arm64: fix the determination of vmemmap and struct_page_size

Currently, the vmemmap ptr addr is determined by the vmcoreinfo of
"SYMBOL(vmemmap)", which leads to an invalid vmemmap addr showed by
"help -m" for dump files without the vmcoreinfo. The value of
vmemmap_end is simply set to -1 for available VA_BITS_ACTUAL case in
arm64_calc_virtual_memory_ranges(), and the struct_page_size value is 0.

  crash> help -m |grep vmem
           vmemmap_vaddr: fffffffeffe00000
             vmemmap_end: ffffffffffffffff
                 vmemmap: 0000000000000000
  crash> help -m |grep struct_page_size
        struct_page_size: 0

Introduce arm64_get_vmemmap_page_ptr() to fix the determination of
vmemmap ptr addr, and fix the determination of vmemmap_end and
struct_page_size in arm64_calc_virtual_memory_ranges().

  crash> help -m |grep vmem
           vmemmap_vaddr: fffffffeffe00000
             vmemmap_end: ffffffffffe00000
                 vmemmap: fffffffefee00000
  crash> help -m |grep struct_page_size
        struct_page_size: 64

Signed-off-by: qiwu.chen <[email protected]>

arm64.c

@@ -160,7 +160,6 @@ arm64_vmemmap_is_page_ptr(ulong addr, physaddr_t *phys)
 	ulong size = SIZE(page);
 	ulong pfn, nr;
 
-
 	if (IS_SPARSEMEM() && (machdep->flags & VMEMMAP) &&
 	    (addr >= VMEMMAP_VADDR && addr <= VMEMMAP_END) &&
 	    !((addr - VMEMMAP_VADDR) % size)) {
@@ -176,6 +175,25 @@ arm64_vmemmap_is_page_ptr(ulong addr, physaddr_t *phys)
 	return FALSE;
 }
 
+static void arm64_get_vmemmap_page_ptr(void)
+{
+	struct machine_specific *ms = machdep->machspec;
+
+	/* If vmemmap exists, it means kernel enabled CONFIG_SPARSEMEM_VMEMMAP */
+	if (arm64_get_vmcoreinfo(&ms->vmemmap, "SYMBOL(vmemmap)", NUM_HEX))
+		goto out;
+
+	/* The global symbol of vmemmap is removed since kernel commit 7bc1a0f9e1765 */
+	if (kernel_symbol_exists("vmemmap"))
+		ms->vmemmap = symbol_value("vmemmap");
+	else
+		ms->vmemmap = ms->vmemmap_vaddr - ((ms->phys_offset >> machdep->pageshift) * ms->struct_page_size);
+
+out:
+	if (ms->vmemmap)
+		machdep->is_page_ptr = arm64_vmemmap_is_page_ptr;
+}
+
 /*
  * Do all necessary machine-specific setup here. This is called several times
  * during initialization.
@@ -463,10 +481,6 @@ arm64_init(int when)
 
 		machdep->stacksize = ARM64_STACK_SIZE;
 		machdep->flags |= VMEMMAP;
-		/* If vmemmap exists, it means kernel enabled CONFIG_SPARSEMEM_VMEMMAP */
-		if (arm64_get_vmcoreinfo(&ms->vmemmap, "SYMBOL(vmemmap)", NUM_HEX))
-			machdep->is_page_ptr = arm64_vmemmap_is_page_ptr;
-
 		machdep->uvtop = arm64_uvtop;
 		machdep->is_uvaddr = arm64_is_uvaddr;
 		machdep->eframe_search = arm64_eframe_search;
@@ -518,6 +532,7 @@ arm64_init(int when)
 		if (!ms->struct_page_size)
 			arm64_calc_virtual_memory_ranges();
 
+		arm64_get_vmemmap_page_ptr();
 		arm64_get_section_size_bits();
 
 		if (!machdep->max_physmem_bits) {
@@ -4947,6 +4962,7 @@ arm64_calc_virtual_memory_ranges(void)
 		return;
 
 	STRUCT_SIZE_INIT(page, "page");
+	ms->struct_page_size = SIZE(page);
 
         switch (machdep->flags & (VM_L2_64K|VM_L3_64K|VM_L3_4K|VM_L4_4K))
         {
@@ -4974,7 +4990,8 @@ arm64_calc_virtual_memory_ranges(void)
 		vmemmap_start = (-vmemmap_size - MEGABYTES(2));
 		ms->vmalloc_end = vmalloc_end - 1;
 		ms->vmemmap_vaddr = vmemmap_start;
-		ms->vmemmap_end = -1;
+		ms->vmemmap_end = vmemmap_start + vmemmap_size;
+
 		return;
 	}