Merge branch 'for-next/alternatives' into for-next/core

* for-next/alternatives:
  : Alternatives (code patching) improvements
  arm64: fix the build with binutils 2.27
  arm64: avoid BUILD_BUG_ON() in alternative-macros
  arm64: alternatives: add shared NOP callback
  arm64: alternatives: add alternative_has_feature_*()
  arm64: alternatives: have callbacks take a cap
  arm64: alternatives: make alt_region const
  arm64: alternatives: hoist print out of __apply_alternatives()
  arm64: alternatives: proton-pack: prepare for cap changes
  arm64: alternatives: kvm: prepare for cap changes
  arm64: cpufeature: make cpus_have_cap() noinstr-safe

1 files changed, 40 insertions, 30 deletions

diff --git a/arch/arm64/kernel/alternative.c b/arch/arm64/kernel/alternative.c
index a97775963f35..64045e3ef03a 100644
--- a/arch/arm64/kernel/alternative.c
+++ b/arch/arm64/kernel/alternative.c
@@ -24,6 +24,9 @@
 #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;
 
@@ -136,8 +139,9 @@ static void clean_dcache_range_nopatch(u64 start, u64 end)
 	} while (cur += d_size, cur < end);
 }
 
-static void __nocfi __apply_alternatives(struct alt_region *region, bool is_module,
-				 unsigned long *feature_mask)
+static void __nocfi __apply_alternatives(const struct alt_region *region,
+					 bool is_module,
+					 unsigned long *feature_mask)
 {
 	struct alt_instr *alt;
 	__le32 *origptr, *updptr;
@@ -145,30 +149,27 @@ static void __nocfi __apply_alternatives(struct alt_region *region, bool is_modu
 
 	for (alt = region->begin; alt < region->end; alt++) {
 		int nr_inst;
+		int cap = ALT_CAP(alt);
 
-		if (!test_bit(alt->cpufeature, feature_mask))
+		if (!test_bit(cap, feature_mask))
 			continue;
 
-		/* Use ARM64_CB_PATCH as an unconditional patch */
-		if (alt->cpufeature < ARM64_CB_PATCH &&
-		    !cpus_have_cap(alt->cpufeature))
+		if (!cpus_have_cap(cap))
 			continue;
 
-		if (alt->cpufeature == ARM64_CB_PATCH)
+		if (ALT_HAS_CB(alt))
 			BUG_ON(alt->alt_len != 0);
 		else
 			BUG_ON(alt->alt_len != alt->orig_len);
 
-		pr_info_once("patching kernel code\n");
-
 		origptr = ALT_ORIG_PTR(alt);
 		updptr = is_module ? origptr : lm_alias(origptr);
 		nr_inst = alt->orig_len / AARCH64_INSN_SIZE;
 
-		if (alt->cpufeature < ARM64_CB_PATCH)
-			alt_cb = patch_alternative;
-		else
+		if (ALT_HAS_CB(alt))
 			alt_cb  = ALT_REPL_PTR(alt);
+		else
+			alt_cb = patch_alternative;
 
 		alt_cb(alt, origptr, updptr, nr_inst);
 
@@ -201,9 +202,9 @@ void apply_alternatives_vdso(void)
 	const struct elf64_hdr *hdr;
 	const struct elf64_shdr *shdr;
 	const struct elf64_shdr *alt;
-	DECLARE_BITMAP(all_capabilities, ARM64_NPATCHABLE);
+	DECLARE_BITMAP(all_capabilities, ARM64_NCAPS);
 
-	bitmap_fill(all_capabilities, ARM64_NPATCHABLE);
+	bitmap_fill(all_capabilities, ARM64_NCAPS);
 
 	hdr = (struct elf64_hdr *)vdso_start;
 	shdr = (void *)hdr + hdr->e_shoff;
@@ -219,30 +220,31 @@ void apply_alternatives_vdso(void)
 	__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)
 {
-	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 (!all_alternatives_applied)
 			cpu_relax();
 		isb();
 	} else {
-		DECLARE_BITMAP(remaining_capabilities, ARM64_NPATCHABLE);
+		DECLARE_BITMAP(remaining_capabilities, ARM64_NCAPS);
 
 		bitmap_complement(remaining_capabilities, boot_capabilities,
-				  ARM64_NPATCHABLE);
+				  ARM64_NCAPS);
 
 		BUG_ON(all_alternatives_applied);
-		__apply_alternatives(&region, false, remaining_capabilities);
+		__apply_alternatives(&kernel_alternatives, false,
+				     remaining_capabilities);
 		/* Barriers provided by the cache flushing */
 		all_alternatives_applied = 1;
 	}
@@ -252,6 +254,8 @@ 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);
@@ -264,15 +268,13 @@ void __init apply_alternatives_all(void)
  */
 void __init apply_boot_alternatives(void)
 {
-	struct alt_region region = {
-		.begin	= (struct alt_instr *)__alt_instructions,
-		.end	= (struct alt_instr *)__alt_instructions_end,
-	};
-
 	/* If called on non-boot cpu things could go wrong */
 	WARN_ON(smp_processor_id() != 0);
 
-	__apply_alternatives(&region, false, &boot_capabilities[0]);
+	pr_info("applying boot alternatives\n");
+
+	__apply_alternatives(&kernel_alternatives, false,
+			     &boot_capabilities[0]);
 }
 
 #ifdef CONFIG_MODULES
@@ -282,10 +284,18 @@ void apply_alternatives_module(void *start, size_t length)
 		.begin	= start,
 		.end	= start + length,
 	};
-	DECLARE_BITMAP(all_capabilities, ARM64_NPATCHABLE);
+	DECLARE_BITMAP(all_capabilities, ARM64_NCAPS);
 
-	bitmap_fill(all_capabilities, ARM64_NPATCHABLE);
+	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);