linux-kernel - [PATCH 2/2] kexec: Provide arch_kexec_protect(unprotect)

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Message-Id: <1450869146-6186-2-git-send-email-xlpang@redhat.com>
Date:	Wed, 23 Dec 2015 19:12:26 +0800
From:	Xunlei Pang <xlpang@...hat.com>
To:	linux-kernel@...r.kernel.org, kexec@...ts.infradead.org
Cc:	akpm@...ux-foundation.org, Eric Biederman <ebiederm@...ssion.com>,
	Xunlei Pang <xlpang@...hat.com>
Subject: [PATCH 2/2] kexec: Provide arch_kexec_protect(unprotect)_crashkres()

Implement the protection method for the crash kernel memory
reservation for the 64-bit x86 kdump.

Signed-off-by: Xunlei Pang <xlpang@...hat.com>
---
Only provided x86_64 implementation, as I've only tested on x86_64 so far.

 arch/x86/kernel/machine_kexec_64.c | 43 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 43 insertions(+)

diff --git a/arch/x86/kernel/machine_kexec_64.c b/arch/x86/kernel/machine_kexec_64.c
index 819ab3f..a3d289c 100644
--- a/arch/x86/kernel/machine_kexec_64.c
+++ b/arch/x86/kernel/machine_kexec_64.c
@@ -536,3 +536,46 @@ overflow:
 	return -ENOEXEC;
 }
 #endif /* CONFIG_KEXEC_FILE */
+
+#ifdef CONFIG_KEXEC_CORE
+static int
+kexec_mark_range(unsigned long start, unsigned long end, bool protect)
+{
+	struct page *page;
+	unsigned int nr_pages;
+
+	if (!start || !end || start >= end)
+		return 0;
+
+	page = pfn_to_page(start >> PAGE_SHIFT);
+	nr_pages = (end + 1 - start) >> PAGE_SHIFT;
+	if (protect)
+		return set_pages_ro(page, nr_pages);
+	else
+		return set_pages_rw(page, nr_pages);
+}
+
+static void kexec_mark_crashkres(bool protect)
+{
+	unsigned long control;
+
+	kexec_mark_range(crashk_low_res.start, crashk_low_res.end, protect);
+
+	/* Don't touch the control code page used in crash_kexec().*/
+	control = PFN_PHYS(page_to_pfn(kexec_crash_image->control_code_page));
+	/* Control code page is located in the 2nd page. */
+	control = control + PAGE_SIZE;
+	kexec_mark_range(crashk_res.start, control - 1, protect);
+	kexec_mark_range(control + PAGE_SIZE, crashk_res.end, protect);
+}
+
+void arch_kexec_protect_crashkres(void)
+{
+	kexec_mark_crashkres(true);
+}
+
+void arch_kexec_unprotect_crashkres(void)
+{
+	kexec_mark_crashkres(false);
+}
+#endif
-- 
2.5.0

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