1 files changed, 177 insertions, 57 deletions

diff --git a/arch/arm64/kernel/alternative.c b/arch/arm64/kernel/alternative.c
index 6dd0a3a3e5c9..91263d09ea65 100644
--- a/arch/arm64/kernel/alternative.c
+++ b/arch/arm64/kernel/alternative.c
@@ -1,66 +1,62 @@
+// SPDX-License-Identifier: GPL-2.0-only
 /*
  * alternative runtime patching
  * inspired by the x86 version
  *
  * Copyright (C) 2014 ARM Ltd.
- *
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License version 2 as
- * published by the Free Software Foundation.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- * GNU General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License
- * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 
 #define pr_fmt(fmt) "alternatives: " fmt
 
 #include <linux/init.h>
 #include <linux/cpu.h>
+#include <linux/elf.h>
 #include <asm/cacheflush.h>
 #include <asm/alternative.h>
 #include <asm/cpufeature.h>
 #include <asm/insn.h>
+#include <asm/module.h>
 #include <asm/sections.h>
+#include <asm/vdso.h>
 #include <linux/stop_machine.h>
 
-#define __ALT_PTR(a,f)		((void *)&(a)->f + (a)->f)
+#define __ALT_PTR(a, f)		((void *)&(a)->f + (a)->f)
 #define ALT_ORIG_PTR(a)		__ALT_PTR(a, orig_offset)
 #define ALT_REPL_PTR(a)		__ALT_PTR(a, alt_offset)
 
+#define ALT_CAP(a)		((a)->cpufeature & ~ARM64_CB_BIT)
+#define ALT_HAS_CB(a)		((a)->cpufeature & ARM64_CB_BIT)
+
+/* Volatile, as we may be patching the guts of READ_ONCE() */
+static volatile int all_alternatives_applied;
+
+static DECLARE_BITMAP(applied_alternatives, ARM64_NCAPS);
+
 struct alt_region {
 	struct alt_instr *begin;
 	struct alt_instr *end;
 };
 
+bool alternative_is_applied(u16 cpufeature)
+{
+	if (WARN_ON(cpufeature >= ARM64_NCAPS))
+		return false;
+
+	return test_bit(cpufeature, applied_alternatives);
+}
+
 /*
  * Check if the target PC is within an alternative block.
  */
-static bool branch_insn_requires_update(struct alt_instr *alt, unsigned long pc)
+static __always_inline bool branch_insn_requires_update(struct alt_instr *alt, unsigned long pc)
 {
-	unsigned long replptr;
-
-	if (kernel_text_address(pc))
-		return 1;
-
-	replptr = (unsigned long)ALT_REPL_PTR(alt);
-	if (pc >= replptr && pc <= (replptr + alt->alt_len))
-		return 0;
-
-	/*
-	 * Branching into *another* alternate sequence is doomed, and
-	 * we're not even trying to fix it up.
-	 */
-	BUG();
+	unsigned long replptr = (unsigned long)ALT_REPL_PTR(alt);
+	return !(pc >= replptr && pc <= (replptr + alt->alt_len));
 }
 
 #define align_down(x, a)	((unsigned long)(x) & ~(((unsigned long)(a)) - 1))
 
-static u32 get_alt_insn(struct alt_instr *alt, __le32 *insnptr, __le32 *altinsnptr)
+static __always_inline u32 get_alt_insn(struct alt_instr *alt, __le32 *insnptr, __le32 *altinsnptr)
 {
 	u32 insn;
 
@@ -105,60 +101,152 @@ static u32 get_alt_insn(struct alt_instr *alt, __le32 *insnptr, __le32 *altinsnp
 	return insn;
 }
 
-static void __apply_alternatives(void *alt_region, bool use_linear_alias)
+static noinstr void patch_alternative(struct alt_instr *alt,
+			      __le32 *origptr, __le32 *updptr, int nr_inst)
+{
+	__le32 *replptr;
+	int i;
+
+	replptr = ALT_REPL_PTR(alt);
+	for (i = 0; i < nr_inst; i++) {
+		u32 insn;
+
+		insn = get_alt_insn(alt, origptr + i, replptr + i);
+		updptr[i] = cpu_to_le32(insn);
+	}
+}
+
+/*
+ * We provide our own, private D-cache cleaning function so that we don't
+ * accidentally call into the cache.S code, which is patched by us at
+ * runtime.
+ */
+static void clean_dcache_range_nopatch(u64 start, u64 end)
+{
+	u64 cur, d_size, ctr_el0;
+
+	ctr_el0 = read_sanitised_ftr_reg(SYS_CTR_EL0);
+	d_size = 4 << cpuid_feature_extract_unsigned_field(ctr_el0,
+							   CTR_EL0_DminLine_SHIFT);
+	cur = start & ~(d_size - 1);
+	do {
+		/*
+		 * We must clean+invalidate to the PoC in order to avoid
+		 * Cortex-A53 errata 826319, 827319, 824069 and 819472
+		 * (this corresponds to ARM64_WORKAROUND_CLEAN_CACHE)
+		 */
+		asm volatile("dc civac, %0" : : "r" (cur) : "memory");
+	} while (cur += d_size, cur < end);
+}
+
+static void __apply_alternatives(const struct alt_region *region,
+				 bool is_module,
+				 unsigned long *feature_mask)
 {
 	struct alt_instr *alt;
-	struct alt_region *region = alt_region;
-	__le32 *origptr, *replptr, *updptr;
+	__le32 *origptr, *updptr;
+	alternative_cb_t alt_cb;
 
 	for (alt = region->begin; alt < region->end; alt++) {
-		u32 insn;
-		int i, nr_inst;
+		int nr_inst;
+		int cap = ALT_CAP(alt);
 
-		if (!cpus_have_cap(alt->cpufeature))
+		if (!test_bit(cap, feature_mask))
 			continue;
 
-		BUG_ON(alt->alt_len != alt->orig_len);
+		if (!cpus_have_cap(cap))
+			continue;
 
-		pr_info_once("patching kernel code\n");
+		if (ALT_HAS_CB(alt))
+			BUG_ON(alt->alt_len != 0);
+		else
+			BUG_ON(alt->alt_len != alt->orig_len);
 
 		origptr = ALT_ORIG_PTR(alt);
-		replptr = ALT_REPL_PTR(alt);
-		updptr = use_linear_alias ? lm_alias(origptr) : origptr;
-		nr_inst = alt->alt_len / sizeof(insn);
+		updptr = is_module ? origptr : lm_alias(origptr);
+		nr_inst = alt->orig_len / AARCH64_INSN_SIZE;
+
+		if (ALT_HAS_CB(alt))
+			alt_cb  = ALT_REPL_PTR(alt);
+		else
+			alt_cb = patch_alternative;
 
-		for (i = 0; i < nr_inst; i++) {
-			insn = get_alt_insn(alt, origptr + i, replptr + i);
-			updptr[i] = cpu_to_le32(insn);
+		alt_cb(alt, origptr, updptr, nr_inst);
+
+		if (!is_module) {
+			clean_dcache_range_nopatch((u64)origptr,
+						   (u64)(origptr + nr_inst));
 		}
+	}
 
-		flush_icache_range((uintptr_t)origptr,
-				   (uintptr_t)(origptr + nr_inst));
+	/*
+	 * The core module code takes care of cache maintenance in
+	 * flush_module_icache().
+	 */
+	if (!is_module) {
+		dsb(ish);
+		icache_inval_all_pou();
+		isb();
+
+		/* Ignore ARM64_CB bit from feature mask */
+		bitmap_or(applied_alternatives, applied_alternatives,
+			  feature_mask, ARM64_NCAPS);
+		bitmap_and(applied_alternatives, applied_alternatives,
+			   cpu_hwcaps, ARM64_NCAPS);
 	}
 }
 
+void apply_alternatives_vdso(void)
+{
+	struct alt_region region;
+	const struct elf64_hdr *hdr;
+	const struct elf64_shdr *shdr;
+	const struct elf64_shdr *alt;
+	DECLARE_BITMAP(all_capabilities, ARM64_NCAPS);
+
+	bitmap_fill(all_capabilities, ARM64_NCAPS);
+
+	hdr = (struct elf64_hdr *)vdso_start;
+	shdr = (void *)hdr + hdr->e_shoff;
+	alt = find_section(hdr, shdr, ".altinstructions");
+	if (!alt)
+		return;
+
+	region = (struct alt_region){
+		.begin	= (void *)hdr + alt->sh_offset,
+		.end	= (void *)hdr + alt->sh_offset + alt->sh_size,
+	};
+
+	__apply_alternatives(&region, false, &all_capabilities[0]);
+}
+
+static const struct alt_region kernel_alternatives = {
+	.begin	= (struct alt_instr *)__alt_instructions,
+	.end	= (struct alt_instr *)__alt_instructions_end,
+};
+
 /*
  * We might be patching the stop_machine state machine, so implement a
  * really simple polling protocol here.
  */
 static int __apply_alternatives_multi_stop(void *unused)
 {
-	static int patched = 0;
-	struct alt_region region = {
-		.begin	= (struct alt_instr *)__alt_instructions,
-		.end	= (struct alt_instr *)__alt_instructions_end,
-	};
-
 	/* We always have a CPU 0 at this point (__init) */
 	if (smp_processor_id()) {
-		while (!READ_ONCE(patched))
+		while (!all_alternatives_applied)
 			cpu_relax();
 		isb();
 	} else {
-		BUG_ON(patched);
-		__apply_alternatives(&region, true);
+		DECLARE_BITMAP(remaining_capabilities, ARM64_NCAPS);
+
+		bitmap_complement(remaining_capabilities, boot_capabilities,
+				  ARM64_NCAPS);
+
+		BUG_ON(all_alternatives_applied);
+		__apply_alternatives(&kernel_alternatives, false,
+				     remaining_capabilities);
 		/* Barriers provided by the cache flushing */
-		WRITE_ONCE(patched, 1);
+		all_alternatives_applied = 1;
 	}
 
 	return 0;
@@ -166,16 +254,48 @@ static int __apply_alternatives_multi_stop(void *unused)
 
 void __init apply_alternatives_all(void)
 {
+	pr_info("applying system-wide alternatives\n");
+
+	apply_alternatives_vdso();
 	/* better not try code patching on a live SMP system */
 	stop_machine(__apply_alternatives_multi_stop, NULL, cpu_online_mask);
 }
 
-void apply_alternatives(void *start, size_t length)
+/*
+ * This is called very early in the boot process (directly after we run
+ * a feature detect on the boot CPU). No need to worry about other CPUs
+ * here.
+ */
+void __init apply_boot_alternatives(void)
+{
+	/* If called on non-boot cpu things could go wrong */
+	WARN_ON(smp_processor_id() != 0);
+
+	pr_info("applying boot alternatives\n");
+
+	__apply_alternatives(&kernel_alternatives, false,
+			     &boot_capabilities[0]);
+}
+
+#ifdef CONFIG_MODULES
+void apply_alternatives_module(void *start, size_t length)
 {
 	struct alt_region region = {
 		.begin	= start,
 		.end	= start + length,
 	};
+	DECLARE_BITMAP(all_capabilities, ARM64_NCAPS);
 
-	__apply_alternatives(&region, false);
+	bitmap_fill(all_capabilities, ARM64_NCAPS);
+
+	__apply_alternatives(&region, true, &all_capabilities[0]);
+}
+#endif
+
+noinstr void alt_cb_patch_nops(struct alt_instr *alt, __le32 *origptr,
+			       __le32 *updptr, int nr_inst)
+{
+	for (int i = 0; i < nr_inst; i++)
+		updptr[i] = cpu_to_le32(aarch64_insn_gen_nop());
 }
+EXPORT_SYMBOL(alt_cb_patch_nops);