update mld commentsHEADmain

2 files changed, 47 insertions, 11 deletions

diff --git a/mld/link.c b/mld/link.c
index dd3fcc6..2abc990 100644
--- a/mld/link.c
+++ b/mld/link.c
@@ -47,6 +47,7 @@ static int load_objects(struct linker *linker)
 skip_obj:
 	}
 
+	// load runtime object if not set to be freestanding
 	if (linker->args->freestanding == false) {
 		#define _STR(x) _STR2(x)
 		#define _STR2(x) #x
@@ -69,6 +70,9 @@ skip_obj:
  */
 static int relocate_segment_name(struct linker *linker, const char *name)
 {
+	// find each segment with the provided segment name,
+	// and then relocate them
+
 	for (size_t i = 0; i < linker->obj_len; i++) {
 		struct object *obj = &linker->objects[i];
 		for (size_t j = 0; j < obj->segment_len; j++) {
@@ -122,6 +126,7 @@ static int relocate_segment_name(struct linker *linker, const char *name)
 				M_SUCCESS) {
 				if (segtab_ent_push(ent, seg))
 					return M_ERROR;
+			// otherwise create a new segment table entry
 			} else {
 				// update vaddr to be page aligned
 				uint32_t m = seg->new_vaddr % SEC_ALIGN;
@@ -134,7 +139,7 @@ static int relocate_segment_name(struct linker *linker, const char *name)
 						linker->data_vaddr += add;
 				}
 
-                                // else create a new segment
+                                // create a new segment
 				if (segtab_push(&linker->segments, NULL, seg))
 					return M_ERROR;
 			}
@@ -146,6 +151,9 @@ static int relocate_segment_name(struct linker *linker, const char *name)
 
 static int relocate_segments(struct linker *linker)
 {
+	// for each object, find each different
+	// unique segment name
+
 	for (size_t i = 0; i < linker->obj_len; i++) {
 		struct object *obj = &linker->objects[i];
 		for (size_t j = 0; j < obj->segment_len; j++) {
@@ -154,6 +162,9 @@ static int relocate_segments(struct linker *linker)
 			// check if the segment has already been relocated
 			if (seg->new_vaddr != 0)
 				continue;
+
+			// relocate each segment with that segment
+			// name
 			if(relocate_segment_name(linker, seg->name))
 				return M_ERROR;
 		}
@@ -165,6 +176,14 @@ static int relocate_segments(struct linker *linker)
 static int relocate_symbol(struct linker *linker, struct object *obj,
 			   struct symbol_table *symtab, const Elf32_Sym *sym)
 {
+	// given the symbol and the object its in
+	// 1. make sure the symbol is valid
+	// 2. get the segment in the object that the symbol is in
+	// 3. get tthe segment table entry that the segment is also
+	//    in. This allows us to get the offset into the segment_table
+	// 4. the new shndx is the offset + 1 (since segments start at
+	//    shndx 1
+
 	size_t shndx = B16(sym->st_shndx);
 	if (shndx == 0 || shndx == SHN_ABS)
 		return M_SUCCESS; // ignore this symbol
@@ -177,11 +196,15 @@ static int relocate_symbol(struct linker *linker, struct object *obj,
 		return M_ERROR;
 	}
 
+	// make sure the symbol name is
+	// in bounds
 	if (B32(sym->st_name) >= symtab->strtab->len) {
 		ERROR("symbol name out of bounds");
 		return M_ERROR;
 	}
 
+	// find the segment that this symbol
+	// is contained in
 	struct segment *sec = NULL;
 	for (size_t i = 0; i < obj->phdr_len; i++) {
 		if (obj->phdr_to_shdr_mapping[i] == shndx) {
@@ -245,13 +268,17 @@ static int relocate_symbol(struct linker *linker, struct object *obj,
 
 static int relocate_symbols(struct linker *linker)
 {
+	// relocate in each object
 	for (size_t i = 0; i < linker->obj_len; i++) {
 		struct object *obj = &linker->objects[i];
+		// look though each shdr entry and find
+		// any symbol tables
 		for (size_t j = 0; j < obj->shdr_len; j++) {
 			struct symbol_table *symtab = &obj->symtabs[j];
 			if (symtab->len < 1)
 				continue;
 
+			// for each symbol in the table, relocate it
 			for (size_t k = 0; k < symtab->len; k++) {
 				const Elf32_Sym *sym = &symtab->syms[k];
 				if (relocate_symbol(linker, obj, symtab, sym))
diff --git a/mld/link.h b/mld/link.h
index 3c9ca42..ef3a4af 100644
--- a/mld/link.h
+++ b/mld/link.h
@@ -92,11 +92,6 @@ struct symbol_table {
 	struct symbol_table_mapping *map;
 };
 
-///
-/// symbol table map
-/// (metadata for each symbol)
-///
-
 int symtab_init(struct symbol_table *symtab);
 void symtab_free(struct symbol_table *symtab);
 
@@ -104,6 +99,13 @@ int symtab_push(struct symbol_table *symtab, const Elf32_Sym *sym);
 int symtab_get(struct symbol_table *symtab, Elf32_Sym **sym, const char *name,
 	       int32_t obj_idx);
 
+///
+/// symbol table map
+/// (metadata for each symbol)
+/// stores each object that a symbol
+/// is in
+///
+
 struct symbol_table_mapping {
 	uint32_t len;
 	uint32_t size;
@@ -163,6 +165,9 @@ int segment_load(struct object *object, struct segment *segment, size_t index);
 
 ///
 /// segment table
+/// holds each segment that
+/// share the same name
+/// (i.e. all .text segments)
 ///
 
 struct segment_table_entry {
@@ -172,6 +177,7 @@ struct segment_table_entry {
 	uint32_t off;
 	uint32_t vaddr;
 	// weak segment pointers. we do not own these!!!
+	// (but we own the array)
 	struct segment **parts;
 };
 
@@ -181,9 +187,10 @@ void segtab_ent_free(struct segment_table_entry *ent);
 int segtab_ent_push(struct segment_table_entry *ent, struct segment *seg);
 uint32_t segtab_ent_size(struct segment_table_entry *ent);
 
-// holds each segment by name
-// and all the segment parts from each of the
-// object files
+///
+/// segment table
+/// holds each segment table entry by name
+///
 struct segment_table {
 	uint32_t len;
 	uint32_t size;
@@ -215,14 +222,16 @@ struct object {
 	Elf32_Ehdr *ehdr;
 
 	// section header table
-	Elf32_Shdr *shdr;
+	Elf32_Shdr *shdr; // weak
 	size_t shdr_len;
 
 	// program table
-	Elf32_Phdr *phdr;
+	Elf32_Phdr *phdr; // owned
 	size_t phdr_len;
 
 	// phdr <=> shdr mappings
+	// need a way to find any assoiciated
+	// phdr with a shdr, and also reverse
 	uint32_t *phdr_to_shdr_mapping;
 
 	// object meta