Nathan Chancellor <natechancellor@xxxxxxxxx> writes:
> On Wed, Sep 02, 2020 at 05:12:22PM +0530, Aneesh Kumar K.V wrote:
>> pte_clear_tests operate on an existing pte entry. Make sure that
>> is not a none pte entry.
>>
>> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxx>
>> ---
>> mm/debug_vm_pgtable.c | 7 ++++---
>> 1 file changed, 4 insertions(+), 3 deletions(-)
>>
>> diff --git a/mm/debug_vm_pgtable.c b/mm/debug_vm_pgtable.c
>> index 9afa1354326b..c36530c69e33 100644
>> --- a/mm/debug_vm_pgtable.c
>> +++ b/mm/debug_vm_pgtable.c
>> @@ -542,9 +542,10 @@ static void __init pgd_populate_tests(struct mm_struct *mm, pgd_t *pgdp,
>> #endif /* PAGETABLE_P4D_FOLDED */
>>
>> static void __init pte_clear_tests(struct mm_struct *mm, pte_t *ptep,
>> - unsigned long vaddr)
>> + unsigned long pfn, unsigned long vaddr,
>> + pgprot_t prot)
>> {
>> - pte_t pte = ptep_get(ptep);
>> + pte_t pte = pfn_pte(pfn, prot);
>>
>> pr_debug("Validating PTE clear\n");
>> pte = __pte(pte_val(pte) | RANDOM_ORVALUE);
>> @@ -1049,7 +1050,7 @@ static int __init debug_vm_pgtable(void)
>>
>> ptl = pte_lockptr(mm, pmdp);
>> spin_lock(ptl);
>> - pte_clear_tests(mm, ptep, vaddr);
>> + pte_clear_tests(mm, ptep, pte_aligned, vaddr, prot);
>> pte_advanced_tests(mm, vma, ptep, pte_aligned, vaddr, prot);
>> pte_unmap_unlock(ptep, ptl);
>>
>> --
> This patch causes a panic at boot for RISC-V defconfig. The rootfs is here if it is needed:
> https://github.com/ClangBuiltLinux/boot-utils/blob/3b21a5b71451742866349ba4f18638c5a754e660/images/riscv/rootfs.cpio.zst
>
> $ make -skj"$(nproc)" ARCH=riscv CROSS_COMPILE=riscv64-linux- O=out/riscv distclean defconfig Image
>
> $ qemu-system-riscv64 -bios default -M virt -display none -initrd rootfs.cpio -kernel Image -m 512m -nodefaults -serial mon:stdio
> ...
>
> OpenSBI v0.6
> ____ _____ ____ _____
> / __ \ / ____| _ \_ _|
> | | | |_ __ ___ _ __ | (___ | |_) || |
> | | | | '_ \ / _ \ '_ \ \___ \| _ < | |
> | |__| | |_) | __/ | | |____) | |_) || |_
> \____/| .__/ \___|_| |_|_____/|____/_____|
> | |
> |_|
>
> Platform Name : QEMU Virt Machine
> Platform HART Features : RV64ACDFIMSU
> Platform Max HARTs : 8
> Current Hart : 0
> Firmware Base : 0x80000000
> Firmware Size : 120 KB
> Runtime SBI Version : 0.2
>
> MIDELEG : 0x0000000000000222
> MEDELEG : 0x000000000000b109
> PMP0 : 0x0000000080000000-0x000000008001ffff (A)
> PMP1 : 0x0000000000000000-0xffffffffffffffff (A,R,W,X)
> [ 0.000000] Linux version 5.9.0-rc4-next-20200910 (nathan@ubuntu-n2-xlarge-x86) (riscv64-linux-gcc (GCC) 10.2.0, GNU ld (GNU Binutils) 2.35) #1 SMP Thu Sep 10 19:10:43 MST 2020
> ...
> [ 0.294593] NET: Registered protocol family 17
> [ 0.295781] 9pnet: Installing 9P2000 support
> [ 0.296153] Key type dns_resolver registered
> [ 0.296694] debug_vm_pgtable: [debug_vm_pgtable ]: Validating architecture page table helpers
> [ 0.297635] Unable to handle kernel paging request at virtual address 0a7fffe01dafefc8
> [ 0.298029] Oops [#1]
> [ 0.298153] Modules linked in:
> [ 0.298433] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.9.0-rc4-next-20200910 #1
> [ 0.298792] epc: ffffffe000205afc ra : ffffffe0008be0aa sp : ffffffe01ae73d40
> [ 0.299078] gp : ffffffe0010b9b48 tp : ffffffe01ae68000 t0 : ffffffe008152000
> [ 0.299362] t1 : 0000000000000000 t2 : 0000000000000000 s0 : ffffffe01ae73d60
> [ 0.299648] s1 : bffffffffffffffb a0 : 0a7fffe01dafefc8 a1 : bffffffffffffffb
> [ 0.299948] a2 : ffffffe0010a2698 a3 : 0000000000000001 a4 : 0000000000000003
> [ 0.300231] a5 : 0000000000000800 a6 : fffffffff0000080 a7 : 000000001b642000
> [ 0.300521] s2 : ffffffe0081517b8 s3 : ffffffe008150a80 s4 : ffffffe01af30000
> [ 0.300806] s5 : ffffffe01f8ca9b8 s6 : ffffffe008150000 s7 : ffffffe0010bb100
> [ 0.301161] s8 : ffffffe0010bb108 s9 : 0000000000080202 s10: ffffffe0010bb928
> [ 0.301481] s11: 000000002008085b t3 : 0000000000000000 t4 : 0000000000000000
> [ 0.301722] t5 : 0000000000000000 t6 : ffffffe008150000
> [ 0.301947] status: 0000000000000120 badaddr: 0a7fffe01dafefc8 cause: 000000000000000f
> [ 0.302569] ---[ end trace 7ffb153d816164cf ]---
> [ 0.302797] note: swapper/0[1] exited with preempt_count 1
> [ 0.303101] Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b
> [ 0.303614] ---[ end Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b ]---
I guess it is the combination of a valid pte and usage of
RANDOM_ORVALUE. The below change get the kernel to boot. Can somebody
faimilar with riscv pte format take a look at the RANDOM_ORVALUE?
modified mm/debug_vm_pgtable.c
@@ -548,7 +548,7 @@ static void __init pte_clear_tests(struct mm_struct *mm, pte_t *ptep,
pte_t pte = pfn_pte(pfn, prot);
pr_debug("Validating PTE clear\n");
- pte = __pte(pte_val(pte) | RANDOM_ORVALUE);
+// pte = __pte(pte_val(pte) | RANDOM_ORVALUE);
set_pte_at(mm, vaddr, ptep, pte);
barrier();
pte_clear(mm, vaddr, ptep);
