riscv: sifive: Apply errata "cip-453" patch

Add sign extension to the $badaddr before addressing the instruction page
fault and instruction access fault to workaround the issue "cip-453".

To avoid affecting the existing code sequence, this patch will creates two
trampolines to add sign extension to the $badaddr. By the "alternative"
mechanism, these two trampolines will replace the original exception
handler of instruction page fault and instruction access fault in the
excp_vect_table. In this case, only the specific SiFive CPU core jumps to
the do_page_fault and do_trap_insn_fault through these two trampolines.
Other CPUs are not affected.

Signed-off-by: Vincent Chen <vincent.chen@sifive.com>
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>

arch/riscv/Kconfig.erratas

@@ -19,4 +19,15 @@ config ERRATA_SIFIVE
 
 	  Otherwise, please say "N" here to avoid unnecessary overhead.
 
+config ERRATA_SIFIVE_CIP_453
+	bool "Apply SiFive errata CIP-453"
+	depends on ERRATA_SIFIVE
+	default y
+	help
+	  This will apply the SiFive CIP-453 errata to add sign extension
+	  to the $badaddr when exception type is instruction page fault
+	  and instruction access fault.
+
+	  If you don't know what to do here, say "Y".
+
 endmenu

arch/riscv/errata/sifive/Makefile

@@ -1 +1,2 @@
+obj-y += errata_cip_453.o
 obj-y += errata.o

arch/riscv/errata/sifive/errata.c

@@ -16,6 +16,26 @@ struct errata_info_t {
 	bool (*check_func)(unsigned long  arch_id, unsigned long impid);
 };
 
+static bool errata_cip_453_check_func(unsigned long  arch_id, unsigned long impid)
+{
+	/*
+	 * Affected cores:
+	 * Architecture ID: 0x8000000000000007
+	 * Implement ID: 0x20181004 <= impid <= 0x20191105
+	 */
+	if (arch_id != 0x8000000000000007 ||
+	    (impid < 0x20181004 || impid > 0x20191105))
+		return false;
+	return true;
+}
+
+static struct errata_info_t errata_list[ERRATA_SIFIVE_NUMBER] = {
+	{
+		.name = "cip-453",
+		.check_func = errata_cip_453_check_func
+	},
+};
+
 static u32 __init sifive_errata_probe(unsigned long archid, unsigned long impid)
 {
 	int idx;

arch/riscv/errata/sifive/errata_cip_453.S

@@ -0,0 +1,38 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) 2021 SiFive
+ */
+
+#include <linux/linkage.h>
+#include <asm/asm.h>
+#include <asm/asm-offsets.h>
+#include <asm/alternative.h>
+
+.macro ADD_SIGN_EXT pt_reg badaddr tmp_reg
+	REG_L \badaddr, PT_BADADDR(\pt_reg)
+	li \tmp_reg,1
+	slli \tmp_reg,\tmp_reg,0x26
+	and \tmp_reg,\tmp_reg,\badaddr
+	beqz \tmp_reg, 1f
+	li \tmp_reg,-1
+	slli \tmp_reg,\tmp_reg,0x27
+	or \badaddr,\tmp_reg,\badaddr
+	REG_S \badaddr, PT_BADADDR(\pt_reg)
+1:
+.endm
+
+ENTRY(sifive_cip_453_page_fault_trp)
+	ADD_SIGN_EXT a0, t0, t1
+#ifdef CONFIG_MMU
+	la t0, do_page_fault
+#else
+	la t0, do_trap_unknown
+#endif
+	jr t0
+END(sifive_cip_453_page_fault_trp)
+
+ENTRY(sifive_cip_453_insn_fault_trp)
+	ADD_SIGN_EXT a0, t0, t1
+	la t0, do_trap_insn_fault
+	jr t0
+END(sifive_cip_453_insn_fault_trp)

arch/riscv/include/asm/errata_list.h

@@ -5,8 +5,27 @@
 #ifndef ASM_ERRATA_LIST_H
 #define ASM_ERRATA_LIST_H
 
+#include <asm/alternative.h>
+#include <asm/vendorid_list.h>
+
 #ifdef CONFIG_ERRATA_SIFIVE
-#define	ERRATA_SIFIVE_NUMBER 0
+#define	ERRATA_SIFIVE_CIP_453 0
+#define	ERRATA_SIFIVE_NUMBER 1
 #endif
 
+#ifdef __ASSEMBLY__
+
+#define ALT_INSN_FAULT(x)						\
+ALTERNATIVE(__stringify(RISCV_PTR do_trap_insn_fault),			\
+	    __stringify(RISCV_PTR sifive_cip_453_insn_fault_trp),	\
+	    SIFIVE_VENDOR_ID, ERRATA_SIFIVE_CIP_453,			\
+	    CONFIG_ERRATA_SIFIVE_CIP_453)
+
+#define ALT_PAGE_FAULT(x)						\
+ALTERNATIVE(__stringify(RISCV_PTR do_page_fault),			\
+	    __stringify(RISCV_PTR sifive_cip_453_page_fault_trp),	\
+	    SIFIVE_VENDOR_ID, ERRATA_SIFIVE_CIP_453,			\
+	    CONFIG_ERRATA_SIFIVE_CIP_453)
+#endif /* __ASSEMBLY__ */
+
 #endif

arch/riscv/kernel/entry.S

@@ -12,6 +12,7 @@
 #include <asm/unistd.h>
 #include <asm/thread_info.h>
 #include <asm/asm-offsets.h>
+#include <asm/errata_list.h>
 
 #if !IS_ENABLED(CONFIG_PREEMPTION)
 .set resume_kernel, restore_all
@@ -450,7 +451,7 @@ ENDPROC(__switch_to)
 	/* Exception vector table */
 ENTRY(excp_vect_table)
 	RISCV_PTR do_trap_insn_misaligned
-	RISCV_PTR do_trap_insn_fault
+	ALT_INSN_FAULT(RISCV_PTR do_trap_insn_fault)
 	RISCV_PTR do_trap_insn_illegal
 	RISCV_PTR do_trap_break
 	RISCV_PTR do_trap_load_misaligned
@@ -461,7 +462,8 @@ ENTRY(excp_vect_table)
 	RISCV_PTR do_trap_ecall_s
 	RISCV_PTR do_trap_unknown
 	RISCV_PTR do_trap_ecall_m
-	RISCV_PTR do_page_fault   /* instruction page fault */
+	/* instruciton page fault */
+	ALT_PAGE_FAULT(RISCV_PTR do_page_fault)
 	RISCV_PTR do_page_fault   /* load page fault */
 	RISCV_PTR do_trap_unknown
 	RISCV_PTR do_page_fault   /* store page fault */