[Crash-utility] [PATCH v3 0/3] vmalloc translation support for PPC

[Dave Anderson]

----- Original Message -----
...
> > So just do the same thing -- no verbose expanation is required.
> 
> There are two ways to fix this :
> 
> 1) Fix dump_mem_map*() to print the header only when there is
> information to dump.
> 
> --- a/memory.c
> +++ b/memory.c
> @@ -4637,13 +4637,6 @@ dump_mem_map_SPARSEMEM(struct meminfo *mi)
>                          continue;
>                  }
>   
> -               if (print_hdr) {
> -                       if (!(pc->curcmd_flags & HEADER_PRINTED))
> -                               fprintf(fp, "%s", hdr);
> -                       print_hdr = FALSE;
> -                       pc->curcmd_flags |= HEADER_PRINTED;
> -               }
> -
>                  pp = section_mem_map_addr(section);
>                  pp = sparse_decode_mem_map(pp, section_nr);
>                  phys = (physaddr_t) section_nr * PAGES_PER_SECTION()
>                  * PAGESIZE();
> @@ -4854,6 +4847,13 @@ dump_mem_map_SPARSEMEM(struct meminfo *mi)
>                          }
>   
>                          if (bufferindex > buffersize) {
> +                               if (print_hdr) {
> +                                       if (!(pc->curcmd_flags & HEADER_PRINTED))
> +                                               fprintf(fp, "%s", hdr);
> +                                       print_hdr = FALSE;
> +                                       pc->curcmd_flags |= HEADER_PRINTED;
> +                               }
> +
>                                  fprintf(fp, "%s", outputbuffer);
>                                  bufferindex = 0;
>                          }
> @@ -4867,6 +4867,13 @@ dump_mem_map_SPARSEMEM(struct meminfo *mi)
>          }
>   
>          if (bufferindex > 0) {
> +               if (print_hdr) {
> +                       if (!(pc->curcmd_flags & HEADER_PRINTED))
> +                               fprintf(fp, "%s", hdr);
> +                       print_hdr = FALSE;
> +                       pc->curcmd_flags |= HEADER_PRINTED;
> +               }
> +
>                  fprintf(fp, "%s", outputbuffer);
>          }
> 
> Similarly for the dump_mem_map().
> 
> 2) Fix ppc_pgd_vtop() to return FALSE if the paddr > machdep->memsize
> 
> --- a/ppc.c
> +++ b/ppc.c
> @@ -438,6 +438,10 @@ ppc_pgd_vtop(ulong *pgd, ulong vaddr, physaddr_t
> *paddr, int verbose)
>   
>          *paddr = PAGEBASE(pte) + PAGEOFFSET(vaddr);
>   
> +       if (*paddr > machdep->memsize)
> +       /* We don't have pages above System RAM */
> +               return FALSE;
> +
>          return TRUE;
>   
>   no_page:
> 
> I prefer the (1). What do you think ?

Hi Suzuki,

Hmmm -- with respect to (1), I suppose that would work, although
given that both x86 and x86_64 pass through dump_mem_map_SPARSEMEM()
without printing the header in a non-existent-page case, I don't 
understand why ppc is different?  

And I'm thinking that a more general solution might be to change
do_vtop() here, and not even bother calling the relevant dump_mem_map()
function if there's no page struct associated with it:

--- memory.c    10 Feb 2012 16:41:38 -0000      1.273
+++ memory.c    16 Feb 2012 14:18:03 -0000
@@ -2796,7 +2796,7 @@
 do_vtop(ulong vaddr, struct task_context *tc, ulong vtop_flags)
 {
        physaddr_t paddr; 
-       ulong vma;
+       ulong vma, pageptr;
        int page_exists;
         struct meminfo meminfo;
         char buf1[BUFSIZE];
@@ -2930,7 +2930,7 @@
 
        fprintf(fp, "\n");
 
-       if (page_exists) { 
+       if (page_exists && phys_to_page(paddr, &pageptr)) { 
                if ((pc->flags & DEVMEM) && (paddr >= VTOP(vt->high_memory)))
                        return;
                BZERO(&meminfo, sizeof(struct meminfo));

And w/respect to (2), wouldn't that just cause the generic kvtop()
to fail?  And if so, it kind of re-defines the meaning of kvtop(),
even though its current callers pretty much expect to receive
a legitimate physical memory address.  But if a virtual address
resolves to a PTE with any legitimate address in it, then kvtop()
should return whatever's there.

But I'm still wondering what makes ppc behave differently in
dump_mem_map_SPARSEMEM()?

Dave