[Crash-utility] Why module's global symbol cannot be displayed in crash? [ARM]

[Dave Anderson]

----- Original Message -----

> > In this case the original PGD is lost forever. But we can certainly detect
> > that and bail out instead of confusing our users. Maybe something like the
> > patch below?
> > 
> > Note that I have not tested it on 3.2+ dump (I have none) but it works on the
> > dumps I have.
> > 
> > Per, Jan, any comments on this?
> > 
> > diff --git a/arm.c b/arm.c
> > index a3a7c23..03f63e6 100644
> > --- a/arm.c
> > +++ b/arm.c
> > @@ -265,6 +265,10 @@ arm_init(int when)
> >  		    STRUCT_EXISTS("pteval_t"))
> >  			machdep->flags |= PGTABLE_V2;
> >  
> > +		if (THIS_KERNEL_VERSION >= LINUX(3,2,0) ||
> > +		    symbol_exists("idmap_pgd"))
> > +			machdep->flags |= IDMAP_PGD;
> > +
> >  		machdep->section_size_bits = _SECTION_SIZE_BITS;
> >  		machdep->max_physmem_bits = _MAX_PHYSMEM_BITS;
> >  
> > @@ -352,6 +356,8 @@ arm_dump_machdep_table(ulong arg)
> >  		fprintf(fp, "%sPHYS_BASE", others++ ? "|" : "");
> >  	if (machdep->flags & PGTABLE_V2)
> >  		fprintf(fp, "%sPGTABLE_V2", others++ ? "|" : "");
> > +	if (machdep->flags & IDMAP_PGD)
> > +		fprintf(fp, "%sIDMAP_PGD", others++ ? "|" : "");
> >          fprintf(fp, ")\n");
> >  
> >  	fprintf(fp, "             kvbase: %lx\n", machdep->kvbase);
> > @@ -1042,6 +1048,15 @@ arm_uvtop(struct task_context *tc, ulong
> > uvaddr, physaddr_t *paddr, int verbose)
> >  	if (!tc)
> >  		error(FATAL, "current context invalid\n");
> >  
> > +	/*
> > +	 * Before idmap_pgd was introduced with upstream commit 2c8951ab0c
> > +	 * (ARM: idmap: use idmap_pgd when setting up mm for reboot), the
> > +	 * panic task pgd was overwritten by soft reboot code, so we can't do
> > +	 * any vtop translations.
> > +	 */
> > +	if (!(machdep->flags & IDMAP_PGD) && tc->task == tt->panic_task)
> > +		error(FATAL, "panic task pgd is trashed by soft reboot code\n");
> > +
> >  	*paddr = 0;
> >  
> >          if (is_kernel_thread(tc->task) && IS_KVADDR(uvaddr)) {
> > diff --git a/defs.h b/defs.h
> > index 1f693c3..8b8b9f3 100755
> > --- a/defs.h
> > +++ b/defs.h
> > @@ -4649,6 +4649,7 @@ struct arm_pt_regs {
> >  #define KSYMS_START	(0x1)
> >  #define PHYS_BASE	(0x2)
> >  #define PGTABLE_V2	(0x4)
> > +#define IDMAP_PGD	(0x8)
> >  
> >  struct machine_specific {
> >  	ulong phys_base;
> > 
> 
> Unless NAK'd by Per or Jan, then consider it queued for crash-6.1.5.
> 
> Thanks,
>   Dave

Actually, I think this part of the patch should be changed to be
"THIS_KERNEL_VERSION >= LINUX(3,3,0)":

+		if (THIS_KERNEL_VERSION >= LINUX(3,2,0) ||
+		    symbol_exists("idmap_pgd"))
+			machdep->flags |= IDMAP_PGD;
+

because:

 $ git describe --contains 2c8951ab0c337cb198236df07ad55f9dd4892c26
 v3.3-rc1~18^2~3^2~15^2~2
 $

If you download the base linux-3.2.tar.gz and linux-3.3.tar.gz files,
you'll set that "idmap_pgd" does not exist in linux-3.2, but it does
show up in linux-3.3.  

I'll change that...

Thanks, 
  Dave