Merge tag 'riscv-for-linus-5.0-rc7' of git://git.kernel.org/pub/scm/l…

…inux/kernel/git/palmer/riscv-linux

Pull RISC-V fixes from Palmer Dabbelt:
 "This contains a pair of bug fixes that I'd like to include in 5.0:

   - A fix to disambiguate swap from invalid PTEs, which fixes an error
     when trying to unmap PROT_NONE pages.

   - A revert to an optimization of the size of flat binaries. This is
     really a workaround to prevent breaking existing boot flows, but
     since the change was introduced as part of the 5.0 merge window I'd
     like to have the fix in before 5.0 so we can avoid a regression for
     any proper releases.

  With these I hope we're out of patches for 5.0 in RISC-V land"

* tag 'riscv-for-linus-5.0-rc7' of git://git.kernel.org/pub/scm/linux/kernel/git/palmer/riscv-linux:
  Revert "RISC-V: Make BSS section as the last section in vmlinux.lds.S"
  riscv: Add pte bit to distinguish swap from invalid

arch/riscv/include/asm/pgtable-bits.h

@@ -35,6 +35,12 @@
 #define _PAGE_SPECIAL   _PAGE_SOFT
 #define _PAGE_TABLE     _PAGE_PRESENT
 
+/*
+ * _PAGE_PROT_NONE is set on not-present pages (and ignored by the hardware) to
+ * distinguish them from swapped out pages
+ */
+#define _PAGE_PROT_NONE _PAGE_READ
+
 #define _PAGE_PFN_SHIFT 10
 
 /* Set of bits to preserve across pte_modify() */

arch/riscv/include/asm/pgtable.h

@@ -44,7 +44,7 @@
 /* Page protection bits */
 #define _PAGE_BASE	(_PAGE_PRESENT | _PAGE_ACCESSED | _PAGE_USER)
 
-#define PAGE_NONE		__pgprot(0)
+#define PAGE_NONE		__pgprot(_PAGE_PROT_NONE)
 #define PAGE_READ		__pgprot(_PAGE_BASE | _PAGE_READ)
 #define PAGE_WRITE		__pgprot(_PAGE_BASE | _PAGE_READ | _PAGE_WRITE)
 #define PAGE_EXEC		__pgprot(_PAGE_BASE | _PAGE_EXEC)
@@ -98,7 +98,7 @@ extern unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)];
 
 static inline int pmd_present(pmd_t pmd)
 {
-	return (pmd_val(pmd) & _PAGE_PRESENT);
+	return (pmd_val(pmd) & (_PAGE_PRESENT | _PAGE_PROT_NONE));
 }
 
 static inline int pmd_none(pmd_t pmd)
@@ -178,7 +178,7 @@ static inline pte_t *pte_offset_kernel(pmd_t *pmd, unsigned long addr)
 
 static inline int pte_present(pte_t pte)
 {
-	return (pte_val(pte) & _PAGE_PRESENT);
+	return (pte_val(pte) & (_PAGE_PRESENT | _PAGE_PROT_NONE));
 }
 
 static inline int pte_none(pte_t pte)
@@ -380,7 +380,7 @@ static inline int ptep_clear_flush_young(struct vm_area_struct *vma,
  *
  * Format of swap PTE:
  *	bit            0:	_PAGE_PRESENT (zero)
- *	bit            1:	reserved for future use (zero)
+ *	bit            1:	_PAGE_PROT_NONE (zero)
  *	bits      2 to 6:	swap type
  *	bits 7 to XLEN-1:	swap offset
  */

arch/riscv/kernel/vmlinux.lds.S

@@ -18,8 +18,6 @@
 #include <asm/cache.h>
 #include <asm/thread_info.h>
 
-#define MAX_BYTES_PER_LONG	0x10
-
 OUTPUT_ARCH(riscv)
 ENTRY(_start)
 
@@ -76,17 +74,15 @@ SECTIONS
 		*(.sbss*)
 	}
 
+	BSS_SECTION(PAGE_SIZE, PAGE_SIZE, 0)
+
 	EXCEPTION_TABLE(0x10)
 	NOTES
 
 	.rel.dyn : {
 		*(.rel.dyn*)
 	}
 
-	BSS_SECTION(MAX_BYTES_PER_LONG,
-		    MAX_BYTES_PER_LONG,
-		    MAX_BYTES_PER_LONG)
-
 	_end = .;
 
 	STABS_DEBUG