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

5 files changed, 76 insertions, 25 deletions

diff --git a/arch/arm64/include/asm/alternative-macros.h b/arch/arm64/include/asm/alternative-macros.h
index 7e157ab6cd50..b5ac0b85c9bb 100644
--- a/arch/arm64/include/asm/alternative-macros.h
+++ b/arch/arm64/include/asm/alternative-macros.h
@@ -2,10 +2,22 @@
 #ifndef __ASM_ALTERNATIVE_MACROS_H
 #define __ASM_ALTERNATIVE_MACROS_H
 
+#include <linux/bits.h>
+#include <linux/const.h>
+
 #include <asm/cpucaps.h>
 #include <asm/insn-def.h>
 
-#define ARM64_CB_PATCH ARM64_NCAPS
+/*
+ * Binutils 2.27.0 can't handle a 'UL' suffix on constants, so for the assembly
+ * macros below we must use we must use `(1 << ARM64_CB_SHIFT)`.
+ */
+#define ARM64_CB_SHIFT	15
+#define ARM64_CB_BIT	BIT(ARM64_CB_SHIFT)
+
+#if ARM64_NCAPS >= ARM64_CB_BIT
+#error "cpucaps have overflown ARM64_CB_BIT"
+#endif
 
 #ifndef __ASSEMBLY__
 
@@ -73,8 +85,8 @@
 #define _ALTERNATIVE_CFG(oldinstr, newinstr, feature, cfg, ...)	\
 	__ALTERNATIVE_CFG(oldinstr, newinstr, feature, IS_ENABLED(cfg))
 
-#define ALTERNATIVE_CB(oldinstr, cb) \
-	__ALTERNATIVE_CFG_CB(oldinstr, ARM64_CB_PATCH, 1, cb)
+#define ALTERNATIVE_CB(oldinstr, feature, cb) \
+	__ALTERNATIVE_CFG_CB(oldinstr, (1 << ARM64_CB_SHIFT) | (feature), 1, cb)
 #else
 
 #include <asm/assembler.h>
@@ -82,7 +94,7 @@
 .macro altinstruction_entry orig_offset alt_offset feature orig_len alt_len
 	.word \orig_offset - .
 	.word \alt_offset - .
-	.hword \feature
+	.hword (\feature)
 	.byte \orig_len
 	.byte \alt_len
 .endm
@@ -141,10 +153,10 @@
 661:
 .endm
 
-.macro alternative_cb cb
+.macro alternative_cb cap, cb
 	.set .Lasm_alt_mode, 0
 	.pushsection .altinstructions, "a"
-	altinstruction_entry 661f, \cb, ARM64_CB_PATCH, 662f-661f, 0
+	altinstruction_entry 661f, \cb, (1 << ARM64_CB_SHIFT) | \cap, 662f-661f, 0
 	.popsection
 661:
 .endm
@@ -207,4 +219,46 @@ alternative_endif
 #define ALTERNATIVE(oldinstr, newinstr, ...)   \
 	_ALTERNATIVE_CFG(oldinstr, newinstr, __VA_ARGS__, 1)
 
+#ifndef __ASSEMBLY__
+
+#include <linux/types.h>
+
+static __always_inline bool
+alternative_has_feature_likely(unsigned long feature)
+{
+	compiletime_assert(feature < ARM64_NCAPS,
+			   "feature must be < ARM64_NCAPS");
+
+	asm_volatile_goto(
+	ALTERNATIVE_CB("b	%l[l_no]", %[feature], alt_cb_patch_nops)
+	:
+	: [feature] "i" (feature)
+	:
+	: l_no);
+
+	return true;
+l_no:
+	return false;
+}
+
+static __always_inline bool
+alternative_has_feature_unlikely(unsigned long feature)
+{
+	compiletime_assert(feature < ARM64_NCAPS,
+			   "feature must be < ARM64_NCAPS");
+
+	asm_volatile_goto(
+	ALTERNATIVE("nop", "b	%l[l_yes]", %[feature])
+	:
+	: [feature] "i" (feature)
+	:
+	: l_yes);
+
+	return false;
+l_yes:
+	return true;
+}
+
+#endif /* __ASSEMBLY__ */
+
 #endif /* __ASM_ALTERNATIVE_MACROS_H */
diff --git a/arch/arm64/include/asm/assembler.h b/arch/arm64/include/asm/assembler.h
index cf8e72e733de..e5957a53be39 100644
--- a/arch/arm64/include/asm/assembler.h
+++ b/arch/arm64/include/asm/assembler.h
@@ -293,7 +293,7 @@ alternative_endif
 alternative_if_not ARM64_KVM_PROTECTED_MODE
 	ASM_BUG()
 alternative_else_nop_endif
-alternative_cb kvm_compute_final_ctr_el0
+alternative_cb ARM64_ALWAYS_SYSTEM, kvm_compute_final_ctr_el0
 	movz	\reg, #0
 	movk	\reg, #0, lsl #16
 	movk	\reg, #0, lsl #32
@@ -877,7 +877,7 @@ alternative_endif
 
 	.macro __mitigate_spectre_bhb_loop      tmp
 #ifdef CONFIG_MITIGATE_SPECTRE_BRANCH_HISTORY
-alternative_cb  spectre_bhb_patch_loop_iter
+alternative_cb ARM64_ALWAYS_SYSTEM, spectre_bhb_patch_loop_iter
 	mov	\tmp, #32		// Patched to correct the immediate
 alternative_cb_end
 .Lspectre_bhb_loop\@:
@@ -890,7 +890,7 @@ alternative_cb_end
 
 	.macro mitigate_spectre_bhb_loop	tmp
 #ifdef CONFIG_MITIGATE_SPECTRE_BRANCH_HISTORY
-alternative_cb	spectre_bhb_patch_loop_mitigation_enable
+alternative_cb ARM64_ALWAYS_SYSTEM, spectre_bhb_patch_loop_mitigation_enable
 	b	.L_spectre_bhb_loop_done\@	// Patched to NOP
 alternative_cb_end
 	__mitigate_spectre_bhb_loop	\tmp
@@ -904,7 +904,7 @@ alternative_cb_end
 	stp	x0, x1, [sp, #-16]!
 	stp	x2, x3, [sp, #-16]!
 	mov	w0, #ARM_SMCCC_ARCH_WORKAROUND_3
-alternative_cb	smccc_patch_fw_mitigation_conduit
+alternative_cb ARM64_ALWAYS_SYSTEM, smccc_patch_fw_mitigation_conduit
 	nop					// Patched to SMC/HVC #0
 alternative_cb_end
 	ldp	x2, x3, [sp], #16
@@ -914,7 +914,7 @@ alternative_cb_end
 
 	.macro mitigate_spectre_bhb_clear_insn
 #ifdef CONFIG_MITIGATE_SPECTRE_BRANCH_HISTORY
-alternative_cb	spectre_bhb_patch_clearbhb
+alternative_cb ARM64_ALWAYS_SYSTEM, spectre_bhb_patch_clearbhb
 	/* Patched to NOP when not supported */
 	clearbhb
 	isb
diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h
index a08672286b4c..f73f11b55042 100644
--- a/arch/arm64/include/asm/cpufeature.h
+++ b/arch/arm64/include/asm/cpufeature.h
@@ -6,6 +6,7 @@
 #ifndef __ASM_CPUFEATURE_H
 #define __ASM_CPUFEATURE_H
 
+#include <asm/alternative-macros.h>
 #include <asm/cpucaps.h>
 #include <asm/cputype.h>
 #include <asm/hwcap.h>
@@ -419,12 +420,8 @@ static __always_inline bool is_hyp_code(void)
 }
 
 extern DECLARE_BITMAP(cpu_hwcaps, ARM64_NCAPS);
-extern struct static_key_false cpu_hwcap_keys[ARM64_NCAPS];
-extern struct static_key_false arm64_const_caps_ready;
 
-/* ARM64 CAPS + alternative_cb */
-#define ARM64_NPATCHABLE (ARM64_NCAPS + 1)
-extern DECLARE_BITMAP(boot_capabilities, ARM64_NPATCHABLE);
+extern DECLARE_BITMAP(boot_capabilities, ARM64_NCAPS);
 
 #define for_each_available_cap(cap)		\
 	for_each_set_bit(cap, cpu_hwcaps, ARM64_NCAPS)
@@ -440,7 +437,7 @@ unsigned long cpu_get_elf_hwcap2(void);
 
 static __always_inline bool system_capabilities_finalized(void)
 {
-	return static_branch_likely(&arm64_const_caps_ready);
+	return alternative_has_feature_likely(ARM64_ALWAYS_SYSTEM);
 }
 
 /*
@@ -448,11 +445,11 @@ static __always_inline bool system_capabilities_finalized(void)
  *
  * Before the capability is detected, this returns false.
  */
-static inline bool cpus_have_cap(unsigned int num)
+static __always_inline bool cpus_have_cap(unsigned int num)
 {
 	if (num >= ARM64_NCAPS)
 		return false;
-	return test_bit(num, cpu_hwcaps);
+	return arch_test_bit(num, cpu_hwcaps);
 }
 
 /*
@@ -467,7 +464,7 @@ static __always_inline bool __cpus_have_const_cap(int num)
 {
 	if (num >= ARM64_NCAPS)
 		return false;
-	return static_branch_unlikely(&cpu_hwcap_keys[num]);
+	return alternative_has_feature_unlikely(num);
 }
 
 /*
diff --git a/arch/arm64/include/asm/kvm_mmu.h b/arch/arm64/include/asm/kvm_mmu.h
index b208da3bebec..7784081088e7 100644
--- a/arch/arm64/include/asm/kvm_mmu.h
+++ b/arch/arm64/include/asm/kvm_mmu.h
@@ -63,7 +63,7 @@
  * specific registers encoded in the instructions).
  */
 .macro kern_hyp_va	reg
-alternative_cb kvm_update_va_mask
+alternative_cb ARM64_ALWAYS_SYSTEM, kvm_update_va_mask
 	and     \reg, \reg, #1		/* mask with va_mask */
 	ror	\reg, \reg, #1		/* rotate to the first tag bit */
 	add	\reg, \reg, #0		/* insert the low 12 bits of the tag */
@@ -97,7 +97,7 @@ alternative_cb_end
 	hyp_pa	\reg, \tmp
 
 	/* Load kimage_voffset. */
-alternative_cb kvm_get_kimage_voffset
+alternative_cb ARM64_ALWAYS_SYSTEM, kvm_get_kimage_voffset
 	movz	\tmp, #0
 	movk	\tmp, #0, lsl #16
 	movk	\tmp, #0, lsl #32
@@ -131,6 +131,7 @@ static __always_inline unsigned long __kern_hyp_va(unsigned long v)
 				    "add %0, %0, #0\n"
 				    "add %0, %0, #0, lsl 12\n"
 				    "ror %0, %0, #63\n",
+				    ARM64_ALWAYS_SYSTEM,
 				    kvm_update_va_mask)
 		     : "+r" (v));
 	return v;
diff --git a/arch/arm64/include/asm/lse.h b/arch/arm64/include/asm/lse.h
index 29c85810ae69..c503db8e73b0 100644
--- a/arch/arm64/include/asm/lse.h
+++ b/arch/arm64/include/asm/lse.h
@@ -13,14 +13,13 @@
 #include <linux/jump_label.h>
 #include <linux/stringify.h>
 #include <asm/alternative.h>
+#include <asm/alternative-macros.h>
 #include <asm/atomic_lse.h>
 #include <asm/cpucaps.h>
 
-extern struct static_key_false cpu_hwcap_keys[ARM64_NCAPS];
-
 static __always_inline bool system_uses_lse_atomics(void)
 {
-	return static_branch_likely(&cpu_hwcap_keys[ARM64_HAS_LSE_ATOMICS]);
+	return alternative_has_feature_likely(ARM64_HAS_LSE_ATOMICS);
 }
 
 #define __lse_ll_sc_body(op, ...)					\