[Crash-utility] [PATCH v2 1/2] arm64: read pagesize

[Andrew Jones]

Thanks to kernel commit 9d372c9fab34 "arm64: Add page size to the
kernel image header", we don't need a heuristic to determine the
pagesize on arm64. Keep the heuristic for older kernels, but try
reading the header first.
---
 arm64.c | 30 ++++++++++++++++++++++++++++++
 defs.h  |  1 +
 2 files changed, 31 insertions(+)

diff --git a/arm64.c b/arm64.c
index 5f8e2f6852434..d85ad7214dd39 100644
--- a/arm64.c
+++ b/arm64.c
@@ -19,6 +19,7 @@
 
 #include "defs.h"
 #include <elf.h>
+#include <endian.h>
 
 #define NOT_IMPLEMENTED(X) error((X), "%s: function not implemented\n", __func__)
 
@@ -97,6 +98,32 @@ arm64_init(int when)
 		break;
 
 	case PRE_GDB:
+		if (!machdep->pagesize) {
+			/*
+			 * Kerneldoc Documentation/arm64/booting.txt describes
+			 * the kernel image header flags field.
+			 */
+			value = machdep->machspec->kernel_flags;
+			value = (value >> 1) & 3;
+
+			switch(value)
+			{
+			case 0:
+				break;
+			case 1:
+				machdep->pagesize = 4096;
+				break;
+			case 2:
+				/* TODO: machdep->pagesize = 16384; */
+				error(FATAL, "16K pages not supported.");
+				break;
+			case 3:
+				machdep->pagesize = 65536;
+				break;
+			}
+
+		}
+
 		if (!machdep->pagesize &&
 		    kernel_symbol_exists("swapper_pg_dir") &&
 		    kernel_symbol_exists("idmap_pg_dir")) {
@@ -305,6 +332,9 @@ arm64_verify_symbol(const char *name, ulong value, char type)
 	if (!name || !strlen(name))
 		return FALSE;
 
+	if (STREQ(name, "_kernel_flags_le"))
+		machdep->machspec->kernel_flags = le64toh(value);
+
 	if (((type == 'A') || (type == 'a')) && (highest_bit_long(value) != 63))
 		return FALSE;
 
diff --git a/defs.h b/defs.h
index 7004619017e41..3e5dbd99942b2 100644
--- a/defs.h
+++ b/defs.h
@@ -2944,6 +2944,7 @@ struct machine_specific {
 	ulong crash_kexec_end;
 	ulong crash_save_cpu_start;
 	ulong crash_save_cpu_end;
+	ulong kernel_flags;
 };
 
 struct arm64_stackframe {
-- 
2.4.3