riscv: implement kernel ifunc resolution

This completes the set of architectures implementing this feature.

Move the calls to sched_instance_select() and link_elf_ireloc() later in
initriscv(), after identify_cpu(0). There will be more information
available to any resolver functions at this time.

Reviewed by:	imp, kib
MFC after:	2 weeks
Sponsored by:	The FreeBSD Foundation
Differential Revision:	https://reviews.freebsd.org/D55082

sys/conf/kern.pre.mk

@@ -119,10 +119,9 @@ CFLAGS+=	${CONF_CFLAGS}
 LDFLAGS+=	--build-id=sha1
 .endif
 
-.if ${MACHINE_CPUARCH} != "riscv" && \
-    defined(LINKER_FEATURES) && ${LINKER_FEATURES:Mifunc} == "" && \
+.if defined(LINKER_FEATURES) && ${LINKER_FEATURES:Mifunc} == "" && \
     !make(install)
-.error amd64/arm/arm64/i386/ppc* kernel requires linker ifunc support
+.error kernel requires linker ifunc support
 .endif
 .if ${MACHINE_CPUARCH} == "amd64"
 LDFLAGS+=	-z max-page-size=2097152

sys/kern/link_elf.c

@@ -2041,7 +2041,6 @@ link_elf_propagate_vnets(linker_file_t lf)
 }
 #endif
 
-#if !defined(__riscv)
 /*
  * Use this lookup routine when performing relocations early during boot.
  * The generic lookup routine depends on kobj, which is not initialized
@@ -2104,4 +2103,3 @@ link_elf_late_ireloc(void)
 	relocate_file1(ef, elf_lookup_ifunc, elf_reloc_late, true);
 }
 #endif
-#endif

sys/riscv/include/ifunc.h

@@ -30,8 +30,6 @@
 #ifndef __RISCV_IFUNC_H
 #define	__RISCV_IFUNC_H
 
-#define	 __DO_NOT_HAVE_SYS_IFUNCS	1
-
 #define	DEFINE_IFUNC(qual, ret_type, name, args)			\
     static ret_type (*name##_resolver(void))args __used;		\
     qual ret_type name args __attribute__((ifunc(#name "_resolver")));	\

sys/riscv/riscv/elf_machdep.c

@@ -271,10 +271,10 @@ reloctype_to_str(int type)
 }
 
 bool
-elf_is_ifunc_reloc(Elf_Size r_info __unused)
+elf_is_ifunc_reloc(Elf_Size r_info)
 {
 
-	return (false);
+	return (ELF_R_TYPE(r_info) == R_RISCV_IRELATIVE);
 }
 
 /*
@@ -501,7 +501,12 @@ elf_reloc_internal(linker_file_t lf, Elf_Addr relocbase, const void *data,
 			    (local ? 'l' : 'g'), reloctype_to_str(rtype),
 			    before32, *insn32p);
 		break;
-
+	case R_RISCV_IRELATIVE:
+		addr = relocbase + addend;
+		val = ((Elf64_Addr (*)(void))addr)();
+		if (*where != val)
+			*where = val;
+		break;
 	default:
 		printf("kldload: unexpected relocation type %ld, "
 		    "symbol index %ld\n", rtype, symidx);

sys/riscv/riscv/machdep.c

@@ -479,8 +479,6 @@ parse_metadata(void)
 
 	/* Initialize preload_kmdp */
 	preload_initkmdp(true);
-	sched_instance_select();
-	/* link_elf_ireloc(); */
 
 	/* Read the boot metadata */
 	boothowto = MD_FETCH(preload_kmdp, MODINFOMD_HOWTO, int);
@@ -626,6 +624,10 @@ initriscv(struct riscv_bootparams *rvbp)
 	 */
 	identify_cpu(0);
 
+	sched_instance_select();
+
+	link_elf_ireloc();
+
 	/* Do basic tuning, hz etc */
 	init_param1();