[PATCH] makedumpfile: ppc64: do page traversal if vmemmap_list not populated
HAGIO KAZUHITO(萩尾 一仁)
k-hagio-ab at nec.com
Tue Sep 26 23:32:44 PDT 2023
On 2023/09/14 18:22, Aditya Gupta wrote:
> Currently 'makedumpfile' fails to collect vmcore on upstream kernel,
> with the errors:
>
> readpage_elf: Attempt to read non-existent page at 0x4000000000000000.
> readmem: type_addr: 0, addr:0, size:8
> get_vmemmap_list_info: Can't get vmemmap region addresses
> get_machdep_info_ppc64: Can't get vmemmap list info.
>
> This occurs since makedumpfile depends on 'vmemmap_list' for translating
> vmemmap addresses. But with below commit in Linux, vmemmap_list can be
> empty, in case of Radix MMU on PowerPC64
>
> 368a0590d954: (powerpc/book3s64/vmemmap: switch radix to use a
> different vmemmap handling function)
>
> In case vmemmap_list is empty, then it's head is NULL, which causes
> makedumpfile to fail with above error.
>
> Since with above commit, 'vmemmap_list' is not populated (when MMU is
> Radix MMU), kernel populates corresponding page table entries in kernel
> page table. Hence, instead of depending on 'vmemmap_list' for address
> translation for vmemmap addresses, do a kernel pagetable walk.
>
> And since the pte can also be introduced at higher levels in the page
> table, such as at PMD level, add hugepage support, by checking for
> PAGE_PTE flag
>
> Reported-by: Sachin Sant <sachinp at linux.ibm.com>
> Signed-off-by: Aditya Gupta <adityag at linux.ibm.com>
Thank you for the patch, applied.
https://github.com/makedumpfile/makedumpfile/commit/a34f017965583e89c4cb0b00117c200a6c191e54
Sorry for the delay, exceptionally busy this month..
Thanks,
Kazu
> ---
> arch/ppc64.c | 111 ++++++++++++++++++++++++++++++++++---------------
> makedumpfile.h | 6 +++
> 2 files changed, 84 insertions(+), 33 deletions(-)
>
> diff --git a/arch/ppc64.c b/arch/ppc64.c
> index 5e70acb51aba..9456b8b570c5 100644
> --- a/arch/ppc64.c
> +++ b/arch/ppc64.c
> @@ -196,6 +196,10 @@ ppc64_vmemmap_init(void)
> int psize, shift;
> ulong head;
>
> + /* initialise vmemmap_list in case SYMBOL(vmemmap_list) is not found */
> + info->vmemmap_list = NULL;
> + info->vmemmap_cnt = 0;
> +
> if ((SYMBOL(vmemmap_list) == NOT_FOUND_SYMBOL)
> || (SYMBOL(mmu_psize_defs) == NOT_FOUND_SYMBOL)
> || (SYMBOL(mmu_vmemmap_psize) == NOT_FOUND_SYMBOL)
> @@ -216,15 +220,24 @@ ppc64_vmemmap_init(void)
> return FALSE;
> info->vmemmap_psize = 1 << shift;
>
> - if (!readmem(VADDR, SYMBOL(vmemmap_list), &head, sizeof(unsigned long)))
> - return FALSE;
> -
> /*
> - * Get vmemmap list count and populate vmemmap regions info
> - */
> - info->vmemmap_cnt = get_vmemmap_list_info(head);
> - if (info->vmemmap_cnt == 0)
> - return FALSE;
> + * vmemmap_list symbol can be missing or set to 0 in the kernel.
> + * This would imply vmemmap region is mapped in the kernel pagetable.
> + *
> + * So, read vmemmap_list anyway, and use 'vmemmap_list' if it's not empty
> + * (head != NULL), or we will do a kernel pagetable walk for vmemmap address
> + * translation later
> + **/
> + readmem(VADDR, SYMBOL(vmemmap_list), &head, sizeof(unsigned long));
> +
> + if (head) {
> + /*
> + * Get vmemmap list count and populate vmemmap regions info
> + */
> + info->vmemmap_cnt = get_vmemmap_list_info(head);
> + if (info->vmemmap_cnt == 0)
> + return FALSE;
> + }
>
> info->flag_vmemmap = TRUE;
> return TRUE;
> @@ -347,29 +360,6 @@ ppc64_vmalloc_init(void)
> return TRUE;
> }
>
> -/*
> - * If the vmemmap address translation information is stored in the kernel,
> - * make the translation.
> - */
> -static unsigned long long
> -ppc64_vmemmap_to_phys(unsigned long vaddr)
> -{
> - int i;
> - ulong offset;
> - unsigned long long paddr = NOT_PADDR;
> -
> - for (i = 0; i < info->vmemmap_cnt; i++) {
> - if ((vaddr >= info->vmemmap_list[i].virt) && (vaddr <
> - (info->vmemmap_list[i].virt + info->vmemmap_psize))) {
> - offset = vaddr - info->vmemmap_list[i].virt;
> - paddr = info->vmemmap_list[i].phys + offset;
> - break;
> - }
> - }
> -
> - return paddr;
> -}
> -
> static unsigned long long
> ppc64_vtop_level4(unsigned long vaddr)
> {
> @@ -379,6 +369,8 @@ ppc64_vtop_level4(unsigned long vaddr)
> unsigned long long pgd_pte, pud_pte;
> unsigned long long pmd_pte, pte;
> unsigned long long paddr = NOT_PADDR;
> + uint is_hugepage = 0;
> + uint pdshift;
> uint swap = 0;
>
> if (info->page_buf == NULL) {
> @@ -413,6 +405,13 @@ ppc64_vtop_level4(unsigned long vaddr)
> if (!pgd_pte)
> return NOT_PADDR;
>
> + if (IS_HUGEPAGE(pgd_pte)) {
> + is_hugepage = 1;
> + pte = pgd_pte;
> + pdshift = info->l4_shift;
> + goto out;
> + }
> +
> /*
> * Sometimes we don't have level3 pagetable entries
> */
> @@ -426,6 +425,13 @@ ppc64_vtop_level4(unsigned long vaddr)
> pud_pte = swap64(ULONG((info->page_buf + PAGEOFFSET(page_upper))), swap);
> if (!pud_pte)
> return NOT_PADDR;
> +
> + if (IS_HUGEPAGE(pud_pte)) {
> + is_hugepage = 1;
> + pte = pud_pte;
> + pdshift = info->l3_shift;
> + goto out;
> + }
> } else {
> pud_pte = pgd_pte;
> }
> @@ -440,6 +446,13 @@ ppc64_vtop_level4(unsigned long vaddr)
> if (!(pmd_pte))
> return NOT_PADDR;
>
> + if (IS_HUGEPAGE(pmd_pte)) {
> + is_hugepage = 1;
> + pte = pmd_pte;
> + pdshift = info->l2_shift;
> + goto out;
> + }
> +
> pmd_pte = pmd_page_vaddr_l4(pmd_pte);
> page_table = (ulong *)(pmd_pte)
> + (BTOP(vaddr) & (info->ptrs_per_l1 - 1));
> @@ -456,8 +469,40 @@ ppc64_vtop_level4(unsigned long vaddr)
> if (!pte)
> return NOT_PADDR;
>
> - paddr = PAGEBASE(PTOB((pte & info->pte_rpn_mask) >> info->pte_rpn_shift))
> +out:
> + if (is_hugepage) {
> + paddr = PAGEBASE(PTOB((pte & info->pte_rpn_mask) >> info->pte_rpn_shift))
> + + (vaddr & ((1UL << pdshift) - 1));
> + } else {
> + paddr = PAGEBASE(PTOB((pte & info->pte_rpn_mask) >> info->pte_rpn_shift))
> + PAGEOFFSET(vaddr);
> + }
> +
> + return paddr;
> +}
> +
> +/*
> + * If the vmemmap address translation information is stored in the kernel,
> + * make the translation.
> + */
> +static unsigned long long
> +ppc64_vmemmap_to_phys(unsigned long vaddr)
> +{
> + int i;
> + ulong offset;
> + unsigned long long paddr = NOT_PADDR;
> +
> + if (!info->vmemmap_list)
> + return ppc64_vtop_level4(vaddr);
> +
> + for (i = 0; i < info->vmemmap_cnt; i++) {
> + if ((vaddr >= info->vmemmap_list[i].virt) && (vaddr <
> + (info->vmemmap_list[i].virt + info->vmemmap_psize))) {
> + offset = vaddr - info->vmemmap_list[i].virt;
> + paddr = info->vmemmap_list[i].phys + offset;
> + break;
> + }
> + }
>
> return paddr;
> }
> @@ -567,8 +612,8 @@ get_machdep_info_ppc64(void)
> return FALSE;
> }
>
> + info->vmemmap_start = VMEMMAP_REGION_ID << REGION_SHIFT;
> if (SYMBOL(vmemmap_list) != NOT_FOUND_SYMBOL) {
> - info->vmemmap_start = VMEMMAP_REGION_ID << REGION_SHIFT;
> info->vmemmap_end = info->vmemmap_start;
> if (ppc64_vmemmap_init() == FALSE) {
> ERRMSG("Can't get vmemmap list info.\n");
> diff --git a/makedumpfile.h b/makedumpfile.h
> index 85e5a4932983..056aee191519 100644
> --- a/makedumpfile.h
> +++ b/makedumpfile.h
> @@ -678,6 +678,12 @@ unsigned long get_kvbase_arm64(void);
> #define REGION_SHIFT (60UL)
> #define VMEMMAP_REGION_ID (0xfUL)
>
> +/*
> + * If PAGE_PTE is set, then it's a leaf PTE for hugepage
> + */
> +#define PAGE_PTE (1UL << 62)
> +#define IS_HUGEPAGE(pte) (!!((pte) & PAGE_PTE))
> +
> /* 4-level page table support */
>
> /* 4K pagesize */
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