Add LoongArch support for kpatch

kpatch-build/Makefile

@@ -21,7 +21,7 @@ PLUGIN_CFLAGS := $(filter-out -std=gnu11 -Wconversion, $(CFLAGS))
 PLUGIN_CFLAGS += -shared -I$(GCC_PLUGINS_DIR)/include \
 		   -Igcc-plugins -fPIC -fno-rtti -O2 -Wall
 endif
-ifeq ($(filter $(ARCH),s390x x86_64 ppc64le),)
+ifeq ($(filter $(ARCH),s390x x86_64 ppc64le loongarch64),)
 $(error Unsupported architecture ${ARCH}, check https://github.com/dynup/kpatch/#supported-architectures)
 endif
 

kpatch-build/create-diff-object.c

@@ -180,6 +180,8 @@ static bool is_gcc6_localentry_bundled_sym(struct kpatch_elf *kelf,
 		return false;
 	case S390:
 		return false;
+	case LOONGARCH64:
+		return false;
 	default:
 		ERROR("unsupported arch");
 	}
@@ -615,9 +617,11 @@ static void kpatch_compare_correlated_section(struct section *sec)
 	     !is_text_section(sec1)))
 		DIFF_FATAL("%s section header details differ from %s", sec1->name, sec2->name);
 
-	/* Short circuit for mcount sections, we rebuild regardless */
+	/* Short circuit for mcount/patchable sections, we rebuild regardless */
 	if (!strcmp(sec->name, ".rela__mcount_loc") ||
-	    !strcmp(sec->name, "__mcount_loc")) {
+	    !strcmp(sec->name, "__mcount_loc") ||
+	    !strcmp(sec->name, ".rela__patchable_function_entries") ||
+	    !strcmp(sec->name, "__patchable_function_entries")) {
 		sec->status = SAME;
 		goto out;
 	}
@@ -689,6 +693,11 @@ static bool insn_is_load_immediate(struct kpatch_elf *kelf, void *addr)
 
 		break;
 
+	case LOONGARCH64:
+		/* to be done */
+
+		break;
+
 	case S390:
 		/* arg2: lghi %r3, imm */
 		if (insn[0] == 0xa7 && insn[1] == 0x39)
@@ -2415,22 +2424,22 @@ static bool static_call_sites_group_filter(struct lookup_table *lookup,
 static struct special_section special_sections[] = {
 	{
 		.name		= "__bug_table",
-		.arch		= X86_64 | PPC64 | S390,
+		.arch		= X86_64 | PPC64 | S390 | LOONGARCH64,
 		.group_size	= bug_table_group_size,
 	},
 	{
 		.name		= ".fixup",
-		.arch		= X86_64 | PPC64 | S390,
+		.arch		= X86_64 | PPC64 | S390 | LOONGARCH64,
 		.group_size	= fixup_group_size,
 	},
 	{
 		.name		= "__ex_table", /* must come after .fixup */
-		.arch		= X86_64 | PPC64 | S390,
+		.arch		= X86_64 | PPC64 | S390 | LOONGARCH64,
 		.group_size	= ex_table_group_size,
 	},
 	{
 		.name		= "__jump_table",
-		.arch		= X86_64 | PPC64 | S390,
+		.arch		= X86_64 | PPC64 | S390 | LOONGARCH64,
 		.group_size	= jump_table_group_size,
 		.group_filter	= jump_table_group_filter,
 	},
@@ -2451,7 +2460,7 @@ static struct special_section special_sections[] = {
 	},
 	{
 		.name		= ".altinstructions",
-		.arch		= X86_64 | S390,
+		.arch		= X86_64 | S390 | LOONGARCH64,
 		.group_size	= altinstructions_group_size,
 	},
 	{
@@ -3699,7 +3708,22 @@ static void kpatch_create_mcount_sections(struct kpatch_elf *kelf)
 			nr++;
 
 	/* create text/rela section pair */
-	sec = create_section_pair(kelf, "__mcount_loc", sizeof(void*), nr);
+	if (kelf->arch == LOONGARCH64) {
+		sec = create_section_pair(kelf, "__patchable_function_entries", sizeof(void *), nr);
+		/*
+		 * With -fpatchable-function-entry, LoongArch GCC sets WAL flags
+		 * for section __patchable_function_entries in object file
+		 * (certainly include patch-hook.o) by default.
+		 * Kpatch sets A flags for output.o in create_section_pair().
+		 * So here assign sh_flags = WAL to fix error:
+		 * "ld: __patchable_function_entries has both ordered and
+		 * unordered sections" when link patch-hook.o and output.o.
+		 */
+		sec->sh.sh_flags = SHF_WRITE | SHF_ALLOC | SHF_LINK_ORDER;
+		sec->sh.sh_link = 1;
+	} else
+		sec = create_section_pair(kelf, "__mcount_loc", sizeof(void *), nr);
+
 	relasec = sec->rela;
 
 	/* populate sections */
@@ -3779,6 +3803,20 @@ static void kpatch_create_mcount_sections(struct kpatch_elf *kelf)
 			insn_offset = sym->sym.st_value;
 			break;
 		}
+		case LOONGARCH64: {
+#define LOONGARCH_NOP 0x03400000
+			bool found = false;
+			unsigned int *insn = sym->sec->data->d_buf + sym->sym.st_value;
+
+			if (*insn == LOONGARCH_NOP && *(insn + 1) == LOONGARCH_NOP)
+				found = true;
+
+			if (!found)
+				ERROR("%s: unexpected instruction at the start of the function", sym->name);
+
+			insn_offset = 0;
+			break;
+		}
 		default:
 			ERROR("unsupported arch");
 		}
@@ -3984,6 +4022,22 @@ static void kpatch_find_func_profiling_calls(struct kpatch_elf *kelf)
 				insn[4] == 0x00 && insn[5] == 0x00)
 				sym->has_func_profiling = 1;
 			break;
+		case LOONGARCH64:
+			struct section *sec;
+
+			sec = find_section_by_name(&kelf->sections,
+					"__patchable_function_entries");
+			if (sec) {
+				list_for_each_entry(rela, &sec->rela->relas, list) {
+					if (rela->sym->sec == sym->sec &&
+					   (rela->sym->sym.st_value +
+					   rela->addend) == sym->sym.st_value) {
+						sym->has_func_profiling = 1;
+						break;
+					}
+				}
+			}
+			break;
 		default:
 			ERROR("unsupported arch");
 		}

kpatch-build/kpatch-build

@@ -393,6 +393,9 @@ find_special_section_data() {
 		"s390x")
 			check[a]=true					# alt_instr
 			;;
+		"loongarch64")
+			check[a]=true					# alt_instr
+			;;
 	esac
 
 	# Kernel CONFIG_ features

kpatch-build/kpatch-elf.c

@@ -142,6 +142,8 @@ unsigned int absolute_rela_type(struct kpatch_elf *kelf)
 		return R_X86_64_64;
 	case S390:
 		return R_390_64;
+	case LOONGARCH64:
+		return R_LARCH_64;
 	default:
 		ERROR("unsupported arch");
 	}
@@ -206,6 +208,7 @@ long rela_target_offset(struct kpatch_elf *kelf, struct section *relasec,
 
 	switch(kelf->arch) {
 	case PPC64:
+	case LOONGARCH64:
 		add_off = 0;
 		break;
 	case X86_64:
@@ -261,6 +264,7 @@ unsigned int insn_length(struct kpatch_elf *kelf, void *addr)
 		return decoded_insn.length;
 
 	case PPC64:
+	case LOONGARCH64:
 		return 4;
 
 	case S390:
@@ -332,6 +336,21 @@ static void kpatch_create_rela_list(struct kpatch_elf *kelf,
 				      rela->sym->name, rela->addend);
 		}
 
+		if (kelf->arch == LOONGARCH64) {
+			/*
+			 * LoongArch GCC creates local labels such as .LBB7266,
+			 * replace them with section symbols.
+			 */
+			if (rela->sym->sec && (rela->sym->type == STT_NOTYPE) &&
+				(rela->sym->bind == STB_LOCAL)) {
+				log_debug("local label: %s -> ", rela->sym->name);
+
+				rela->addend += rela->sym->sym.st_value;
+				rela->sym = rela->sym->sec->secsym;
+				log_debug("section symbol: %s\n", rela->sym->name);
+			}
+		}
+
 		if (skip)
 			continue;
 		log_debug("offset %d, type %d, %s %s %ld", rela->offset,
@@ -593,6 +612,9 @@ struct kpatch_elf *kpatch_elf_open(const char *name)
 	case EM_S390:
 		kelf->arch = S390;
 		break;
+	case EM_LOONGARCH:
+		kelf->arch = LOONGARCH64;
+		break;
 	default:
 		ERROR("Unsupported target architecture");
 	}
@@ -608,6 +630,18 @@ struct kpatch_elf *kpatch_elf_open(const char *name)
 		kpatch_create_rela_list(kelf, relasec);
 	}
 
+	if (kelf->arch == LOONGARCH64) {
+		struct symbol *sym, *tmp;
+
+		/* Delete local labels created by LoongArch GCC */
+		list_for_each_entry_safe(sym, tmp, &kelf->symbols, list) {
+			if (sym->sec && !is_rela_section(sym->sec) &&
+				(sym->type == STT_NOTYPE) &&
+				(sym->bind == STB_LOCAL))
+				list_del(&sym->list);
+		}
+	}
+
 	return kelf;
 }
 

kpatch-build/kpatch-elf.h

@@ -31,6 +31,11 @@
 #define SHF_RELA_LIVEPATCH	0x00100000
 #define SHN_LIVEPATCH		0xff20
 
+#ifndef __loongarch__
+#define EM_LOONGARCH		258     /* LoongArch */
+#define R_LARCH_64              2
+#endif
+
 /*******************
  * Data structures
  * ****************/
@@ -115,6 +120,7 @@ enum architecture {
 	PPC64  = 0x1 << 0,
 	X86_64 = 0x1 << 1,
 	S390   = 0x1 << 2,
+	LOONGARCH64 = 0x1 << 3,
 };
 
 struct kpatch_elf {