s390:compel: Enable s390 in compel/

Add s390 parts to common code files.

Patch history
-------------
v2->v3:

 * Add: s390: Consolidate -msoft-float into Makefile.compel
Reviewed-by: Alice Frosi <alice@linux.vnet.ibm.com>
Signed-off-by: Michael Holzheu <holzheu@linux.vnet.ibm.com>
Reviewed-by: Dmitry Safonov <dsafonov@virtuozzo.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>

Makefile.compel

@@ -70,3 +70,11 @@ compel/$(LIBCOMPEL_SO): compel/$(LIBCOMPEL_A)
 compel-install-targets	+= compel/$(LIBCOMPEL_SO)
 compel-install-targets	+= compel/compel
 compel-install-targets	+= $(compel-plugins)
+
+# We assume that compel code does not change floating point registers.
+# On s390 gcc uses fprs to cache gprs. Therefore disable floating point
+# with -msoft-float.
+ifeq ($(ARCH),s390)
+CFLAGS += -msoft-float
+HOSTCFLAGS += -msoft-float
+endif

compel/.gitignore

 arch/x86/plugins/std/sys-exec-tbl-64.c
 arch/x86/plugins/std/syscalls-64.S
 arch/arm/plugins/std/syscalls/syscalls.S
+arch/s390/plugins/std/syscalls/syscalls.S
 include/version.h
 plugins/include/uapi/std/asm/syscall-types.h
 plugins/include/uapi/std/syscall-64.h

compel/src/lib/handle-elf.c

@@ -542,6 +542,31 @@ int __handle_elf(void *mem, size_t size)
 				break;
 #endif
 
+#ifdef ELF_S390
+			/*
+			 * See also arch/s390/kernel/module.c/apply_rela():
+			 * A PLT reads the GOT (global offest table). We can handle it like
+			 * R_390_PC32DBL because we have linked statically.
+			 */
+			case R_390_PLT32DBL: /* PC relative on a PLT (predure link table) */
+				pr_debug("\t\t\t\tR_390_PLT32DBL   at 0x%-4lx val 0x%x\n", place, value32 + addend32);
+				*((int32_t *)where) = (value64 + addend64 - place) >> 1;
+				break;
+			case R_390_PC32DBL: /* PC relative on a symbol */
+				pr_debug("\t\t\t\tR_390_PC32DBL    at 0x%-4lx val 0x%x\n", place, value32 + addend32);
+				*((int32_t *)where) = (value64 + addend64 - place) >> 1;
+				break;
+			case R_390_64: /* 64 bit absolute address */
+				pr_debug("\t\t\t\tR_390_64         at 0x%-4lx val 0x%lx\n", place, (long)value64);
+				pr_out("	{ .offset = 0x%-8x, .type = COMPEL_TYPE_LONG, "
+				       ".addend = %-8ld, .value = 0x%-16lx, }, /* R_390_64 */\n",
+				       (unsigned int)place, (long)addend64, (long)value64);
+				break;
+			case R_390_PC64: /* 64 bit relative address */
+				*((int64_t *)where) = value64 + addend64 - place;
+				pr_debug("\t\t\t\tR_390_PC64       at 0x%-4lx val 0x%lx\n", place, (long)value64);
+				break;
+#endif
 			default:
 				pr_err("Unsupported relocation of type %lu\n",
 					(unsigned long)ELF_R_TYPE(r->rel.r_info));

compel/src/main.c

@@ -52,6 +52,9 @@ static const flags_t flags = {
 #elif defined CONFIG_PPC64
 	.arch		= "ppc64",
 	.cflags		= COMPEL_CFLAGS_PIE,
+#elif defined CONFIG_S390
+	.arch		= "s390",
+	.cflags		= COMPEL_CFLAGS_PIE,
 #else
 #error "CONFIG_<ARCH> not defined, or unsupported ARCH"
 #endif