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authorChristoph Hellwig <hch@lst.de>2019-10-28 13:10:41 +0100
committerPaul Walmsley <paul.walmsley@sifive.com>2019-11-17 15:17:39 -0800
commit6bd33e1ece528f67646db33bf97406b747dafda0 (patch)
treef78c5001071a475fa5bed9781c07a609118684f7 /arch/riscv/include/asm/pgtable.h
parent9e80635619b51ddc56bdeca4da4056eb7a2a77e0 (diff)
downloadlinux-6bd33e1ece528f67646db33bf97406b747dafda0.tar.gz
riscv: add nommu support
The kernel runs in M-mode without using page tables, and thus can't run bare metal without help from additional firmware. Most of the patch is just stubbing out code not needed without page tables, but there is an interesting detail in the signals implementation: - The normal RISC-V syscall ABI only implements rt_sigreturn as VDSO entry point, but the ELF VDSO is not supported for nommu Linux. We instead copy the code to call the syscall onto the stack. In addition to enabling the nommu code a new defconfig for a small kernel image that can run in nommu mode on qemu is also provided, to run a kernel in qemu you can use the following command line: qemu-system-riscv64 -smp 2 -m 64 -machine virt -nographic \ -kernel arch/riscv/boot/loader \ -drive file=rootfs.ext2,format=raw,id=hd0 \ -device virtio-blk-device,drive=hd0 Contains contributions from Damien Le Moal <Damien.LeMoal@wdc.com>. Signed-off-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Anup Patel <anup@brainfault.org> [paul.walmsley@sifive.com: updated to apply; add CONFIG_MMU guards around PCI_IOBASE definition to fix build issues; fixed checkpatch issues; move the PCI_IO_* and VMEMMAP address space macros along with the others; resolve sparse warning] Signed-off-by: Paul Walmsley <paul.walmsley@sifive.com>
Diffstat (limited to 'arch/riscv/include/asm/pgtable.h')
-rw-r--r--arch/riscv/include/asm/pgtable.h94
1 files changed, 53 insertions, 41 deletions
diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h
index d3221017194d..beb5f0865e39 100644
--- a/arch/riscv/include/asm/pgtable.h
+++ b/arch/riscv/include/asm/pgtable.h
@@ -25,6 +25,7 @@
#include <asm/pgtable-32.h>
#endif /* CONFIG_64BIT */
+#ifdef CONFIG_MMU
/* Number of entries in the page global directory */
#define PTRS_PER_PGD (PAGE_SIZE / sizeof(pgd_t))
/* Number of entries in the page table */
@@ -32,7 +33,6 @@
/* Number of PGD entries that a user-mode program can use */
#define USER_PTRS_PER_PGD (TASK_SIZE / PGDIR_SIZE)
-#define FIRST_USER_ADDRESS 0
/* Page protection bits */
#define _PAGE_BASE (_PAGE_PRESENT | _PAGE_ACCESSED | _PAGE_USER)
@@ -84,42 +84,6 @@ extern pgd_t swapper_pg_dir[];
#define __S110 PAGE_SHARED_EXEC
#define __S111 PAGE_SHARED_EXEC
-#define VMALLOC_SIZE (KERN_VIRT_SIZE >> 1)
-#define VMALLOC_END (PAGE_OFFSET - 1)
-#define VMALLOC_START (PAGE_OFFSET - VMALLOC_SIZE)
-#define PCI_IO_SIZE SZ_16M
-
-/*
- * Roughly size the vmemmap space to be large enough to fit enough
- * struct pages to map half the virtual address space. Then
- * position vmemmap directly below the VMALLOC region.
- */
-#define VMEMMAP_SHIFT \
- (CONFIG_VA_BITS - PAGE_SHIFT - 1 + STRUCT_PAGE_MAX_SHIFT)
-#define VMEMMAP_SIZE BIT(VMEMMAP_SHIFT)
-#define VMEMMAP_END (VMALLOC_START - 1)
-#define VMEMMAP_START (VMALLOC_START - VMEMMAP_SIZE)
-
-#define vmemmap ((struct page *)VMEMMAP_START)
-
-#define PCI_IO_END VMEMMAP_START
-#define PCI_IO_START (PCI_IO_END - PCI_IO_SIZE)
-#define FIXADDR_TOP PCI_IO_START
-
-#ifdef CONFIG_64BIT
-#define FIXADDR_SIZE PMD_SIZE
-#else
-#define FIXADDR_SIZE PGDIR_SIZE
-#endif
-#define FIXADDR_START (FIXADDR_TOP - FIXADDR_SIZE)
-
-/*
- * ZERO_PAGE is a global shared page that is always zero,
- * used for zero-mapped memory areas, etc.
- */
-extern unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)];
-#define ZERO_PAGE(vaddr) (virt_to_page(empty_zero_page))
-
static inline int pmd_present(pmd_t pmd)
{
return (pmd_val(pmd) & (_PAGE_PRESENT | _PAGE_PROT_NONE));
@@ -430,11 +394,34 @@ static inline int ptep_clear_flush_young(struct vm_area_struct *vma,
#define __pte_to_swp_entry(pte) ((swp_entry_t) { pte_val(pte) })
#define __swp_entry_to_pte(x) ((pte_t) { (x).val })
-#define kern_addr_valid(addr) (1) /* FIXME */
+#define VMALLOC_SIZE (KERN_VIRT_SIZE >> 1)
+#define VMALLOC_END (PAGE_OFFSET - 1)
+#define VMALLOC_START (PAGE_OFFSET - VMALLOC_SIZE)
-extern void *dtb_early_va;
-extern void setup_bootmem(void);
-extern void paging_init(void);
+/*
+ * Roughly size the vmemmap space to be large enough to fit enough
+ * struct pages to map half the virtual address space. Then
+ * position vmemmap directly below the VMALLOC region.
+ */
+#define VMEMMAP_SHIFT \
+ (CONFIG_VA_BITS - PAGE_SHIFT - 1 + STRUCT_PAGE_MAX_SHIFT)
+#define VMEMMAP_SIZE BIT(VMEMMAP_SHIFT)
+#define VMEMMAP_END (VMALLOC_START - 1)
+#define VMEMMAP_START (VMALLOC_START - VMEMMAP_SIZE)
+
+#define vmemmap ((struct page *)VMEMMAP_START)
+
+#define PCI_IO_SIZE SZ_16M
+#define PCI_IO_END VMEMMAP_START
+#define PCI_IO_START (PCI_IO_END - PCI_IO_SIZE)
+
+#define FIXADDR_TOP PCI_IO_START
+#ifdef CONFIG_64BIT
+#define FIXADDR_SIZE PMD_SIZE
+#else
+#define FIXADDR_SIZE PGDIR_SIZE
+#endif
+#define FIXADDR_START (FIXADDR_TOP - FIXADDR_SIZE)
/*
* Task size is 0x4000000000 for RV64 or 0x9fc00000 for RV32.
@@ -446,6 +433,31 @@ extern void paging_init(void);
#define TASK_SIZE FIXADDR_START
#endif
+#else /* CONFIG_MMU */
+
+#define PAGE_KERNEL __pgprot(0)
+#define swapper_pg_dir NULL
+#define VMALLOC_START 0
+
+#define TASK_SIZE 0xffffffffUL
+
+#endif /* !CONFIG_MMU */
+
+#define kern_addr_valid(addr) (1) /* FIXME */
+
+extern void *dtb_early_va;
+void setup_bootmem(void);
+void paging_init(void);
+
+#define FIRST_USER_ADDRESS 0
+
+/*
+ * ZERO_PAGE is a global shared page that is always zero,
+ * used for zero-mapped memory areas, etc.
+ */
+extern unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)];
+#define ZERO_PAGE(vaddr) (virt_to_page(empty_zero_page))
+
#include <asm-generic/pgtable.h>
#endif /* !__ASSEMBLY__ */