[Crash-utility] [PATCH v2] x86_64: Make the conversion between 4level and 5level paging automatically

[Dave Anderson]

Hello Dou,

This patch was failing on most -- but not all -- of my test dumpfiles, because of 
fatal read or seek errors during session initialization. 

As it turns out, the "l5_enabled" local variable needs to be zeroed-out, because 
if neither the "if" or the "else" are true, it uses whatever old stack garbage 
that l5_enabled contains:

> +		/* Check for 5-level paging */
> +		if (!(machdep->flags & VM_5LEVEL)) {
> +			int l5_enabled;
> +			if ((string = pc->read_vmcoreinfo("NUMBER(pgtable_l5_enabled)"))) {
> +				l5_enabled = 1;
> +				free(string);
> +			} else if (kernel_symbol_exists("__pgtable_l5_enabled"))
> +				readmem(symbol_value("__pgtable_l5_enabled"), KVADDR,
> +					&l5_enabled, sizeof(int), "__pgtable_l5_enabled",
> +					FAULT_ON_ERROR);
> +
> +			if (l5_enabled)
> +				machdep->flags |= VM_5LEVEL;
> +		}

I'll fix that and retest.

Thanks,
  Dave





----- Original Message -----
> Currently, Crash only enable support for kernel-only 5-level page tables by
> entering the command line option "--machdep vm=5level". Since Linux 4.17,
> the Linux kernel can be both 4level and 5level page tables. This command line
> can't work well for this.
> 
> Using the "pgtable_l5_enabled" to detect whether the kernel proper for 5
> level
> page tables automatically. Also move the 5-level paging setup from
> machdep_init(PRE_GDB)
> to machdep_init(POST_RELOC).
> 
> Signed-off-by: Dave Anderson <anderson at redhat.com>
> Signed-off-by: Dou Liyang <douly.fnst at cn.fujitsu.com>
> ---
> Changelog v1 --> v2
> 
>  1. Make it support live systems suggested by Dave
>  2. Using __pgtable_l5_enabled for check.
>  3. Do some tests in both kdump(5level and 4level) and virsh dump(5level and
>  4level)
> ---
>  x86_64.c | 56 +++++++++++++++++++++++++++++++++++++-------------------
>  1 file changed, 37 insertions(+), 19 deletions(-)
> 
> diff --git a/x86_64.c b/x86_64.c
> index 6d1ae2f..07b6aa9 100644
> --- a/x86_64.c
> +++ b/x86_64.c
> @@ -294,25 +294,6 @@ x86_64_init(int when)
>  			machdep->machspec->pgdir_shift = PGDIR_SHIFT;
>  			machdep->machspec->ptrs_per_pgd = PTRS_PER_PGD;
>  			break;
> -
> -		case VM_5LEVEL:
> -			machdep->machspec->userspace_top = USERSPACE_TOP_5LEVEL;
> -			machdep->machspec->page_offset = PAGE_OFFSET_5LEVEL;
> -			machdep->machspec->vmalloc_start_addr = VMALLOC_START_ADDR_5LEVEL;
> -			machdep->machspec->vmalloc_end = VMALLOC_END_5LEVEL;
> -			machdep->machspec->modules_vaddr = MODULES_VADDR_5LEVEL;
> -			machdep->machspec->modules_end = MODULES_END_5LEVEL;
> -			machdep->machspec->vmemmap_vaddr = VMEMMAP_VADDR_5LEVEL;
> -			machdep->machspec->vmemmap_end = VMEMMAP_END_5LEVEL;
> -			if (symbol_exists("vmemmap_populate"))
> -				machdep->flags |= VMEMMAP;
> -			machdep->machspec->physical_mask_shift = __PHYSICAL_MASK_SHIFT_5LEVEL;
> -			machdep->machspec->pgdir_shift = PGDIR_SHIFT_5LEVEL;
> -			machdep->machspec->ptrs_per_pgd = PTRS_PER_PGD_5LEVEL;
> -			if ((machdep->machspec->p4d = (char *)malloc(PAGESIZE())) == NULL)
> -				error(FATAL, "cannot malloc p4d space.");
> -			machdep->machspec->last_p4d_read = 0;
> -			machdep->uvtop = x86_64_uvtop_level4;  /* 5-level is optional per-task */
>  		}
>  	        machdep->kvbase = (ulong)PAGE_OFFSET;
>  		machdep->identity_map_base = (ulong)PAGE_OFFSET;
> @@ -346,6 +327,43 @@ x86_64_init(int when)
>  		break;
>  
>  	case POST_RELOC:
> +		/* Check for 5-level paging */
> +		if (!(machdep->flags & VM_5LEVEL)) {
> +			int l5_enabled;
> +			if ((string = pc->read_vmcoreinfo("NUMBER(pgtable_l5_enabled)"))) {
> +				l5_enabled = 1;
> +				free(string);
> +			} else if (kernel_symbol_exists("__pgtable_l5_enabled"))
> +				readmem(symbol_value("__pgtable_l5_enabled"), KVADDR,
> +					&l5_enabled, sizeof(int), "__pgtable_l5_enabled",
> +					FAULT_ON_ERROR);
> +
> +			if (l5_enabled)
> +				machdep->flags |= VM_5LEVEL;
> +		}
> +		if (machdep->flags & VM_5LEVEL) {
> +			machdep->machspec->userspace_top = USERSPACE_TOP_5LEVEL;
> +			machdep->machspec->page_offset = PAGE_OFFSET_5LEVEL;
> +			machdep->machspec->vmalloc_start_addr = VMALLOC_START_ADDR_5LEVEL;
> +			machdep->machspec->vmalloc_end = VMALLOC_END_5LEVEL;
> +			machdep->machspec->modules_vaddr = MODULES_VADDR_5LEVEL;
> +			machdep->machspec->modules_end = MODULES_END_5LEVEL;
> +			machdep->machspec->vmemmap_vaddr = VMEMMAP_VADDR_5LEVEL;
> +			machdep->machspec->vmemmap_end = VMEMMAP_END_5LEVEL;
> +			if (symbol_exists("vmemmap_populate"))
> +				machdep->flags |= VMEMMAP;
> +			machdep->machspec->physical_mask_shift = __PHYSICAL_MASK_SHIFT_5LEVEL;
> +			machdep->machspec->pgdir_shift = PGDIR_SHIFT_5LEVEL;
> +			machdep->machspec->ptrs_per_pgd = PTRS_PER_PGD_5LEVEL;
> +			if ((machdep->machspec->p4d = (char *)malloc(PAGESIZE())) == NULL)
> +				error(FATAL, "cannot malloc p4d space.");
> +			machdep->machspec->last_p4d_read = 0;
> +			machdep->uvtop = x86_64_uvtop_level4;  /* 5-level is optional per-task */
> +			machdep->kvbase = (ulong)PAGE_OFFSET;
> +			machdep->identity_map_base = (ulong)PAGE_OFFSET;
> +
> +		}
> +
>  		/*
>  		 *  Check for CONFIG_RANDOMIZE_MEMORY, and set page_offset here.
>  		 *  The remainder of the virtual address range setups will get
> --
> 2.14.3
> 
> 
> 
>