Re: Fatal trap 12: page fault on Acer Chromebook 720 (peppy)

> On 22. Aug 2018, at 23:15, Konstantin Belousov <kostikbel_at_gmail.com> wrote:
> 
>> On Wed, Aug 22, 2018 at 10:03:54PM +0200, Michael Gmelin wrote:
>> 
>> 
>>>> On 22. Aug 2018, at 17:46, Konstantin Belousov <kostikbel_at_gmail.com> wrote:
>>>> 
>>>> On Tue, Aug 21, 2018 at 12:14:35AM +0200, Michael Gmelin wrote:
>>>> 
>>>> 
>>>>>> On 20. Aug 2018, at 17:09, Konstantin Belousov <kostikbel_at_gmail.com> wrote:
>>>>>> 
>>>>>> On Mon, Aug 20, 2018 at 12:45:12AM +0200, Michael Gmelin wrote:
>>>>>> 
>>>>>> See here for a screenshot (also including the output of "show pte
>>>>>> 0xfffff80001000000"):
>>>>>> 
>>>>>> https://gist.github.com/grembo/78d0f2a100dd4f16775b85a118769658#file-ddb1-png
>>>>> It is too early for ddb routines to register.
>>>>> Ok can you try the following debugging patch, to verify my guess ?
>>>>> 
>>>>> diff --git a/sys/amd64/amd64/pmap.c b/sys/amd64/amd64/pmap.c
>>>>> index 18777d23f09..cd05fdb763f 100644
>>>>> --- a/sys/amd64/amd64/pmap.c
>>>>> +++ b/sys/amd64/amd64/pmap.c
>>>>> _at__at_ -1052,8 +1052,7 _at__at_ create_pagetables(vm_paddr_t *firstaddr)
>>>>>      pd_p = (pd_entry_t *)DMPDkernphys;
>>>>>      for (i = 0; i < (NPDEPG * nkdmpde); i++)
>>>>>          pd_p[i] = (i << PDRSHIFT) | X86_PG_V | PG_PS | pg_g |
>>>>> -                X86_PG_M | X86_PG_A | pg_nx |
>>>>> -                bootaddr_rwx(i << PDRSHIFT);
>>>>> +                X86_PG_M | X86_PG_A | pg_nx | X86_PG_RW;
>>>>>      for (i = 0; i < nkdmpde; i++)
>>>>>          pdp_p[i] = (DMPDkernphys + ptoa(i)) | X86_PG_RW |
>>>>>              X86_PG_V;
>>>> 
>>>> With this change it boots okay (mptramp_pagetables is 0x1000000, as expected).
>>> 
>>> Can you apply the following on top of the previous debugging patch and show
>>> me the line printed ?
>>> 
>>> diff --git a/sys/amd64/amd64/pmap.c b/sys/amd64/amd64/pmap.c
>>> index 3d70532b7fd..613fa9f2165 100644
>>> --- a/sys/amd64/amd64/pmap.c
>>> +++ b/sys/amd64/amd64/pmap.c
>>> _at__at_ -2662,6 +2662,7 _at__at_ pmap_pinit0(pmap_t pmap)
>>>       pmap->pm_pcids[i].pm_gen = 1;
>>>   }
>>>   pmap_activate_boot(pmap);
>>> +printf("bootaddr addr %#lx rwx %#lx btext %#lx _end %#lx brwsection %#lx etext %#lx KERNBASE %#lx\n", 0x1000000UL, bootaddr_rwx(0x1000000UL), (uintptr_t)btext, (uintptr_t)_end, (uintptr_t)brwsection, (uintptr_t)etext, (uintptr_t)KERNBASE);
>>> }
>>> 
>>> void
>> 
>> bootaddr addr 0x1000000 rwx 0 btext 0xffffffff80342000 _end 0xffffffff823cf840 brwsection #ffffffff81a00000 etext 0xffffffff812041e4 KERNBASE 0xffffffff80000000
>> 
> 
> Try this, please.  Revert all debugging pmap.c patches that I provided
> before.
> 
> diff --git a/sys/amd64/amd64/mp_machdep.c b/sys/amd64/amd64/mp_machdep.c
> index 4ca2e07e578..2ee8f862854 100644
> --- a/sys/amd64/amd64/mp_machdep.c
> +++ b/sys/amd64/amd64/mp_machdep.c
> _at__at_ -87,6 +87,8 _at__at_ __FBSDID("$FreeBSD$");
> 
> #define GiB(v)            (v ## ULL << 30)
> 
> +#define    AP_BOOTPT_SZ        (PAGE_SIZE * 3)
> +
> extern    struct pcpu __pcpu[];
> 
> /* Temporary variables for init_secondary()  */
> _at__at_ -101,45 +103,78 _at__at_ char *dbg_stack;
> 
> static int    start_ap(int apic_id);
> 
> +static bool
> +is_kernel_paddr(vm_paddr_t pa)
> +{
> +
> +    return (pa >= trunc_2mpage(btext - KERNBASE) &&
> +       pa < round_page(_end - KERNBASE));
> +}
> +
> +static bool
> +is_mpboot_good(vm_paddr_t start, vm_paddr_t end)
> +{
> +
> +    return (start + AP_BOOTPT_SZ <= GiB(4) &&
> +        end >= start + AP_BOOTPT_SZ && atop(end) < Maxmem);
> +}
> +
> /*
>  * Calculate usable address in base memory for AP trampoline code.
>  */
> void
> mp_bootaddress(vm_paddr_t *physmap, unsigned int *physmap_idx)
> {
> +    vm_paddr_t start, end;
>    unsigned int i;
>    bool allocated;
> 
>    alloc_ap_trampoline(physmap, physmap_idx);
> 
> +    /*
> +     * Find a memory region big enough below the 4GB boundary to
> +     * store the initial page tables.  Region must be mapped by
> +     * the direct map.
> +     *
> +     * Note that it needs to be aligned to a page boundary.
> +     */
>    allocated = false;
>    for (i = *physmap_idx; i <= *physmap_idx; i -= 2) {
>        /*
> -         * Find a memory region big enough below the 4GB
> -         * boundary to store the initial page tables.  Region
> -         * must be mapped by the direct map.
> -         *
> -         * Note that it needs to be aligned to a page
> -         * boundary.
> +         * First, try to chomp at the start of the physmap region.
> +         * Kernel binary might claim it already.
> +         */
> +        start = round_page(physmap[i]);
> +        end = trunc_page(physmap[i + 1]);
> +        if (is_mpboot_good(start, end) &&
> +            !is_kernel_paddr(start) && !is_kernel_paddr(end - 1)) {
> +            allocated = true;
> +            physmap[i] = start + AP_BOOTPT_SZ;
> +            break;
> +        }
> +
> +        /*
> +         * Second, try to chomp at the end.  Again, check
> +         * against kernel.
>         */
> -        if (physmap[i] >= GiB(4) || physmap[i + 1] -
> -            round_page(physmap[i]) < PAGE_SIZE * 3 ||
> -            atop(physmap[i + 1]) > Maxmem)
> -            continue;
> -
> -        allocated = true;
> -        mptramp_pagetables = round_page(physmap[i]);
> -        physmap[i] = round_page(physmap[i]) + (PAGE_SIZE * 3);
> +        end = trunc_page(physmap[i + 1]);
> +        start = end - AP_BOOTPT_SZ;
> +        if (start >= physmap[i] && is_mpboot_good(start, end) &&
> +            !is_kernel_paddr(start) && !is_kernel_paddr(end - 1)) {
> +            allocated = true;
> +            physmap[i + 1] = start;
> +            break;
> +        }
> +    }
> +    if (allocated) {
> +        mptramp_pagetables = start;
>        if (physmap[i] == physmap[i + 1] && *physmap_idx != 0) {
>            memmove(&physmap[i], &physmap[i + 2],
>                sizeof(*physmap) * (*physmap_idx - i + 2));
>            *physmap_idx -= 2;
>        }
> -        break;
> -    }
> -
> -    if (!allocated) {
> -        mptramp_pagetables = trunc_page(boot_address) - (PAGE_SIZE * 3);
> +    } else {
> +        mptramp_pagetables = trunc_page(boot_address) - AP_BOOTPT_SZ;
>        if (bootverbose)
>            printf(
> "Cannot find enough space for the initial AP page tables, placing them at %#x",

Reverted back to r337813 and applied the patch. Unfortunately it panics just like before. Adding back physmap debugging like before shows that it’s still using pages 0x1000-0x1003 (Stopped at native_start_all_aps+0x92: movq %rax,(%rsi))

Best,
Michael