Merge tag 'arm64-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux

Pull arm64 fixes from Catalin Marinas:

 - Revert the moving of the jump labels initialisation before
   setup_machine_fdt(). The bug was fixed in drivers/char/random.c.

 - Ftrace fixes: branch range check and consistent handling of PLTs.

 - Clean rather than invalidate FROM_DEVICE buffers at start of DMA
   transfer (safer if such buffer is mapped in user space). A cache
   invalidation is done already at the end of the transfer.

 - A couple of clean-ups (unexport symbol, remove unused label).

* tag 'arm64-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux:
  arm64: mm: Don't invalidate FROM_DEVICE buffers at start of DMA transfer
  arm64/cpufeature: Unexport set_cpu_feature()
  arm64: ftrace: remove redundant label
  arm64: ftrace: consistently handle PLTs.
  arm64: ftrace: fix branch range checks
  Revert "arm64: Initialize jump labels before setup_machine_fdt()"

arch/arm64/kernel/cpufeature.c

@@ -3101,7 +3101,6 @@ void cpu_set_feature(unsigned int num)
 	WARN_ON(num >= MAX_CPU_FEATURES);
 	elf_hwcap |= BIT(num);
 }
-EXPORT_SYMBOL_GPL(cpu_set_feature);
 
 bool cpu_have_feature(unsigned int num)
 {

arch/arm64/kernel/entry-ftrace.S

@@ -102,7 +102,6 @@ SYM_INNER_LABEL(ftrace_call, SYM_L_GLOBAL)
  * x19-x29 per the AAPCS, and we created frame records upon entry, so we need
  * to restore x0-x8, x29, and x30.
  */
-ftrace_common_return:
 	/* Restore function arguments */
 	ldp	x0, x1, [sp]
 	ldp	x2, x3, [sp, #S_X2]

arch/arm64/kernel/ftrace.c

@@ -78,47 +78,76 @@ static struct plt_entry *get_ftrace_plt(struct module *mod, unsigned long addr)
 }
 
 /*
- * Turn on the call to ftrace_caller() in instrumented function
+ * Find the address the callsite must branch to in order to reach '*addr'.
+ *
+ * Due to the limited range of 'BL' instructions, modules may be placed too far
+ * away to branch directly and must use a PLT.
+ *
+ * Returns true when '*addr' contains a reachable target address, or has been
+ * modified to contain a PLT address. Returns false otherwise.
  */
-int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
+static bool ftrace_find_callable_addr(struct dyn_ftrace *rec,
+				      struct module *mod,
+				      unsigned long *addr)
 {
 	unsigned long pc = rec->ip;
-	u32 old, new;
-	long offset = (long)pc - (long)addr;
+	long offset = (long)*addr - (long)pc;
+	struct plt_entry *plt;
 
-	if (offset < -SZ_128M || offset >= SZ_128M) {
-		struct module *mod;
-		struct plt_entry *plt;
+	/*
+	 * When the target is within range of the 'BL' instruction, use 'addr'
+	 * as-is and branch to that directly.
+	 */
+	if (offset >= -SZ_128M && offset < SZ_128M)
+		return true;
 
-		if (!IS_ENABLED(CONFIG_ARM64_MODULE_PLTS))
-			return -EINVAL;
+	/*
+	 * When the target is outside of the range of a 'BL' instruction, we
+	 * must use a PLT to reach it. We can only place PLTs for modules, and
+	 * only when module PLT support is built-in.
+	 */
+	if (!IS_ENABLED(CONFIG_ARM64_MODULE_PLTS))
+		return false;
 
-		/*
-		 * On kernels that support module PLTs, the offset between the
-		 * branch instruction and its target may legally exceed the
-		 * range of an ordinary relative 'bl' opcode. In this case, we
-		 * need to branch via a trampoline in the module.
-		 *
-		 * NOTE: __module_text_address() must be called with preemption
-		 * disabled, but we can rely on ftrace_lock to ensure that 'mod'
-		 * retains its validity throughout the remainder of this code.
-		 */
+	/*
+	 * 'mod' is only set at module load time, but if we end up
+	 * dealing with an out-of-range condition, we can assume it
+	 * is due to a module being loaded far away from the kernel.
+	 *
+	 * NOTE: __module_text_address() must be called with preemption
+	 * disabled, but we can rely on ftrace_lock to ensure that 'mod'
+	 * retains its validity throughout the remainder of this code.
+	 */
+	if (!mod) {
 		preempt_disable();
 		mod = __module_text_address(pc);
 		preempt_enable();
+	}
 
-		if (WARN_ON(!mod))
-			return -EINVAL;
+	if (WARN_ON(!mod))
+		return false;
 
-		plt = get_ftrace_plt(mod, addr);
-		if (!plt) {
-			pr_err("ftrace: no module PLT for %ps\n", (void *)addr);
-			return -EINVAL;
-		}
-
-		addr = (unsigned long)plt;
+	plt = get_ftrace_plt(mod, *addr);
+	if (!plt) {
+		pr_err("ftrace: no module PLT for %ps\n", (void *)*addr);
+		return false;
 	}
 
+	*addr = (unsigned long)plt;
+	return true;
+}
+
+/*
+ * Turn on the call to ftrace_caller() in instrumented function
+ */
+int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
+{
+	unsigned long pc = rec->ip;
+	u32 old, new;
+
+	if (!ftrace_find_callable_addr(rec, NULL, &addr))
+		return -EINVAL;
+
 	old = aarch64_insn_gen_nop();
 	new = aarch64_insn_gen_branch_imm(pc, addr, AARCH64_INSN_BRANCH_LINK);
 
@@ -132,6 +161,11 @@ int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
 	unsigned long pc = rec->ip;
 	u32 old, new;
 
+	if (!ftrace_find_callable_addr(rec, NULL, &old_addr))
+		return -EINVAL;
+	if (!ftrace_find_callable_addr(rec, NULL, &addr))
+		return -EINVAL;
+
 	old = aarch64_insn_gen_branch_imm(pc, old_addr,
 					  AARCH64_INSN_BRANCH_LINK);
 	new = aarch64_insn_gen_branch_imm(pc, addr, AARCH64_INSN_BRANCH_LINK);
@@ -181,54 +215,15 @@ int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec,
 		    unsigned long addr)
 {
 	unsigned long pc = rec->ip;
-	bool validate = true;
 	u32 old = 0, new;
-	long offset = (long)pc - (long)addr;
 
-	if (offset < -SZ_128M || offset >= SZ_128M) {
-		u32 replaced;
-
-		if (!IS_ENABLED(CONFIG_ARM64_MODULE_PLTS))
-			return -EINVAL;
-
-		/*
-		 * 'mod' is only set at module load time, but if we end up
-		 * dealing with an out-of-range condition, we can assume it
-		 * is due to a module being loaded far away from the kernel.
-		 */
-		if (!mod) {
-			preempt_disable();
-			mod = __module_text_address(pc);
-			preempt_enable();
-
-			if (WARN_ON(!mod))
-				return -EINVAL;
-		}
-
-		/*
-		 * The instruction we are about to patch may be a branch and
-		 * link instruction that was redirected via a PLT entry. In
-		 * this case, the normal validation will fail, but we can at
-		 * least check that we are dealing with a branch and link
-		 * instruction that points into the right module.
-		 */
-		if (aarch64_insn_read((void *)pc, &replaced))
-			return -EFAULT;
-
-		if (!aarch64_insn_is_bl(replaced) ||
-		    !within_module(pc + aarch64_get_branch_offset(replaced),
-				   mod))
-			return -EINVAL;
-
-		validate = false;
-	} else {
-		old = aarch64_insn_gen_branch_imm(pc, addr,
-						  AARCH64_INSN_BRANCH_LINK);
-	}
+	if (!ftrace_find_callable_addr(rec, mod, &addr))
+		return -EINVAL;
 
+	old = aarch64_insn_gen_branch_imm(pc, addr, AARCH64_INSN_BRANCH_LINK);
 	new = aarch64_insn_gen_nop();
 
-	return ftrace_modify_code(pc, old, new, validate);
+	return ftrace_modify_code(pc, old, new, true);
 }
 
 void arch_ftrace_update_code(int command)

arch/arm64/kernel/setup.c

@@ -303,14 +303,13 @@ void __init __no_sanitize_address setup_arch(char **cmdline_p)
 	early_fixmap_init();
 	early_ioremap_init();
 
+	setup_machine_fdt(__fdt_pointer);
+
 	/*
 	 * Initialise the static keys early as they may be enabled by the
-	 * cpufeature code, early parameters, and DT setup.
+	 * cpufeature code and early parameters.
 	 */
 	jump_label_init();
-
-	setup_machine_fdt(__fdt_pointer);
-
 	parse_early_param();
 
 	/*

arch/arm64/mm/cache.S

@@ -218,8 +218,6 @@ SYM_FUNC_ALIAS(__dma_flush_area, __pi___dma_flush_area)
  */
 SYM_FUNC_START(__pi___dma_map_area)
 	add	x1, x0, x1
-	cmp	w2, #DMA_FROM_DEVICE
-	b.eq	__pi_dcache_inval_poc
 	b	__pi_dcache_clean_poc
 SYM_FUNC_END(__pi___dma_map_area)
 SYM_FUNC_ALIAS(__dma_map_area, __pi___dma_map_area)