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

[Dave Anderson]

----- Original Message -----
> 
> 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.

It still fails on 4.17 and later kernels that have this in their VMCOREINFO:

  NUMBER(pgtable_l5_enabled)=0

You need to do atoi(string) to get its value.  I'll fix that and retest again...

Dave


> 
> 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
> > 
> > 
> > 
> > 
> 
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