RISC-V: Add EFI runtime services

This patch adds EFI runtime service support for RISC-V.

Signed-off-by: Atish Patra <atish.patra@wdc.com>
[ardb: - Remove the page check]
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>

8 files changed, 132 insertions, 3 deletions

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index 6ef2394be857..c8e57d77c144 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -412,7 +412,9 @@ config EFI
 	select EFI_PARAMS_FROM_FDT
 	select EFI_STUB
 	select EFI_GENERIC_STUB
+	select EFI_RUNTIME_WRAPPERS
 	select RISCV_ISA_C
+	depends on MMU
 	default y
 	help
 	  This option provides support for runtime services provided
diff --git a/arch/riscv/include/asm/efi.h b/arch/riscv/include/asm/efi.h
index bf6a40e20a8e..7542282f1141 100644
--- a/arch/riscv/include/asm/efi.h
+++ b/arch/riscv/include/asm/efi.h
@@ -5,11 +5,28 @@
 #ifndef _ASM_EFI_H
 #define _ASM_EFI_H
 
+#include <asm/csr.h>
 #include <asm/io.h>
 #include <asm/mmu_context.h>
 #include <asm/ptrace.h>
 #include <asm/tlbflush.h>
 
+#ifdef CONFIG_EFI
+extern void efi_init(void);
+#else
+#define efi_init()
+#endif
+
+int efi_create_mapping(struct mm_struct *mm, efi_memory_desc_t *md);
+int efi_set_mapping_permissions(struct mm_struct *mm, efi_memory_desc_t *md);
+
+#define arch_efi_call_virt_setup()      efi_virtmap_load()
+#define arch_efi_call_virt_teardown()   efi_virtmap_unload()
+
+#define arch_efi_call_virt(p, f, args...) p->f(args)
+
+#define ARCH_EFI_IRQ_FLAGS_MASK (SR_IE | SR_SPIE)
+
 /* on RISC-V, the FDT may be located anywhere in system RAM */
 static inline unsigned long efi_get_max_fdt_addr(unsigned long image_addr)
 {
@@ -32,4 +49,7 @@ static inline void efifb_setup_from_dmi(struct screen_info *si, const char *opt)
 {
 }
 
+void efi_virtmap_load(void);
+void efi_virtmap_unload(void);
+
 #endif /* _ASM_EFI_H */
diff --git a/arch/riscv/include/asm/mmu.h b/arch/riscv/include/asm/mmu.h
index 967eacb01ab5..dabcf2cfb3dc 100644
--- a/arch/riscv/include/asm/mmu.h
+++ b/arch/riscv/include/asm/mmu.h
@@ -20,6 +20,8 @@ typedef struct {
 #endif
 } mm_context_t;
 
+void __init create_pgd_mapping(pgd_t *pgdp, uintptr_t va, phys_addr_t pa,
+			       phys_addr_t sz, pgprot_t prot);
 #endif /* __ASSEMBLY__ */
 
 #endif /* _ASM_RISCV_MMU_H */
diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h
index 815f8c959dd4..183f1f4b2ae6 100644
--- a/arch/riscv/include/asm/pgtable.h
+++ b/arch/riscv/include/asm/pgtable.h
@@ -100,6 +100,10 @@
 
 #define PAGE_KERNEL		__pgprot(_PAGE_KERNEL)
 #define PAGE_KERNEL_EXEC	__pgprot(_PAGE_KERNEL | _PAGE_EXEC)
+#define PAGE_KERNEL_READ	__pgprot(_PAGE_KERNEL & ~_PAGE_WRITE)
+#define PAGE_KERNEL_EXEC	__pgprot(_PAGE_KERNEL | _PAGE_EXEC)
+#define PAGE_KERNEL_READ_EXEC	__pgprot((_PAGE_KERNEL & ~_PAGE_WRITE) \
+					 | _PAGE_EXEC)
 
 #define PAGE_TABLE		__pgprot(_PAGE_TABLE)
 
diff --git a/arch/riscv/kernel/Makefile b/arch/riscv/kernel/Makefile
index dc93710f0b2f..fa896c5f7ccb 100644
--- a/arch/riscv/kernel/Makefile
+++ b/arch/riscv/kernel/Makefile
@@ -55,4 +55,6 @@ obj-$(CONFIG_KGDB)		+= kgdb.o
 
 obj-$(CONFIG_JUMP_LABEL)	+= jump_label.o
 
+obj-$(CONFIG_EFI)		+= efi.o
+
 clean:
diff --git a/arch/riscv/kernel/efi.c b/arch/riscv/kernel/efi.c
new file mode 100644
index 000000000000..024159298231
--- /dev/null
+++ b/arch/riscv/kernel/efi.c
@@ -0,0 +1,96 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2020 Western Digital Corporation or its affiliates.
+ * Adapted from arch/arm64/kernel/efi.c
+ */
+
+#include <linux/efi.h>
+#include <linux/init.h>
+
+#include <asm/efi.h>
+#include <asm/pgtable.h>
+#include <asm/pgtable-bits.h>
+
+/*
+ * Only regions of type EFI_RUNTIME_SERVICES_CODE need to be
+ * executable, everything else can be mapped with the XN bits
+ * set. Also take the new (optional) RO/XP bits into account.
+ */
+static __init pgprot_t efimem_to_pgprot_map(efi_memory_desc_t *md)
+{
+	u64 attr = md->attribute;
+	u32 type = md->type;
+
+	if (type == EFI_MEMORY_MAPPED_IO)
+		return PAGE_KERNEL;
+
+	/* R-- */
+	if ((attr & (EFI_MEMORY_XP | EFI_MEMORY_RO)) ==
+	    (EFI_MEMORY_XP | EFI_MEMORY_RO))
+		return PAGE_KERNEL_READ;
+
+	/* R-X */
+	if (attr & EFI_MEMORY_RO)
+		return PAGE_KERNEL_READ_EXEC;
+
+	/* RW- */
+	if (((attr & (EFI_MEMORY_RP | EFI_MEMORY_WP | EFI_MEMORY_XP)) ==
+	     EFI_MEMORY_XP) ||
+	    type != EFI_RUNTIME_SERVICES_CODE)
+		return PAGE_KERNEL;
+
+	/* RWX */
+	return PAGE_KERNEL_EXEC;
+}
+
+int __init efi_create_mapping(struct mm_struct *mm, efi_memory_desc_t *md)
+{
+	pgprot_t prot = __pgprot(pgprot_val(efimem_to_pgprot_map(md)) &
+				~(_PAGE_GLOBAL));
+	int i;
+
+	/* RISC-V maps one page at a time */
+	for (i = 0; i < md->num_pages; i++)
+		create_pgd_mapping(mm->pgd, md->virt_addr + i * PAGE_SIZE,
+				   md->phys_addr + i * PAGE_SIZE,
+				   PAGE_SIZE, prot);
+	return 0;
+}
+
+static int __init set_permissions(pte_t *ptep, unsigned long addr, void *data)
+{
+	efi_memory_desc_t *md = data;
+	pte_t pte = READ_ONCE(*ptep);
+	unsigned long val;
+
+	if (md->attribute & EFI_MEMORY_RO) {
+		val = pte_val(pte) & ~_PAGE_WRITE;
+		val = pte_val(pte) | _PAGE_READ;
+		pte = __pte(val);
+	}
+	if (md->attribute & EFI_MEMORY_XP) {
+		val = pte_val(pte) & ~_PAGE_EXEC;
+		pte = __pte(val);
+	}
+	set_pte(ptep, pte);
+
+	return 0;
+}
+
+int __init efi_set_mapping_permissions(struct mm_struct *mm,
+				       efi_memory_desc_t *md)
+{
+	BUG_ON(md->type != EFI_RUNTIME_SERVICES_CODE &&
+	       md->type != EFI_RUNTIME_SERVICES_DATA);
+
+	/*
+	 * Calling apply_to_page_range() is only safe on regions that are
+	 * guaranteed to be mapped down to pages. Since we are only called
+	 * for regions that have been mapped using efi_create_mapping() above
+	 * (and this is checked by the generic Memory Attributes table parsing
+	 * routines), there is no need to check that again here.
+	 */
+	return apply_to_page_range(mm, md->virt_addr,
+				   md->num_pages << EFI_PAGE_SHIFT,
+				   set_permissions, md);
+}
diff --git a/arch/riscv/kernel/setup.c b/arch/riscv/kernel/setup.c
index 41ef96d0d97a..4c96ac198e14 100644
--- a/arch/riscv/kernel/setup.c
+++ b/arch/riscv/kernel/setup.c
@@ -17,6 +17,7 @@
 #include <linux/sched/task.h>
 #include <linux/swiotlb.h>
 #include <linux/smp.h>
+#include <linux/efi.h>
 
 #include <asm/cpu_ops.h>
 #include <asm/early_ioremap.h>
@@ -26,11 +27,12 @@
 #include <asm/tlbflush.h>
 #include <asm/thread_info.h>
 #include <asm/kasan.h>
+#include <asm/efi.h>
 
 #include "head.h"
 
-#ifdef CONFIG_DUMMY_CONSOLE
-struct screen_info screen_info = {
+#if defined(CONFIG_DUMMY_CONSOLE) || defined(CONFIG_EFI)
+struct screen_info screen_info __section(.data) = {
 	.orig_video_lines	= 30,
 	.orig_video_cols	= 80,
 	.orig_video_mode	= 0,
@@ -75,6 +77,7 @@ void __init setup_arch(char **cmdline_p)
 	early_ioremap_setup();
 	parse_early_param();
 
+	efi_init();
 	setup_bootmem();
 	paging_init();
 #if IS_ENABLED(CONFIG_BUILTIN_DTB)
diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
index 63acc8185bfa..c888c4470b34 100644
--- a/arch/riscv/mm/init.c
+++ b/arch/riscv/mm/init.c
@@ -390,7 +390,7 @@ static void __init create_pmd_mapping(pmd_t *pmdp,
 #define fixmap_pgd_next		fixmap_pte
 #endif
 
-static void __init create_pgd_mapping(pgd_t *pgdp,
+void __init create_pgd_mapping(pgd_t *pgdp,
 				      uintptr_t va, phys_addr_t pa,
 				      phys_addr_t sz, pgprot_t prot)
 {