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authorArd Biesheuvel <ardb@kernel.org>2021-11-19 16:43:55 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2021-11-20 10:35:54 -0800
commit825c43f50e3aa811a291ffcb40e02fbf6d91ba86 (patch)
tree729daf64405cf0fe6c772150b5ec0eb283c0fb8c /mm
parentd78f3853f831eee46c6dbe726debf3be9e9c0d05 (diff)
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> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm')
-rw-r--r--mm/Kconfig3
-rw-r--r--mm/highmem.c32
2 files changed, 24 insertions, 11 deletions
diff --git a/mm/Kconfig b/mm/Kconfig
index 068ce591a13a..28edafc820ad 100644
--- a/mm/Kconfig
+++ b/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
diff --git a/mm/highmem.c b/mm/highmem.c
index 88f65f155845..ca9fa8c92593 100644
--- a/mm/highmem.c
+++ b/mm/highmem.c
@@ -503,16 +503,22 @@ static inline int kmap_local_calc_idx(int idx)
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 long pfn, pgprot_t prot)
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);
}
}