With this commit, I hereby pronounce gensetdefs past its use-by date.

Replace the a.out emulation of 'struct linker_set' with something
a little more flexible.  <sys/linker_set.h> now provides macros for
accessing elements and completely hides the implementation.

The linker_set.h macros have been on the back burner in various
forms since 1998 and has ideas and code from Mike Smith (SET_FOREACH()),
John Polstra (ELF clue) and myself (cleaned up API and the conversion
of the rest of the kernel to use it).

The macros declare a strongly typed set.  They return elements with the
type that you declare the set with, rather than a generic void *.

For ELF, we use the magic ld symbols (__start_<setname> and
__stop_<setname>).  Thanks to Richard Henderson <rth@redhat.com> for the
trick about how to force ld to provide them for kld's.

For a.out, we use the old linker_set struct.

NOTE: the item lists are no longer null terminated.  This is why
the code impact is high in certain areas.

The runtime linker has a new method to find the linker set
boundaries depending on which backend format is in use.

linker sets are still module/kld unfriendly and should never be used
for anything that may be modular one day.

Reviewed by:	eivind

1 files changed, 61 insertions, 0 deletions

diff --git a/sys/kern/link_elf_obj.c b/sys/kern/link_elf_obj.c
index 32f45ce..da7462a 100644
--- a/sys/kern/link_elf_obj.c
+++ b/sys/kern/link_elf_obj.c
@@ -108,6 +108,8 @@ static int	link_elf_search_symbol(linker_file_t, caddr_t value,
 
 static void	link_elf_unload_file(linker_file_t);
 static void	link_elf_unload_preload(linker_file_t);
+static int	link_elf_lookup_set(linker_file_t, const char *,
+				    void ***, void ***, int *);
 
 static kobj_method_t link_elf_methods[] = {
     KOBJMETHOD(linker_lookup_symbol,	link_elf_lookup_symbol),
@@ -117,6 +119,7 @@ static kobj_method_t link_elf_methods[] = {
     KOBJMETHOD(linker_load_file,	link_elf_load_file),
     KOBJMETHOD(linker_link_preload,	link_elf_link_preload),
     KOBJMETHOD(linker_link_preload_finish, link_elf_link_preload_finish),
+    KOBJMETHOD(linker_lookup_set,	link_elf_lookup_set),
     { 0, 0 }
 };
 
@@ -1075,3 +1078,61 @@ link_elf_search_symbol(linker_file_t lf, caddr_t value,
 
 	return 0;
 }
+
+/*
+ * Look up a linker set on an ELF system.
+ */
+static int
+link_elf_lookup_set(linker_file_t lf, const char *name,
+		    void ***startp, void ***stopp, int *countp)
+{
+	c_linker_sym_t sym;
+	linker_symval_t symval;
+	char *setsym;
+	void **start, **stop;
+	int len, error = 0, count;
+
+	len = strlen(name) + sizeof("__start_set_"); /* sizeof includes \0 */
+	setsym = malloc(len, M_LINKER, M_WAITOK);
+	if (setsym == NULL)
+		return ENOMEM;
+
+	/* get address of first entry */
+	snprintf(setsym, len, "%s%s", "__start_set_", name);
+	error = link_elf_lookup_symbol(lf, setsym, &sym);
+	if (error)
+		goto out;
+	link_elf_symbol_values(lf, sym, &symval);
+	if (symval.value == 0) {
+		error = ESRCH;
+		goto out;
+	}
+	start = (void **)symval.value;
+
+	/* get address of last entry */
+	snprintf(setsym, len, "%s%s", "__stop_set_", name);
+	error = link_elf_lookup_symbol(lf, setsym, &sym);
+	if (error)
+		goto out;
+	link_elf_symbol_values(lf, sym, &symval);
+	if (symval.value == 0) {
+		error = ESRCH;
+		goto out;
+	}
+	stop = (void **)symval.value;
+
+	/* and the number of entries */
+	count = stop - start;
+
+	/* and copy out */
+	if (startp)
+		*startp = start;
+	if (stopp)
+		*stopp = stop;
+	if (countp)
+		*countp = count;
+
+out:
+	free(setsym, M_LINKER);
+	return error;
+}