The patch titled
Subject: mips: vdso: prefer do_mmap() to mmap_region()
has been added to the -mm mm-unstable branch. Its filename is
mips-vdso-prefer-do_mmap-to-mmap_region.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mips-vdso-prefer-do_mmap-to-mmap_region.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Lorenzo Stoakes <lorenzo.stoakes@xxxxxxxxxx>
Subject: mips: vdso: prefer do_mmap() to mmap_region()
Date: Thu, 2 Jan 2025 12:10:51 +0000
Patch series "mm: update mips to use do_mmap(), make mmap_region()
internal".
Currently the only user of mmap_region() outside of the memory management
code is the MIPS VDSO implementation.
This uses mmap_region() to map a 'delay slot emulation page' at the top of
the stack which is read-only and executable.
This mapping requires that an already-acquired mmap write lock is utilised
and that uffd and populate logic is ignored. This rules out vm_mmap(),
however do_mmap() fits the bill.
Adapt this code to use do_mmap() and then once done, make mmap_region()
internal and userland testable, and avoid any other uses of mmap_region(),
which is absolutely and strictly an internal mm function which bypasses a
great number of checks and logic.
This patch (of 2):
mmap_region() is an internal memory management implementation detail that
is not intended to be used outside of the memory management subsystem.
Map the delay slot emulation page using do_mmap() which makes use of the
already-held mmap write lock and bypasses unneeded populate and
userfaultfd logic.
This should have the precise same behaviour as the existing logic.
Link: https://lkml.kernel.org/r/cover.1735819274.git.lorenzo.stoakes@xxxxxxxxxx
Link: https://lkml.kernel.org/r/ef076e381570f709e5c2c142dc030ec5b3309a0e.1735819274.git.lorenzo.stoakes@xxxxxxxxxx
Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@xxxxxxxxxx>
Cc: Jann Horn <jannh@xxxxxxxxxx>
Cc: Liam R. Howlett <Liam.Howlett@xxxxxxxxxx>
Cc: Thomas Bogendoerfer <tsbogend@xxxxxxxxxxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
arch/mips/kernel/vdso.c | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)
--- a/arch/mips/kernel/vdso.c~mips-vdso-prefer-do_mmap-to-mmap_region
+++ a/arch/mips/kernel/vdso.c
@@ -11,6 +11,7 @@
#include <linux/ioport.h>
#include <linux/kernel.h>
#include <linux/mm.h>
+#include <linux/mman.h>
#include <linux/random.h>
#include <linux/sched.h>
#include <linux/slab.h>
@@ -97,11 +98,12 @@ int arch_setup_additional_pages(struct l
return -EINTR;
if (IS_ENABLED(CONFIG_MIPS_FP_SUPPORT)) {
+ unsigned long unused;
+
/* Map delay slot emulation page */
- base = mmap_region(NULL, STACK_TOP, PAGE_SIZE,
- VM_READ | VM_EXEC |
- VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC,
- 0, NULL);
+ base = do_mmap(NULL, STACK_TOP, PAGE_SIZE, PROT_READ | PROT_EXEC,
+ MAP_ANONYMOUS | MAP_PRIVATE | MAP_FIXED, 0, 0, &unused,
+ NULL);
if (IS_ERR_VALUE(base)) {
ret = base;
goto out;
_
Patches currently in -mm which might be from lorenzo.stoakes@xxxxxxxxxx are
mm-vma-move-brk-internals-to-mm-vmac.patch
mm-vma-move-brk-internals-to-mm-vmac-fix.patch
mm-vma-move-unmapped_area-internals-to-mm-vmac.patch
mm-abstract-get_arg_page-stack-expansion-and-mmap-read-lock.patch
mm-vma-move-stack-expansion-logic-to-mm-vmac.patch
mm-vma-move-__vm_munmap-to-mm-vmac.patch
selftests-mm-add-fork-cow-guard-page-test.patch
mm-enforce-__must_check-on-vma-merge-and-split.patch
mm-perform-all-memfd-seal-checks-in-a-single-place.patch
mm-perform-all-memfd-seal-checks-in-a-single-place-fix.patch
maintainers-update-memory-mapping-section.patch
mm-assert-mmap-write-lock-held-on-do_mmap-mmap_region.patch
mm-add-comments-to-do_mmap-mmap_region-and-vm_mmap.patch
tools-testing-add-simple-__mmap_region-userland-test.patch
mips-vdso-prefer-do_mmap-to-mmap_region.patch
mm-make-mmap_region-internal.patch
