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Message-ID: <20210201200734.GC15399@p4>
Date: Mon, 1 Feb 2021 20:07:37 +0000
From: Giancarlo Ferrari <giancarlo.ferrari89@...il.com>
To: Russell King - ARM Linux admin <linux@...linux.org.uk>
Cc: Mark Rutland <mark.rutland@....com>, linux-kernel@...r.kernel.org,
penberg@...nel.org, geert@...ux-m68k.org,
linux-arm-kernel@...ts.infradead.org, akpm@...ux-foundation.org,
rppt@...nel.org, giancarlo.ferrari@...ia.com
Subject: Re: [PATCH] ARM: kexec: Fix panic after TLB are invalidated
Hi,
On Mon, Feb 01, 2021 at 04:08:38PM +0000, Russell King - ARM Linux admin wrote:
> On Mon, Feb 01, 2021 at 01:57:14PM +0000, Mark Rutland wrote:
> > We could simplify this slightly if we moved the kexec_& variables into a
> > struct (using asm-offset KEXEC_VAR_* offsets and a KEXEC_VAR_SIZE region
> > reserved in the asm), then here we could do something like:
> >
> > static struct kexec_vars *kexec_buffer_vars(void *buffer)
> > {
> > unsigned long code = ((unisigned long)relocate_new_kernel) & ~1;
> > unsigned long vars - (unsigned long)relocate_vars;
> > unsigned long offset = vars - code;
> >
> > return buffer + offset;
> > }
> >
> > ... and in machine_kexec() do:
> >
> > struct kexec_vars *kv = kexec_buffer_vars(reboot_code_buffer);
> >
> > kv->start_address = image->start;
> > kv->indirection_page = page_list;
> > kv->mach_type = machine-arch_type;
> > kv->boot_atags = arch.kernel_r2;
> >
> > ... if that looks any better to you?
>
> Something like this?
>
> diff --git a/arch/arm/include/asm/kexec-internal.h b/arch/arm/include/asm/kexec-internal.h
> new file mode 100644
> index 000000000000..ecc2322db7aa
> --- /dev/null
> +++ b/arch/arm/include/asm/kexec-internal.h
> @@ -0,0 +1,12 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +#ifndef _ARM_KEXEC_INTERNAL_H
> +#define _ARM_KEXEC_INTERNAL_H
> +
> +struct kexec_relocate_data {
> + unsigned long kexec_start_address;
> + unsigned long kexec_indirection_page;
> + unsigned long kexec_mach_type;
> + unsigned long kexec_r2;
> +};
> +
> +#endif
> diff --git a/arch/arm/kernel/asm-offsets.c b/arch/arm/kernel/asm-offsets.c
> index a1570c8bab25..be8050b0c3df 100644
> --- a/arch/arm/kernel/asm-offsets.c
> +++ b/arch/arm/kernel/asm-offsets.c
> @@ -12,6 +12,7 @@
> #include <linux/mm.h>
> #include <linux/dma-mapping.h>
> #include <asm/cacheflush.h>
> +#include <asm/kexec-internal.h>
> #include <asm/glue-df.h>
> #include <asm/glue-pf.h>
> #include <asm/mach/arch.h>
> @@ -170,5 +171,9 @@ int main(void)
> DEFINE(MPU_RGN_PRBAR, offsetof(struct mpu_rgn, prbar));
> DEFINE(MPU_RGN_PRLAR, offsetof(struct mpu_rgn, prlar));
> #endif
> + DEFINE(KEXEC_START_ADDR, offsetof(struct kexec_relocate_data, kexec_start_address));
> + DEFINE(KEXEC_INDIR_PAGE, offsetof(struct kexec_relocate_data, kexec_indirection_page));
> + DEFINE(KEXEC_MACH_TYPE, offsetof(struct kexec_relocate_data, kexec_mach_type));
> + DEFINE(KEXEC_R2, offsetof(struct kexec_relocate_data, kexec_r2));
> return 0;
> }
> diff --git a/arch/arm/kernel/machine_kexec.c b/arch/arm/kernel/machine_kexec.c
> index 5d84ad333f05..2b09dad7935e 100644
> --- a/arch/arm/kernel/machine_kexec.c
> +++ b/arch/arm/kernel/machine_kexec.c
> @@ -13,6 +13,7 @@
> #include <linux/of_fdt.h>
> #include <asm/mmu_context.h>
> #include <asm/cacheflush.h>
> +#include <asm/kexec-internal.h>
> #include <asm/fncpy.h>
> #include <asm/mach-types.h>
> #include <asm/smp_plat.h>
> @@ -22,11 +23,6 @@
> extern void relocate_new_kernel(void);
> extern const unsigned int relocate_new_kernel_size;
>
> -extern unsigned long kexec_start_address;
> -extern unsigned long kexec_indirection_page;
> -extern unsigned long kexec_mach_type;
> -extern unsigned long kexec_boot_atags;
> -
> static atomic_t waiting_for_crash_ipi;
>
> /*
> @@ -159,6 +155,7 @@ void (*kexec_reinit)(void);
> void machine_kexec(struct kimage *image)
> {
> unsigned long page_list, reboot_entry_phys;
> + struct kexec_relocate_data *data;
> void (*reboot_entry)(void);
> void *reboot_code_buffer;
>
> @@ -174,18 +171,17 @@ void machine_kexec(struct kimage *image)
>
> reboot_code_buffer = page_address(image->control_code_page);
>
> - /* Prepare parameters for reboot_code_buffer*/
> - set_kernel_text_rw();
> - kexec_start_address = image->start;
> - kexec_indirection_page = page_list;
> - kexec_mach_type = machine_arch_type;
> - kexec_boot_atags = image->arch.kernel_r2;
> -
> /* copy our kernel relocation code to the control code page */
> reboot_entry = fncpy(reboot_code_buffer,
> &relocate_new_kernel,
> relocate_new_kernel_size);
>
> + data = reboot_code_buffer + relocate_new_kernel_size;
> + data->kexec_start_address = image->start;
> + data->kexec_indirection_page = page_list;
> + data->kexec_mach_type = machine_arch_type;
> + data->kexec_r2 = image->arch.kernel_r2;
> +
> /* get the identity mapping physical address for the reboot code */
> reboot_entry_phys = virt_to_idmap(reboot_entry);
>
> diff --git a/arch/arm/kernel/relocate_kernel.S b/arch/arm/kernel/relocate_kernel.S
> index 72a08786e16e..218d524360fc 100644
> --- a/arch/arm/kernel/relocate_kernel.S
> +++ b/arch/arm/kernel/relocate_kernel.S
> @@ -5,14 +5,16 @@
>
> #include <linux/linkage.h>
> #include <asm/assembler.h>
> +#include <asm/asm-offsets.h>
> #include <asm/kexec.h>
>
> .align 3 /* not needed for this code, but keeps fncpy() happy */
>
> ENTRY(relocate_new_kernel)
>
> - ldr r0,kexec_indirection_page
> - ldr r1,kexec_start_address
> + adr r7, relocate_new_kernel_end
> + ldr r0, [r7, #KEXEC_INDIR_PAGE]
> + ldr r1, [r7, #KEXEC_START_ADDR]
>
> /*
> * If there is no indirection page (we are doing crashdumps)
> @@ -57,34 +59,16 @@ ENTRY(relocate_new_kernel)
>
> 2:
> /* Jump to relocated kernel */
> - mov lr,r1
> - mov r0,#0
> - ldr r1,kexec_mach_type
> - ldr r2,kexec_boot_atags
> - ARM( ret lr )
> - THUMB( bx lr )
> -
> - .align
> -
> - .globl kexec_start_address
> -kexec_start_address:
> - .long 0x0
> -
> - .globl kexec_indirection_page
> -kexec_indirection_page:
> - .long 0x0
> -
> - .globl kexec_mach_type
> -kexec_mach_type:
> - .long 0x0
> -
> - /* phy addr of the atags for the new kernel */
> - .globl kexec_boot_atags
> -kexec_boot_atags:
> - .long 0x0
> + mov lr, r1
> + mov r0, #0
> + ldr r1, [r7, #KEXEC_MACH_TYPE]
> + ldr r2, [r7, #KEXEC_R2]
> + ARM( ret lr )
> + THUMB( bx lr )
>
> ENDPROC(relocate_new_kernel)
>
> + .align 3
Nice.
Why we should align 3 ? For the fncpy I suppose.
> relocate_new_kernel_end:
>
> .globl relocate_new_kernel_size
>
> --
> RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
> FTTP is here! 40Mbps down 10Mbps up. Decent connectivity at last!
I don't know now how to proceed now, as you (Mark and you) do completely
the patch.
You see is my first kernel patch submission :) .
Thanks,
GF
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