12;
+    regset.system[13] = regs._sys.r13;
+    regset.system[14] = regs._sys.r14;
+    regset.system[15] = regs._sys.r15;
+    
+    iterate_call_frame_instructions(&cie, cie.instructions, cie.instructions_length, &regs, &regset, 0);
+    
+    return(regset);
 }
 
 static struct dwarf_regset
-eh_frame_find_pc(struct mi_process proc, struct dwarf_fde *fde, struct dwarf_regset regs, u64 pc)
+eh_frame_find_pc(struct mi_process proc, struct dwarf_fde fde, struct mi_registers regs, struct dwarf_regset regset, u64 pc)
-{
-    
-}
-
-static u64
-eh_frame_compute_cfa(struct mi_process proc, struct dwarf_regset regs)
 {
+    regset.loc = fde.low_pc;
+    iterate_call_frame_instructions(&fde.cie, fde.instructions, fde.instructions_length, &regs, &regset, pc);
+    return(regset);
 }

elf_dwarf.h

@@ -649,7 +649,9 @@ struct dwarf_cie {
     u32 return_address_register;
     u32 augmentation_data_length;
     u8 *augmentation_data;
+    
     u8 *instructions;
+    u32 instructions_length;
     
     int has_z;
     enum dwarf_cie_pointer_format pointer_format;
@@ -660,14 +662,41 @@ struct dwarf_cie {
 struct dwarf_fde {
     u32 length;
     u64 optional_length;
-    struct dwarf_cie *cie;
+    struct dwarf_cie cie;
     u64 low_pc;
     u64 high_pc;
     u32 augmentation_data_length;
     u8 *augmentation_data;
+    
     u8 *instructions;
+    u32 instructions_length;
+};
+
+enum dwarf_regset_register {
+    RAX = 0,
+    RDX = 1,
+    RCX = 2,
+    RBX = 3,
+    RSI = 4,
+    RDI = 5,
+    RBP = 6,
+    RSP = 7,
+    R8 = 8,
+    R9 = 9,
+    R10 = 10,
+    R11 = 11,
+    R12 = 12,
+    R13 = 13,
+    R14 = 14,
+    R15 = 15,
+    RA = 16
 };
 
 struct dwarf_regset {
-    s64 cfa;
+    u64 loc;
+    u64 cfa;
+    u64 system[17];
+    
+    enum dwarf_regset_register cfa_register;
+    u32 cfa_offset;
 };

main.c

@@ -22,7 +22,6 @@ main(int argc, char *argv[])
     char *last_command = malloc(max_command_length + 1);
     
     parse_debug_info(process.elf, &process.debug);
-    parse_eh_frame(process);
     
     process.base_address = 0x555555554000UL; // get_executable_base_address(file, proc.pid);
     process.main_address = get_address_of_subroutine(process, "main");
@@ -35,6 +34,15 @@ main(int argc, char *argv[])
     
     parse_debug_line(process.elf, &process.debug);
     
+#if 0
+    command_start(process);
+    command_step(process);
+    command_step(process);
+    command_print(process, "test", 4);
+    return(0);
+#endif
+    
+    
     while ((command_length = getline(&command, &max_command_length, stdin))) {
         if (command_length == 1) {
             memset(command, 0, max_command_length);

res/004-scoped-variables.c

@@ -31,7 +31,7 @@ f1()
 int
 main(int argc, char **argv)
 {
-	int a_main = 0;
+	int a_main = 123123;
 	f1();
 	f3();
 	return(0);

util.c

@@ -298,17 +298,53 @@ get_function_around_pc(struct mi_process proc, u64 pc)
     return(0);
 }
 
+static struct mi_variable *
+get_variable(struct mi_process proc, char *name, int length, u64 pc)
+{
+    struct mi_debuginfo debug = proc.debug;
+    
+    for (int c = 0; c < debug.cu_count; ++c) {
+        struct mi_compunit *unit = debug.compilation_units + c;
+        
+        if (unit->low_pc <= pc && pc < unit->high_pc) {
+            
+            for (int f = 0; f < unit->functions_count; ++f) {
+                struct mi_function *func = debug.functions + unit->functions_from + f;
+                
+                if (func->low_pc <= pc && pc < func->high_pc) {
+                    
+                    for (int v = 0; v < func->variables_count; ++v) {
+                        struct mi_variable *variable = debug.variables + func->variables_from + v;
+                        if (0 == strncmp(name, variable->name, length)) {
+                            return(variable);
+                        }
+                    }
+                    
+                    return(0);
+                }
+                
+            }
+            
+            break;
+        }
+        
+    }
+    
+    return(0);
+}
+
 static u64
 get_cfa_at_pc(struct mi_process proc, u64 pc)
 {
-    struct dwarf_fde *fde = eh_frame_find_fde(proc, pc);
+    struct dwarf_fde fde = eh_frame_find_fde(proc, pc);
-    if (!fde) {
+    if (!fde.length) {
         DIE("could not find FDE for pc!\n");
     }
     
-    struct dwarf_regset regs = eh_frame_init_registers(proc, fde->cie);
+    struct mi_registers regs = get_process_registers(proc);
-    regs = eh_frame_find_pc(proc, fde, regs, pc);
+    struct dwarf_regset regset = eh_frame_init_registers(proc, regs, fde.cie);
-    u64 cfa = eh_frame_compute_cfa(proc, regs);
+    
+    regset = eh_frame_find_pc(proc, fde, regs, regset, pc);
     
-    return(cfa);
+    return(regset.cfa);
 }