[PATCH] makedumpfile: ppc64: get vmalloc start address from vmcoreinfo

[Aditya Gupta]

Below error was noticed when running makedumpfile on linux-next kernel
crash (linux-next tag next-20240121):

    ...
    Checking for memory holes : [100.0 %] | readpage_elf: Attempt to read non-existent page at 0xc000000000000.
    [ 17.551718] kdump.sh[404]: readmem: type_addr: 0, addr:c00c000000000000, size:16384
    [ 17.551793] kdump.sh[404]: __exclude_unnecessary_pages: Can't read the buffer of struct page.
    [ 17.551864] kdump.sh[404]: create_2nd_bitmap: Can't exclude unnecessary pages.
    [ 17.562632] kdump.sh[404]: The kernel version is not supported.
    [ 17.562708] kdump.sh[404]: The makedumpfile operation may be incomplete.
    [ 17.562773] kdump.sh[404]: makedumpfile Failed.
    [ 17.564335] kdump[406]: saving vmcore failed, _exitcode:1

Above error was due to 'vmap_area_list' and 'vmlist' symbols missing
from the vmcore.

'vmap_area_list' was removed in the linux kernel with below commit:

    commit 378eb24a0658dd922b29524e0ce35c6c43f56cba
         mm/vmalloc: remove vmap_area_list

Subsequently the commit also introduced 'VMALLOC_START' in vmcoreinfo to
get base address of vmalloc area, instead of depending on 'vmap_area_list'

Hence if 'VMALLOC_START' symbol is there in vmcoreinfo:
  1. Set vmalloc_start based on 'VMALLOC_START'
  2. Don't error if vmap_area_list/vmlist are not defined

Reported-by: Sachin Sant <sachinp at linux.ibm.com>
Signed-off-by: Aditya Gupta <adityag at linux.ibm.com>
---
 arch/ppc64.c   | 19 +++++++++++++------
 makedumpfile.c |  3 ++-
 makedumpfile.h |  6 +++---
 3 files changed, 18 insertions(+), 10 deletions(-)

diff --git a/arch/ppc64.c b/arch/ppc64.c
index 96c357cb0335..bb62e2cd199a 100644
--- a/arch/ppc64.c
+++ b/arch/ppc64.c
@@ -568,7 +568,9 @@ get_machdep_info_ppc64(void)
 	/*
 	 * Get vmalloc_start value from either vmap_area_list or vmlist.
 	 */
-	if ((SYMBOL(vmap_area_list) != NOT_FOUND_SYMBOL)
+	if (NUMBER(vmalloc_start) != NOT_FOUND_SYMBOL) {
+		vmalloc_start = NUMBER(vmalloc_start);
+	} else if ((SYMBOL(vmap_area_list) != NOT_FOUND_SYMBOL)
 	    && (OFFSET(vmap_area.va_start) != NOT_FOUND_STRUCTURE)
 	    && (OFFSET(vmap_area.list) != NOT_FOUND_STRUCTURE)) {
 		if (!readmem(VADDR, SYMBOL(vmap_area_list) + OFFSET(list_head.next),
@@ -684,11 +686,16 @@ vaddr_to_paddr_ppc64(unsigned long vaddr)
 	if ((SYMBOL(vmap_area_list) == NOT_FOUND_SYMBOL)
 	    || (OFFSET(vmap_area.va_start) == NOT_FOUND_STRUCTURE)
 	    || (OFFSET(vmap_area.list) == NOT_FOUND_STRUCTURE)) {
-		if ((SYMBOL(vmlist) == NOT_FOUND_SYMBOL)
-		    || (OFFSET(vm_struct.addr) == NOT_FOUND_STRUCTURE)) {
-			ERRMSG("Can't get info for vmalloc translation.\n");
-			return NOT_PADDR;
-		}
+		/*
+		 * Don't depend on vmap_area_list/vmlist if vmalloc_start is set in
+		 * vmcoreinfo, in that case proceed without error
+		 */
+		if (NUMBER(vmalloc_start) == NOT_FOUND_NUMBER)
+			if ((SYMBOL(vmlist) == NOT_FOUND_SYMBOL)
+				|| (OFFSET(vm_struct.addr) == NOT_FOUND_STRUCTURE)) {
+				ERRMSG("Can't get info for vmalloc translation.\n");
+				return NOT_PADDR;
+			}
 	}
 
 	return ppc64_vtop_level4(vaddr);
diff --git a/makedumpfile.c b/makedumpfile.c
index b004b93fecb7..b6c63fad15f3 100644
--- a/makedumpfile.c
+++ b/makedumpfile.c
@@ -2978,6 +2978,8 @@ read_vmcoreinfo(void)
 	READ_NUMBER("PAGE_OFFLINE_MAPCOUNT_VALUE", PAGE_OFFLINE_MAPCOUNT_VALUE);
 	READ_NUMBER("phys_base", phys_base);
 	READ_NUMBER("KERNEL_IMAGE_SIZE", KERNEL_IMAGE_SIZE);
+
+	READ_NUMBER_UNSIGNED("VMALLOC_START", vmalloc_start);
 #ifdef __aarch64__
 	READ_NUMBER("VA_BITS", VA_BITS);
 	READ_NUMBER("TCR_EL1_T1SZ", TCR_EL1_T1SZ);
@@ -2989,7 +2991,6 @@ read_vmcoreinfo(void)
 	READ_NUMBER("VA_BITS", va_bits);
 	READ_NUMBER_UNSIGNED("phys_ram_base", phys_ram_base);
 	READ_NUMBER_UNSIGNED("PAGE_OFFSET", page_offset);
-	READ_NUMBER_UNSIGNED("VMALLOC_START", vmalloc_start);
 	READ_NUMBER_UNSIGNED("VMALLOC_END", vmalloc_end);
 	READ_NUMBER_UNSIGNED("VMEMMAP_START", vmemmap_start);
 	READ_NUMBER_UNSIGNED("VMEMMAP_END", vmemmap_end);
diff --git a/makedumpfile.h b/makedumpfile.h
index 59c83e1d9df3..4021c5af2a34 100644
--- a/makedumpfile.h
+++ b/makedumpfile.h
@@ -541,8 +541,6 @@ do { \
  * The value of dependence on machine
  */
 #define PAGE_OFFSET		(info->page_offset)
-#define VMALLOC_START		(info->vmalloc_start)
-#define VMALLOC_END		(info->vmalloc_end)
 #define VMEMMAP_START		(info->vmemmap_start)
 #define VMEMMAP_END		(info->vmemmap_end)
 #define PMASK			(0x7ffffffffffff000UL)
@@ -2262,6 +2260,9 @@ struct number_table {
 	long    HUGETLB_PAGE_DTOR;
 	long	phys_base;
 	long	KERNEL_IMAGE_SIZE;
+
+	unsigned long vmalloc_start;
+
 #ifdef __aarch64__
 	long 	VA_BITS;
 	long	TCR_EL1_T1SZ;
@@ -2272,7 +2273,6 @@ struct number_table {
 	long va_bits;
 	unsigned long phys_ram_base;
 	unsigned long page_offset;
-	unsigned long vmalloc_start;
 	unsigned long vmalloc_end;
 	unsigned long vmemmap_start;
 	unsigned long vmemmap_end;
-- 
2.43.0