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Wed, 29 Apr 2020 14:50:19 -0700 (PDT) Date: Wed, 29 Apr 2020 23:49:52 +0200 In-Reply-To: <20200429214954.44866-1-jannh@google.com> Message-Id: <20200429214954.44866-4-jannh@google.com> Mime-Version: 1.0 References: <20200429214954.44866-1-jannh@google.com> X-Mailer: git-send-email 2.26.2.526.g744177e7f7-goog Subject: [PATCH v2 3/5] coredump: Refactor page range dumping into common helper From: Jann Horn To: Andrew Morton Cc: Linus Torvalds , Christoph Hellwig , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, Alexander Viro , "Eric W . Biederman" , Oleg Nesterov , Russell King , linux-arm-kernel@lists.infradead.org, Mark Salter , Aurelien Jacquiot , linux-c6x-dev@linux-c6x.org, Yoshinori Sato , Rich Felker , linux-sh@vger.kernel.org X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Both fs/binfmt_elf.c and fs/binfmt_elf_fdpic.c need to dump ranges of pages into the coredump file. Extract that logic into a common helper. Any other binfmt that actually wants to create coredumps will probably need the same function; so stop making get_dump_page() depend on CONFIG_ELF_CORE. Signed-off-by: Jann Horn --- fs/binfmt_elf.c | 22 ++-------------------- fs/binfmt_elf_fdpic.c | 18 +++--------------- fs/coredump.c | 33 +++++++++++++++++++++++++++++++++ include/linux/coredump.h | 2 ++ mm/gup.c | 2 -- 5 files changed, 40 insertions(+), 37 deletions(-) diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c index b29b84595b09f..fb36469848323 100644 --- a/fs/binfmt_elf.c +++ b/fs/binfmt_elf.c @@ -2323,26 +2323,8 @@ static int elf_core_dump(struct coredump_params *cprm) for (i = 0, vma = first_vma(current, gate_vma); vma != NULL; vma = next_vma(vma, gate_vma)) { - unsigned long addr; - unsigned long end; - - end = vma->vm_start + vma_filesz[i++]; - - for (addr = vma->vm_start; addr < end; addr += PAGE_SIZE) { - struct page *page; - int stop; - - page = get_dump_page(addr); - if (page) { - void *kaddr = kmap(page); - stop = !dump_emit(cprm, kaddr, PAGE_SIZE); - kunmap(page); - put_page(page); - } else - stop = !dump_skip(cprm, PAGE_SIZE); - if (stop) - goto cleanup; - } + if (!dump_user_range(cprm, vma->vm_start, vma_filesz[i++])) + goto cleanup; } dump_truncate(cprm); diff --git a/fs/binfmt_elf_fdpic.c b/fs/binfmt_elf_fdpic.c index f5b47076fa762..938f66f4de9b2 100644 --- a/fs/binfmt_elf_fdpic.c +++ b/fs/binfmt_elf_fdpic.c @@ -1500,21 +1500,9 @@ static bool elf_fdpic_dump_segments(struct coredump_params *cprm) if (!maydump(vma, cprm->mm_flags)) continue; - for (addr = vma->vm_start; addr < vma->vm_end; - addr += PAGE_SIZE) { - bool res; - struct page *page = get_dump_page(addr); - if (page) { - void *kaddr = kmap(page); - res = dump_emit(cprm, kaddr, PAGE_SIZE); - kunmap(page); - put_page(page); - } else { - res = dump_skip(cprm, PAGE_SIZE); - } - if (!res) - return false; - } + if (!dump_user_range(cprm, vma->vm_start, + vma->vma_end - vma->vm_start)) + return false; } return true; } diff --git a/fs/coredump.c b/fs/coredump.c index d6fcc36a7db1f..88f625eecaac1 100644 --- a/fs/coredump.c +++ b/fs/coredump.c @@ -859,6 +859,39 @@ int dump_skip(struct coredump_params *cprm, size_t nr) } EXPORT_SYMBOL(dump_skip); +#ifdef CONFIG_ELF_CORE +int dump_user_range(struct coredump_params *cprm, unsigned long start, + unsigned long len) +{ + unsigned long addr; + + for (addr = start; addr < start + len; addr += PAGE_SIZE) { + struct page *page; + int stop; + + /* + * To avoid having to allocate page tables for virtual address + * ranges that have never been used yet, use a helper that + * returns NULL when encountering an empty page table entry that + * would otherwise have been filled with the zero page. + */ + page = get_dump_page(addr); + if (page) { + void *kaddr = kmap(page); + + stop = !dump_emit(cprm, kaddr, PAGE_SIZE); + kunmap(page); + put_page(page); + } else { + stop = !dump_skip(cprm, PAGE_SIZE); + } + if (stop) + return 0; + } + return 1; +} +#endif + int dump_align(struct coredump_params *cprm, int align) { unsigned mod = cprm->pos & (align - 1); diff --git a/include/linux/coredump.h b/include/linux/coredump.h index abf4b4e65dbb9..4289dc21c04ff 100644 --- a/include/linux/coredump.h +++ b/include/linux/coredump.h @@ -16,6 +16,8 @@ extern int dump_skip(struct coredump_params *cprm, size_t nr); extern int dump_emit(struct coredump_params *cprm, const void *addr, int nr); extern int dump_align(struct coredump_params *cprm, int align); extern void dump_truncate(struct coredump_params *cprm); +int dump_user_range(struct coredump_params *cprm, unsigned long start, + unsigned long len); #ifdef CONFIG_COREDUMP extern void do_coredump(const kernel_siginfo_t *siginfo); #else diff --git a/mm/gup.c b/mm/gup.c index 76080c4dbff05..9a7e83772f1fe 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -1550,7 +1550,6 @@ static long __get_user_pages_locked(struct task_struct *tsk, * * Called without mmap_sem, but after all other threads have been killed. */ -#ifdef CONFIG_ELF_CORE struct page *get_dump_page(unsigned long addr) { struct vm_area_struct *vma; @@ -1563,7 +1562,6 @@ struct page *get_dump_page(unsigned long addr) flush_cache_page(vma, addr, page_to_pfn(page)); return page; } -#endif /* CONFIG_ELF_CORE */ #if defined(CONFIG_FS_DAX) || defined (CONFIG_CMA) static bool check_dax_vmas(struct vm_area_struct **vmas, long nr_pages)