objtool: Constify 'struct elf *' parameters

In preparation to parallelize certain parts of objtool, map out which uses
of various data structures are read-only vs. read-write.

As a first step constify 'struct elf' pointer passing, most of the secondary
uses of it in find_symbol_*() methods are read-only.

Also, while at it, better group the 'struct elf' handling methods in elf.h.
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sami Tolvanen <samitolvanen@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20200422103205.61900-2-mingo@kernel.org

tools/objtool/elf.c

@@ -127,7 +127,7 @@ static int symbol_by_offset(const void *key, const struct rb_node *node)
 	return 0;
 }
 
-struct section *find_section_by_name(struct elf *elf, const char *name)
+struct section *find_section_by_name(const struct elf *elf, const char *name)
 {
 	struct section *sec;
 
@@ -217,7 +217,7 @@ struct symbol *find_func_containing(struct section *sec, unsigned long offset)
 	return NULL;
 }
 
-struct symbol *find_symbol_by_name(struct elf *elf, const char *name)
+struct symbol *find_symbol_by_name(const struct elf *elf, const char *name)
 {
 	struct symbol *sym;
 
@@ -228,7 +228,7 @@ struct symbol *find_symbol_by_name(struct elf *elf, const char *name)
 	return NULL;
 }
 
-struct rela *find_rela_by_dest_range(struct elf *elf, struct section *sec,
+struct rela *find_rela_by_dest_range(const struct elf *elf, struct section *sec,
 				     unsigned long offset, unsigned int len)
 {
 	struct rela *rela, *r = NULL;
@@ -257,7 +257,7 @@ struct rela *find_rela_by_dest_range(struct elf *elf, struct section *sec,
 	return NULL;
 }
 
-struct rela *find_rela_by_dest(struct elf *elf, struct section *sec, unsigned long offset)
+struct rela *find_rela_by_dest(const struct elf *elf, struct section *sec, unsigned long offset)
 {
 	return find_rela_by_dest_range(elf, sec, offset, 1);
 }
@@ -769,7 +769,7 @@ int elf_rebuild_rela_section(struct section *sec)
 	return 0;
 }
 
-int elf_write(struct elf *elf)
+int elf_write(const struct elf *elf)
 {
 	struct section *sec;
 	Elf_Scn *s;

tools/objtool/elf.h

@@ -114,22 +114,22 @@ static inline u32 rela_hash(struct rela *rela)
 }
 
 struct elf *elf_read(const char *name, int flags);
-struct section *find_section_by_name(struct elf *elf, const char *name);
+struct section *elf_create_section(struct elf *elf, const char *name, size_t entsize, int nr);
+struct section *elf_create_rela_section(struct elf *elf, struct section *base);
+void elf_add_rela(struct elf *elf, struct rela *rela);
+int elf_write(const struct elf *elf);
+void elf_close(struct elf *elf);
+
+struct section *find_section_by_name(const struct elf *elf, const char *name);
 struct symbol *find_func_by_offset(struct section *sec, unsigned long offset);
 struct symbol *find_symbol_by_offset(struct section *sec, unsigned long offset);
-struct symbol *find_symbol_by_name(struct elf *elf, const char *name);
+struct symbol *find_symbol_by_name(const struct elf *elf, const char *name);
 struct symbol *find_symbol_containing(struct section *sec, unsigned long offset);
-struct rela *find_rela_by_dest(struct elf *elf, struct section *sec, unsigned long offset);
-struct rela *find_rela_by_dest_range(struct elf *elf, struct section *sec,
+struct rela *find_rela_by_dest(const struct elf *elf, struct section *sec, unsigned long offset);
+struct rela *find_rela_by_dest_range(const struct elf *elf, struct section *sec,
 				     unsigned long offset, unsigned int len);
 struct symbol *find_func_containing(struct section *sec, unsigned long offset);
-struct section *elf_create_section(struct elf *elf, const char *name, size_t
-				   entsize, int nr);
-struct section *elf_create_rela_section(struct elf *elf, struct section *base);
 int elf_rebuild_rela_section(struct section *sec);
-int elf_write(struct elf *elf);
-void elf_close(struct elf *elf);
-void elf_add_rela(struct elf *elf, struct rela *rela);
 
 #define for_each_sec(file, sec)						\
 	list_for_each_entry(sec, &file->elf->sections, list)