Add two hooks to signal module load and module unload to MD code.

The primary reason for this is to allow MD code to process machine
specific attributes, segments or sections in the ELF file and
update machine specific state accordingly. An immediate use of this
is in the ia64 port where unwind information is updated to allow
debugging and tracing in/across modules. Note that this commit
does not add the functionality to the ia64 port. See revision 1.9
of ia64/ia64/elf_machdep.c.

Validated on: alpha, i386, ia64

sys/alpha/alpha/elf_machdep.c

@@ -172,3 +172,17 @@ elf_reloc(linker_file_t lf, const void *data, int type)
 	}
 	return(0);
 }
+
+int
+elf_cpu_load_file(linker_file_t lf __unused)
+{
+
+	return (0);
+}
+
+int
+elf_cpu_unload_file(linker_file_t lf __unused)
+{
+
+	return (0);
+}

sys/amd64/amd64/elf_machdep.c

@@ -169,3 +169,17 @@ elf_reloc(linker_file_t lf, const void *data, int type)
 	}
 	return(0);
 }
+
+int
+elf_cpu_load_file(linker_file_t lf __unused)
+{
+
+	return (0);
+}
+
+int
+elf_cpu_unload_file(linker_file_t lf __unused)
+{
+
+	return (0);
+}

sys/i386/i386/elf_machdep.c

@@ -169,3 +169,17 @@ elf_reloc(linker_file_t lf, const void *data, int type)
 	}
 	return(0);
 }
+
+int
+elf_cpu_load_file(linker_file_t lf __unused)
+{
+
+	return (0);
+}
+
+int
+elf_cpu_unload_file(linker_file_t lf __unused)
+{
+
+	return (0);
+}

sys/ia64/ia64/elf_machdep.c

@@ -46,6 +46,7 @@
 
 #include <machine/elf.h>
 #include <machine/md_var.h>
+#include <machine/unwind.h>
 
 struct sysentvec elf64_freebsd_sysvec = {
 	SYS_MAXSYSCALL,
@@ -215,3 +216,17 @@ elf_reloc(linker_file_t lf, const void *data, int type)
 
 	return (0);
 }
+
+int
+elf_cpu_load_file(linker_file_t lf __unused)
+{
+
+	return (0);
+}
+
+int
+elf_cpu_unload_file(linker_file_t lf __unused)
+{
+
+	return (0);
+}

sys/kern/link_elf.c

@@ -222,6 +222,12 @@ link_elf_link_common_finish(linker_file_t lf)
     elf_file_t ef = (elf_file_t)lf;
     char *newfilename;
 #endif
+    int error;
+
+    /* Notify MD code that a module is being loaded. */
+    error = elf_cpu_load_file(lf);
+    if (error)
+	return (error);
 
 #ifdef DDB
     GDB_STATE(RT_ADD);
@@ -838,6 +844,9 @@ link_elf_unload_file(linker_file_t file)
     }
 #endif
 
+    /* Notify MD code that a module is being unloaded. */
+    elf_cpu_unload_file(file);
+
     if (ef->preloaded) {
 	link_elf_unload_preload(file);
 	return;

sys/kern/link_elf_obj.c

@@ -222,6 +222,12 @@ link_elf_link_common_finish(linker_file_t lf)
     elf_file_t ef = (elf_file_t)lf;
     char *newfilename;
 #endif
+    int error;
+
+    /* Notify MD code that a module is being loaded. */
+    error = elf_cpu_load_file(lf);
+    if (error)
+	return (error);
 
 #ifdef DDB
     GDB_STATE(RT_ADD);
@@ -838,6 +844,9 @@ link_elf_unload_file(linker_file_t file)
     }
 #endif
 
+    /* Notify MD code that a module is being unloaded. */
+    elf_cpu_unload_file(file);
+
     if (ef->preloaded) {
 	link_elf_unload_preload(file);
 	return;

sys/powerpc/powerpc/elf_machdep.c

@@ -163,3 +163,17 @@ elf_reloc(linker_file_t lf, const void *data, int type)
 	}
 	return(0);
 }
+
+int
+elf_cpu_load_file(linker_file_t lf __unused)
+{
+
+	return (0);
+}
+
+int
+elf_cpu_unload_file(linker_file_t lf __unused)
+{
+
+	return (0);
+}

sys/sparc64/sparc64/elf_machdep.c

@@ -312,3 +312,17 @@ elf_reloc(linker_file_t lf, const void *data, int type)
 
 	return (0);
 }
+
+int
+elf_cpu_load_file(linker_file_t lf __unused)
+{
+
+	return (0);
+}
+
+int
+elf_cpu_unload_file(linker_file_t lf __unused)
+{
+
+	return (0);
+}

sys/sys/linker.h

@@ -233,6 +233,9 @@ Elf_Addr elf_lookup(linker_file_t, Elf_Word, int);
 const Elf_Sym *elf_get_sym(linker_file_t _lf, Elf_Word _symidx);
 const char *elf_get_symname(linker_file_t _lf, Elf_Word _symidx);
 
+int elf_cpu_load_file(linker_file_t);
+int elf_cpu_unload_file(linker_file_t);
+
 /* values for type */
 #define ELF_RELOC_REL	1
 #define ELF_RELOC_RELA	2