linux-kernel - [Patch V6 09/16] xen: check for kernel memory conflicting with memory layout

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Message-Id: <1437108697-4115-10-git-send-email-jgross@suse.com>
Date:	Fri, 17 Jul 2015 06:51:30 +0200
From:	Juergen Gross <jgross@...e.com>
To:	linux-kernel@...r.kernel.org, xen-devel@...ts.xensource.com,
	konrad.wilk@...cle.com, david.vrabel@...rix.com,
	boris.ostrovsky@...cle.com
Cc:	Juergen Gross <jgross@...e.com>
Subject: [Patch V6 09/16] xen: check for kernel memory conflicting with memory layout

Checks whether the pre-allocated memory of the loaded kernel is in
conflict with the target memory map. If this is the case, just panic
instead of run into problems later, as there is nothing we can do
to repair this situation.

Signed-off-by: Juergen Gross <jgross@...e.com>
Reviewed-by: David Vrabel <david.vrabel@...rix.com>
Acked-by: Konrad Rzeszutek Wilk <Konrad.wilk@...cle.com>
---
 arch/x86/xen/setup.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/arch/x86/xen/setup.c b/arch/x86/xen/setup.c
index 973d294..9bd3f35 100644
--- a/arch/x86/xen/setup.c
+++ b/arch/x86/xen/setup.c
@@ -27,6 +27,7 @@
 #include <xen/interface/memory.h>
 #include <xen/interface/physdev.h>
 #include <xen/features.h>
+#include <xen/hvc-console.h>
 #include "xen-ops.h"
 #include "vdso.h"
 #include "p2m.h"
@@ -790,6 +791,17 @@ char * __init xen_memory_setup(void)
 
 	sanitize_e820_map(e820.map, ARRAY_SIZE(e820.map), &e820.nr_map);
 
+	/*
+	 * Check whether the kernel itself conflicts with the target E820 map.
+	 * Failing now is better than running into weird problems later due
+	 * to relocating (and even reusing) pages with kernel text or data.
+	 */
+	if (xen_is_e820_reserved(__pa_symbol(_text),
+			__pa_symbol(__bss_stop) - __pa_symbol(_text))) {
+		xen_raw_console_write("Xen hypervisor allocated kernel memory conflicts with E820 map\n");
+		BUG();
+	}
+
 	xen_reserve_xen_mfnlist();
 
 	/*
-- 
2.1.4

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