kpatch-build: Add sym->has_func_profiling support for aarch64

The "has_function_profiling" support field in the symbol struct is used to show
that a function symbol is able to be patched. This is necessary to check that
functions which need to be patched are able to be.

On arm64 this means the presence of 2 NOP instructions at function entry
which are patched by ftrace to call the ftrace handling code. These 2 NOPs
are inserted by the compiler and the location of them is recorded in a
section called "__patchable_function_entries". Check whether a symbol has a
corresponding entry in the "__patchable_function_entries" section and if so
mark it as "has_func_profiling".

Signed-off-by: Suraj Jitindar Singh <surajjs@amazon.com>
[Modify to use __patchable_function_entries support added upstream]
Signed-off-by: Puranjay Mohan <pjy@amazon.com>

Author: Suraj Jitindar Singh

kpatch-build/create-diff-object.c

@@ -1700,8 +1700,8 @@ static void kpatch_check_func_profiling_calls(struct kpatch_elf *kelf)
 		    (sym->parent && sym->parent->status == CHANGED))
 			continue;
 		if (!sym->twin->has_func_profiling) {
-			log_error("function %s has no fentry/mcount call, unable to patch\n",
-				  sym->name);
+			log_error("function %s doesn't have patchable function entry, unable to patch\n",
+				   sym->name);
 			errs++;
 		}
 	}
@@ -4180,6 +4180,10 @@ static void kpatch_find_func_profiling_calls(struct kpatch_elf *kelf)
 				insn[4] == 0x00 && insn[5] == 0x00)
 				sym->has_func_profiling = 1;
 			break;
+		case AARCH64:
+			if (kpatch_symbol_has_pfe_entry(kelf, sym))
+				sym->has_func_profiling = 1;
+			break;
 		default:
 			ERROR("unsupported arch");
 		}

kpatch-build/kpatch-elf.c

@@ -594,6 +594,9 @@ struct kpatch_elf *kpatch_elf_open(const char *name)
 	case EM_S390:
 		kelf->arch = S390;
 		break;
+	case EM_AARCH64:
+		kelf->arch = ARM64;
+		break;
 	default:
 		ERROR("Unsupported target architecture");
 	}

kpatch-build/kpatch-elf.h

@@ -116,6 +116,7 @@ enum architecture {
 	PPC64  = 0x1 << 0,
 	X86_64 = 0x1 << 1,
 	S390   = 0x1 << 2,
+	AARCH64  = 0x1 << 3,
 };
 
 struct kpatch_elf {