Christophe Leroy [off-list ref] writes:
quoted hunk ↗ jump to hunk
Use the generic version of arch_get_unmapped_area() which
is now available at all time instead of its copy
radix__arch_get_unmapped_area()
Instead of setting mm->get_unmapped_area() to either
arch_get_unmapped_area() or generic_get_unmapped_area(),
always set it to arch_get_unmapped_area() and call
generic_get_unmapped_area() from there when radix is enabled.
Do the same with radix__arch_get_unmapped_area_topdown()
Signed-off-by: Christophe Leroy <redacted>
---
arch/powerpc/mm/mmap.c | 127 ++---------------------------------------
1 file changed, 6 insertions(+), 121 deletions(-)
diff --git a/arch/powerpc/mm/mmap.c b/arch/powerpc/mm/mmap.c
index 9b0d6e395bc0..46781d0103d1 100644
--- a/arch/powerpc/mm/mmap.c
+++ b/arch/powerpc/mm/mmap.c
@@ -81,115 +81,15 @@ static inline unsigned long mmap_base(unsigned long rnd,
}
#ifdef HAVE_ARCH_UNMAPPED_AREA
-#ifdef CONFIG_PPC_RADIX_MMU
-/*
- * Same function as generic code used only for radix, because we don't need to overload
- * the generic one. But we will have to duplicate, because hash select
- * HAVE_ARCH_UNMAPPED_AREA
- */
-static unsigned long
-radix__arch_get_unmapped_area(struct file *filp, unsigned long addr,
- unsigned long len, unsigned long pgoff,
- unsigned long flags)
-{
- struct mm_struct *mm = current->mm;
- struct vm_area_struct *vma;
- int fixed = (flags & MAP_FIXED);
- unsigned long high_limit;
- struct vm_unmapped_area_info info;
-
- high_limit = DEFAULT_MAP_WINDOW;
- if (addr >= high_limit || (fixed && (addr + len > high_limit)))
- high_limit = TASK_SIZE;
-
- if (len > high_limit)
- return -ENOMEM;
There are some differences in the above vs the generic code, the generic
arch_get_unmapped_area_topdown() in mm/mmap.c does:
const unsigned long mmap_end = arch_get_mmap_end(addr);
if (len > mmap_end - mmap_min_addr)
return -ENOMEM;
if (flags & MAP_FIXED)
return addr;
Our current code adjusts high_limit for fixed mappings that span above
the default map window. We added that logic in:
35602f82d0c7 ("powerpc/64s/hash: Allow MAP_FIXED allocations to cross 128TB boundary")
That means a fixed mapping that crosses the 128T boundary will be
allowed by our code.
On the other hand the generic code will allow a fixed mapping to cross
the 128T boundary, but only if the size of the mapping is < ~128T.
(The actual size limit is (128T - mmap_min_addr), which is usually 4K or
64K, but is adjustable.)
It's unlikely that any apps are doing fixed mappings larger than 128T
that cross the 128T boundary, but I think we need to allow it. 128T
seems like a lot, but is not compared to the entire 4PB address space.
So I think we need to fix that in the generic code.
The easiest option is probably to pass flags to arch_get_mmap_end(), and
then the arches can decide whether to adjust the return value based on
flags.
Then there's also the extra check we have here:
- if (fixed) {
- if (addr > high_limit - len)
- return -ENOMEM;
- return addr;
- }
I think we can drop that when converting to the generic version, the
only case in which it matters is when high_limit == TASK_SIZE, and
get_unmapped_area() already does that check after calling us:
if (addr > TASK_SIZE - len)
return -ENOMEM;
cheers