[Crash-utility] [PATCH v9 2/4] crash-utility/arm64: assign page_offset with kernel configure value

[Pingfan Liu]

On RHEL9, crash hits a bug when executing "crash /proc/kcore" : seek
error: kernel virtual address: ffff6a0f3fff0000 type: "pmd page"

The kernel virtual address does not vary with va_actual bits, instead,
is determined by configuration value. But crash does not observe this
fact.

Since vabits_actual related kernel commit is introduced after arm64 mm
layout flip commit, so changes are safe under the condition if
(ms->VA_BITS_ACTUAL), and keep else branch untouched.

Signed-off-by: Pingfan Liu <piliu at redhat.com>
Cc: HAGIO KAZUHITO <k-hagio-ab at nec.com>
Cc: Lianbo Jiang <lijiang at redhat.com>
Cc: Bhupesh Sharma <bhupesh.sharma at linaro.org>
To: crash-utility at redhat.com
---
 arm64.c | 7 ++++---
 defs.h  | 1 +
 2 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/arm64.c b/arm64.c
index 9fe1a4a..149db36 100644
--- a/arm64.c
+++ b/arm64.c
@@ -220,9 +220,10 @@ arm64_init(int when)
 
 		/* vabits_actual introduced after mm flip, so it should be flipped layout */
 		if (ms->VA_BITS_ACTUAL) {
-			ms->page_offset = ARM64_FLIP_PAGE_OFFSET_ACTUAL;
-			machdep->identity_map_base = ARM64_FLIP_PAGE_OFFSET_ACTUAL;
-			machdep->kvbase = ARM64_FLIP_PAGE_OFFSET_ACTUAL;
+			ms->page_offset = ARM64_FLIP_PAGE_OFFSET;
+			/* useless on arm64 */
+			machdep->identity_map_base = ARM64_FLIP_PAGE_OFFSET;
+			machdep->kvbase = ARM64_FLIP_PAGE_OFFSET;
 			ms->userspace_top = ARM64_USERSPACE_TOP_ACTUAL;
 		} else {
 			ms->page_offset = ARM64_PAGE_OFFSET;
diff --git a/defs.h b/defs.h
index af0dc8f..60dcd39 100644
--- a/defs.h
+++ b/defs.h
@@ -3233,6 +3233,7 @@ 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)
 
-- 
2.29.2