[Crash-utility] [PATCH] arm64: store phy_offset and memstart_addr separately

[Pingfan Liu]

With kernel commit 7bc1a0f9e176 ("arm64: mm: use single quantity to
represent the PA to VA translation"), memstart_addr can be negative,
which makes it different from real phy_offset.

In crash utility, PTOV() needs memstart_addr, while getting PFN offset
in a dumpfile, phy_offset is required. So storing them separately for
different purpose.

Signed-off-by: Pingfan Liu <piliu at redhat.com>
Cc: Lianbo Jiang <lijiang at redhat.com>
To: crash-utility at redhat.com
---
 arm64.c | 22 +++++++++++++++++++---
 defs.h  |  1 +
 2 files changed, 20 insertions(+), 3 deletions(-)

diff --git a/arm64.c b/arm64.c
index 37aed07..e560d07 100644
--- a/arm64.c
+++ b/arm64.c
@@ -687,6 +687,7 @@ arm64_dump_machdep_table(ulong arg)
 		fprintf(fp, "        kimage_voffset: %016lx\n", ms->kimage_voffset);
 	}
 	fprintf(fp, "           phys_offset: %lx\n", ms->phys_offset);
+	fprintf(fp, "         memstart_addr: %lx\n", ms->memstart_addr);
 	fprintf(fp, "__exception_text_start: %lx\n", ms->__exception_text_start);
 	fprintf(fp, "  __exception_text_end: %lx\n", ms->__exception_text_end);
 	fprintf(fp, " __irqentry_text_start: %lx\n", ms->__irqentry_text_start);
@@ -987,7 +988,7 @@ arm64_calc_physvirt_offset(void)
 	ulong physvirt_offset;
 	struct syment *sp;
 
-	ms->physvirt_offset = ms->phys_offset - ms->page_offset;
+	ms->physvirt_offset = ms->memstart_addr - ms->page_offset;
 
 	if ((sp = kernel_symbol_search("physvirt_offset")) &&
 			machdep->machspec->kimage_voffset) {
@@ -1028,7 +1029,11 @@ arm64_calc_phys_offset(void)
 		    ms->kimage_voffset && (sp = kernel_symbol_search("memstart_addr"))) {
 			if (pc->flags & PROC_KCORE) {
 				if ((string = pc->read_vmcoreinfo("NUMBER(PHYS_OFFSET)"))) {
-					ms->phys_offset = htol(string, QUIET, NULL);
+					ms->memstart_addr = htol(string, QUIET, NULL);
+					if (ms->memstart_addr < 0)
+						ms->phys_offset = ms->memstart_addr + 0xffff000000000000 - 0xfff0000000000000;
+					else
+						ms->phys_offset = ms->memstart_addr;
 					free(string);
 					return;
 				}
@@ -1080,7 +1085,18 @@ arm64_calc_phys_offset(void)
 	} else if (DISKDUMP_DUMPFILE() && diskdump_phys_base(&phys_offset)) {
 		ms->phys_offset = phys_offset;
 	} else if (KDUMP_DUMPFILE() && arm64_kdump_phys_base(&phys_offset)) {
-		ms->phys_offset = phys_offset;
+		/*
+		 * When running a 52bits kernel on 48bits hardware. Kernel plays a trick:
+		 * if (IS_ENABLED(CONFIG_ARM64_VA_BITS_52) && (vabits_actual != 52))
+                 *       memstart_addr -= _PAGE_OFFSET(48) - _PAGE_OFFSET(52);
+		 *
+		 * In crash, this should be detected to get a real physical start address.
+		 */
+		ms->memstart_addr = phys_offset;
+		if ((long)phys_offset < 0)
+			ms->phys_offset = phys_offset + 0xffff000000000000 - 0xfff0000000000000;
+		else
+			ms->phys_offset = phys_offset;
 	} else {
 		error(WARNING,
 			"phys_offset cannot be determined from the dumpfile.\n");
diff --git a/defs.h b/defs.h
index 35b983a..64f2bcb 100644
--- a/defs.h
+++ b/defs.h
@@ -3290,6 +3290,7 @@ struct machine_specific {
 	ulong modules_vaddr;
 	ulong modules_end;
 	ulong phys_offset;
+	long memstart_addr;
 	ulong __exception_text_start;
 	ulong __exception_text_end;
 	struct arm64_pt_regs *panic_task_regs;
-- 
2.29.2