arch/arm64/kernel/probes/decode-insn.c

Source file repositories/reference/linux-study-clean/arch/arm64/kernel/probes/decode-insn.c

File Facts

System
Linux kernel
Corpus path
arch/arm64/kernel/probes/decode-insn.c
Extension
.c
Size
5607 bytes
Lines
188
Domain
Architecture Layer
Bucket
arch/arm64
Inferred role
Architecture Layer: implementation source
Status
source implementation candidate

Why This File Exists

CPU and platform-specific kernel glue: boot entry, traps, syscall entry, interrupts, page tables, context switch, and low-level barriers.

Dependency Surface

Detected Declarations

Annotated Snippet

aarch64_insn_is_cbnz(insn)) {
		api->handler = simulate_cbz_cbnz;
	} else if (aarch64_insn_is_tbz(insn) ||
	    aarch64_insn_is_tbnz(insn)) {
		api->handler = simulate_tbz_tbnz;
	} else if (aarch64_insn_is_adr_adrp(insn)) {
		api->handler = simulate_adr_adrp;
	} else if (aarch64_insn_is_b(insn) ||
	    aarch64_insn_is_bl(insn)) {
		api->handler = simulate_b_bl;
	} else if (aarch64_insn_is_br(insn) ||
		aarch64_insn_is_blr(insn)) {
		api->handler = simulate_br_blr;
	} else if (aarch64_insn_is_ret(insn)) {
		api->handler = simulate_ret;
	} else {
		/*
		 * Instruction cannot be stepped out-of-line and we don't
		 * (yet) simulate it.
		 */
		return INSN_REJECTED;
	}

	return INSN_GOOD_NO_SLOT;
}

#ifdef CONFIG_KPROBES
static bool __kprobes
is_probed_address_atomic(kprobe_opcode_t *scan_start, kprobe_opcode_t *scan_end)
{
	while (scan_start >= scan_end) {
		/*
		 * atomic region starts from exclusive load and ends with
		 * exclusive store.
		 */
		if (aarch64_insn_is_store_ex(le32_to_cpu(*scan_start)))
			return false;
		else if (aarch64_insn_is_load_ex(le32_to_cpu(*scan_start)))
			return true;
		scan_start--;
	}

	return false;
}

enum probe_insn __kprobes
arm_kprobe_decode_insn(kprobe_opcode_t *addr, struct arch_specific_insn *asi)
{
	enum probe_insn decoded;
	u32 insn = le32_to_cpu(*addr);
	kprobe_opcode_t *scan_end = NULL;
	unsigned long size = 0, offset = 0;
	struct arch_probe_insn *api = &asi->api;

	if (aarch64_insn_is_ldr_lit(insn)) {
		api->handler = simulate_ldr_literal;
		decoded = INSN_GOOD_NO_SLOT;
	} else if (aarch64_insn_is_ldrsw_lit(insn)) {
		api->handler = simulate_ldrsw_literal;
		decoded = INSN_GOOD_NO_SLOT;
	} else {
		decoded = arm_probe_decode_insn(insn, &asi->api);
	}

	/*
	 * If there's a symbol defined in front of and near enough to
	 * the probe address assume it is the entry point to this
	 * code and use it to further limit how far back we search
	 * when determining if we're in an atomic sequence. If we could
	 * not find any symbol skip the atomic test altogether as we
	 * could otherwise end up searching irrelevant text/literals.
	 * KPROBES depends on KALLSYMS so this last case should never
	 * happen.
	 */
	if (kallsyms_lookup_size_offset((unsigned long) addr, &size, &offset)) {
		if (offset < (MAX_ATOMIC_CONTEXT_SIZE*sizeof(kprobe_opcode_t)))
			scan_end = addr - (offset / sizeof(kprobe_opcode_t));
		else
			scan_end = addr - MAX_ATOMIC_CONTEXT_SIZE;
	}

	if (decoded != INSN_REJECTED && scan_end)
		if (is_probed_address_atomic(addr - 1, scan_end))
			return INSN_REJECTED;

	return decoded;
}
#endif

Annotation

Implementation Notes