From d61f0d59683d9c899211c300254d4140c482a6c0 Mon Sep 17 00:00:00 2001 From: Lorenzo Stoakes Date: Mon, 29 Jul 2024 12:50:37 +0100 Subject: mm: move vma_shrink(), vma_expand() to internal header The vma_shrink() and vma_expand() functions are internal VMA manipulation functions which we ought to abstract for use outside of memory management code. To achieve this, we replace shift_arg_pages() in fs/exec.c with an invocation of a new relocate_vma_down() function implemented in mm/mmap.c, which enables us to also move move_page_tables() and vma_iter_prev_range() to internal.h. The purpose of doing this is to isolate key VMA manipulation functions in order that we can both abstract them and later render them easily testable. Link: https://lkml.kernel.org/r/3cfcd9ec433e032a85f636fdc0d7d98fafbd19c5.1722251717.git.lorenzo.stoakes@oracle.com Signed-off-by: Lorenzo Stoakes Reviewed-by: Vlastimil Babka Reviewed-by: Liam R. Howlett Cc: Alexander Viro Cc: Brendan Higgins Cc: Christian Brauner Cc: David Gow Cc: Eric W. Biederman Cc: Jan Kara Cc: Kees Cook Cc: Matthew Wilcox (Oracle) Cc: Rae Moar Cc: SeongJae Park Cc: Shuah Khan Cc: Suren Baghdasaryan Cc: Pengfei Xu Signed-off-by: Andrew Morton --- fs/exec.c | 81 +++++---------------------------------------------------------- 1 file changed, 6 insertions(+), 75 deletions(-) (limited to 'fs/exec.c') diff --git a/fs/exec.c b/fs/exec.c index 50e76cc633c4..9009e2b2805e 100644 --- a/fs/exec.c +++ b/fs/exec.c @@ -711,80 +711,6 @@ static int copy_strings_kernel(int argc, const char *const *argv, #ifdef CONFIG_MMU -/* - * During bprm_mm_init(), we create a temporary stack at STACK_TOP_MAX. Once - * the binfmt code determines where the new stack should reside, we shift it to - * its final location. The process proceeds as follows: - * - * 1) Use shift to calculate the new vma endpoints. - * 2) Extend vma to cover both the old and new ranges. This ensures the - * arguments passed to subsequent functions are consistent. - * 3) Move vma's page tables to the new range. - * 4) Free up any cleared pgd range. - * 5) Shrink the vma to cover only the new range. - */ -static int shift_arg_pages(struct vm_area_struct *vma, unsigned long shift) -{ - struct mm_struct *mm = vma->vm_mm; - unsigned long old_start = vma->vm_start; - unsigned long old_end = vma->vm_end; - unsigned long length = old_end - old_start; - unsigned long new_start = old_start - shift; - unsigned long new_end = old_end - shift; - VMA_ITERATOR(vmi, mm, new_start); - struct vm_area_struct *next; - struct mmu_gather tlb; - - BUG_ON(new_start > new_end); - - /* - * ensure there are no vmas between where we want to go - * and where we are - */ - if (vma != vma_next(&vmi)) - return -EFAULT; - - vma_iter_prev_range(&vmi); - /* - * cover the whole range: [new_start, old_end) - */ - if (vma_expand(&vmi, vma, new_start, old_end, vma->vm_pgoff, NULL)) - return -ENOMEM; - - /* - * move the page tables downwards, on failure we rely on - * process cleanup to remove whatever mess we made. - */ - if (length != move_page_tables(vma, old_start, - vma, new_start, length, false, true)) - return -ENOMEM; - - lru_add_drain(); - tlb_gather_mmu(&tlb, mm); - next = vma_next(&vmi); - if (new_end > old_start) { - /* - * when the old and new regions overlap clear from new_end. - */ - free_pgd_range(&tlb, new_end, old_end, new_end, - next ? next->vm_start : USER_PGTABLES_CEILING); - } else { - /* - * otherwise, clean from old_start; this is done to not touch - * the address space in [new_end, old_start) some architectures - * have constraints on va-space that make this illegal (IA64) - - * for the others its just a little faster. - */ - free_pgd_range(&tlb, old_start, old_end, new_end, - next ? next->vm_start : USER_PGTABLES_CEILING); - } - tlb_finish_mmu(&tlb); - - vma_prev(&vmi); - /* Shrink the vma to just the new range */ - return vma_shrink(&vmi, vma, new_start, new_end, vma->vm_pgoff); -} - /* * Finalizes the stack vm_area_struct. The flags and permissions are updated, * the stack is optionally relocated, and some extra space is added. @@ -877,7 +803,12 @@ int setup_arg_pages(struct linux_binprm *bprm, /* Move stack pages down in memory. */ if (stack_shift) { - ret = shift_arg_pages(vma, stack_shift); + /* + * During bprm_mm_init(), we create a temporary stack at STACK_TOP_MAX. Once + * the binfmt code determines where the new stack should reside, we shift it to + * its final location. + */ + ret = relocate_vma_down(vma, stack_shift); if (ret) goto out_unlock; } -- cgit v1.2.3-70-g09d2