Add the sysctl "kern.function_list", which currently exports all

function symbols in the kernel in a list of C strings, with an extra
nul-termination at the end.

This sysctl requires addition of a new linker operation.  Now,
linker_file_t's need to respond to "each_function_name" to export
their function symbols.

Note that the sysctl doesn't currently allow distinguishing multiple
symbols with the same name from different modules, but could quite
easily without a change to the linker operation.  This will be a nicety
to have when it can be used.

Obtained from:	NAI Labs CBOSS project
Funded by:	DARPA

sys/kern/kern_linker.c

@@ -1702,3 +1702,34 @@ linker_load_dependancies(linker_file_t lf)
     linker_addmodules(lf, start, stop, 0);
     return error;
 }
+
+static int
+sysctl_kern_function_list_iterate(const char *name, void *opaque)
+{
+	struct sysctl_req *req;
+
+	req = opaque;
+	return (SYSCTL_OUT(req, name, strlen(name) + 1));
+}
+
+/*
+ * Export a nul-separated, double-nul-terminated list of all function names
+ * in the kernel.
+ */
+static int
+sysctl_kern_function_list(SYSCTL_HANDLER_ARGS)
+{
+	linker_file_t lf;
+	int error;
+
+	TAILQ_FOREACH(lf, &linker_files, link) {
+		error = LINKER_EACH_FUNCTION_NAME(lf,
+		    sysctl_kern_function_list_iterate, req);
+		if (error)
+			return (error);
+	}
+	return (SYSCTL_OUT(req, "", 1));
+}
+
+SYSCTL_PROC(_kern, OID_AUTO, function_list, CTLFLAG_RD,
+	NULL, 0, sysctl_kern_function_list, "", "kernel function list");

sys/kern/link_elf.c

@@ -113,6 +113,9 @@ 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 int	link_elf_each_function_name(linker_file_t,
+				int (*)(const char *, void *),
+				void *);
 
 static kobj_method_t link_elf_methods[] = {
     KOBJMETHOD(linker_lookup_symbol,	link_elf_lookup_symbol),
@@ -123,6 +126,7 @@ static kobj_method_t link_elf_methods[] = {
     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),
+    KOBJMETHOD(linker_each_function_name, link_elf_each_function_name),
     { 0, 0 }
 };
 
@@ -1149,3 +1153,22 @@ link_elf_lookup_set(linker_file_t lf, const char *name,
 	free(setsym, M_LINKER);
 	return error;
 }
+
+static int
+link_elf_each_function_name(linker_file_t file,
+  int (*callback)(const char *, void *), void *opaque) {
+    elf_file_t ef = (elf_file_t)file;
+    const Elf_Sym* symp;
+    int i, error;
+	
+    /* Exhaustive search */
+    for (i = 0, symp = ef->ddbsymtab; i < ef->ddbsymcnt; i++, symp++) {
+	if (symp->st_value != 0 &&
+	    ELF_ST_TYPE(symp->st_info) == STT_FUNC) {
+		error = callback(ef->ddbstrtab + symp->st_name, opaque);
+		if (error)
+		    return (error);
+	}
+    }
+    return (0);
+}

sys/kern/link_elf_obj.c

@@ -113,6 +113,9 @@ 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 int	link_elf_each_function_name(linker_file_t,
+				int (*)(const char *, void *),
+				void *);
 
 static kobj_method_t link_elf_methods[] = {
     KOBJMETHOD(linker_lookup_symbol,	link_elf_lookup_symbol),
@@ -123,6 +126,7 @@ static kobj_method_t link_elf_methods[] = {
     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),
+    KOBJMETHOD(linker_each_function_name, link_elf_each_function_name),
     { 0, 0 }
 };
 
@@ -1149,3 +1153,22 @@ link_elf_lookup_set(linker_file_t lf, const char *name,
 	free(setsym, M_LINKER);
 	return error;
 }
+
+static int
+link_elf_each_function_name(linker_file_t file,
+  int (*callback)(const char *, void *), void *opaque) {
+    elf_file_t ef = (elf_file_t)file;
+    const Elf_Sym* symp;
+    int i, error;
+	
+    /* Exhaustive search */
+    for (i = 0, symp = ef->ddbsymtab; i < ef->ddbsymcnt; i++, symp++) {
+	if (symp->st_value != 0 &&
+	    ELF_ST_TYPE(symp->st_info) == STT_FUNC) {
+		error = callback(ef->ddbstrtab + symp->st_name, opaque);
+		if (error)
+		    return (error);
+	}
+    }
+    return (0);
+}

sys/kern/linker_if.m

@@ -53,6 +53,16 @@ METHOD int search_symbol {
     long*		diffp;
 };
 
+#
+# Call the callback with each specified function defined in the file.
+# Stop and return the error if the callback returns an error.
+#
+METHOD int each_function_name {
+	linker_file_t	file;
+	linker_function_name_callback_t	callback;
+	void*		opaque;
+};
+
 #
 # Search for a linker set in a file.  Return a pointer to the first
 # entry (which is itself a pointer), and the number of entries.

sys/sys/linker.h

@@ -46,6 +46,7 @@ typedef TAILQ_HEAD(, linker_file) linker_file_list_t;
 
 typedef caddr_t linker_sym_t;		/* opaque symbol */
 typedef c_caddr_t c_linker_sym_t;	/* const opaque symbol */
+typedef int (*linker_function_name_callback_t)(const char *, void *);
 
 /*
  * expanded out linker_sym_t