From a506edf4f27f422452213f730211dd6d74409e17 Mon Sep 17 00:00:00 2001
From: "A.Olokhtonov" <a.olokhtonov@norsi-trans.ru>
Date: Sat, 17 Jul 2021 14:15:29 +0300
Subject: [PATCH] Parse and use the directory table from .debug_line

---
 common.h | 11 +++++++++--
 dwarf.c  | 26 +++++++++++++++++++++-----
 main.c   | 10 ++++++----
 util.c   | 13 +++++++------
 4 files changed, 43 insertions(+), 17 deletions(-)

diff --git a/common.h b/common.h
index 1ebf049..7f78f4a 100644
--- a/common.h
+++ b/common.h
@@ -58,6 +58,12 @@ struct mi_debuginfo {
     char *comp_dir;
 };
 
+struct mi_sourcefile {
+    char *filename;
+    char *dir;
+    struct mi_buffer file;
+};
+
 struct mi_process {
     pid_t pid;
     
@@ -69,9 +75,10 @@ struct mi_process {
     
     struct mi_debuginfo debug;
     
-    char **source_file_names;
-    struct mi_buffer *source_files;
     int source_file_count;
+    int source_dirs_count;
+    struct mi_sourcefile *source_files;
+    char **source_directories;
 };
 
 struct mi_registers {
diff --git a/dwarf.c b/dwarf.c
index c3d5a91..c47b9a6 100644
--- a/dwarf.c
+++ b/dwarf.c
@@ -314,7 +314,9 @@ parse_debug_info(u8 *file, struct mi_debuginfo *dest)
 }
 
 static void
-parse_debug_line(u8 *file, struct mi_sourcepoint *dest, char **dest_files, int *dest_size, int *dest_files_size)
+parse_debug_line(u8 *file, 
+                 struct mi_sourcepoint *dest, struct mi_sourcefile *dest_files, char **dest_directories,
+                 int *dest_size, int *dest_files_size, int *dest_directories_size)
 {
     u64 dl_offset = get_section_offset(file, ".debug_line");
     
@@ -336,7 +338,12 @@ is followed by a single null byte." */
     u8 *p = file + dl_offset;
     
     while (*p != 0) {
+        if (dest_directories) {
+            dest_directories[ndirs] = (char *) p;
+        }
+        
         ++ndirs;
+        
         while (*p != 0) {
             ++p;
         }
@@ -352,11 +359,9 @@ is followed by a single null byte." */
     while (*p != 0) {
         /* null-terminated string */
         if (dest_files) {
-            dest_files[nfiles] = (char *) p;
+            dest_files[nfiles].filename = (char *) p;
         }
         
-        ++nfiles;
-        
         while (*p != 0) {
             ++p;
         }
@@ -364,12 +369,19 @@ is followed by a single null byte." */
         ++p;
         
         u64 offset = 0;
+        u32 dir_index = 0;
         u32 dummy = 0;
         
-        offset += decode_leb128(p, &dummy);
+        offset += decode_leb128(p, &dir_index);
         offset += decode_leb128(p, &dummy);
         offset += decode_leb128(p, &dummy);
         
+        if (dest_files) {
+            dest_files[nfiles].dir = dest_directories[dir_index - 1];
+        }
+        
+        ++nfiles;
+        
         p += offset;
     }
     
@@ -619,6 +631,10 @@ is followed by a single null byte." */
     if (dest_size) {
         *dest_size = pc_count;
     }
+    
+    if (dest_directories_size) {
+        *dest_directories_size = ndirs;
+    }
 }
 
 static u64
diff --git a/main.c b/main.c
index 6d1985b..1e1c849 100644
--- a/main.c
+++ b/main.c
@@ -4,6 +4,8 @@
 #include "util.c"
 #include "command.c"
 
+// TODO: read the directory table, get full path as comp_dir + directory_table (can be ".." or w/e) + filename
+
 int
 main(int argc, char *argv[])
 {
@@ -31,11 +33,11 @@ main(int argc, char *argv[])
     printf("> ");
     fflush(stdout);
     
-    parse_debug_line(process.elf, 0, 0, &process.debug.sp_count, &process.source_file_count);
+    parse_debug_line(process.elf, 0, 0, 0, &process.debug.sp_count, &process.source_file_count, &process.source_dirs_count);
     process.debug.sp_table = malloc(process.debug.sp_count * sizeof(struct mi_sourcepoint));
-    process.source_file_names = malloc(process.source_file_count * sizeof(char *));
-    process.source_files = malloc(process.source_file_count * sizeof(char *));
-    parse_debug_line(process.elf, process.debug.sp_table, process.source_file_names, 0, 0);
+    process.source_directories = malloc(process.source_dirs_count * sizeof(char *));
+    process.source_files = malloc(process.source_file_count * sizeof(struct mi_sourcefile));
+    parse_debug_line(process.elf, process.debug.sp_table, process.source_files, process.source_directories, 0, 0, 0);
     
     while ((command_length = getline(&command, &max_command_length, stdin))) {
         if (command_length == 1) {
diff --git a/util.c b/util.c
index a2e25bd..690c675 100644
--- a/util.c
+++ b/util.c
@@ -59,18 +59,19 @@ static void
 print_sourcepoint(struct mi_process proc, struct mi_sourcepoint *sp)
 {
     // NOTE: sourcepoint file indices are 1-based
-    if (proc.source_files[sp->file - 1].data == 0) {
-        char *filename = proc.source_file_names[sp->file - 1];
-        char *dir = proc.debug.comp_dir;
+    if (proc.source_files[sp->file - 1].file.data == 0) {
+        char *file_filename = proc.source_files[sp->file - 1].filename;
+        char *file_dirname = proc.source_files[sp->file - 1].dir;
+        char *comp_dir = proc.debug.comp_dir;
         
         char full_path[512] = { 0 };
-        snprintf(full_path, 511, "%s/%s", dir, filename);
+        snprintf(full_path, 511, "%s/%s/%s", comp_dir, file_dirname, file_filename);
         
         struct mi_buffer file = read_file_mmap(full_path);
-        proc.source_files[sp->file - 1] = file;
+        proc.source_files[sp->file - 1].file = file;
     }
     
-    struct mi_buffer file = proc.source_files[sp->file - 1];
+    struct mi_buffer file = proc.source_files[sp->file - 1].file;
     
     char *source = (char *) file.data;
     u64 size = file.size;