[PATCH v2 03/19] gendwarfksyms: Add address matching

[Sami Tolvanen <samitolvanen@google.com>]

The compiler may choose not to emit type information in DWARF for all
aliases, but it's possible for each alias to be exported separately.
To ensure we find type information for the aliases as well, read
{section, address} tuples from the symbol table and match symbols also
by address.

Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
---
 scripts/gendwarfksyms/gendwarfksyms.c |   2 +
 scripts/gendwarfksyms/gendwarfksyms.h |   7 ++
 scripts/gendwarfksyms/symbols.c       | 161 +++++++++++++++++++++++++-
 3 files changed, 165 insertions(+), 5 deletions(-)

diff --git a/scripts/gendwarfksyms/gendwarfksyms.c b/scripts/gendwarfksyms/gendwarfksyms.c
index d209b237766b..e2f8ee5a4bf3 100644
--- a/scripts/gendwarfksyms/gendwarfksyms.c
+++ b/scripts/gendwarfksyms/gendwarfksyms.c
@@ -118,6 +118,8 @@ int main(int argc, const char **argv)
 			return -1;
 		}
 
+		check(symbol_read_symtab(fd));
+
 		dwfl = dwfl_begin(&callbacks);
 		if (!dwfl) {
 			error("dwfl_begin failed for '%s': %s", object_files[n],
diff --git a/scripts/gendwarfksyms/gendwarfksyms.h b/scripts/gendwarfksyms/gendwarfksyms.h
index 03f3e408a839..cb9106dfddb9 100644
--- a/scripts/gendwarfksyms/gendwarfksyms.h
+++ b/scripts/gendwarfksyms/gendwarfksyms.h
@@ -61,6 +61,10 @@ extern bool debug;
 /*
  * symbols.c
  */
+struct symbol_addr {
+	uint32_t section;
+	Elf64_Addr address;
+};
 
 static inline u32 name_hash(const char *name)
 {
@@ -69,10 +73,13 @@ static inline u32 name_hash(const char *name)
 
 struct symbol {
 	const char *name;
+	struct symbol_addr addr;
+	struct hlist_node addr_hash;
 	struct hlist_node name_hash;
 };
 
 extern int symbol_read_exports(FILE *file);
+extern int symbol_read_symtab(int fd);
 extern struct symbol *symbol_get(const char *name);
 
 /*
diff --git a/scripts/gendwarfksyms/symbols.c b/scripts/gendwarfksyms/symbols.c
index 673ad9cf9e77..f96acb941196 100644
--- a/scripts/gendwarfksyms/symbols.c
+++ b/scripts/gendwarfksyms/symbols.c
@@ -6,11 +6,43 @@
 #include "gendwarfksyms.h"
 
 #define SYMBOL_HASH_BITS 15
+
+/* struct symbol_addr -> struct symbol */
+static DEFINE_HASHTABLE(symbol_addrs, SYMBOL_HASH_BITS);
+/* name -> struct symbol */
 static DEFINE_HASHTABLE(symbol_names, SYMBOL_HASH_BITS);
 
+static inline u32 symbol_addr_hash(const struct symbol_addr *addr)
+{
+	return jhash(addr, sizeof(struct symbol_addr), 0);
+}
+
 typedef int (*symbol_callback_t)(struct symbol *, void *arg);
 
-static int for_each(const char *name, symbol_callback_t func, void *data)
+static int __for_each_addr(struct symbol *sym, symbol_callback_t func,
+			   void *data)
+{
+	struct hlist_node *tmp;
+	struct symbol *match = NULL;
+	int processed = 0;
+
+	hash_for_each_possible_safe(symbol_addrs, match, tmp, addr_hash,
+				    symbol_addr_hash(&sym->addr)) {
+		if (match == sym)
+			continue; /* Already processed */
+
+		if (match->addr.section == sym->addr.section &&
+		    match->addr.address == sym->addr.address) {
+			check(func(match, data));
+			++processed;
+		}
+	}
+
+	return processed;
+}
+
+static int for_each(const char *name, bool name_only, symbol_callback_t func,
+		    void *data)
 {
 	struct hlist_node *tmp;
 	struct symbol *match;
@@ -23,9 +55,13 @@ static int for_each(const char *name, symbol_callback_t func, void *data)
 		if (strcmp(match->name, name))
 			continue;
 
+		/* Call func for the match, and all address matches */
 		if (func)
 			check(func(match, data));
 
+		if (!name_only && match->addr.section != SHN_UNDEF)
+			return checkp(__for_each_addr(match, func, data)) + 1;
+
 		return 1;
 	}
 
@@ -34,7 +70,7 @@ static int for_each(const char *name, symbol_callback_t func, void *data)
 
 static bool is_exported(const char *name)
 {
-	return checkp(for_each(name, NULL, NULL)) > 0;
+	return checkp(for_each(name, true, NULL, NULL)) > 0;
 }
 
 int symbol_read_exports(FILE *file)
@@ -57,13 +93,14 @@ int symbol_read_exports(FILE *file)
 		if (is_exported(name))
 			continue; /* Ignore duplicates */
 
-		sym = malloc(sizeof(struct symbol));
+		sym = calloc(1, sizeof(struct symbol));
 		if (!sym) {
-			error("malloc failed");
+			error("calloc failed");
 			return -1;
 		}
 
 		sym->name = name;
+		sym->addr.section = SHN_UNDEF;
 		name = NULL;
 
 		hash_add(symbol_names, &sym->name_hash, name_hash(sym->name));
@@ -91,6 +128,120 @@ struct symbol *symbol_get(const char *name)
 {
 	struct symbol *sym = NULL;
 
-	for_each(name, get_symbol, &sym);
+	for_each(name, false, get_symbol, &sym);
 	return sym;
 }
+
+typedef int (*elf_symbol_callback_t)(const char *name, GElf_Sym *sym,
+				     Elf32_Word xndx, void *arg);
+
+static int elf_for_each_symbol(int fd, elf_symbol_callback_t func, void *arg)
+{
+	size_t sym_size;
+	GElf_Shdr shdr_mem;
+	GElf_Shdr *shdr;
+	Elf_Data *xndx_data = NULL;
+	Elf_Scn *scn;
+	Elf *elf;
+
+	if (elf_version(EV_CURRENT) != EV_CURRENT) {
+		error("elf_version failed: %s", elf_errmsg(-1));
+		return -1;
+	}
+
+	elf = elf_begin(fd, ELF_C_READ_MMAP, NULL);
+	if (!elf) {
+		error("elf_begin failed: %s", elf_errmsg(-1));
+		return -1;
+	}
+
+	sym_size = gelf_getclass(elf) == ELFCLASS32 ? sizeof(Elf32_Sym) :
+						      sizeof(Elf64_Sym);
+
+	scn = elf_nextscn(elf, NULL);
+
+	while (scn) {
+		shdr = gelf_getshdr(scn, &shdr_mem);
+
+		if (shdr && shdr->sh_type == SHT_SYMTAB_SHNDX) {
+			xndx_data = elf_getdata(scn, NULL);
+			break;
+		}
+
+		scn = elf_nextscn(elf, scn);
+	}
+
+	scn = elf_nextscn(elf, NULL);
+
+	while (scn) {
+		shdr = gelf_getshdr(scn, &shdr_mem);
+
+		if (shdr && shdr->sh_type == SHT_SYMTAB) {
+			Elf_Data *data = elf_getdata(scn, NULL);
+			unsigned int nsyms = data->d_size / sym_size;
+			unsigned int n;
+
+			for (n = 0; n < nsyms; ++n) {
+				const char *name = NULL;
+				Elf32_Word xndx = 0;
+				GElf_Sym sym_mem;
+				GElf_Sym *sym;
+
+				sym = gelf_getsymshndx(data, xndx_data, n,
+						       &sym_mem, &xndx);
+
+				if (sym->st_shndx != SHN_XINDEX)
+					xndx = sym->st_shndx;
+
+				name = elf_strptr(elf, shdr->sh_link,
+						  sym->st_name);
+
+				/* Skip empty symbol names */
+				if (name && *name &&
+				    checkp(func(name, sym, xndx, arg)) > 0)
+					break;
+			}
+		}
+
+		scn = elf_nextscn(elf, scn);
+	}
+
+	return check(elf_end(elf));
+}
+
+static int set_symbol_addr(struct symbol *sym, void *arg)
+{
+	struct symbol_addr *addr = arg;
+
+	if (sym->addr.section == SHN_UNDEF) {
+		sym->addr.section = addr->section;
+		sym->addr.address = addr->address;
+		hash_add(symbol_addrs, &sym->addr_hash,
+			 symbol_addr_hash(&sym->addr));
+
+		debug("%s -> { %u, %lx }", sym->name, sym->addr.section,
+		      sym->addr.address);
+	} else {
+		warn("multiple addresses for symbol %s?", sym->name);
+	}
+
+	return 0;
+}
+
+static int process_symbol(const char *name, GElf_Sym *sym, Elf32_Word xndx,
+			  void *arg)
+{
+	struct symbol_addr addr = { .section = xndx, .address = sym->st_value };
+
+	/* Set addresses for exported symbols */
+	if (GELF_ST_BIND(sym->st_info) != STB_LOCAL &&
+	    addr.section != SHN_UNDEF)
+		checkp(for_each(name, true, set_symbol_addr, &addr));
+
+	return 0;
+}
+
+int symbol_read_symtab(int fd)
+{
+	return elf_for_each_symbol(fd, process_symbol, NULL);
+}
-- 
2.46.0.184.g6999bdac58-goog