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Date: Tue, 19 Dec 2017 15:42:11 +0100
From: Michal Hocko <mhocko@...nel.org>
To: Matthew Wilcox <willy@...radead.org>
Cc: linux-mm@...ck.org, "Tobin C. Harding" <me@...in.cc>,
kernel-hardening@...ts.openwall.com
Subject: Re: [PATCH] Provide useful debugging information for VM_BUG
On Tue 19-12-17 05:32:36, Matthew Wilcox wrote:
>
> From: Matthew Wilcox <mawilcox@...rosoft.com>
>
> With the recent addition of hashed kernel pointers, places which need
> to produce useful debug output have to specify %px, not %p. This patch
> fixes all the VM debug to use %px. This is appropriate because it's
> debug output that the user should never be able to trigger, and kernel
> developers need to see the actual pointers.
Agreed. This is essentially a BUG_ON so we shouldn't hide information.
I am just wondering why %px rather than %lx (like __show_regs e.g.)?
> Signed-off-by: Matthew Wilcox <mawilcox@...rosoft.com>
Acked-by: Michal Hocko <mhocko@...e.com>
> diff --git a/mm/debug.c b/mm/debug.c
> index d947f3e03b0d..56e2d9125ea5 100644
> --- a/mm/debug.c
> +++ b/mm/debug.c
> @@ -50,7 +50,7 @@ void __dump_page(struct page *page, const char *reason)
> */
> int mapcount = PageSlab(page) ? 0 : page_mapcount(page);
>
> - pr_emerg("page:%p count:%d mapcount:%d mapping:%p index:%#lx",
> + pr_emerg("page:%px count:%d mapcount:%d mapping:%px index:%#lx",
> page, page_ref_count(page), mapcount,
> page->mapping, page_to_pgoff(page));
> if (PageCompound(page))
> @@ -69,7 +69,7 @@ void __dump_page(struct page *page, const char *reason)
>
> #ifdef CONFIG_MEMCG
> if (page->mem_cgroup)
> - pr_alert("page->mem_cgroup:%p\n", page->mem_cgroup);
> + pr_alert("page->mem_cgroup:%px\n", page->mem_cgroup);
> #endif
> }
>
> @@ -84,10 +84,10 @@ EXPORT_SYMBOL(dump_page);
>
> void dump_vma(const struct vm_area_struct *vma)
> {
> - pr_emerg("vma %p start %p end %p\n"
> - "next %p prev %p mm %p\n"
> - "prot %lx anon_vma %p vm_ops %p\n"
> - "pgoff %lx file %p private_data %p\n"
> + pr_emerg("vma %px start %px end %px\n"
> + "next %px prev %px mm %px\n"
> + "prot %lx anon_vma %px vm_ops %px\n"
> + "pgoff %lx file %px private_data %px\n"
> "flags: %#lx(%pGv)\n",
> vma, (void *)vma->vm_start, (void *)vma->vm_end, vma->vm_next,
> vma->vm_prev, vma->vm_mm,
> @@ -100,27 +100,27 @@ EXPORT_SYMBOL(dump_vma);
>
> void dump_mm(const struct mm_struct *mm)
> {
> - pr_emerg("mm %p mmap %p seqnum %d task_size %lu\n"
> + pr_emerg("mm %px mmap %px seqnum %d task_size %lu\n"
> #ifdef CONFIG_MMU
> - "get_unmapped_area %p\n"
> + "get_unmapped_area %px\n"
> #endif
> "mmap_base %lu mmap_legacy_base %lu highest_vm_end %lu\n"
> - "pgd %p mm_users %d mm_count %d pgtables_bytes %lu map_count %d\n"
> + "pgd %px mm_users %d mm_count %d pgtables_bytes %lu map_count %d\n"
> "hiwater_rss %lx hiwater_vm %lx total_vm %lx locked_vm %lx\n"
> "pinned_vm %lx data_vm %lx exec_vm %lx stack_vm %lx\n"
> "start_code %lx end_code %lx start_data %lx end_data %lx\n"
> "start_brk %lx brk %lx start_stack %lx\n"
> "arg_start %lx arg_end %lx env_start %lx env_end %lx\n"
> - "binfmt %p flags %lx core_state %p\n"
> + "binfmt %px flags %lx core_state %px\n"
> #ifdef CONFIG_AIO
> - "ioctx_table %p\n"
> + "ioctx_table %px\n"
> #endif
> #ifdef CONFIG_MEMCG
> - "owner %p "
> + "owner %px "
> #endif
> - "exe_file %p\n"
> + "exe_file %px\n"
> #ifdef CONFIG_MMU_NOTIFIER
> - "mmu_notifier_mm %p\n"
> + "mmu_notifier_mm %px\n"
> #endif
> #ifdef CONFIG_NUMA_BALANCING
> "numa_next_scan %lu numa_scan_offset %lu numa_scan_seq %d\n"
>
> --
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--
Michal Hocko
SUSE Labs
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