From e3bdc32aab5d8fe09b679cf394da8ba8826e207f Mon Sep 17 00:00:00 2001
From: Pingfan Liu <piliu@redhat.com>
Date: Thu, 24 Feb 2022 11:52:12 +0800
Subject: [PATCH] arm64: deduce the start address of kernel code, based on
 kernel version

After kernel commit e2a073dde921 ("arm64: omit [_text, _stext) from
permanent kernel mapping"), the range [_text, _stext] is reclaimed. But
the current crash code still assumes kernel starting from "_text".

This change only affects the vmalloced area on arm64 and may result a
false in arm64_IS_VMALLOC_ADDR().

Since vmcore has no extra information about this trival change, it can
only be deduced from kernel version, which means ms->kimage_text can not
be correctly initialized until kernel_init() finishes. Here on arm64, it
can be done at the point machdep_init(POST_GDB). This is fine
since there is no access to vmalloced area at this stage.

Signed-off-by: Pingfan Liu <piliu@redhat.com>
---
 arm64.c | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/arm64.c b/arm64.c
index de1038a..3ab8489 100644
--- a/arm64.c
+++ b/arm64.c
@@ -92,6 +92,20 @@ static void arm64_calc_VA_BITS(void);
 static int arm64_is_uvaddr(ulong, struct task_context *);
 static void arm64_calc_KERNELPACMASK(void);
 
+static void arm64_calc_kernel_start(void)
+{
+	struct machine_specific *ms = machdep->machspec;
+	struct syment *sp;
+
+	if (THIS_KERNEL_VERSION >= LINUX(5,11,0))
+		sp = kernel_symbol_search("_stext");
+	else
+		sp = kernel_symbol_search("_text");
+
+	ms->kimage_text = (sp ? sp->value : 0);
+	sp = kernel_symbol_search("_end");
+	ms->kimage_end = (sp ? sp->value : 0);
+}
 
 /*
  * Do all necessary machine-specific setup here. This is called several times
@@ -241,6 +255,7 @@ arm64_init(int when)
 		if (machdep->flags & NEW_VMEMMAP) {
 			struct syment *sp;
 
+			/* It is finally decided in arm64_calc_kernel_start() */
 			sp = kernel_symbol_search("_text");
 			ms->kimage_text = (sp ? sp->value : 0);
 			sp = kernel_symbol_search("_end");
@@ -387,6 +402,8 @@ arm64_init(int when)
 		break;
 
 	case POST_GDB:
+		/* Rely on kernel version to decide the kernel start address */
+		arm64_calc_kernel_start();
 		arm64_calc_virtual_memory_ranges();
 		arm64_get_section_size_bits();
 
-- 
2.31.1