RISC-V: enable XIP

Introduce XIP (eXecute In Place) support for RISC-V platforms.
It allows code to be executed directly from non-volatile storage
directly addressable by the CPU, such as QSPI NOR flash which can
be found on many RISC-V platforms. This makes way for significant
optimization of RAM footprint. The XIP kernel is not compressed
since it has to run directly from flash, so it will occupy more
space on the non-volatile storage. The physical flash address used
to link the kernel object files and for storing it has to be known
at compile time and is represented by a Kconfig option.

XIP on RISC-V will for the time being only work on MMU-enabled
kernels.

Signed-off-by: Vitaly Wool <vitaly.wool@konsulko.com>
[Alex: Rebase on top of "Move kernel mapping outside the linear mapping" ]
Signed-off-by: Alexandre Ghiti <alex@ghiti.fr>
[Palmer: disable XIP for allyesconfig]
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>

1 files changed, 109 insertions, 8 deletions

diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
index 3cb4c1b6cee1..788eb222deac 100644
--- a/arch/riscv/mm/init.c
+++ b/arch/riscv/mm/init.c
@@ -31,6 +31,9 @@
 
 unsigned long kernel_virt_addr = KERNEL_LINK_ADDR;
 EXPORT_SYMBOL(kernel_virt_addr);
+#ifdef CONFIG_XIP_KERNEL
+#define kernel_virt_addr       (*((unsigned long *)XIP_FIXUP(&kernel_virt_addr)))
+#endif
 
 unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)]
 							__page_aligned_bss;
@@ -38,8 +41,8 @@ EXPORT_SYMBOL(empty_zero_page);
 
 extern char _start[];
 #define DTB_EARLY_BASE_VA      PGDIR_SIZE
-void *dtb_early_va __initdata;
-uintptr_t dtb_early_pa __initdata;
+void *_dtb_early_va __initdata;
+uintptr_t _dtb_early_pa __initdata;
 
 struct pt_alloc_ops {
 	pte_t *(*get_pte_virt)(phys_addr_t pa);
@@ -124,6 +127,10 @@ void __init setup_bootmem(void)
 	phys_addr_t dram_end = memblock_end_of_DRAM();
 	phys_addr_t max_mapped_addr = __pa(~(ulong)0);
 
+#ifdef CONFIG_XIP_KERNEL
+	vmlinux_start = __pa_symbol(&_sdata);
+#endif
+
 	/* The maximal physical memory size is -PAGE_OFFSET. */
 	memblock_enforce_memory_limit(-PAGE_OFFSET);
 
@@ -165,17 +172,41 @@ void __init setup_bootmem(void)
 	memblock_allow_resize();
 }
 
+#ifdef CONFIG_XIP_KERNEL
+
+extern char _xiprom[], _exiprom[];
+extern char _sdata[], _edata[];
+
+#endif /* CONFIG_XIP_KERNEL */
+
 #ifdef CONFIG_MMU
-static struct pt_alloc_ops pt_ops __ro_after_init;
+static struct pt_alloc_ops _pt_ops __ro_after_init;
+
+#ifdef CONFIG_XIP_KERNEL
+#define pt_ops (*(struct pt_alloc_ops *)XIP_FIXUP(&_pt_ops))
+#else
+#define pt_ops _pt_ops
+#endif
 
 /* Offset between linear mapping virtual address and kernel load address */
 unsigned long va_pa_offset __ro_after_init;
 EXPORT_SYMBOL(va_pa_offset);
-#ifdef CONFIG_64BIT
+#ifdef CONFIG_XIP_KERNEL
+#define va_pa_offset   (*((unsigned long *)XIP_FIXUP(&va_pa_offset)))
+#endif
 /* Offset between kernel mapping virtual address and kernel load address */
+#ifdef CONFIG_64BIT
 unsigned long va_kernel_pa_offset;
 EXPORT_SYMBOL(va_kernel_pa_offset);
 #endif
+#ifdef CONFIG_XIP_KERNEL
+#define va_kernel_pa_offset    (*((unsigned long *)XIP_FIXUP(&va_kernel_pa_offset)))
+#endif
+unsigned long va_kernel_xip_pa_offset;
+EXPORT_SYMBOL(va_kernel_xip_pa_offset);
+#ifdef CONFIG_XIP_KERNEL
+#define va_kernel_xip_pa_offset        (*((unsigned long *)XIP_FIXUP(&va_kernel_xip_pa_offset)))
+#endif
 unsigned long pfn_base __ro_after_init;
 EXPORT_SYMBOL(pfn_base);
 
@@ -185,6 +216,12 @@ pte_t fixmap_pte[PTRS_PER_PTE] __page_aligned_bss;
 
 pgd_t early_pg_dir[PTRS_PER_PGD] __initdata __aligned(PAGE_SIZE);
 
+#ifdef CONFIG_XIP_KERNEL
+#define trampoline_pg_dir      ((pgd_t *)XIP_FIXUP(trampoline_pg_dir))
+#define fixmap_pte             ((pte_t *)XIP_FIXUP(fixmap_pte))
+#define early_pg_dir           ((pgd_t *)XIP_FIXUP(early_pg_dir))
+#endif /* CONFIG_XIP_KERNEL */
+
 void __set_fixmap(enum fixed_addresses idx, phys_addr_t phys, pgprot_t prot)
 {
 	unsigned long addr = __fix_to_virt(idx);
@@ -260,6 +297,12 @@ pmd_t fixmap_pmd[PTRS_PER_PMD] __page_aligned_bss;
 pmd_t early_pmd[PTRS_PER_PMD] __initdata __aligned(PAGE_SIZE);
 pmd_t early_dtb_pmd[PTRS_PER_PMD] __initdata __aligned(PAGE_SIZE);
 
+#ifdef CONFIG_XIP_KERNEL
+#define trampoline_pmd ((pmd_t *)XIP_FIXUP(trampoline_pmd))
+#define fixmap_pmd     ((pmd_t *)XIP_FIXUP(fixmap_pmd))
+#define early_pmd      ((pmd_t *)XIP_FIXUP(early_pmd))
+#endif /* CONFIG_XIP_KERNEL */
+
 static pmd_t *__init get_pmd_virt_early(phys_addr_t pa)
 {
 	/* Before MMU is enabled */
@@ -376,6 +419,19 @@ static uintptr_t __init best_map_size(phys_addr_t base, phys_addr_t size)
 	return PMD_SIZE;
 }
 
+#ifdef CONFIG_XIP_KERNEL
+/* called from head.S with MMU off */
+asmlinkage void __init __copy_data(void)
+{
+	void *from = (void *)(&_sdata);
+	void *end = (void *)(&_end);
+	void *to = (void *)CONFIG_PHYS_RAM_BASE;
+	size_t sz = (size_t)(end - from + 1);
+
+	memcpy(to, from, sz);
+}
+#endif
+
 /*
  * setup_vm() is called from head.S with MMU-off.
  *
@@ -395,7 +451,35 @@ static uintptr_t __init best_map_size(phys_addr_t base, phys_addr_t size)
 #endif
 
 uintptr_t load_pa, load_sz;
+#ifdef CONFIG_XIP_KERNEL
+#define load_pa        (*((uintptr_t *)XIP_FIXUP(&load_pa)))
+#define load_sz        (*((uintptr_t *)XIP_FIXUP(&load_sz)))
+#endif
 
+#ifdef CONFIG_XIP_KERNEL
+uintptr_t xiprom, xiprom_sz;
+#define xiprom_sz      (*((uintptr_t *)XIP_FIXUP(&xiprom_sz)))
+#define xiprom         (*((uintptr_t *)XIP_FIXUP(&xiprom)))
+
+static void __init create_kernel_page_table(pgd_t *pgdir, uintptr_t map_size)
+{
+	uintptr_t va, end_va;
+
+	/* Map the flash resident part */
+	end_va = kernel_virt_addr + xiprom_sz;
+	for (va = kernel_virt_addr; va < end_va; va += map_size)
+		create_pgd_mapping(pgdir, va,
+				   xiprom + (va - kernel_virt_addr),
+				   map_size, PAGE_KERNEL_EXEC);
+
+	/* Map the data in RAM */
+	end_va = kernel_virt_addr + XIP_OFFSET + load_sz;
+	for (va = kernel_virt_addr + XIP_OFFSET; va < end_va; va += map_size)
+		create_pgd_mapping(pgdir, va,
+				   load_pa + (va - (kernel_virt_addr + XIP_OFFSET)),
+				   map_size, PAGE_KERNEL);
+}
+#else
 static void __init create_kernel_page_table(pgd_t *pgdir, uintptr_t map_size)
 {
 	uintptr_t va, end_va;
@@ -406,16 +490,28 @@ static void __init create_kernel_page_table(pgd_t *pgdir, uintptr_t map_size)
 				   load_pa + (va - kernel_virt_addr),
 				   map_size, PAGE_KERNEL_EXEC);
 }
+#endif
 
 asmlinkage void __init setup_vm(uintptr_t dtb_pa)
 {
-	uintptr_t pa;
+	uintptr_t __maybe_unused pa;
 	uintptr_t map_size;
 #ifndef __PAGETABLE_PMD_FOLDED
 	pmd_t fix_bmap_spmd, fix_bmap_epmd;
 #endif
+
+#ifdef CONFIG_XIP_KERNEL
+	xiprom = (uintptr_t)CONFIG_XIP_PHYS_ADDR;
+	xiprom_sz = (uintptr_t)(&_exiprom) - (uintptr_t)(&_xiprom);
+
+	load_pa = (uintptr_t)CONFIG_PHYS_RAM_BASE;
+	load_sz = (uintptr_t)(&_end) - (uintptr_t)(&_sdata);
+
+	va_kernel_xip_pa_offset = kernel_virt_addr - xiprom;
+#else
 	load_pa = (uintptr_t)(&_start);
 	load_sz = (uintptr_t)(&_end) - load_pa;
+#endif
 
 	va_pa_offset = PAGE_OFFSET - load_pa;
 #ifdef CONFIG_64BIT
@@ -451,8 +547,13 @@ asmlinkage void __init setup_vm(uintptr_t dtb_pa)
 	/* Setup trampoline PGD and PMD */
 	create_pgd_mapping(trampoline_pg_dir, kernel_virt_addr,
 			   (uintptr_t)trampoline_pmd, PGDIR_SIZE, PAGE_TABLE);
+#ifdef CONFIG_XIP_KERNEL
+	create_pmd_mapping(trampoline_pmd, kernel_virt_addr,
+			   xiprom, PMD_SIZE, PAGE_KERNEL_EXEC);
+#else
 	create_pmd_mapping(trampoline_pmd, kernel_virt_addr,
 			   load_pa, PMD_SIZE, PAGE_KERNEL_EXEC);
+#endif
 #else
 	/* Setup trampoline PGD */
 	create_pgd_mapping(trampoline_pg_dir, kernel_virt_addr,
@@ -485,7 +586,7 @@ asmlinkage void __init setup_vm(uintptr_t dtb_pa)
 	 * whereas dtb_early_va will be used before setup_vm_final installs
 	 * the linear mapping.
 	 */
-	dtb_early_va = kernel_mapping_pa_to_va(dtb_pa);
+	dtb_early_va = kernel_mapping_pa_to_va(XIP_FIXUP(dtb_pa));
 #else
 	dtb_early_va = __va(dtb_pa);
 #endif /* CONFIG_64BIT */
@@ -501,7 +602,7 @@ asmlinkage void __init setup_vm(uintptr_t dtb_pa)
 	dtb_early_va = (void *)DTB_EARLY_BASE_VA + (dtb_pa & (PGDIR_SIZE - 1));
 #else /* CONFIG_BUILTIN_DTB */
 #ifdef CONFIG_64BIT
-	dtb_early_va = kernel_mapping_pa_to_va(dtb_pa);
+	dtb_early_va = kernel_mapping_pa_to_va(XIP_FIXUP(dtb_pa));
 #else
 	dtb_early_va = __va(dtb_pa);
 #endif /* CONFIG_64BIT */
@@ -540,7 +641,7 @@ asmlinkage void __init setup_vm(uintptr_t dtb_pa)
 #endif
 }
 
-#ifdef CONFIG_64BIT
+#if defined(CONFIG_64BIT) && !defined(CONFIG_XIP_KERNEL)
 void protect_kernel_linear_mapping_text_rodata(void)
 {
 	unsigned long text_start = (unsigned long)lm_alias(_start);