This patch adds support for "high" userspace addresses that are
optionally supported on the system and have to be requested via a hint
mechanism ("high" addr parameter to mmap).
Architectures such as powerpc and x86 achieve this by making changes to
their architectural versions of arch_get_unmapped_* functions. However,
on arm64 we use the generic versions of these functions.
Rather than duplicate the generic arch_get_unmapped_* implementations
for arm64, this patch instead introduces two architectural helper macros
and applies them to arch_get_unmapped_*:
arch_get_mmap_end(addr) - get mmap upper limit depending on addr hint
arch_get_mmap_base(addr, base) - get mmap_base depending on addr hint
If these macros are not defined in architectural code then they default
to (TASK_SIZE) and (base) so should not introduce any behavioural
changes to architectures that do not define them.
Signed-off-by: Steve Capper <steve.capper@xxxxxxx>
Reviewed-by: Catalin Marinas <catalin.marinas@xxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
Changed in V4, added Catalin's reviewed by
Changed in V3, commit log cleared up, explanation given for why core
code change over just architectural change
---
mm/mmap.c | 25 ++++++++++++++++++-------
1 file changed, 18 insertions(+), 7 deletions(-)
diff --git a/mm/mmap.c b/mm/mmap.c
index 6c04292e16a7..7bb64381e77c 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -2066,6 +2066,15 @@ unsigned long unmapped_area_topdown(struct vm_unmapped_area_info *info)
return gap_end;
}
+
+#ifndef arch_get_mmap_end
+#define arch_get_mmap_end(addr) (TASK_SIZE)
+#endif
+
+#ifndef arch_get_mmap_base
+#define arch_get_mmap_base(addr, base) (base)
+#endif
+
/* Get an address range which is currently unmapped.
* For shmat() with addr=0.
*
@@ -2085,8 +2094,9 @@ arch_get_unmapped_area(struct file *filp, unsigned long addr,
struct mm_struct *mm = current->mm;
struct vm_area_struct *vma, *prev;
struct vm_unmapped_area_info info;
+ const unsigned long mmap_end = arch_get_mmap_end(addr);
- if (len > TASK_SIZE - mmap_min_addr)
+ if (len > mmap_end - mmap_min_addr)
return -ENOMEM;
if (flags & MAP_FIXED)
@@ -2095,7 +2105,7 @@ arch_get_unmapped_area(struct file *filp, unsigned long addr,
if (addr) {
addr = PAGE_ALIGN(addr);
vma = find_vma_prev(mm, addr, &prev);
- if (TASK_SIZE - len >= addr && addr >= mmap_min_addr &&
+ if (mmap_end - len >= addr && addr >= mmap_min_addr &&
(!vma || addr + len <= vm_start_gap(vma)) &&
(!prev || addr >= vm_end_gap(prev)))
return addr;
@@ -2104,7 +2114,7 @@ arch_get_unmapped_area(struct file *filp, unsigned long addr,
info.flags = 0;
info.length = len;
info.low_limit = mm->mmap_base;
- info.high_limit = TASK_SIZE;
+ info.high_limit = mmap_end;
info.align_mask = 0;
return vm_unmapped_area(&info);
}
@@ -2124,9 +2134,10 @@ arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0,
struct mm_struct *mm = current->mm;
unsigned long addr = addr0;
struct vm_unmapped_area_info info;
+ const unsigned long mmap_end = arch_get_mmap_end(addr);
/* requested length too big for entire address space */
- if (len > TASK_SIZE - mmap_min_addr)
+ if (len > mmap_end - mmap_min_addr)
return -ENOMEM;
if (flags & MAP_FIXED)
@@ -2136,7 +2147,7 @@ arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0,
if (addr) {
addr = PAGE_ALIGN(addr);
vma = find_vma_prev(mm, addr, &prev);
- if (TASK_SIZE - len >= addr && addr >= mmap_min_addr &&
+ if (mmap_end - len >= addr && addr >= mmap_min_addr &&
(!vma || addr + len <= vm_start_gap(vma)) &&
(!prev || addr >= vm_end_gap(prev)))
return addr;
@@ -2145,7 +2156,7 @@ arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0,
info.flags = VM_UNMAPPED_AREA_TOPDOWN;
info.length = len;
info.low_limit = max(PAGE_SIZE, mmap_min_addr);
- info.high_limit = mm->mmap_base;
+ info.high_limit = arch_get_mmap_base(addr, mm->mmap_base);
info.align_mask = 0;
addr = vm_unmapped_area(&info);
@@ -2159,7 +2170,7 @@ arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0,
VM_BUG_ON(addr != -ENOMEM);
info.flags = 0;
info.low_limit = TASK_UNMAPPED_BASE;
- info.high_limit = TASK_SIZE;
+ info.high_limit = mmap_end;
addr = vm_unmapped_area(&info);
}
--
2.19.2
