[Crash-utility] using crash for ARM

[paawan oza]

Isn't the problem actually that we read the section entry wrong?
The following (and attached) is the fix I've been using for this.

Oza: it is not a problem as none of the kernel section level translations goes through vtop.
if you look at 


arm_kvtop(struct task_context *tc, ulong kvaddr, physaddr_t *paddr, int verbose)
{
  
    if (!IS_KVADDR(kvaddr))
        return FALSE;

    if (!vt->vmalloc_start) {
        *paddr = VTOP(kvaddr);
        return TRUE;
    }

    if (!IS_VMALLOC_ADDR(kvaddr)) {
        *paddr = VTOP(kvaddr);
        if (!verbose)
            return TRUE;
    }

    return arm_vtop(kvaddr, (ulong *)vt->kernel_pgd[0], paddr, verbose);

it just uses VTOP for any kernel address other than vmalloc.
and vmalloc addresses are not falling in sections.

may in kernel_init part it might be called, but it is a problem only if 20th bit set; and while section translation we mask 20th bit.


Regards,
Oza.


________________________________
 From: Rabin Vincent <rabin at rab.in>
To: "Discussion list for crash utility usage, maintenance and development" <crash-utility at redhat.com> 
Cc: Thomas Fänge <thomas.fange at sonymobile.com> 
Sent: Thursday, 4 October 2012 2:35 PM
Subject: Re: [Crash-utility] using crash for ARM
 
2012/10/4 Mika Westerberg <mika.westerberg at iki.fi>:
> The unity-mapped region is mapped using 1MB pages. However, we actually have
> (when using the Linux ARM 2-level translation scheme):
>
> see arch/arm/include/asm/pgtable-2level.h:
>
> #define PMD_SHIFT               21
> #define PGDIR_SHIFT             21
>
> #define PTRS_PER_PGD            2048
>
> So we have 2048 entries in a PGD instead of 4096 making a PGD entry an array
> of "two pointers".
>
> Anyway as you and Paawan suggested it looks like a bug - we always use the
> first entry instead of the second given that bit 20 is set in the virtual
> address.

Isn't the problem actually that we read the section entry wrong?
The following (and attached) is the fix I've been using for this.

Rabin

diff --git a/arm.c b/arm.c
index 5930c02..4e7b6dc 100644
--- a/arm.c
+++ b/arm.c
@@ -957,12 +957,14 @@ arm_vtop(ulong vaddr, ulong *pgd, physaddr_t
*paddr, int verbose)
            MKSTR((ulong)page_middle)), pmd_pte);

    if ((pmd_pte & PMD_TYPE_MASK) == PMD_TYPE_SECT) {
+        ulong sectionbase = pmd_pte & _SECTION_PAGE_MASK;
+
        if (verbose) {
            fprintf(fp, " PAGE: %s  (1MB)\n\n",
                mkstring(buf, VADDR_PRLEN, RJUST | LONG_HEX,
-                MKSTR(PAGEBASE(pmd_pte))));
+                MKSTR(sectionbase)));
        }
-        *paddr = PAGEBASE(pmd_pte) + (vaddr & ~_SECTION_PAGE_MASK);
+        *paddr = sectionbase + (vaddr & ~_SECTION_PAGE_MASK);
        return TRUE;
    }

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