Add arm64(AArch64) support

src/bio_helper.c

@@ -588,8 +588,7 @@ int bio_needs_cow(struct bio *bio, struct inode *inode)
         bio_iter_t iter;
         bio_iter_bvec_t bvec;
 
-#if defined HAVE_ENUM_REQ_OPF || (defined HAVE_ENUM_REQ_OP && defined HAVE_ENUM_REQ_OPF_WRITE_ZEROES)
-        //#if LINUX_VERSION_CODE >= KERNEL_VERSION(4,10,0)
+#if defined HAVE_ENUM_REQ_OP_WRITE_ZEROES
         if (bio_op(bio) == REQ_OP_WRITE_ZEROES)
                 return 1;
 #endif

src/bio_request_callback.h

@@ -28,8 +28,14 @@
 // length of `% call __fentry__` on x86_64 - uses a 1 byte op and 4 byte
 // relative address
 #define FENTRY_CALL_INSTR_BYTES 5
+#elif defined(CONFIG_ARM64)
+// arm64 ftrace patch site: two 4-byte instructions emitted by
+// -fpatchable-function-entry=2. NOTE: the passthrough using this
+// (dattobd_submit_bio_real in submit_bio.c) is dead code on blk-mq devices, so
+// this value is not load-bearing here -- it only needs to let the file compile.
+#define FENTRY_CALL_INSTR_BYTES (2 * 4)
 #else
-#pragma error "Unsupported architecture"
+#error "Unsupported architecture"
 #endif
 
 #define BIO_REQUEST_CALLBACK_FN submit_bio_fn

src/configure-tests/feature-tests/ftrace_regs_set_instruction_pointer.c

@@ -0,0 +1,14 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+/*
+ * Copyright (C) 2026 Datto Inc.
+ */
+
+#include "includes.h"
+
+MODULE_LICENSE("GPL");
+
+static inline void dummy(void){
+	struct ftrace_regs *fregs = NULL;
+	ftrace_regs_set_instruction_pointer(fregs, 0);
+}

src/ftrace_hooking.c

@@ -378,14 +378,13 @@ static int resolve_hook_address(struct ftrace_hook *hook)
 static void notrace ftrace_callback_handler(unsigned long ip, unsigned long parent_ip,
 		struct ftrace_ops *ops, struct ftrace_regs *fregs)
 {
-	struct pt_regs *regs = ftrace_get_regs(fregs);
 	struct ftrace_hook *hook = container_of(ops, struct ftrace_hook, ops);
 
 #if USE_FENTRY_OFFSET
-	regs->ip = (unsigned long)hook->function;
+	dattobd_ftrace_set_ip(fregs, hook->function);
 #else
 	if (!dattobd_within_module(parent_ip, THIS_MODULE))
-		regs->ip = (unsigned long)hook->function;
+		dattobd_ftrace_set_ip(fregs, hook->function);
 #endif //USE_FENTRY_OFFSET
 }
 
@@ -409,7 +408,11 @@ static int register_hook(struct ftrace_hook *hook)
 	}
 
 	hook->ops.func = ftrace_callback_handler;
-	hook->ops.flags = FTRACE_OPS_FL_SAVE_REGS | FTRACE_OPS_FL_RECURSION | FTRACE_OPS_FL_IPMODIFY;
+	hook->ops.flags = FTRACE_OPS_FL_RECURSION | FTRACE_OPS_FL_IPMODIFY;
+
+#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
+	hook->ops.flags |= FTRACE_OPS_FL_SAVE_REGS;
+#endif
 
 	ret = ftrace_set_filter_ip(&hook->ops, hook->address, 0, 0);
 	if (ret) {

src/ftrace_hooking.h

@@ -44,6 +44,25 @@ static __always_inline struct pt_regs *ftrace_get_regs(struct ftrace_regs *fregs
 }
 #endif
 
+/**
+   dattobd_ftrace_set_ip() - redirect execution from the ftrace callback by
+   setting the traced function's instruction pointer to our hook.
+ */
+#ifdef HAVE_FTRACE_REGS_SET_INSTRUCTION_POINTER
+#define dattobd_ftrace_set_ip(fregs, addr)                                     \
+	ftrace_regs_set_instruction_pointer((fregs), (unsigned long)(addr))
+#elif defined(CONFIG_ARM64)
+#define dattobd_ftrace_set_ip(fregs, addr)                                     \
+	do {                                                                       \
+		ftrace_get_regs(fregs)->pc = (unsigned long)(addr);                    \
+	} while (0)
+#else
+#define dattobd_ftrace_set_ip(fregs, addr)                                     \
+	do {                                                                       \
+		ftrace_get_regs(fregs)->ip = (unsigned long)(addr);                    \
+	} while (0)
+#endif
+
 #ifndef UMOUNT_NOFOLLOW
 #define UMOUNT_NOFOLLOW 0
 #endif

src/paging_helper.c

@@ -7,6 +7,8 @@
 #include "includes.h"
 #include "paging_helper.h"
 
+#ifdef CONFIG_X86
+
 //#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,22)
 #ifndef X86_CR0_WP
 #define X86_CR0_WP (1UL << 16)
@@ -53,3 +55,24 @@ void reenable_page_protection(unsigned long *cr0)
 {
         write_cr0(*cr0);
 }
+
+#else
+
+/**
+ * Page-level write-protect toggling via the CR0 register is x86-specific. It is
+ * only used by the legacy syscall-table hooking path, which is unused on the
+ * ftrace-based builds (5.9+) that non-x86 arches such as arm64 target. These
+ * functions have no callers in such builds, so provide no-op stubs to keep the
+ * module buildable on non-x86 without pulling in read_cr0()/write_cr0().
+ */
+void disable_page_protection(unsigned long *cr0)
+{
+        *cr0 = 0;
+}
+
+void reenable_page_protection(unsigned long *cr0)
+{
+        (void)cr0;
+}
+
+#endif

src/tracer.c

@@ -272,8 +272,7 @@ static int inc_trace_bio(struct snap_device *dev, struct bio *bio)
         bio_iter_t iter;
         bio_iter_bvec_t bvec;
 
-#ifdef HAVE_ENUM_REQ_OPF
-        //#if LINUX_VERSION_CODE >= KERNEL_VERSION(4,10,0)
+#if defined HAVE_ENUM_REQ_OP_WRITE_ZEROES
         if (bio_op(bio) == REQ_OP_WRITE_ZEROES) {
                 ret = inc_make_sset(dev, bio_sector(bio),
                                     bio_size(bio) / SECTOR_SIZE);