[PATCH V2 1/4] mm: mmap: Allow for "high" userspace addresses
From: Steve Capper <hidden>
Date: 2018-10-17 16:35:25
Also in:
linux-mm
Subsystem:
memory management, memory mapping, the rest · Maintainers:
Andrew Morton, Liam R. Howlett, Lorenzo Stoakes, Linus Torvalds
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).
Rather than duplicate the arch_get_unmapped_* stock implementations,
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 <redacted>
---
Changed in V2, these alterations are made to mm/mmap.c rather than
copied over to arch/arm64 and modified there.
---
mm/mmap.c | 25 ++++++++++++++++++-------
1 file changed, 18 insertions(+), 7 deletions(-)
diff --git a/mm/mmap.c b/mm/mmap.c
index 5f2b2b184c60..396b8ae12783 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c@@ -2042,6 +2042,15 @@ 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. *
@@ -2061,8 +2070,9 @@ 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)
@@ -2071,7 +2081,7 @@ 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;
@@ -2080,7 +2090,7 @@ 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); }
@@ -2100,9 +2110,10 @@ 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)
@@ -2112,7 +2123,7 @@ 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;
@@ -2121,7 +2132,7 @@ 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);
@@ -2135,7 +2146,7 @@ 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); }
--
2.11.0