[Crash-utility] Re: [PATCH] Fix compound_head() and "bt -F" option on Linux 7.1 and later

Add Kairui and Baoquan who could help to review this patch On 7/23/26 1:09 PM, HAGIO KAZUHITO(萩尾 一仁) wrote: > From: Kazuhito Hagio <k-hagio-ab(a)nec.com&gt; > > Kernel commit d50569612c29 ("mm: rename the 'compound_head' field in the > 'struct page' to 'compound_info'") and related patches [1] changed the > field name and its value. > > Without the patch, crash prints the following warning during startup, > > WARNING: SLUB: cannot determine how compound pages are linked > > and "bt -F" option fails with the following error. > > crash> bt -F > > bt: invalid structure member offset: page_first_page > FILE: memory.c LINE: 20238 FUNCTION: compound_head() > > [1] https://lore.kernel.org/all/20260227194302.274384-1-kas@kernel.org/ > > Signed-off-by: Kazuhito Hagio <k-hagio-ab(a)nec.com&gt; > --- > defs.h | 1 + > memory.c | 44 ++++++++++++++++++++++++++++++++++++-------- > symbols.c | 1 + > 3 files changed, 38 insertions(+), 8 deletions(-) > > diff --git a/defs.h b/defs.h > index e3027e2b9141..88b7bbeb2372 100644 > --- a/defs.h > +++ b/defs.h > @@ -2295,6 +2295,7 @@ struct offset_table { /* stash of commonly-used offsets */ > long page_compound_order; > long folio__folio_order; > long folio__flags_1; > + long page_compound_info; > }; > > struct size_table { /* stash of commonly-used sizes */ > diff --git a/memory.c b/memory.c > index 3f3aa274ab5a..7102e951f1d5 100644 > --- a/memory.c > +++ b/memory.c > @@ -414,6 +414,7 @@ mem_init(void) > #define FOLIO_ORDER_V2 2 > #define FOLIO_ORDER_V3 3 > static int folio_order_version; > +static int compound_info_has_mask = FALSE; > > /* > * Stash a few popular offsets and some basic kernel virtual memory > @@ -547,6 +548,7 @@ vm_init(void) > MEMBER_OFFSET_INIT(page_compound_head, "page", "compound_head"); > if (INVALID_MEMBER(page_compound_head)) > ANON_MEMBER_OFFSET_INIT(page_compound_head, "page", "compound_head"); > + MEMBER_OFFSET_INIT(page_compound_info, "page", "compound_info"); > MEMBER_OFFSET_INIT(page_private, "page", "private"); > MEMBER_OFFSET_INIT(page_freelist, "page", "freelist"); > MEMBER_OFFSET_INIT(page_page_type, "page", "page_type"); > @@ -1352,6 +1354,17 @@ vm_init(void) > } else if (CRASHDEBUG(1)) > error(NOTE, "page_hash_table does not exist in this kernel\n"); > > + /* > + * on Linux 7.1 and later, zone.vmemmap_tails is defined only when > + * CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP is enabled. > + */ > +#define is_power_of_2(n) (n - 1 < (n ^ (n - 1))) > + if (VALID_MEMBER(page_compound_info) && > + is_power_of_2(SIZE(page)) && MEMBER_EXISTS("zone", "vmemmap_tails")) > + compound_info_has_mask = TRUE; > + if (CRASHDEBUG(1)) > + error(NOTE, "compound_info_has_mask = %d\n", compound_info_has_mask); > + > kmem_cache_init(); > > page_flags_init(); > @@ -5642,10 +5655,11 @@ PG_slab_flag_init(void) > } > } > > - if (VALID_MEMBER(page_compound_head)) { > + if (VALID_MEMBER(page_compound_head) || VALID_MEMBER(page_compound_info)) { > if (CRASHDEBUG(2)) > fprintf(fp, > - "PG_head_tail_mask: (UNUSED): page.compound_head exists!\n"); > + "PG_head_tail_mask: (UNUSED): page.compound_head or " > + "page.compound_info exists!\n"); > } else if (vt->flags & KMALLOC_SLUB) { > /* > * PG_slab and the following are hardwired for > @@ -9858,7 +9872,8 @@ vaddr_to_kmem_cache(ulong vaddr, char *buf, int verbose) > &page_flags, sizeof(ulong), "page.flags", > FAULT_ON_ERROR); > if (!page_slab(page, page_flags)) { > - if (((vt->flags & KMALLOC_SLUB) || VALID_MEMBER(page_compound_head)) || > + if (((vt->flags & KMALLOC_SLUB) || VALID_MEMBER(page_compound_head) || > + VALID_MEMBER(page_compound_info)) || > ((vt->flags & KMALLOC_COMMON) && > VALID_MEMBER(page_slab) && VALID_MEMBER(page_first_page))) { > readmem(compound_head(page)+OFFSET(page_flags), KVADDR, > @@ -9873,7 +9888,8 @@ vaddr_to_kmem_cache(ulong vaddr, char *buf, int verbose) > > if ((vt->flags & KMALLOC_SLUB) || > ((vt->flags & KMALLOC_COMMON) && VALID_MEMBER(page_slab) && > - (VALID_MEMBER(page_compound_head) || VALID_MEMBER(page_first_page)))) { > + (VALID_MEMBER(page_compound_head) || VALID_MEMBER(page_compound_info) || > + VALID_MEMBER(page_first_page)))) { > readmem(compound_head(page)+OFFSET(page_slab), > KVADDR, &cache, sizeof(void *), > "page.slab", FAULT_ON_ERROR); > @@ -9904,7 +9920,8 @@ is_slab_overload_page(ulong vaddr, ulong *page_head, char *buf) > > if ((vt->flags & SLAB_OVERLOAD_PAGE) && > is_page_ptr(vaddr, NULL) && VALID_MEMBER(page_slab) && > - (VALID_MEMBER(page_compound_head) || VALID_MEMBER(page_first_page))) { > + (VALID_MEMBER(page_compound_head) || VALID_MEMBER(page_compound_info) || > + VALID_MEMBER(page_first_page))) { > readmem(compound_head(vaddr)+OFFSET(page_slab), > KVADDR, &cache, sizeof(void *), > "page.slab", FAULT_ON_ERROR); > @@ -9944,7 +9961,8 @@ vaddr_to_slab(ulong vaddr) > > slab = 0; > > - if ((vt->flags & KMALLOC_SLUB) || VALID_MEMBER(page_compound_head)) > + if ((vt->flags & KMALLOC_SLUB) || VALID_MEMBER(page_compound_head) || > + VALID_MEMBER(page_compound_info)) > slab = compound_head(page); > else if (vt->flags & SLAB_OVERLOAD_PAGE) > slab = compound_head(page); > @@ -20222,11 +20240,21 @@ get_kmem_cache_child_list(ulong **cache_buf, ulong root) > static ulong > compound_head(ulong page) > { > - ulong flags, first_page, compound_head; > + ulong flags, first_page, compound_head, info, mask; > > first_page = page; > > - if (VALID_MEMBER(page_compound_head)) { > + if (VALID_MEMBER(page_compound_info)) { > + if (readmem(page + OFFSET(page_compound_info), KVADDR, &info, > + sizeof(ulong), "page.compound_info", RETURN_ON_ERROR)) { > + if (compound_info_has_mask) { > + mask = (info & 1) - 1; > + mask |= info; > + first_page = page & mask; > + } else if (info & 1) > + first_page = info - 1; > + } > + } else if (VALID_MEMBER(page_compound_head)) { > if (readmem(page+OFFSET(page_compound_head), KVADDR, &compound_head, > sizeof(ulong), "page.compound_head", RETURN_ON_ERROR)) { > if (compound_head & 1) > diff --git a/symbols.c b/symbols.c > index 03511c8cbe8c..2071bdf77819 100644 > --- a/symbols.c > +++ b/symbols.c > @@ -10504,6 +10504,7 @@ dump_offset_table(char *spec, ulong makestruct) > OFFSET(page_active)); > fprintf(fp, " page_compound_head: %ld\n", > OFFSET(page_compound_head)); > + fprintf(fp, " page_compound_info: %ld\n", OFFSET(page_compound_info)); > fprintf(fp, " page_private: %ld\n", OFFSET(page_private)); > fprintf(fp, " page_page_type: %ld\n", > OFFSET(page_page_type)); -- Crash-utility mailing list -- devel(a)lists.crash-utility.osci.io To unsubscribe send an email to devel-leave(a)lists.crash-utility.osci.io https://${domain_name}/admin/lists/devel.lists.crash-utility.osci.io/ Contribution Guidelines: https://github.com/crash-utility/crash/wiki