kpatch-build: Enable ARM64 support

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

Signed-off-by: Suraj Jitindar Singh <[email protected]>

---

V1->V2:
 - Add # shellcheck disable=SC2086
 - Add comment to kpatch_is_mapping_symbol()

Author: Suraj Jitindar Singh

README.md

@@ -51,7 +51,7 @@ Supported Architectures
 
 - [x] x86-64
 - [x] ppc64le
-- [ ] arm64
+- [x] arm64
 - [ ] s390
 
 Installation

kpatch-build/Makefile

@@ -22,6 +22,7 @@ GCC_PLUGINS_DIR := $(shell 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 ifeq ($(ARCH),aarch64)
 else
 $(error Unsupported architecture ${ARCH}, check https://github.com/dynup/kpatch/#supported-architectures)
 endif

kpatch-build/create-diff-object.c

@@ -62,7 +62,9 @@
 
 #ifdef __powerpc64__
 #define ABSOLUTE_RELA_TYPE R_PPC64_ADDR64
-#else
+#elif defined(__aarch64__)
+#define ABSOLUTE_RELA_TYPE R_AARCH64_ABS64
+#elif defined(__x86_64__)
 #define ABSOLUTE_RELA_TYPE R_X86_64_64
 #endif
 
@@ -214,6 +216,28 @@ static struct rela *toc_rela(const struct rela *rela)
 				   (unsigned int)rela->addend);
 }
 
+#ifdef __aarch64__
+/*
+ * 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 "$d" to mark the start of data.
+ */
+static bool kpatch_is_mapping_symbol(struct symbol *sym)
+{
+	if (sym->name && sym->name[0] == '$'
+		&& sym->type == STT_NOTYPE \
+		&& sym->bind == STB_LOCAL)
+		return 1;
+	return 0;
+}
+#else
+static int kpatch_is_mapping_symbol(struct symbol *sym)
+{
+	return 0;
+}
+#endif
+
 /*
  * When compiling with -ffunction-sections and -fdata-sections, almost every
  * symbol gets its own dedicated section.  We call such symbols "bundled"
@@ -564,6 +588,13 @@ static void kpatch_compare_correlated_section(struct section *sec)
 		goto out;
 	}
 
+	/* As above but for aarch64 */
+	if (!strcmp(sec->name, ".rela__patchable_function_entries") ||
+	    !strcmp(sec->name, "__patchable_function_entries")) {
+		sec->status = SAME;
+		goto out;
+	}
+
 	if (sec1->sh.sh_size != sec2->sh.sh_size ||
 	    sec1->data->d_size != sec2->data->d_size) {
 		sec->status = CHANGED;
@@ -1030,6 +1061,9 @@ static void kpatch_correlate_symbols(struct list_head *symlist_orig,
 			    !strncmp(sym_orig->name, ".LC", 3))
 				continue;
 
+			if (kpatch_is_mapping_symbol(sym_orig))
+				continue;
+
 			/* group section symbols must have correlated sections */
 			if (sym_orig->sec &&
 			    sym_orig->sec->sh.sh_type == SHT_GROUP &&
@@ -1539,7 +1573,7 @@ static void kpatch_replace_sections_syms(struct kpatch_elf *kelf)
 				continue;
 			}
 
-#ifdef __powerpc64__
+#if defined(__powerpc64__) || defined(__aarch64__)
 			add_off = 0;
 #else
 			if (rela->type == R_X86_64_PC32 ||
@@ -1571,7 +1605,8 @@ static void kpatch_replace_sections_syms(struct kpatch_elf *kelf)
 				end = sym->sym.st_value + sym->sym.st_size;
 
 				if (!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) {
 
@@ -2047,35 +2082,36 @@ static int parainstructions_group_size(struct kpatch_elf *kelf, int offset)
 	return size;
 }
 
-static int altinstructions_group_size(struct kpatch_elf *kelf, int offset)
+static int smp_locks_group_size(struct kpatch_elf *kelf, int offset)
+{
+	return 4;
+}
+
+static int static_call_sites_group_size(struct kpatch_elf *kelf, int offset)
 {
 	static int size = 0;
 	char *str;
 
 	if (!size) {
-		str = getenv("ALT_STRUCT_SIZE");
+		str = getenv("STATIC_CALL_STRUCT_SIZE");
 		if (!str)
-			ERROR("ALT_STRUCT_SIZE not set");
+			ERROR("STATIC_CALL_STRUCT_SIZE not set");
 		size = atoi(str);
 	}
 
 	return size;
 }
-
-static int smp_locks_group_size(struct kpatch_elf *kelf, int offset)
-{
-	return 4;
-}
-
-static int static_call_sites_group_size(struct kpatch_elf *kelf, int offset)
+#endif
+#if defined(__x86_64__) || defined(__aarch64__)
+static int altinstructions_group_size(struct kpatch_elf *kelf, int offset)
 {
 	static int size = 0;
 	char *str;
 
 	if (!size) {
-		str = getenv("STATIC_CALL_STRUCT_SIZE");
+		str = getenv("ALT_STRUCT_SIZE");
 		if (!str)
-			ERROR("STATIC_CALL_STRUCT_SIZE not set");
+			ERROR("ALT_STRUCT_SIZE not set");
 		size = atoi(str);
 	}
 
@@ -2189,15 +2225,17 @@ static struct special_section special_sections[] = {
 		.name		= ".parainstructions",
 		.group_size	= parainstructions_group_size,
 	},
-	{
-		.name		= ".altinstructions",
-		.group_size	= altinstructions_group_size,
-	},
 	{
 		.name		= ".static_call_sites",
 		.group_size	= static_call_sites_group_size,
 	},
 #endif
+#if defined(__x86_64__) || defined(__aarch64__)
+	{
+		.name		= ".altinstructions",
+		.group_size	= altinstructions_group_size,
+	},
+#endif
 #ifdef __powerpc64__
 	{
 		.name		= "__ftr_fixup",

kpatch-build/kpatch-build

@@ -375,10 +375,58 @@ find_special_section_data_ppc64le() {
 	return
 }
 
+find_special_section_data_aarch64() {
+	[[ "$CONFIG_JUMP_LABEL" -eq 0 ]] && AWK_OPTIONS="-vskip_j=1"
+	[[ "$CONFIG_PRINTK_INDEX" -eq 0 ]] && AWK_OPTIONS="$AWK_OPTIONS -vskip_i=1"
+
+	# shellcheck disable=SC2086
+	SPECIAL_VARS="$(readelf -wi "$VMLINUX" |
+		gawk --non-decimal-data $AWK_OPTIONS '
+		BEGIN { a = b = p = e = o = j = s = i = 0 }
+
+		# Set state if name matches
+		a == 0 && /DW_AT_name.* alt_instr[[:space:]]*$/ {a = 1; next}
+		b == 0 && /DW_AT_name.* bug_entry[[:space:]]*$/ {b = 1; next}
+		e == 0 && /DW_AT_name.* exception_table_entry[[:space:]]*$/ {e = 1; next}
+		j == 0 && /DW_AT_name.* jump_entry[[:space:]]*$/ {j = 1; next}
+		i == 0 && /DW_AT_name.* pi_entry[[:space:]]*$/ {i = 1; next}
+
+		# Reset state unless this abbrev describes the struct size
+		a == 1 && !/DW_AT_byte_size/ { a = 0; next }
+		b == 1 && !/DW_AT_byte_size/ { b = 0; next }
+		e == 1 && !/DW_AT_byte_size/ { e = 0; next }
+		j == 1 && !/DW_AT_byte_size/ { j = 0; next }
+		i == 1 && !/DW_AT_byte_size/ { i = 0; next }
+
+		# Now that we know the size, stop parsing for it
+		a == 1 {printf("export ALT_STRUCT_SIZE=%d\n", $4); a = 2}
+		b == 1 {printf("export BUG_STRUCT_SIZE=%d\n", $4); b = 2}
+		e == 1 {printf("export EX_STRUCT_SIZE=%d\n", $4); e = 2}
+		j == 1 {printf("export JUMP_STRUCT_SIZE=%d\n", $4); j = 2}
+		i == 1 {printf("export PRINTK_INDEX_STRUCT_SIZE=%d\n", $4); i = 2}
+
+		# Bail out once we have everything
+		a == 2 && b == 2 && e == 2 && (j == 2 || skip_j) && (i == 2 || skip_i) {exit}')"
+
+	[[ -n "$SPECIAL_VARS" ]] && eval "$SPECIAL_VARS"
+
+	[[ -z "$ALT_STRUCT_SIZE" ]] && die "can't find special struct alt_instr size"
+	[[ -z "$BUG_STRUCT_SIZE" ]] && die "can't find special struct bug_entry size"
+	[[ -z "$EX_STRUCT_SIZE" ]]  && die "can't find special struct paravirt_patch_site size"
+	[[ -z "$JUMP_STRUCT_SIZE" && "$CONFIG_JUMP_LABEL" -ne 0 ]] && die "can't find special struct jump_entry size"
+	[[ -z "$PRINTK_INDEX_STRUCT_SIZE" && "$CONFIG_PRINTK_INDEX" -ne 0 ]] && die "can't find special struct pi_entry size"
+
+	return
+
+}
+
 find_special_section_data() {
 	if [[ "$ARCH" = "ppc64le" ]]; then
 		find_special_section_data_ppc64le
 		return
+	elif [[ "$ARCH" = "aarch64" ]]; then
+		find_special_section_data_aarch64
+		return
 	fi
 
 	[[ "$CONFIG_PARAVIRT" -eq 0 ]] && AWK_OPTIONS="-vskip_p=1"