RISC-V updates for v5.3-rc7

One significant fix for 32-bit RISC-V systems:
 
 - Fix the RV32 memory map to prevent userspace from corrupting the
   FIXMAP area.  Without this patch, the system can crash very early
   during the boot.
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Merge tag 'riscv/for-v5.3-rc7' of git://git.kernel.org/pub/scm/linux/kernel/git/riscv/linux

Pull RISC-V fix from Paul Walmsley:
 "One significant fix for 32-bit RISC-V systems:

  Fix the RV32 memory map to prevent userspace from corrupting the
  FIXMAP area. Without this patch, the system can crash very early
  during the boot"

* tag 'riscv/for-v5.3-rc7' of git://git.kernel.org/pub/scm/linux/kernel/git/riscv/linux:
  RISC-V: Fix FIXMAP area corruption on RV32 systems

arch/riscv/include/asm/fixmap.h

@@ -30,10 +30,6 @@ enum fixed_addresses {
 	__end_of_fixed_addresses
 };
 
-#define FIXADDR_SIZE		(__end_of_fixed_addresses * PAGE_SIZE)
-#define FIXADDR_TOP		(VMALLOC_START)
-#define FIXADDR_START		(FIXADDR_TOP - FIXADDR_SIZE)
-
 #define FIXMAP_PAGE_IO		PAGE_KERNEL
 
 #define __early_set_fixmap	__set_fixmap

arch/riscv/include/asm/pgtable.h

@@ -420,14 +420,22 @@ static inline void pgtable_cache_init(void)
 #define VMALLOC_END      (PAGE_OFFSET - 1)
 #define VMALLOC_START    (PAGE_OFFSET - VMALLOC_SIZE)
 
+#define FIXADDR_TOP      VMALLOC_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 0xb800000 for RV32.
+ * Task size is 0x4000000000 for RV64 or 0x9fc00000 for RV32.
  * Note that PGDIR_SIZE must evenly divide TASK_SIZE.
  */
 #ifdef CONFIG_64BIT
 #define TASK_SIZE (PGDIR_SIZE * PTRS_PER_PGD / 2)
 #else
-#define TASK_SIZE VMALLOC_START
+#define TASK_SIZE FIXADDR_START
 #endif
 
 #include <asm-generic/pgtable.h>