S390x kpatch support

README.md

@@ -41,7 +41,7 @@ Supported Architectures
 - [x] x86-64
 - [x] ppc64le
 - [ ] arm64
-- [ ] s390
+- [x] s390 [upstream prerequisites](doc/s390-upstream-prerequisites.md)
 
 Installation
 ------------

doc/s390-upstream-prerequisites.md

@@ -0,0 +1,33 @@
+### s390 backporting
+
+**Prerequisite gcc patches (all backported to releases/gcc-11 branch):**
+- gcc-mirror/gcc@a1c1b7a IBM Z: Define NO_PROFILE_COUNTERS
+- gcc-mirror/gcc@0990d93 IBM Z: Use @PLT symbols for local functions in 64-bit mode
+- gcc-mirror/gcc@935b522 S/390: New option -mpic-data-is-text-relative
+- gcc-mirror/gcc@8753b13 IBM Z: fix section type conflict with -mindirect-branch-table
+
+**Prerequisite kernel patches:**
+**v5.19:**
+- 69505e3d9a39 bug: Use normal relative pointers in 'struct bug_entry'
+
+**v5.18:**
+- 602bf1687e6f s390/nospec: align and size extern thunks
+- 1d2ad084800e s390/nospec: add an option to use thunk-extern
+- eed38cd2f46f s390/nospec: generate single register thunks if possible
+- 2268169c14e5 s390: remove unused expoline to BC instructions
+- f0003a9e4c18 s390/entry: remove unused expoline thunk
+
+**v5.16:**
+- torvalds/linux@f6ac18f sched: Improve try_invoke_on_locked_down_task()
+- torvalds/linux@9b3c4ab sched,rcu: Rework try_invoke_on_locked_down_task()
+- torvalds/linux@00619f7 sched,livepatch: Use task_call_func()
+- torvalds/linux@8850cb6 sched: Simplify wake_up_*idle*()
+- torvalds/linux@5de62ea sched,livepatch: Use wake_up_if_idle()
+- torvalds/linux@96611c2 sched: Improve wake_up_all_idle_cpus() take #2
+
+**v5.15**
+- torvalds/linux@de5012b s390/ftrace: implement hotpatching
+- torvalds/linux@67ccddf ftrace: Introduce ftrace_need_init_nop()
+
+**v5.14:**
+- torvalds/linux@7561c14 s390/vdso: add .got.plt in vdso linker script

kpatch-build/Makefile

@@ -21,7 +21,8 @@ GCC_PLUGINS_DIR := $(shell $(CROSS_COMPILE)gcc -print-file-name=plugin)
 PLUGIN_CFLAGS := $(filter-out -Wconversion, $(CFLAGS))
 PLUGIN_CFLAGS += -shared -I$(GCC_PLUGINS_DIR)/include \
 		   -Igcc-plugins -fPIC -fno-rtti -O2 -Wall
-else ifneq ($(ARCH),x86_64)
+endif
+ifeq ($(filter $(ARCH),s390x x86_64 ppc64le),)
 $(error Unsupported architecture ${ARCH}, check https://github.com/dynup/kpatch/#supported-architectures)
 endif
 

kpatch-build/create-diff-object.c

@@ -118,6 +118,16 @@ static bool is_bundleable(struct symbol *sym)
 	    !strcmp(sym->sec->name + 13, sym->name))
 		return true;
 
+	if (sym->type == STT_OBJECT &&
+	    !strncmp(sym->sec->name, ".data.rel.ro.local.", 19) &&
+	    !strcmp(sym->sec->name + 19, sym->name))
+		return 1;
+
+	if (sym->type == STT_OBJECT &&
+	    !strncmp(sym->sec->name, ".data.rel.local.", 16) &&
+	    !strcmp(sym->sec->name + 16, sym->name))
+		return 1;
+
 	if (sym->type == STT_OBJECT &&
 	   !strncmp(sym->sec->name, ".rodata.",8) &&
 	   !strcmp(sym->sec->name + 8, sym->name))
@@ -163,6 +173,8 @@ static bool is_gcc6_localentry_bundled_sym(struct kpatch_elf *kelf,
 			sym->sym.st_value == 8);
 	case X86_64:
 		return false;
+	case S390:
+		return false;
 	default:
 		ERROR("unsupported arch");
 	}
@@ -304,8 +316,7 @@ static bool is_dynamic_debug_symbol(struct symbol *sym)
 
 static bool is_string_literal_section(struct section *sec)
 {
-	return !strncmp(sec->name, ".rodata.", 8) &&
-	       strstr(sec->name, ".str1.");
+	return !strncmp(sec->name, ".rodata.", 8) && strstr(sec->name, ".str");
 }
 
 /*
@@ -2104,6 +2115,17 @@ static int fixup_barrier_nospec_group_size(struct kpatch_elf *kelf, int offset)
 	return 8;
 }
 
+/*
+ * .s390_indirect_jump, .s390_indirect_call, .s390_indirect_branches,
+ * .s390_return_reg, .s390_return_mem contains indirect branch locations. This
+ * is an array of 32 bit elements. These sections could be used during runtime
+ * to replace the expolines with the normal indirect jump.
+ */
+static int s390_expolines_group_size(struct kpatch_elf *kelf, int offset)
+{
+	return 4;
+}
+
 /*
  * The rela groups in the .fixup section vary in size.  The beginning of each
  * .fixup rela group is referenced by the __ex_table section. To find the size
@@ -2157,27 +2179,27 @@ static int fixup_group_size(struct kpatch_elf *kelf, int offset)
 static struct special_section special_sections[] = {
 	{
 		.name		= "__bug_table",
-		.arch		= X86_64 | PPC64,
+		.arch		= X86_64 | PPC64 | S390,
 		.group_size	= bug_table_group_size,
 	},
 	{
 		.name		= ".fixup",
-		.arch		= X86_64 | PPC64,
+		.arch		= X86_64 | PPC64 | S390,
 		.group_size	= fixup_group_size,
 	},
 	{
 		.name		= "__ex_table", /* must come after .fixup */
-		.arch		= X86_64 | PPC64,
+		.arch		= X86_64 | PPC64 | S390,
 		.group_size	= ex_table_group_size,
 	},
 	{
 		.name		= "__jump_table",
-		.arch		= X86_64 | PPC64,
+		.arch		= X86_64 | PPC64 | S390,
 		.group_size	= jump_table_group_size,
 	},
 	{
 		.name		= ".printk_index",
-		.arch		= X86_64 | PPC64,
+		.arch		= X86_64 | PPC64 | S390,
 		.group_size	= printk_index_group_size,
 	},
 	{
@@ -2192,7 +2214,7 @@ static struct special_section special_sections[] = {
 	},
 	{
 		.name		= ".altinstructions",
-		.arch		= X86_64,
+		.arch		= X86_64 | S390,
 		.group_size	= altinstructions_group_size,
 	},
 	{
@@ -2230,6 +2252,31 @@ static struct special_section special_sections[] = {
 		.arch		= PPC64,
 		.group_size	= fixup_barrier_nospec_group_size,
 	},
+	{
+		.name = ".s390_return_mem",
+		.arch = S390,
+		.group_size = s390_expolines_group_size,
+	},
+	{
+		.name = ".s390_return_reg",
+		.arch = S390,
+		.group_size = s390_expolines_group_size,
+	},
+	{
+		.name = ".s390_indirect_call",
+		.arch = S390,
+		.group_size = s390_expolines_group_size,
+	},
+	{
+		.name = ".s390_indirect_branches",
+		.arch = S390,
+		.group_size = s390_expolines_group_size,
+	},
+	{
+		.name = ".s390_indirect_jump",
+		.arch = S390,
+		.group_size = s390_expolines_group_size,
+	},
 	{},
 };
 
@@ -3024,6 +3071,11 @@ static bool kpatch_is_core_module_symbol(char *name)
 		!strcmp(name, "kpatch_shadow_get"));
 }
 
+static bool is_expoline(struct kpatch_elf *kelf, char *name)
+{
+	return kelf->arch == S390 && !strncmp(name, "__s390_indirect_jump_r", 22);
+}
+
 static int function_ptr_rela(const struct rela *rela)
 {
 	const struct rela *rela_toc = toc_rela(rela);
@@ -3082,6 +3134,13 @@ static bool need_dynrela(struct kpatch_elf *kelf, struct lookup_table *table,
 	if (kpatch_is_core_module_symbol(rela->sym->name))
 		return false;
 
+       /*
+        * Allow references to s390 expolines to remain as normal relas.  They
+        * will be generated in the module by the kernel module link.
+        */
+	if (is_expoline(kelf, rela->sym->name))
+		return false;
+
 	if (rela->sym->sec) {
 		/*
 		 * Internal symbols usually don't need dynrelas, because they
@@ -3548,6 +3607,10 @@ static void kpatch_create_mcount_sections(struct kpatch_elf *kelf)
 			rela->type = R_X86_64_PC32;
 			break;
 		}
+		case S390: {
+			insn_offset = sym->sym.st_value;
+			break;
+		}
 		default:
 			ERROR("unsupported arch");
 		}
@@ -3713,6 +3776,7 @@ static void kpatch_find_func_profiling_calls(struct kpatch_elf *kelf)
 {
 	struct symbol *sym;
 	struct rela *rela;
+	unsigned char *insn;
 	list_for_each_entry(sym, &kelf->symbols, list) {
 		if (sym->type != STT_FUNC || !sym->sec || !sym->sec->rela)
 			continue;
@@ -3737,6 +3801,14 @@ static void kpatch_find_func_profiling_calls(struct kpatch_elf *kelf)
 
 			sym->has_func_profiling = 1;
 			break;
+		case S390:
+			/* Check for compiler generated fentry nop - jgnop 0 */
+			insn = sym->sec->data->d_buf;
+			if (insn[0] == 0xc0 && insn[1] == 0x04 &&
+				insn[2] == 0x00 && insn[3] == 0x00 &&
+				insn[4] == 0x00 && insn[5] == 0x00)
+				sym->has_func_profiling = 1;
+			break;
 		default:
 			ERROR("unsupported arch");
 		}

kpatch-build/kpatch-build

@@ -343,12 +343,18 @@ find_special_section_data() {
 	check[e]=true						# exception_table_entry
 
 	# Arch-specific features, without kernel CONFIG_ toggle
-	if [[ "$ARCH" = "x86_64" ]]; then
-		check[a]=true					# alt_instr
-		kernel_version_gte 5.10.0 && check[s]=true	# static_call_site
-	elif [[ "$ARCH" = "ppc64le" ]]; then
-		check[f]=true					# fixup_entry
-	fi
+	case "$ARCH" in
+		"x86_64")
+			check[a]=true					# alt_instr
+			kernel_version_gte 5.10.0 && check[s]=true	# static_call_site
+			;;
+		"ppc64le")
+			check[f]=true					# fixup_entry
+			;;
+		"s390x")
+			check[a]=true					# alt_instr
+			;;
+	esac
 
 	# Kernel CONFIG_ features
 	[[ -n "$CONFIG_PRINTK_INDEX" ]] && check[i]=true	# pi_entry
@@ -856,6 +862,7 @@ trace_on
 	die "openEuler kernel doesn't have 'CONFIG_LIVEPATCH_PER_TASK_CONSISTENCY' enabled"
 
 [[ -z "$CONFIG_DEBUG_INFO" ]] && die "kernel doesn't have 'CONFIG_DEBUG_INFO' enabled"
+[[ "$ARCH" = "s390x" ]] && [[ -z "$CONFIG_EXPOLINE_EXTERN" ]] && [[ -n "$CONFIG_EXPOLINE" ]] && die "kernel doesn't have 'CONFIG_EXPOLINE_EXTERN' enabled"
 
 # Build variables - Set some defaults, then adjust features
 # according to .config and kernel version
@@ -937,6 +944,10 @@ if [[ "$ARCH" = "ppc64le" ]]; then
 	ARCH_KCFLAGS="-mcmodel=large -fplugin=$PLUGINDIR/ppc64le-plugin.so"
 fi
 
+if [[ "$ARCH" = "s390x" ]]; then
+	ARCH_KCFLAGS="-mno-pic-data-is-text-relative -fno-section-anchors"
+fi
+
 export KCFLAGS="-I$DATADIR/patch -ffunction-sections -fdata-sections \
 		$ARCH_KCFLAGS $DEBUG_KCFLAGS"
 

kpatch-build/kpatch-cc

@@ -43,6 +43,9 @@ if [[ "$TOOLCHAINCMD" =~ ^(.*-)?gcc$ || "$TOOLCHAINCMD" =~ ^(.*-)?clang$ ]] ; th
 				drivers/firmware/efi/libstub/*|\
 				arch/powerpc/kernel/prom_init.o|\
 				arch/powerpc/kernel/vdso64/*|\
+				arch/s390/boot/*|\
+				arch/s390/purgatory/*|\
+				arch/s390/kernel/vdso64/*|\
 				lib/*|\
 				.*.o|\
 				*/.lib_exports.o)

kpatch-build/kpatch-elf.c

@@ -140,6 +140,8 @@ unsigned int absolute_rela_type(struct kpatch_elf *kelf)
 		return R_PPC64_ADDR64;
 	case X86_64:
 		return R_X86_64_64;
+	case S390:
+		return R_390_64;
 	default:
 		ERROR("unsupported arch");
 	}
@@ -222,6 +224,23 @@ long rela_target_offset(struct kpatch_elf *kelf, struct section *relasec,
 		} else
 			ERROR("unhandled rela type %d", rela->type);
 		break;
+	case S390:
+		/*
+		 * For branch and relative load instructions,
+		 * add_off is -2.
+		 */
+		if (rela->type == R_390_GOTENT ||
+			rela->type == R_390_PLT32DBL ||
+			rela->type == R_390_PC32DBL)
+			add_off = -2;
+		else if (rela->type == R_390_32 ||
+			rela->type == R_390_64 ||
+			rela->type == R_390_PC32 ||
+			rela->type == R_390_PC64)
+			add_off = 0;
+		else
+			ERROR("unhandled rela type %d", rela->type);
+		break;
 	default:
 		ERROR("unsupported arch\n");
 	}
@@ -479,6 +498,9 @@ struct kpatch_elf *kpatch_elf_open(const char *name)
 	case EM_X86_64:
 		kelf->arch = X86_64;
 		break;
+	case EM_S390:
+		kelf->arch = S390;
+		break;
 	default:
 		ERROR("Unsupported target architecture");
 	}

kpatch-build/lookup.c

@@ -272,12 +272,14 @@ static void symtab_read(struct lookup_table *table, char *path)
 		 * tables.  .dynsym is just a subset of .symtab, so skip it to
 		 * avoid duplicates.
 		 */
-		if (strstr(line, ".dynsym")) {
-			skip = true;
-			continue;
-		} else if (strstr(line, ".symtab")) {
-			skip = false;
-			continue;
+		if (!strncmp(line, "Symbol table ", 13)) {
+			if (strstr(line, ".dynsym")) {
+				skip = true;
+				continue;
+			} else if (strstr(line, ".symtab")) {
+				skip = false;
+				continue;
+			}
 		}
 		if (skip)
 			continue;