riscv: Move KASAN mapping next to the kernel mapping

Now that KASAN_SHADOW_OFFSET is defined at compile time as a config,
this value must remain constant whatever the size of the virtual address
space, which is only possible by pushing this region at the end of the
address space next to the kernel mapping.

Signed-off-by: Alexandre Ghiti <alexandre.ghiti@canonical.com>
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

diff --git a/Documentation/riscv/vm-layout.rst b/Documentation/riscv/vm-layout.rst
index b7f9893..1bd687b 100644 (file)
--- a/Documentation/riscv/vm-layout.rst
+++ b/Documentation/riscv/vm-layout.rst
@@ -47,12 +47,12 @@ RISC-V Linux Kernel SV39
                                                               | Kernel-space virtual memory, shared between all processes:
   ____________________________________________________________|___________________________________________________________
                     |            |                  |         |
-   ffffffc000000000 | -256    GB | ffffffc7ffffffff |   32 GB | kasan
-   ffffffcefee00000 | -196    GB | ffffffcefeffffff |    2 MB | fixmap
-   ffffffceff000000 | -196    GB | ffffffceffffffff |   16 MB | PCI io
-   ffffffcf00000000 | -196    GB | ffffffcfffffffff |    4 GB | vmemmap
-   ffffffd000000000 | -192    GB | ffffffdfffffffff |   64 GB | vmalloc/ioremap space
-   ffffffe000000000 | -128    GB | ffffffff7fffffff |  124 GB | direct mapping of all physical memory
+   ffffffc6fee00000 | -228    GB | ffffffc6feffffff |    2 MB | fixmap
+   ffffffc6ff000000 | -228    GB | ffffffc6ffffffff |   16 MB | PCI io
+   ffffffc700000000 | -228    GB | ffffffc7ffffffff |    4 GB | vmemmap
+   ffffffc800000000 | -224    GB | ffffffd7ffffffff |   64 GB | vmalloc/ioremap space
+   ffffffd800000000 | -160    GB | fffffff6ffffffff |  124 GB | direct mapping of all physical memory
+   fffffff700000000 |  -36    GB | fffffffeffffffff |   32 GB | kasan
   __________________|____________|__________________|_________|____________________________________________________________
                                                               |
                                                               |

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index 7a68a41..7f8aea3 100644 (file)
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -160,12 +160,12 @@ config PAGE_OFFSET
        hex
        default 0xC0000000 if 32BIT
        default 0x80000000 if 64BIT && !MMU
-       default 0xffffffe000000000 if 64BIT
+       default 0xffffffd800000000 if 64BIT
 
 config KASAN_SHADOW_OFFSET
        hex
        depends on KASAN_GENERIC
-       default 0xdfffffc800000000 if 64BIT
+       default 0xdfffffff00000000 if 64BIT
        default 0xffffffff if 32BIT
 
 config ARCH_FLATMEM_ENABLE

diff --git a/arch/riscv/include/asm/kasan.h b/arch/riscv/include/asm/kasan.h
index b00f503..257a249 100644 (file)
--- a/arch/riscv/include/asm/kasan.h
+++ b/arch/riscv/include/asm/kasan.h
@@ -28,8 +28,8 @@
 #define KASAN_SHADOW_SCALE_SHIFT       3
 
 #define KASAN_SHADOW_SIZE      (UL(1) << ((CONFIG_VA_BITS - 1) - KASAN_SHADOW_SCALE_SHIFT))
-#define KASAN_SHADOW_START     KERN_VIRT_START
-#define KASAN_SHADOW_END       (KASAN_SHADOW_START + KASAN_SHADOW_SIZE)
+#define KASAN_SHADOW_START     (KASAN_SHADOW_END - KASAN_SHADOW_SIZE)
+#define KASAN_SHADOW_END       MODULES_LOWEST_VADDR
 #define KASAN_SHADOW_OFFSET    _AC(CONFIG_KASAN_SHADOW_OFFSET, UL)
 
 void kasan_init(void);

diff --git a/arch/riscv/include/asm/page.h b/arch/riscv/include/asm/page.h
index b3e5ff0..a18c989 100644 (file)
--- a/arch/riscv/include/asm/page.h
+++ b/arch/riscv/include/asm/page.h
@@ -33,8 +33,6 @@
  */
 #define PAGE_OFFSET            _AC(CONFIG_PAGE_OFFSET, UL)
 
-#define KERN_VIRT_SIZE (-PAGE_OFFSET)
-
 #ifndef __ASSEMBLY__
 
 #define clear_page(pgaddr)                     memset((pgaddr), 0, PAGE_SIZE)

diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h
index bf204e7..fa400b2 100644 (file)
--- a/arch/riscv/include/asm/pgtable.h
+++ b/arch/riscv/include/asm/pgtable.h
@@ -24,6 +24,17 @@
 #define KERNEL_LINK_ADDR       PAGE_OFFSET
 #endif
 
+/* Number of entries in the page global directory */
+#define PTRS_PER_PGD    (PAGE_SIZE / sizeof(pgd_t))
+/* Number of entries in the page table */
+#define PTRS_PER_PTE    (PAGE_SIZE / sizeof(pte_t))
+
+/*
+ * Half of the kernel address space (half of the entries of the page global
+ * directory) is for the direct mapping.
+ */
+#define KERN_VIRT_SIZE          ((PTRS_PER_PGD / 2 * PGDIR_SIZE) / 2)
+
 #define VMALLOC_SIZE     (KERN_VIRT_SIZE >> 1)
 #define VMALLOC_END      (PAGE_OFFSET - 1)
 #define VMALLOC_START    (PAGE_OFFSET - VMALLOC_SIZE)
@@ -39,8 +50,10 @@
 
 /* Modules always live before the kernel */
 #ifdef CONFIG_64BIT
-#define MODULES_VADDR  (PFN_ALIGN((unsigned long)&_end) - SZ_2G)
-#define MODULES_END    (PFN_ALIGN((unsigned long)&_start))
+/* This is used to define the end of the KASAN shadow region */
+#define MODULES_LOWEST_VADDR   (KERNEL_LINK_ADDR - SZ_2G)
+#define MODULES_VADDR          (PFN_ALIGN((unsigned long)&_end) - SZ_2G)
+#define MODULES_END            (PFN_ALIGN((unsigned long)&_start))
 #endif
 
 /*
@@ -108,11 +121,6 @@
 #endif /* CONFIG_XIP_KERNEL */
 
 #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 */
-#define PTRS_PER_PTE    (PAGE_SIZE / sizeof(pte_t))
-
 /* Number of PGD entries that a user-mode program can use */
 #define USER_PTRS_PER_PGD   (TASK_SIZE / PGDIR_SIZE)
 

diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
index 24b2b80..f515964 100644 (file)
--- a/arch/riscv/mm/init.c
+++ b/arch/riscv/mm/init.c
@@ -103,6 +103,9 @@ static void __init print_vm_layout(void)
        print_mlm("lowmem", (unsigned long)PAGE_OFFSET,
                  (unsigned long)high_memory);
 #ifdef CONFIG_64BIT
+#ifdef CONFIG_KASAN
+       print_mlm("kasan", KASAN_SHADOW_START, KASAN_SHADOW_END);
+#endif
        print_mlm("kernel", (unsigned long)KERNEL_LINK_ADDR,
                  (unsigned long)ADDRESS_SPACE_END);
 #endif
@@ -130,18 +133,8 @@ void __init mem_init(void)
        print_vm_layout();
 }
 
-/*
- * The default maximal physical memory size is -PAGE_OFFSET for 32-bit kernel,
- * whereas for 64-bit kernel, the end of the virtual address space is occupied
- * by the modules/BPF/kernel mappings which reduces the available size of the
- * linear mapping.
- * Limit the memory size via mem.
- */
-#ifdef CONFIG_64BIT
-static phys_addr_t memory_limit = -PAGE_OFFSET - SZ_4G;
-#else
-static phys_addr_t memory_limit = -PAGE_OFFSET;
-#endif
+/* Limit the memory size via mem. */
+static phys_addr_t memory_limit;
 
 static int __init early_mem(char *p)
 {
@@ -612,6 +605,14 @@ asmlinkage void __init setup_vm(uintptr_t dtb_pa)
 
        riscv_pfn_base = PFN_DOWN(kernel_map.phys_addr);
 
+       /*
+        * The default maximal physical memory size is KERN_VIRT_SIZE for 32-bit
+        * kernel, whereas for 64-bit kernel, the end of the virtual address
+        * space is occupied by the modules/BPF/kernel mappings which reduces
+        * the available size of the linear mapping.
+        */
+       memory_limit = KERN_VIRT_SIZE - (IS_ENABLED(CONFIG_64BIT) ? SZ_4G : 0);
+
        /* Sanity check alignment and size */
        BUG_ON((PAGE_OFFSET % PGDIR_SIZE) != 0);
        BUG_ON((kernel_map.phys_addr % PMD_SIZE) != 0);