[PATCH v6 1/4] RISC-V: mm: Restrict address space for sv39,sv48,sv57

Charlie Jenkins
2023-07-14T16:56:09Z

Make sv48 the default address space for mmap as some applications
currently depend on this assumption. A hint address passed to mmap will
cause the largest address space that fits entirely into the hint to be
used. If the hint is less than or equal to 1<<38, an sv39 address will
be used. An exception is that if the hint address is 0, then a sv48
address will be used. After an address space is completely full, the next
smallest address space will be used.

Signed-off-by: Charlie Jenkins <charlie@rivosinc.com>
---
arch/riscv/include/asm/elf.h | 2 +-
arch/riscv/include/asm/pgtable.h | 12 +++++++-
arch/riscv/include/asm/processor.h | 46 +++++++++++++++++++++++++-----
3 files changed, 51 insertions(+), 9 deletions(-)

diff --git a/arch/riscv/include/asm/elf.h b/arch/riscv/include/asm/elf.h
index c24280774caf..5d3368d5585c 100644
--- a/arch/riscv/include/asm/elf.h
+++ b/arch/riscv/include/asm/elf.h
@@ -49,7 +49,7 @@ extern bool compat_elf_check_arch(Elf32_Ehdr *hdr);
* the loader. We need to make sure that it is out of the way of the program
* that it will "exec", and that there is sufficient room for the brk.
*/
-#define ELF_ET_DYN_BASE ((TASK_SIZE / 3) * 2)
+#define ELF_ET_DYN_BASE ((DEFAULT_MAP_WINDOW / 3) * 2)

#ifdef CONFIG_64BIT
#ifdef CONFIG_COMPAT
diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h
index 75970ee2bda2..e13f5872bfe9 100644
--- a/arch/riscv/include/asm/pgtable.h
+++ b/arch/riscv/include/asm/pgtable.h
@@ -63,12 +63,22 @@
* position vmemmap directly below the VMALLOC region.
*/
#ifdef CONFIG_64BIT
+#define VA_BITS_SV39 39
+#define VA_BITS_SV48 48
+#define VA_BITS_SV57 57
+
+#define VA_USER_SV39 (UL(1) << (VA_BITS_SV39 - 1))
+#define VA_USER_SV48 (UL(1) << (VA_BITS_SV48 - 1))
+#define VA_USER_SV57 (UL(1) << (VA_BITS_SV57 - 1))
+
#define VA_BITS (pgtable_l5_enabled ? \
- 57 : (pgtable_l4_enabled ? 48 : 39))
+ VA_BITS_SV57 : (pgtable_l4_enabled ? VA_BITS_SV48 : VA_BITS_SV39))
#else
#define VA_BITS 32
#endif

+#define MMAP_VA_BITS ((VA_BITS >= VA_BITS_SV48) ? VA_BITS_SV48 : VA_BITS)
+
#define VMEMMAP_SHIFT \
(VA_BITS - PAGE_SHIFT - 1 + STRUCT_PAGE_MAX_SHIFT)
#define VMEMMAP_SIZE BIT(VMEMMAP_SHIFT)
diff --git a/arch/riscv/include/asm/processor.h b/arch/riscv/include/asm/processor.h
index c950a8d9edef..14a5396eed3d 100644
--- a/arch/riscv/include/asm/processor.h
+++ b/arch/riscv/include/asm/processor.h
@@ -13,20 +13,52 @@

#include <asm/ptrace.h>

-/*
- * This decides where the kernel will search for a free chunk of vm
- * space during mmap's.
- */
-#define TASK_UNMAPPED_BASE PAGE_ALIGN(TASK_SIZE / 3)
-
-#define STACK_TOP TASK_SIZE
#ifdef CONFIG_64BIT
+#define DEFAULT_MAP_WINDOW (UL(1) << (MMAP_VA_BITS - 1))
#define STACK_TOP_MAX TASK_SIZE_64
+
+#define arch_get_mmap_end(addr, len, flags) \
+({ \
+ unsigned long mmap_end; \
+ if ((addr) >= VA_USER_SV57) \
+ mmap_end = STACK_TOP_MAX; \
+ else if ((((addr) >= VA_USER_SV48)) && (VA_BITS >= VA_BITS_SV48)) \
+ mmap_end = VA_USER_SV48; \
+ else if ((addr) == 0) \
+ mmap_end = DEFAULT_MAP_WINDOW; \
+ else \
+ mmap_end = VA_USER_SV39; \
+ mmap_end; \
+})
+
+#define arch_get_mmap_base(addr, base) \
+({ \
+ unsigned long mmap_base; \
+ if (((addr) >= VA_USER_SV57) && (VA_BITS >= VA_BITS_SV57)) \
+ mmap_base = (base) + (VA_USER_SV57 - DEFAULT_MAP_WINDOW); \
+ else if ((((addr) >= VA_USER_SV48)) && (VA_BITS >= VA_BITS_SV48)) \
+ mmap_base = (base) + (VA_USER_SV48 - DEFAULT_MAP_WINDOW); \
+ else if ((addr) == 0) \
+ mmap_base = (base); \
+ else \
+ mmap_base = (base) + (VA_USER_SV39 - DEFAULT_MAP_WINDOW); \
+ mmap_base; \
+})
+
#else
+#define DEFAULT_MAP_WINDOW TASK_SIZE
#define STACK_TOP_MAX TASK_SIZE
#endif
#define STACK_ALIGN 16

+#define STACK_TOP DEFAULT_MAP_WINDOW
+
+/*
+ * This decides where the kernel will search for a free chunk of vm
+ * space during mmap's.
+ */
+#define TASK_UNMAPPED_BASE PAGE_ALIGN(DEFAULT_MAP_WINDOW / 3)
+
#ifndef __ASSEMBLY__

struct task_struct;
--
2.41.0