Re: [PATCH] ARM: kexec: Fix panic after TLB are invalidated

[Giancarlo Ferrari]

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