[PATCH 2/2] PMFS: Convert to using vm_unmapped_area

Vishal Verma vishal.l.verma at linux.intel.com
Mon Oct 21 18:14:19 EDT 2013


We used to do a manual search for unmapped VMAs.
This method has been depracated.

Signed-off-by: Vishal Verma <vishal.l.verma at linux.intel.com>
---
 arch/x86/kernel/sys_x86_64.c |  150 ------------------------------------------
 fs/pmfs/file.c               |   28 ++++-----
 mm/mmap.c                    |    4 +
 3 files changed, 16 insertions(+), 166 deletions(-)

diff --git a/arch/x86/kernel/sys_x86_64.c b/arch/x86/kernel/sys_x86_64.c
index 69e7eaa..30277e2 100644
--- a/arch/x86/kernel/sys_x86_64.c
+++ b/arch/x86/kernel/sys_x86_64.c
@@ -15,7 +15,6 @@
 #include <linux/random.h>
 #include <linux/uaccess.h>
 #include <linux/elf.h>
-#include <linux/export.h>
 
 #include <asm/ia32.h>
 #include <asm/syscalls.h>
@@ -191,152 +190,3 @@ bottomup:
 	 */
 	return arch_get_unmapped_area(filp, addr0, len, pgoff, flags);
 }
-
-
-static unsigned long arch_get_unmapped_area_bottomup_sz(struct file *file,
-		unsigned long addr, unsigned long len, unsigned long align_size,
-		unsigned long pgoff, unsigned long flags)
-{
-	struct mm_struct *mm = current->mm;
-	struct vm_area_struct *vma;
-	unsigned long start_addr;
-
-	if (len > mm->cached_hole_size) {
-	        start_addr = mm->free_area_cache;
-	} else {
-	        start_addr = TASK_UNMAPPED_BASE;
-	        mm->cached_hole_size = 0;
-	}
-
-full_search:
-	addr = ALIGN(start_addr, align_size);
-
-	for (vma = find_vma(mm, addr); ; vma = vma->vm_next) {
-		/* At this point:  (!vma || addr < vma->vm_end). */
-		if (TASK_SIZE - len < addr) {
-			/*
-			 * Start a new search - just in case we missed
-			 * some holes.
-			 */
-			if (start_addr != TASK_UNMAPPED_BASE) {
-				start_addr = TASK_UNMAPPED_BASE;
-				mm->cached_hole_size = 0;
-				goto full_search;
-			}
-			return -ENOMEM;
-		}
-		if (!vma || addr + len <= vma->vm_start) {
-			mm->free_area_cache = addr + len;
-			return addr;
-		}
-		if (addr + mm->cached_hole_size < vma->vm_start)
-		        mm->cached_hole_size = vma->vm_start - addr;
-		addr = ALIGN(vma->vm_end, align_size);
-	}
-}
-
-static unsigned long arch_get_unmapped_area_topdown_sz(struct file *file,
-		unsigned long addr0, unsigned long len, unsigned long align_size,
-		unsigned long pgoff, unsigned long flags)
-{
-	struct mm_struct *mm = current->mm;
-	struct vm_area_struct *vma, *prev_vma;
-	unsigned long base = mm->mmap_base, addr = addr0;
-	unsigned long largest_hole = mm->cached_hole_size;
-	unsigned long align_mask = ~(align_size - 1);
-	int first_time = 1;
-
-	/* don't allow allocations above current base */
-	if (mm->free_area_cache > base)
-		mm->free_area_cache = base;
-
-	if (len <= largest_hole) {
-	        largest_hole = 0;
-		mm->free_area_cache  = base;
-	}
-try_again:
-	/* make sure it can fit in the remaining address space */
-	if (mm->free_area_cache < len)
-		goto fail;
-
-	/* either no address requested or can't fit in requested address hole */
-	addr = (mm->free_area_cache - len) & align_mask;
-	do {
-		/*
-		 * Lookup failure means no vma is above this address,
-		 * i.e. return with success:
-		 */
-		vma = find_vma(mm, addr);
-		if (!vma)
-			return addr;
-
-		/*
-		 * new region fits between prev_vma->vm_end and
-		 * vma->vm_start, use it:
-		 */
-		prev_vma = vma->vm_prev;
-		if (addr + len <= vma->vm_start &&
-		            (!prev_vma || (addr >= prev_vma->vm_end))) {
-			/* remember the address as a hint for next time */
-		        mm->cached_hole_size = largest_hole;
-		        return (mm->free_area_cache = addr);
-		} else {
-			/* pull free_area_cache down to the first hole */
-		        if (mm->free_area_cache == vma->vm_end) {
-				mm->free_area_cache = vma->vm_start;
-				mm->cached_hole_size = largest_hole;
-			}
-		}
-
-		/* remember the largest hole we saw so far */
-		if (addr + largest_hole < vma->vm_start)
-		        largest_hole = vma->vm_start - addr;
-
-		/* try just below the current vma->vm_start */
-		addr = (vma->vm_start - len) & align_mask;
-	} while (len <= vma->vm_start);
-
-fail:
-	/*
-	 * if hint left us with no space for the requested
-	 * mapping then try again:
-	 */
-	if (first_time) {
-		mm->free_area_cache = base;
-		largest_hole = 0;
-		first_time = 0;
-		goto try_again;
-	}
-	/*
-	 * A failed mmap() very likely causes application failure,
-	 * so fall back to the bottom-up function here. This scenario
-	 * can happen with large stack limits and large mmap()
-	 * allocations.
-	 */
-	mm->free_area_cache = TASK_UNMAPPED_BASE;
-	mm->cached_hole_size = ~0UL;
-	addr = arch_get_unmapped_area_bottomup_sz(file, addr0, len, align_size,
-																pgoff, flags);
-
-	/*
-	 * Restore the topdown base:
-	 */
-	mm->free_area_cache = base;
-	mm->cached_hole_size = ~0UL;
-
-	return addr;
-}
-
-unsigned long arch_get_unmapped_area_sz(struct file *file,
-		unsigned long addr, unsigned long len, unsigned long align_size,
-		unsigned long pgoff, unsigned long flags)
-{
-	struct mm_struct *mm = current->mm;
-	if (mm->get_unmapped_area == arch_get_unmapped_area)
-		return arch_get_unmapped_area_bottomup_sz(file, addr, len, align_size,
-				pgoff, flags);
-	return arch_get_unmapped_area_topdown_sz(file, addr, len, align_size,
-				pgoff, flags);
-}
-EXPORT_SYMBOL(arch_get_unmapped_area_sz);
-
diff --git a/fs/pmfs/file.c b/fs/pmfs/file.c
index 36bdc1d..23eb9cf 100644
--- a/fs/pmfs/file.c
+++ b/fs/pmfs/file.c
@@ -258,10 +258,6 @@ static int pmfs_flush(struct file *file, fl_owner_t id)
 	return ret;
 }
 
-extern unsigned long arch_get_unmapped_area_sz(struct file *file,
-	unsigned long addr0, unsigned long len, unsigned long align_size,
-	unsigned long pgoff, unsigned long flags);
-
 static unsigned long
 pmfs_get_unmapped_area(struct file *file, unsigned long addr,
 			unsigned long len, unsigned long pgoff,
@@ -272,6 +268,7 @@ pmfs_get_unmapped_area(struct file *file, unsigned long addr,
 	struct mm_struct *mm = current->mm;
 	struct inode *inode = file->f_mapping->host;
 	struct pmfs_inode *pi = pmfs_get_inode(inode->i_sb, inode->i_ino);
+	struct vm_unmapped_area_info info;
 
 	if (len > TASK_SIZE)
 		return -ENOMEM;
@@ -300,18 +297,17 @@ pmfs_get_unmapped_area(struct file *file, unsigned long addr,
 			return addr;
 	}
 
-	return arch_get_unmapped_area_sz(file, addr, len, align_size, pgoff,
-					 flags);
-#if 0
-	if (mm->get_unmapped_area == arch_get_unmapped_area)
-		return pmfs_get_unmapped_area_bottomup(file, addr, len,
-							align_size, pgoff,
-							flags);
-	else
-		return pmfs_get_unmapped_area_topdown(file, addr, len,
-						       align_size, pgoff,
-						       flags);
-#endif
+	/*
+	 * FIXME: Using the following values for low_limit and high_limit
+	 * implicitly disables ASLR. Awaiting a better way to have this fixed.
+	 */
+	info.flags = 0;
+	info.length = len;
+	info.low_limit = TASK_UNMAPPED_BASE;
+	info.high_limit = TASK_SIZE;
+	info.align_mask = align_size - 1;
+	info.align_offset = 0;
+	return vm_unmapped_area(&info);
 }
 
 const struct file_operations pmfs_xip_file_operations = {
diff --git a/mm/mmap.c b/mm/mmap.c
index a0d8672..2bdcd55 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1737,6 +1737,8 @@ found:
 	return gap_start;
 }
 
+EXPORT_SYMBOL(unmapped_area);
+
 unsigned long unmapped_area_topdown(struct vm_unmapped_area_info *info)
 {
 	struct mm_struct *mm = current->mm;
@@ -1835,6 +1837,8 @@ found_highest:
 	return gap_end;
 }
 
+EXPORT_SYMBOL(unmapped_area_topdown);
+
 /* Get an address range which is currently unmapped.
  * For shmat() with addr=0.
  *
-- 
1.7.0.4




More information about the Linux-pmfs mailing list