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From: Baoquan He <bhe@redhat.com>
To: linux-kernel@vger.kernel.org
Cc: Baoquan He <bhe@redhat.com>,
	x86@kernel.org, kexec@lists.infradead.org, bp@alien8.de,
	hpa@zytor.com, tglx@linutronix.de, dyoung@redhat.com,
	mingo@kernel.org, kirill.shutemov@linux.intel.com
Subject: [PATCH RESEND 2/3] x86/kexec/64: Error out if try to jump to old 4-level kernel from 5-level kernel
Date: Fri, 25 Jan 2019 10:28:16 +0800	[thread overview]
Message-ID: <20190125022817.29506-3-bhe@redhat.com> (raw)
In-Reply-To: <20190125022817.29506-1-bhe@redhat.com>

In relocate_kernel() CR4.LA57 flag is set before kexec jumping if
the kernel has 5-level paging enabled. Then in boot/compressed/head_64.S,
it will check if the booting kernel is in 4-level or 5-level paging
mode, and handle accordingly. However, the old kernel which doesn't
contain the 5-level codes doesn't know how to cope with it, then #GP
triggered.

Instead of triggering #GP during kexec kernel boot, error out during
kexec loading if find out we are trying to jump to old 4-level kernel
from 5-level kernel.

Signed-off-by: Baoquan He <bhe@redhat.com>
---
 arch/x86/kernel/kexec-bzimage64.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/arch/x86/kernel/kexec-bzimage64.c b/arch/x86/kernel/kexec-bzimage64.c
index 278cd07228dd..5bfb39fc56fe 100644
--- a/arch/x86/kernel/kexec-bzimage64.c
+++ b/arch/x86/kernel/kexec-bzimage64.c
@@ -316,6 +316,11 @@ static int bzImage64_probe(const char *buf, unsigned long len)
 		return ret;
 	}
 
+	if (!(header->xloadflags & XLF_5LEVEL) && pgtable_l5_enabled()) {
+		pr_err("Can not jump to old 4-level kernel from 5-level kernel.\n");
+		return ret;
+	}
+
 	/* I've got a bzImage */
 	pr_debug("It's a relocatable bzImage64\n");
 	ret = 0;
-- 
2.13.6


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WARNING: multiple messages have this Message-ID (diff)
From: Baoquan He <bhe@redhat.com>
To: linux-kernel@vger.kernel.org
Cc: tglx@linutronix.de, mingo@kernel.org, bp@alien8.de,
	hpa@zytor.com, kirill.shutemov@linux.intel.com,
	dyoung@redhat.com, x86@kernel.org, kexec@lists.infradead.org,
	Baoquan He <bhe@redhat.com>
Subject: [PATCH RESEND 2/3] x86/kexec/64: Error out if try to jump to old 4-level kernel from 5-level kernel
Date: Fri, 25 Jan 2019 10:28:16 +0800	[thread overview]
Message-ID: <20190125022817.29506-3-bhe@redhat.com> (raw)
In-Reply-To: <20190125022817.29506-1-bhe@redhat.com>

In relocate_kernel() CR4.LA57 flag is set before kexec jumping if
the kernel has 5-level paging enabled. Then in boot/compressed/head_64.S,
it will check if the booting kernel is in 4-level or 5-level paging
mode, and handle accordingly. However, the old kernel which doesn't
contain the 5-level codes doesn't know how to cope with it, then #GP
triggered.

Instead of triggering #GP during kexec kernel boot, error out during
kexec loading if find out we are trying to jump to old 4-level kernel
from 5-level kernel.

Signed-off-by: Baoquan He <bhe@redhat.com>
---
 arch/x86/kernel/kexec-bzimage64.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/arch/x86/kernel/kexec-bzimage64.c b/arch/x86/kernel/kexec-bzimage64.c
index 278cd07228dd..5bfb39fc56fe 100644
--- a/arch/x86/kernel/kexec-bzimage64.c
+++ b/arch/x86/kernel/kexec-bzimage64.c
@@ -316,6 +316,11 @@ static int bzImage64_probe(const char *buf, unsigned long len)
 		return ret;
 	}
 
+	if (!(header->xloadflags & XLF_5LEVEL) && pgtable_l5_enabled()) {
+		pr_err("Can not jump to old 4-level kernel from 5-level kernel.\n");
+		return ret;
+	}
+
 	/* I've got a bzImage */
 	pr_debug("It's a relocatable bzImage64\n");
 	ret = 0;
-- 
2.13.6


  parent reply	other threads:[~2019-01-25  2:28 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-01-25  2:28 [PATCH RESEND 0/3] Add restrictions for kexec/kdump jumping between 5-level and 4-level kernel Baoquan He
2019-01-25  2:28 ` Baoquan He
2019-01-25  2:28 ` [PATCH RESEND 1/3] x86/boot: Add bit fields into xloadflags for 5-level kernel checking Baoquan He
2019-01-25  2:28   ` Baoquan He
2019-01-29 20:05   ` Thomas Gleixner
2019-01-29 20:05     ` Thomas Gleixner
2019-02-11  7:02     ` Baoquan He
2019-02-11  7:02       ` Baoquan He
2019-02-11  7:40   ` [PATCH v2 1/3] x86/boot: Add xloadflags bits " Baoquan He
2019-02-11  7:40     ` Baoquan He
2019-01-25  2:28 ` Baoquan He [this message]
2019-01-25  2:28   ` [PATCH RESEND 2/3] x86/kexec/64: Error out if try to jump to old 4-level kernel from 5-level kernel Baoquan He
2019-01-25  2:28 ` [PATCH RESEND 3/3] x86/kdump/64: Change the upper limit of crashkernel reservation Baoquan He
2019-01-25  2:28   ` Baoquan He
2019-01-25 12:05 ` [PATCH RESEND 0/3] Add restrictions for kexec/kdump jumping between 5-level and 4-level kernel Kirill A. Shutemov
2019-01-25 12:05   ` Kirill A. Shutemov

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