[Crash-utility] [PATCHv5 3/3] 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 this disagreement only happens if 52-bits kernel on 48 bits platform,
it can be handled only if "phys_offset_nominal < 0".

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 | 10 +++++++++-
 defs.h  |  1 +
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/arm64.c b/arm64.c
index f1bac84..7cc19e8 100644
--- a/arm64.c
+++ b/arm64.c
@@ -221,7 +221,15 @@ arm64_init(int when)
 		arm64_calc_VA_BITS();
 		arm64_calc_KERNELPACMASK();
 		ms = machdep->machspec;
-		if (ms->VA_BITS_ACTUAL) {
+		/* For 52-bits kernel running on 48 bits platform */
+		if (ms->phys_offset_nominal < 0) {
+			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;
+		/* For 52-bits on 52-bits platform, or 48-bits on 48 */
+		} else 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;
diff --git a/defs.h b/defs.h
index 1007c69..f804212 100644
--- a/defs.h
+++ b/defs.h
@@ -3224,6 +3224,7 @@ 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