kpatch-build: Enable ARM64 support

Add the final support required for aarch64 and enable building on that arch.

Signed-off-by: Suraj Jitindar Singh <surajjs@amazon.com>
[kpatch_line_macro_change_only() fixes]
Signed-off-by: Puranjay Mohan <pjy@amazon.com>

Author: Suraj Jitindar Singh

README.md

@@ -40,7 +40,7 @@ Supported Architectures
 
 - [x] x86-64
 - [x] ppc64le
-- [ ] arm64
+- [x] arm64
 - [x] s390 [upstream prerequisites](doc/s390-upstream-prerequisites.md)
 
 Installation

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 aarch64),)
 $(error Unsupported architecture ${ARCH}, check https://github.com/dynup/kpatch/#supported-architectures)
 endif
 

kpatch-build/create-diff-object.c

@@ -173,6 +173,8 @@ static bool is_gcc6_localentry_bundled_sym(struct kpatch_elf *kelf,
 					  struct symbol *sym)
 {
 	switch(kelf->arch) {
+	case AARCH64:
+		return false;
 	case PPC64:
 		return ((PPC64_LOCAL_ENTRY_OFFSET(sym->sym.st_other) != 0) &&
 			sym->sym.st_value == 8);
@@ -228,6 +230,31 @@ static struct rela *toc_rela(const struct rela *rela)
 				   (unsigned int)rela->addend);
 }
 
+/*
+ * Mapping symbols are used to mark and label the transitions between code and
+ * data in elf files. They begin with a "$" dollar symbol. Don't correlate them
+ * as they often all have the same name either "$x" to mark the start of code
+ * or "$d" to mark the start of data.
+ */
+static bool kpatch_is_mapping_symbol(struct kpatch_elf *kelf, struct symbol *sym)
+{
+	switch (kelf->arch) {
+	case AARCH64:
+		if (sym->name && sym->name[0] == '$'
+			&& sym->type == STT_NOTYPE \
+			&& sym->bind == STB_LOCAL)
+			return true;
+	case X86_64:
+	case PPC64:
+	case S390:
+		return false;
+	default:
+		ERROR("unsupported arch");
+	}
+
+	return false;
+}
+
 /*
  * When compiling with -ffunction-sections and -fdata-sections, almost every
  * symbol gets its own dedicated section.  We call such symbols "bundled"
@@ -706,6 +733,12 @@ static bool insn_is_load_immediate(struct kpatch_elf *kelf, void *addr)
 
 		break;
 
+	case AARCH64:
+		/* Verify mov w2 <line number> */
+		if ((insn[0] & 0b11111) == 0x2 && insn[3] == 0x52)
+			return true;
+		break;
+
 	default:
 		ERROR("unsupported arch");
 	}
@@ -746,6 +779,7 @@ static bool kpatch_line_macro_change_only(struct kpatch_elf *kelf,
 	void *data1, *data2, *insn1, *insn2;
 	struct rela *r, *rela;
 	bool found, found_any = false;
+	bool warn_printk_only = (kelf->arch == AARCH64);
 
 	if (sec->status != CHANGED ||
 	    is_rela_section(sec) ||
@@ -809,8 +843,15 @@ static bool kpatch_line_macro_change_only(struct kpatch_elf *kelf,
 			    !strncmp(rela->sym->name, "__func__.", 9))
 				continue;
 
+			if (!strcmp(rela->sym->name, "__warn_printk")) {
+				found = true;
+				break;
+			}
+
+			if (warn_printk_only)
+				return false;
+
 			if (!strncmp(rela->sym->name, "warn_slowpath_", 14) ||
-			    !strcmp(rela->sym->name, "__warn_printk") ||
 			    !strcmp(rela->sym->name, "__might_sleep") ||
 			    !strcmp(rela->sym->name, "___might_sleep") ||
 			    !strcmp(rela->sym->name, "__might_fault") ||
@@ -1075,15 +1116,15 @@ static void kpatch_correlate_sections(struct list_head *seclist_orig,
 	}
 }
 
-static void kpatch_correlate_symbols(struct list_head *symlist_orig,
-		struct list_head *symlist_patched)
+static void kpatch_correlate_symbols(struct kpatch_elf *kelf_orig,
+		struct kpatch_elf *kelf_patched)
 {
 	struct symbol *sym_orig, *sym_patched;
 
-	list_for_each_entry(sym_orig, symlist_orig, list) {
+	list_for_each_entry(sym_orig, &kelf_orig->symbols, list) {
 		if (sym_orig->twin)
 			continue;
-		list_for_each_entry(sym_patched, symlist_patched, list) {
+		list_for_each_entry(sym_patched, &kelf_patched->symbols, list) {
 			if (kpatch_mangled_strcmp(sym_orig->name, sym_patched->name) ||
 			    sym_orig->type != sym_patched->type || sym_patched->twin)
 				continue;
@@ -1103,6 +1144,9 @@ static void kpatch_correlate_symbols(struct list_head *symlist_orig,
 			    !strncmp(sym_orig->name, ".LC", 3))
 				continue;
 
+			if (kpatch_is_mapping_symbol(kelf_orig, sym_orig))
+				continue;
+
 			/* group section symbols must have correlated sections */
 			if (sym_orig->sec &&
 			    sym_orig->sec->sh.sh_type == SHT_GROUP &&
@@ -1508,7 +1552,7 @@ static void kpatch_correlate_elfs(struct kpatch_elf *kelf_orig,
 		struct kpatch_elf *kelf_patched)
 {
 	kpatch_correlate_sections(&kelf_orig->sections, &kelf_patched->sections);
-	kpatch_correlate_symbols(&kelf_orig->symbols, &kelf_patched->symbols);
+	kpatch_correlate_symbols(kelf_orig, kelf_patched);
 }
 
 static void kpatch_compare_correlated_elements(struct kpatch_elf *kelf)
@@ -1624,7 +1668,8 @@ static void kpatch_replace_sections_syms(struct kpatch_elf *kelf)
 
 				if (is_text_section(relasec->base) &&
 				    !is_text_section(sym->sec) &&
-				    rela->type == R_X86_64_32S &&
+				    (rela->type == R_X86_64_32S ||
+				     rela->type == R_AARCH64_ABS64) &&
 				    rela->addend == (long)sym->sec->sh.sh_size &&
 				    end == (long)sym->sec->sh.sh_size) {
 
@@ -2493,28 +2538,28 @@ 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		= AARCH64 | X86_64 | PPC64 | S390,
 		.group_size	= bug_table_group_size,
 	},
 	{
 		.name		= ".fixup",
-		.arch		= X86_64 | PPC64 | S390,
+		.arch		= AARCH64 | X86_64 | PPC64 | S390,
 		.group_size	= fixup_group_size,
 	},
 	{
 		.name		= "__ex_table", /* must come after .fixup */
-		.arch		= X86_64 | PPC64 | S390,
+		.arch		= AARCH64 | X86_64 | PPC64 | S390,
 		.group_size	= ex_table_group_size,
 	},
 	{
 		.name		= "__jump_table",
-		.arch		= X86_64 | PPC64 | S390,
+		.arch		= AARCH64 | X86_64 | PPC64 | S390,
 		.group_size	= jump_table_group_size,
 		.group_filter	= jump_table_group_filter,
 	},
 	{
 		.name		= ".printk_index",
-		.arch		= X86_64 | PPC64 | S390,
+		.arch		= AARCH64 | X86_64 | PPC64 | S390,
 		.group_size	= printk_index_group_size,
 	},
 	{
@@ -2529,7 +2574,7 @@ static struct special_section special_sections[] = {
 	},
 	{
 		.name		= ".altinstructions",
-		.arch		= X86_64 | S390,
+		.arch		= AARCH64 | X86_64 | S390,
 		.group_size	= altinstructions_group_size,
 	},
 	{

kpatch-build/kpatch-build

@@ -402,6 +402,9 @@ find_special_section_data() {
 		"s390x")
 			check[a]=true					# alt_instr
 			;;
+		"aarch64")
+			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 AARCH64:
+		return R_AARCH64_ABS64;
 	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 AARCH64:
 		add_off = 0;
 		break;
 	case X86_64:
@@ -255,6 +258,8 @@ unsigned int insn_length(struct kpatch_elf *kelf, void *addr)
 
 	switch(kelf->arch) {
 
+	case AARCH64:
+		return 4;
 	case X86_64:
 		insn_init(&decoded_insn, addr, 1);
 		insn_get_length(&decoded_insn);
@@ -595,7 +600,7 @@ struct kpatch_elf *kpatch_elf_open(const char *name)
 		kelf->arch = S390;
 		break;
 	case EM_AARCH64:
-		kelf->arch = ARM64;
+		kelf->arch = AARCH64;
 		break;
 	default:
 		ERROR("Unsupported target architecture");