[PATCH v2] makedumpfile: arm64: Fix page table walk of 1GB section

[Bradley Bolen]

From: Bradley Bolen <bbolen at lexmark.com>

makedumpfile was generating large (> 500MB) vmcore files for an arm64
board with 2GB of DRAM.  It was not excluding any pages because the
mem_map address was not being converted correctly.

readmem: Can't convert a virtual address(ffffffc07fff6000) to physical
address.
readmem: type_addr: 0, addr:ffffffc07fff6000, size:16
section_mem_map_addr: Can't get a struct mem_section(ffffffc07fff6000).
mem_map (0)
mem_map : 0

makedumpfile was not handling 1GB sections in the PGD and was trying to
drill down to a PTE in which it was trying to dereference invalid
memory.  This patch adds code to check the PGD for a section type and
handle it instead of treating it as a table entry.

Signed-off-by: Bradley Bolen <bradleybolen at gmail.com>
---
Changes in v2:
- updated comments

 arch/arm64.c | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/arch/arm64.c b/arch/arm64.c
index 958f57f..25d7a1f 100644
--- a/arch/arm64.c
+++ b/arch/arm64.c
@@ -57,6 +57,8 @@ static unsigned long kimage_voffset;
 #define PGDIR_SHIFT		((PAGESHIFT() - 3) * pgtable_level + 3)
 #define PTRS_PER_PGD		(1 << (va_bits - PGDIR_SHIFT))
 #define PUD_SHIFT		get_pud_shift_arm64()
+#define PUD_SIZE		(1UL << PUD_SHIFT)
+#define PUD_MASK		(~(PUD_SIZE - 1))
 #define PTRS_PER_PTE		(1 << (PAGESHIFT() - 3))
 #define PTRS_PER_PUD		PTRS_PER_PTE
 #define PMD_SHIFT		((PAGESHIFT() - 3) * 2 + 3)
@@ -79,6 +81,10 @@ static unsigned long kimage_voffset;
 #define PMD_TYPE_SECT		1
 #define PMD_TYPE_TABLE		3
 
+#define PUD_TYPE_MASK		3
+#define PUD_TYPE_SECT		1
+#define PUD_TYPE_TABLE		3
+
 #define pgd_index(vaddr) 		(((vaddr) >> PGDIR_SHIFT) & (PTRS_PER_PGD - 1))
 #define pgd_offset(pgdir, vaddr)	((pgd_t *)(pgdir) + pgd_index(vaddr))
 
@@ -253,6 +259,13 @@ vaddr_to_paddr_arm64(unsigned long vaddr)
 		return NOT_PADDR;
 	}
 
+	if ((pud_val(pudv) & PUD_TYPE_MASK) == PUD_TYPE_SECT) {
+		/* 1GB section for Page Table level = 4 and Page Size = 4KB */
+		paddr = (pud_val(pudv) & (PUD_MASK & PMD_SECTION_MASK))
+					+ (vaddr & (PUD_SIZE - 1));
+		return paddr;
+	}
+
 	pmda = pmd_offset(puda, &pudv, vaddr);
 	if (!readmem(PADDR, (unsigned long long)pmda, &pmdv, sizeof(pmdv))) {
 		ERRMSG("Can't read pmd\n");
@@ -278,7 +291,7 @@ vaddr_to_paddr_arm64(unsigned long vaddr)
 		}
 		break;
 	case PMD_TYPE_SECT:
-		/* 1GB section */
+		/* 512MB section for Page Table level = 3 and Page Size = 64KB*/
 		paddr = (pmd_val(pmdv) & (PMD_MASK & PMD_SECTION_MASK))
 					+ (vaddr & (PMD_SIZE - 1));
 		break;
-- 
1.9.3