[Crash-utility] [PATCHv6 1/4] crash-utility/arm64: introduce a dedicated field to record the mem layout changes

[Pingfan Liu]

At present, we have the following important changes for arm64 memory
layout:

-1. redesigned ARM64 kernel virtual memory layout and associated KASLR
    support that was introduced in Linux 4.6. And NEW_VMEMMAP is used to
    flag it.
-2. memory layout flipped just right before introducing 52-bits kernel.
-3. introducing of vabits_actual and phyvirt_offset in kernel
-4. removing phyvirt_offset.

These changes have effects on PTOV()/VTOP() formula. So introducing a
dedicate field mmlayout_flags to record it.

Among above, 2 and 3 are introduced closely, and are not distinguished
in current implement. And this patch also keep this practice and use
vabits_actual as a hint to flag mem flipped.

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 | 11 +++++++++++
 defs.h  |  1 +
 2 files changed, 12 insertions(+)

diff --git a/arm64.c b/arm64.c
index 4787fa6..e678982 100644
--- a/arm64.c
+++ b/arm64.c
@@ -88,6 +88,10 @@ static int arm64_is_uvaddr(ulong, struct task_context *);
 static void arm64_calc_KERNELPACMASK(void);
 
 
+/* arm64 kernel layout experiences changes, using these flags to distinguish them */
+#define MMLAYOUT_FLAGS_FLIP	0x1
+#define MMLAYOUT_FLAGS_HAS_PHYSVIRT_OFFSET	0x2
+
 /*
  * Do all necessary machine-specific setup here. This is called several times
  * during initialization.
@@ -994,6 +998,7 @@ arm64_calc_physvirt_offset(void)
 		if (READMEM(pc->mfd, &physvirt_offset, sizeof(physvirt_offset),
 			sp->value, sp->value -
 			machdep->machspec->kimage_voffset) > 0) {
+				machdep->machspec->mmlayout_flags |= MMLAYOUT_FLAGS_HAS_PHYSVIRT_OFFSET;
 				ms->physvirt_offset = physvirt_offset;
 		}
 	}
@@ -3923,6 +3928,7 @@ arm64_calc_VA_BITS(void)
 	if (kernel_symbol_exists("vabits_actual")) {
 		if (pc->flags & PROC_KCORE) {
 			vabits_actual = symbol_value_from_proc_kallsyms("vabits_actual");
+			machdep->machspec->mmlayout_flags |= MMLAYOUT_FLAGS_FLIP;
 			if ((vabits_actual != BADVAL) && (READMEM(pc->mfd, &value, sizeof(ulong),
 		    	    vabits_actual, KCORE_USE_VADDR) > 0)) {
 				if (CRASHDEBUG(1))
@@ -3952,6 +3958,11 @@ arm64_calc_VA_BITS(void)
 				machdep->machspec->VA_BITS_ACTUAL = value;
 				machdep->machspec->VA_BITS = value;
 				machdep->machspec->VA_START = _VA_START(machdep->machspec->VA_BITS_ACTUAL);
+				/*
+				 * The mm flip commit is introduced before 52-bits VA, which is before the
+				 * commit to export NUMBER(TCR_EL1_T1SZ)
+				 */
+				machdep->machspec->mmlayout_flags |= MMLAYOUT_FLAGS_FLIP;
 			} else if (machdep->machspec->VA_BITS_ACTUAL) {
 				machdep->machspec->VA_BITS = machdep->machspec->VA_BITS_ACTUAL;
 				machdep->machspec->VA_START = _VA_START(machdep->machspec->VA_BITS_ACTUAL);
diff --git a/defs.h b/defs.h
index f9c711c..6da3e75 100644
--- a/defs.h
+++ b/defs.h
@@ -3282,6 +3282,7 @@ struct arm64_pt_regs {
 struct machine_specific {
 	ulong flags;
 	ulong userspace_top;
+	ulong mmlayout_flags;
 	ulong page_offset;
 	ulong vmalloc_start_addr;
 	ulong vmalloc_end;
-- 
2.29.2