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From: Giancarlo Ferrari <giancarlo.ferrari89@gmail.com>
To: linux-arm-kernel@lists.infradead.org, linux@armlinux.org.uk
Cc: linux-kernel@vger.kernel.org, akpm@linux-foundation.org,
	rppt@kernel.org, penberg@kernel.org, geert@linux-m68k.org,
	giancarlo.ferrari@nokia.com,
	Giancarlo Ferrari <giancarlo.ferrari89@gmail.com>
Subject: [PATCH] ARM: kexec: Fix panic after TLB are invalidated
Date: Mon,  1 Feb 2021 00:44:56 +0000
Message-ID: <1612140296-12546-1-git-send-email-giancarlo.ferrari89@gmail.com> (raw)

machine_kexec() need to set rw permission in text and rodata sections
to assign some variables (e.g. kexec_start_address). To do that at
the end (after flushing pdm in memory, etc.) it needs to invalidate
TLB [section] entries.

If during the TLB invalidation an interrupt occours, which might cause
a context switch, there is the risk to inject invalid TLBs, with ro
permissions.

When trying to assign .text labels, this lead to the following:

 Unable to handle kernel paging request at virtual address 80112f38
 pgd = fd7ef03e
 [80112f38] *pgd=0001141e(bad)
 Internal error: Oops: 80d [#1] PREEMPT SMP ARM
 ...

Signed-off-by: Giancarlo Ferrari <giancarlo.ferrari89@gmail.com>
---
 arch/arm/kernel/machine_kexec.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/arch/arm/kernel/machine_kexec.c b/arch/arm/kernel/machine_kexec.c
index 5d84ad3..23e8816 100644
--- a/arch/arm/kernel/machine_kexec.c
+++ b/arch/arm/kernel/machine_kexec.c
@@ -174,6 +174,13 @@ void machine_kexec(struct kimage *image)
 
 	reboot_code_buffer = page_address(image->control_code_page);
 
+	/*
+	 * If below part is not atomic TLB entries might be corrupted after TLB
+	 * invalidation, which leads to Data Abort in .text variable assignment
+	 */
+	raw_local_irq_disable();
+	local_fiq_disable();
+
 	/* Prepare parameters for reboot_code_buffer*/
 	set_kernel_text_rw();
 	kexec_start_address = image->start;
@@ -181,6 +188,9 @@ void machine_kexec(struct kimage *image)
 	kexec_mach_type = machine_arch_type;
 	kexec_boot_atags = image->arch.kernel_r2;
 
+	local_fiq_enable();
+	raw_local_irq_enable();
+
 	/* copy our kernel relocation code to the control code page */
 	reboot_entry = fncpy(reboot_code_buffer,
 			     &relocate_new_kernel,
-- 
2.7.4


             reply index

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-02-01  0:44 Giancarlo Ferrari [this message]
2021-02-01 11:34 ` Russell King - ARM Linux admin
2021-02-01 12:47 ` Mark Rutland
2021-02-01 13:03   ` Russell King - ARM Linux admin
2021-02-01 13:57     ` Mark Rutland
2021-02-01 16:08       ` Russell King - ARM Linux admin
2021-02-01 16:32         ` Mark Rutland
2021-02-01 16:37           ` Russell King - ARM Linux admin
2021-02-01 20:07         ` Giancarlo Ferrari
2021-02-01 20:16           ` Russell King - ARM Linux admin
2021-02-01 22:18             ` Giancarlo Ferrari
2021-02-04 23:48               ` Giancarlo Ferrari
2021-02-05  0:18                 ` Russell King - ARM Linux admin
2021-02-05  0:40                   ` Giancarlo Ferrari
2021-02-05  0:45                     ` Giancarlo Ferrari
2021-02-05  9:44                     ` Russell King - ARM Linux admin
2021-02-05 14:36                       ` Giancarlo Ferrari
2021-02-01 14:39   ` Giancarlo Ferrari
2021-02-01 15:30     ` Mark Rutland
2021-02-01 19:09       ` Giancarlo Ferrari
  -- strict thread matches above, loose matches on Subject: below --
2021-01-12 16:49 Giancarlo Ferrari
2021-02-01 10:10 ` Giancarlo Ferrari

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