From: Andrew Morton <akpm@linux-foundation.org>
To: akpm@linux-foundation.org, ardb@kernel.org,
linus.walleij@linaro.org, linux-mm@kvack.org,
mm-commits@vger.kernel.org, quanyang.wang@windriver.com,
rmk+kernel@armlinux.org.uk, stable@vger.kernel.org,
tglx@linutronix.de, torvalds@linux-foundation.org
Subject: [patch 14/15] kmap_local: don't assume kmap PTEs are linear arrays in memory
Date: Fri, 19 Nov 2021 16:43:55 -0800 [thread overview]
Message-ID: <20211120004355.3d5IhALrg%akpm@linux-foundation.org> (raw)
In-Reply-To: <20211119164248.50feee07c5d2cc6cc4addf97@linux-foundation.org>
From: Ard Biesheuvel <ardb@kernel.org>
Subject: kmap_local: don't assume kmap PTEs are linear arrays in memory
The kmap_local conversion broke the ARM architecture, because the new code
assumes that all PTEs used for creating kmaps form a linear array in
memory, and uses array indexing to look up the kmap PTE belonging to a
certain kmap index.
On ARM, this cannot work, not only because the PTE pages may be
non-adjacent in memory, but also because ARM/!LPAE interleaves hardware
entries and extended entries (carrying software-only bits) in a way that
is not compatible with array indexing.
Fortunately, this only seems to affect configurations with more than 8
CPUs, due to the way the per-CPU kmap slots are organized in memory.
Work around this by permitting an architecture to set a Kconfig symbol
that signifies that the kmap PTEs do not form a lineary array in memory,
and so the only way to locate the appropriate one is to walk the page
tables.
Link: https://lore.kernel.org/linux-arm-kernel/20211026131249.3731275-1-ardb@kernel.org/
Link: https://lkml.kernel.org/r/20211116094737.7391-1-ardb@kernel.org
Fixes: 2a15ba82fa6c ("ARM: highmem: Switch to generic kmap atomic")
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Reported-by: Quanyang Wang <quanyang.wang@windriver.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---
arch/arm/Kconfig | 1 +
mm/Kconfig | 3 +++
mm/highmem.c | 32 +++++++++++++++++++++-----------
3 files changed, 25 insertions(+), 11 deletions(-)
--- a/arch/arm/Kconfig~kmap_local-dont-assume-kmap-ptes-are-linear-arrays-in-memory
+++ a/arch/arm/Kconfig
@@ -1463,6 +1463,7 @@ config HIGHMEM
bool "High Memory Support"
depends on MMU
select KMAP_LOCAL
+ select KMAP_LOCAL_NON_LINEAR_PTE_ARRAY
help
The address space of ARM processors is only 4 Gigabytes large
and it has to accommodate user address space, kernel address
--- a/mm/highmem.c~kmap_local-dont-assume-kmap-ptes-are-linear-arrays-in-memory
+++ a/mm/highmem.c
@@ -503,16 +503,22 @@ static inline int kmap_local_calc_idx(in
static pte_t *__kmap_pte;
-static pte_t *kmap_get_pte(void)
+static pte_t *kmap_get_pte(unsigned long vaddr, int idx)
{
+ if (IS_ENABLED(CONFIG_KMAP_LOCAL_NON_LINEAR_PTE_ARRAY))
+ /*
+ * Set by the arch if __kmap_pte[-idx] does not produce
+ * the correct entry.
+ */
+ return virt_to_kpte(vaddr);
if (!__kmap_pte)
__kmap_pte = virt_to_kpte(__fix_to_virt(FIX_KMAP_BEGIN));
- return __kmap_pte;
+ return &__kmap_pte[-idx];
}
void *__kmap_local_pfn_prot(unsigned long pfn, pgprot_t prot)
{
- pte_t pteval, *kmap_pte = kmap_get_pte();
+ pte_t pteval, *kmap_pte;
unsigned long vaddr;
int idx;
@@ -524,9 +530,10 @@ void *__kmap_local_pfn_prot(unsigned lon
preempt_disable();
idx = arch_kmap_local_map_idx(kmap_local_idx_push(), pfn);
vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
- BUG_ON(!pte_none(*(kmap_pte - idx)));
+ kmap_pte = kmap_get_pte(vaddr, idx);
+ BUG_ON(!pte_none(*kmap_pte));
pteval = pfn_pte(pfn, prot);
- arch_kmap_local_set_pte(&init_mm, vaddr, kmap_pte - idx, pteval);
+ arch_kmap_local_set_pte(&init_mm, vaddr, kmap_pte, pteval);
arch_kmap_local_post_map(vaddr, pteval);
current->kmap_ctrl.pteval[kmap_local_idx()] = pteval;
preempt_enable();
@@ -559,7 +566,7 @@ EXPORT_SYMBOL(__kmap_local_page_prot);
void kunmap_local_indexed(void *vaddr)
{
unsigned long addr = (unsigned long) vaddr & PAGE_MASK;
- pte_t *kmap_pte = kmap_get_pte();
+ pte_t *kmap_pte;
int idx;
if (addr < __fix_to_virt(FIX_KMAP_END) ||
@@ -584,8 +591,9 @@ void kunmap_local_indexed(void *vaddr)
idx = arch_kmap_local_unmap_idx(kmap_local_idx(), addr);
WARN_ON_ONCE(addr != __fix_to_virt(FIX_KMAP_BEGIN + idx));
+ kmap_pte = kmap_get_pte(addr, idx);
arch_kmap_local_pre_unmap(addr);
- pte_clear(&init_mm, addr, kmap_pte - idx);
+ pte_clear(&init_mm, addr, kmap_pte);
arch_kmap_local_post_unmap(addr);
current->kmap_ctrl.pteval[kmap_local_idx()] = __pte(0);
kmap_local_idx_pop();
@@ -607,7 +615,7 @@ EXPORT_SYMBOL(kunmap_local_indexed);
void __kmap_local_sched_out(void)
{
struct task_struct *tsk = current;
- pte_t *kmap_pte = kmap_get_pte();
+ pte_t *kmap_pte;
int i;
/* Clear kmaps */
@@ -634,8 +642,9 @@ void __kmap_local_sched_out(void)
idx = arch_kmap_local_map_idx(i, pte_pfn(pteval));
addr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
+ kmap_pte = kmap_get_pte(addr, idx);
arch_kmap_local_pre_unmap(addr);
- pte_clear(&init_mm, addr, kmap_pte - idx);
+ pte_clear(&init_mm, addr, kmap_pte);
arch_kmap_local_post_unmap(addr);
}
}
@@ -643,7 +652,7 @@ void __kmap_local_sched_out(void)
void __kmap_local_sched_in(void)
{
struct task_struct *tsk = current;
- pte_t *kmap_pte = kmap_get_pte();
+ pte_t *kmap_pte;
int i;
/* Restore kmaps */
@@ -663,7 +672,8 @@ void __kmap_local_sched_in(void)
/* See comment in __kmap_local_sched_out() */
idx = arch_kmap_local_map_idx(i, pte_pfn(pteval));
addr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
- set_pte_at(&init_mm, addr, kmap_pte - idx, pteval);
+ kmap_pte = kmap_get_pte(addr, idx);
+ set_pte_at(&init_mm, addr, kmap_pte, pteval);
arch_kmap_local_post_map(addr, pteval);
}
}
--- a/mm/Kconfig~kmap_local-dont-assume-kmap-ptes-are-linear-arrays-in-memory
+++ a/mm/Kconfig
@@ -890,6 +890,9 @@ config MAPPING_DIRTY_HELPERS
config KMAP_LOCAL
bool
+config KMAP_LOCAL_NON_LINEAR_PTE_ARRAY
+ bool
+
# struct io_mapping based helper. Selected by drivers that need them
config IO_MAPPING
bool
_
next prev parent reply other threads:[~2021-11-20 0:43 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-11-20 0:42 incoming Andrew Morton
2021-11-20 0:43 ` [patch 01/15] mm/swap.c:put_pages_list(): reinitialise the page list Andrew Morton
2021-11-20 0:43 ` [patch 02/15] ipc: WARN if trying to remove ipc object which is absent Andrew Morton
2021-11-20 0:43 ` [patch 03/15] shm: extend forced shm destroy to support objects from several IPC nses Andrew Morton
2021-11-20 0:43 ` [patch 04/15] mm: emit the "free" trace report before freeing memory in kmem_cache_free() Andrew Morton
2021-11-20 0:43 ` [patch 05/15] hexagon: export raw I/O routines for modules Andrew Morton
2021-11-20 0:43 ` [patch 06/15] hexagon: clean up timer-regs.h Andrew Morton
2021-11-20 0:43 ` [patch 07/15] hexagon: ignore vmlinux.lds Andrew Morton
2021-11-20 0:43 ` [patch 08/15] mm: kmemleak: slob: respect SLAB_NOLEAKTRACE flag Andrew Morton
2021-11-20 0:43 ` [patch 09/15] hugetlb: fix hugetlb cgroup refcounting during mremap Andrew Morton
2021-11-20 0:43 ` [patch 10/15] hugetlb, userfaultfd: fix reservation restore on userfaultfd error Andrew Morton
2021-11-20 0:43 ` [patch 11/15] kasan: test: silence intentional read overflow warnings Andrew Morton
2021-11-20 0:43 ` [patch 12/15] mm/damon/dbgfs: use '__GFP_NOWARN' for user-specified size buffer allocation Andrew Morton
2021-11-20 0:43 ` [patch 13/15] mm/damon/dbgfs: fix missed use of damon_dbgfs_lock Andrew Morton
2021-11-20 0:43 ` Andrew Morton [this message]
2021-11-20 0:43 ` [patch 15/15] proc/vmcore: fix clearing user buffer by properly using clear_user() Andrew Morton
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