From f53b73e8380bca054cebd2b61ff118c46609429b Mon Sep 17 00:00:00 2001

From: Pingfan Liu <piliu@redhat.com>

Date: Fri, 2 Jul 2021 10:14:24 +0800

Subject: [PATCH 4/4] arm64: implement switchable PTOV()/VTOP() for kernels >=

 5.10

Crash encounters a bug like the following:

    ...

    SECTION_SIZE_BITS: 30

    CONFIG_ARM64_VA_BITS: 52

          VA_BITS_ACTUAL: 48

    (calculated) VA_BITS: 48

     PAGE_OFFSET: ffff000000000000

        VA_START: ffff800000000000

         modules: ffff800008000000 - ffff80000fffffff

         vmalloc: ffff800010000000 - ffffffdfdffeffff

    kernel image: ffff800010000000 - ffff800012750000

         vmemmap: ffffffdfffe00000 - ffffffffffffffff

    <readmem: ffff800011c53bc8, KVADDR, "nr_irqs", 4, (FOE), b47bdc>

    <read_kdump: addr: ffff800011c53bc8 paddr: eb453bc8 cnt: 4>

    read_netdump: addr: ffff800011c53bc8 paddr: eb453bc8 cnt: 4 offset: 1c73bc8

    irq_stack_ptr:

      type: 1, TYPE_CODE_PTR

      target_typecode: 8, TYPE_CODE_INT

      target_length: 8

      length: 8

    GNU_GET_DATATYPE[thread_union]: returned via gdb_error_hook

    <readmem: ffff000b779c0050, KVADDR, "IRQ stack pointer", 8, (ROE), 3a37bea0>

    <read_kdump: addr: ffff000b779c0050 paddr: fff1000bf79c0050 cnt: 8>

    read_netdump: READ_ERROR: offset not found for paddr: fff1000bf79c0050

    crash: read error: kernel virtual address: ffff000b779c0050  type: "IRQ stack pointer"

    ...

Apparently, for a normal system, the 'paddr: fff1000bf79c0050' is

unreasonable.

This bug connects with kernel commit 7bc1a0f9e176 ("arm64: mm: use

single quantity to represent the PA to VA translation"), which removed

physvirt_offset kernel variable and changed the PTOV()/VTOP() formulas.

Implement switchable PTOV()/VTOP() to cope with different kernel

version.

Signed-off-by: Pingfan Liu <piliu@redhat.com>

---

 arm64.c | 37 +++++++++++++++++++++++++++++++++----

 defs.h  |  9 ++++-----

 2 files changed, 37 insertions(+), 9 deletions(-)

diff --git a/arm64.c b/arm64.c

index b04369f..d73d5c5 100644

--- a/arm64.c

+++ b/arm64.c

@@ -994,8 +994,6 @@ arm64_calc_physvirt_offset(void)

 	ulong physvirt_offset;

 	struct syment *sp;

-	ms->physvirt_offset = ms->phys_offset - ms->page_offset;

-

 	if ((sp = kernel_symbol_search("physvirt_offset")) &&

 			machdep->machspec->kimage_voffset) {

 		if (READMEM(pc->mfd, &physvirt_offset, sizeof(physvirt_offset),

@@ -1003,8 +1001,13 @@ arm64_calc_physvirt_offset(void)

 			machdep->machspec->kimage_voffset) > 0) {

 				machdep->flags |= HAS_PHYSVIRT_OFFSET;

 				ms->physvirt_offset = physvirt_offset;

+				return;

 		}

 	}

+

+	/* Useless if no symbol 'physvirt_offset', just keep semantics */

+	ms->physvirt_offset = ms->phys_offset - ms->page_offset;

+

 }

 static void

@@ -1051,6 +1054,7 @@ arm64_calc_phys_offset(void)

 			if (READMEM(pc->mfd, &phys_offset, sizeof(phys_offset),

 			    vaddr, paddr) > 0) {

 				ms->phys_offset = phys_offset;

+

 				return;

 			}

 		}

@@ -1178,6 +1182,21 @@ arm64_init_kernel_pgd(void)

                 vt->kernel_pgd[i] = value;

 }

+ulong arm64_PTOV(ulong paddr)

+{

+	struct machine_specific *ms = machdep->machspec;

+

+	/*

+	 * Either older kernel before kernel has 'physvirt_offset' or newer

+	 * kernel which removes 'physvirt_offset' has the same formula:

+	 * #define __phys_to_virt(x)   ((unsigned long)((x) - PHYS_OFFSET) | PAGE_OFFSET)

+	 */

+	if (!(machdep->flags & HAS_PHYSVIRT_OFFSET))

+		return (paddr - ms->phys_offset) | PAGE_OFFSET;

+	else

+		return paddr - ms->physvirt_offset;

+}

+

 ulong

 arm64_VTOP(ulong addr)

 {

@@ -1188,8 +1207,18 @@ arm64_VTOP(ulong addr)

 			return addr - machdep->machspec->kimage_voffset;

 		}

-		if (addr >= machdep->machspec->page_offset)

-			return addr + machdep->machspec->physvirt_offset;

+		if (addr >= machdep->machspec->page_offset) {

+			if (machdep->flags & HAS_PHYSVIRT_OFFSET) {

+				return addr + machdep->machspec->physvirt_offset;

+			} else {

+				/*

+				 * Either older kernel before kernel has 'physvirt_offset' or newer

+				 * kernel which removes 'physvirt_offset' has the same formula:

+				 * #define __lm_to_phys(addr)	(((addr) & ~PAGE_OFFSET) + PHYS_OFFSET)

+				 */

+				return (addr & ~PAGE_OFFSET) + machdep->machspec->phys_offset;

+			}

+		}

 		else if (machdep->machspec->kimage_voffset)

 			return addr - machdep->machspec->kimage_voffset;

 		else /* no randomness */

diff --git a/defs.h b/defs.h

index eca145c..c91177a 100644

--- a/defs.h

+++ b/defs.h

@@ -3092,11 +3092,6 @@ typedef u64 pte_t;

 #define _64BIT_

 #define MACHINE_TYPE       "ARM64"    

-#define PTOV(X) \

-	((unsigned long)(X) - (machdep->machspec->physvirt_offset))

-

-#define VTOP(X)               arm64_VTOP((ulong)(X))

-

 #define USERSPACE_TOP   (machdep->machspec->userspace_top)

 #define PAGE_OFFSET     (machdep->machspec->page_offset)

 #define VMALLOC_START   (machdep->machspec->vmalloc_start_addr)

@@ -3106,6 +3101,9 @@ typedef u64 pte_t;

 #define MODULES_VADDR   (machdep->machspec->modules_vaddr)

 #define MODULES_END     (machdep->machspec->modules_end)

+#define PTOV(X)	arm64_PTOV((ulong)(X))

+#define VTOP(X)	arm64_VTOP((ulong)(X))

+

 #define IS_VMALLOC_ADDR(X)    arm64_IS_VMALLOC_ADDR((ulong)(X))

 #define PAGEBASE(X)     (((ulong)(X)) & (ulong)machdep->pagemask)

@@ -5910,6 +5908,7 @@ void unwind_backtrace(struct bt_info *);

 void arm64_init(int);

 void arm64_dump_machdep_table(ulong);

 ulong arm64_VTOP(ulong);

+ulong arm64_PTOV(ulong);

 int arm64_IS_VMALLOC_ADDR(ulong);

 ulong arm64_swp_type(ulong);

 ulong arm64_swp_offset(ulong);

-- 

2.29.2