[Crash-utility] [PATCH] arm64: Use VA_BITS for page_offset calculation

[HAGIO KAZUHITO(萩尾 一仁)]

Hi,

Here is a patch for the issue reported by Ankur.
Could you help test this with your ramdumps and arm64 machines?

--
>From 028ddf655c847c16cce23198017d2ff0169bb4de Mon Sep 17 00:00:00 2001
From: Kazuhito Hagio <k-hagio-ab at nec.com>
Date: Mon, 25 Oct 2021 16:53:26 +0900
Subject: [PATCH] arm64: Use VA_BITS for page_offset calculation

Commit 167d37e347fe ("arm64: assign page_offset with VA_BITS kernel
configuration value") changed the page_offset calculation from
using VA_BITS_ACTUAL to CONFIG_ARM64_VA_BITS.  This caused an error
for ramdumps without vmcoreinfo like this:

  crash: vmlinux and /var/tmp/ramdump_elf_XUtCMT do not match!

Set the vmcoreinfo value to VA_BITS if available, and use VA_BITS
for page_offset calculation instead.

Also remove ARM64_FLIP_PAGE_OFFSET_ACTUAL because it's not used
actually.

Reported-by: Ankur Bansal <er.ankurbansal at gmail.com>
Signed-off-by: Kazuhito Hagio <k-hagio-ab at nec.com>
---
 arm64.c | 5 ++++-
 defs.h  | 4 +---
 2 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/arm64.c b/arm64.c
index 7069312671cf..3dcbcc642fda 100644
--- a/arm64.c
+++ b/arm64.c
@@ -404,7 +404,7 @@ arm64_init(int when)
 				fprintf(fp, "CONFIG_ARM64_VA_BITS: %ld\n", ms->CONFIG_ARM64_VA_BITS);
 				fprintf(fp, "      VA_BITS_ACTUAL: %ld\n", ms->VA_BITS_ACTUAL);
 				fprintf(fp, "(calculated) VA_BITS: %ld\n", ms->VA_BITS);
-				fprintf(fp, " PAGE_OFFSET: %lx\n", ARM64_FLIP_PAGE_OFFSET_ACTUAL);
+				fprintf(fp, " PAGE_OFFSET: %lx\n", ARM64_FLIP_PAGE_OFFSET);
 				fprintf(fp, "    VA_START: %lx\n", ms->VA_START);
 				fprintf(fp, "     modules: %lx - %lx\n", ms->modules_vaddr, ms->modules_end);
 				fprintf(fp, "     vmalloc: %lx - %lx\n", ms->vmalloc_start_addr, ms->vmalloc_end);
@@ -4031,6 +4031,9 @@ arm64_calc_VA_BITS(void)
 				error(FATAL, "cannot determine VA_BITS_ACTUAL\n");
 		}
 
+		if (machdep->machspec->CONFIG_ARM64_VA_BITS)
+			machdep->machspec->VA_BITS = machdep->machspec->CONFIG_ARM64_VA_BITS;
+
 		/*
 		 * The mm flip commit is introduced before 52-bits VA, which is before the
 		 * commit to export NUMBER(TCR_EL1_T1SZ)
diff --git a/defs.h b/defs.h
index 8b356d5e8959..971005596506 100644
--- a/defs.h
+++ b/defs.h
@@ -3238,9 +3238,7 @@ typedef signed int s32;
 #define ARM64_PAGE_OFFSET    ((0xffffffffffffffffUL) \
 					<< (machdep->machspec->VA_BITS - 1))
 /* kernels >= v5.4 the kernel VA space is flipped */
-#define ARM64_FLIP_PAGE_OFFSET (-(1UL) << machdep->machspec->CONFIG_ARM64_VA_BITS)
-#define ARM64_FLIP_PAGE_OFFSET_ACTUAL ((0xffffffffffffffffUL) \
-					- ((1UL) << machdep->machspec->VA_BITS_ACTUAL) + 1)
+#define ARM64_FLIP_PAGE_OFFSET (-(1UL) << machdep->machspec->VA_BITS)
 
 #define ARM64_USERSPACE_TOP  ((1UL) << machdep->machspec->VA_BITS)
 #define ARM64_USERSPACE_TOP_ACTUAL  ((1UL) << machdep->machspec->VA_BITS_ACTUAL)
-- 
2.27.0