[0/5] cramfs refresh for embedded usage
diff mbox

Message ID alpine.LFD.2.20.1708150001380.17016@knanqh.ubzr
State New
Headers show

Commit Message

Nicolas Pitre Aug. 15, 2017, 4:10 a.m. UTC
On Mon, 14 Aug 2017, Chris Brandt wrote:

> On Monday, August 14, 2017, Nicolas Pitre wrote:
> > > However, now with your mkcramfs tool, I can no longer mount my cramfs
> > > image as the rootfs on boot. I was able to do that before (ie, 30
> > minutes
> > > ago) when using the community mkcramfs (ie, 30 minutes ago).
> > >
> > > I get this:
> > >
> > > [    1.712425] cramfs: checking physical address 0x1b000000 for linear
> > cramfs image
> > > [    1.720531] cramfs: linear cramfs image appears to be 15744 KB in
> > size
> > > [    1.728656] VFS: Mounted root (cramfs_physmem filesystem) readonly on
> > device 0:12.
> > > [    1.737062] devtmpfs: mounted
> > > [    1.741139] Freeing unused kernel memory: 48K
> > > [    1.745545] This architecture does not have kernel memory protection.
> > > [    1.760381] Starting init: /sbin/init exists but couldn't execute it
> > (error -22)
> > > [    1.769685] Starting init: /bin/sh exists but couldn't execute it
> > (error -14)
> > 
> > Is /sbin/init a link to busybox?
> 
> Yes.
> 
> 
> > I suppose it just boots if you do mkcramfs without -X?
> 
> Correct. I just created another image and removed the "-X -X" when 
> creating it. Now I can boot that image as my rootfs.
>   (I'm using -X -X because I'm using a Cortex-A9 with MMU).
> 
> 
> > If so could you share your non-working cramfs image with me?
> 
> I will send it (in a separate email)

I was able to reproduce. The following patch on top should partially fix 
it.  I'm trying to figure out how to split a vma and link it properly in 
the case the vma cannot be mapped entirely. In the mean time shared libs 
won't be XIP.

Comments

Chris Brandt Aug. 15, 2017, 11 a.m. UTC | #1
On Tuesday, August 15, 2017 1, Nicolas Pitre wrote:
> I was able to reproduce. The following patch on top should partially fix
> it.  I'm trying to figure out how to split a vma and link it properly in
> the case the vma cannot be mapped entirely. In the mean time shared libs
> won't be XIP.
> 
> 
> diff --git a/fs/cramfs/inode.c b/fs/cramfs/inode.c
> index 5aedbd224e..4c7f01fcd2 100644
> --- a/fs/cramfs/inode.c
> +++ b/fs/cramfs/inode.c


Yes, now I can boot with my rootfs being a XIP cramfs.

However, like you said, libc is not XIP.

$ cat /proc/self/maps
00008000-000a1000 r-xp 1b005000 00:0c 18192      /bin/busybox
000a9000-000aa000 rw-p 00099000 00:0c 18192      /bin/busybox
000aa000-000ac000 rw-p 00000000 00:00 0          [heap]
b6ed8000-b6fb1000 r-xp 00000000 00:0c 766540     /lib/libc-2.18-2013.10.so
b6fb1000-b6fb9000 ---p 000d9000 00:0c 766540     /lib/libc-2.18-2013.10.so
b6fb9000-b6fbb000 r--p 000d9000 00:0c 766540     /lib/libc-2.18-2013.10.so
b6fbb000-b6fbc000 rw-p 000db000 00:0c 766540     /lib/libc-2.18-2013.10.so
b6fbc000-b6fbf000 rw-p 00000000 00:00 0
b6fbf000-b6fd6000 r-xp 00000000 00:0c 670372     /lib/ld-2.18-2013.10.so
b6fd9000-b6fda000 rw-p 00000000 00:00 0
b6fdb000-b6fdd000 rw-p 00000000 00:00 0
b6fdd000-b6fde000 r--p 00016000 00:0c 670372     /lib/ld-2.18-2013.10.so
b6fde000-b6fdf000 rw-p 00017000 00:0c 670372     /lib/ld-2.18-2013.10.so
be81f000-be840000 rw-p 00000000 00:00 0          [stack]
beb19000-beb1a000 r-xp 00000000 00:00 0          [sigpage]
ffff0000-ffff1000 r-xp 00000000 00:00 0          [vectors]


Chris

Patch
diff mbox

diff --git a/fs/cramfs/inode.c b/fs/cramfs/inode.c
index 5aedbd224e..4c7f01fcd2 100644
--- a/fs/cramfs/inode.c
+++ b/fs/cramfs/inode.c
@@ -285,10 +285,10 @@  static void *cramfs_read(struct super_block *sb, unsigned int offset,
 
 /*
  * For a mapping to be possible, we need a range of uncompressed and
- * contiguous blocks. Return the offset for the first block if that
- * verifies, or zero otherwise.
+ * contiguous blocks. Return the offset for the first block and number of
+ * valid blocks for which that is true, or zero otherwise.
  */
-static u32 cramfs_get_block_range(struct inode *inode, u32 pgoff, u32 pages)
+static u32 cramfs_get_block_range(struct inode *inode, u32 pgoff, u32 *pages)
 {
 	struct super_block *sb = inode->i_sb;
 	struct cramfs_sb_info *sbi = CRAMFS_SB(sb);
@@ -306,11 +306,16 @@  static u32 cramfs_get_block_range(struct inode *inode, u32 pgoff, u32 pages)
 	do {
 		u32 expect = blockaddr + i * (PAGE_SIZE >> 2);
 		expect |= CRAMFS_BLK_FLAG_DIRECT_PTR|CRAMFS_BLK_FLAG_UNCOMPRESSED;
-		pr_debug("range: block %d/%d got %#x expects %#x\n",
-			 pgoff+i, pgoff+pages-1, blockptrs[i], expect);
-		if (blockptrs[i] != expect)
-			return 0;
-	} while (++i < pages);
+		if (blockptrs[i] != expect) {
+			pr_debug("range: block %d/%d got %#x expects %#x\n",
+				 pgoff+i, pgoff+*pages-1, blockptrs[i], expect);
+			if (i == 0)
+				return 0;
+			break;
+		}
+	} while (++i < *pages);
+
+	*pages = i;
 
 	/* stored "direct" block ptrs are shifted down by 2 bits */
 	return blockaddr << 2;
@@ -321,8 +326,8 @@  static int cramfs_physmem_mmap(struct file *file, struct vm_area_struct *vma)
 	struct inode *inode = file_inode(file);
 	struct super_block *sb = inode->i_sb;
 	struct cramfs_sb_info *sbi = CRAMFS_SB(sb);
-	unsigned int pages, max_pages, offset;
-	unsigned long length, address;
+	unsigned int pages, vma_pages, max_pages, offset;
+	unsigned long address;
 	char *fail_reason;
 	int ret;
 
@@ -332,17 +337,20 @@  static int cramfs_physmem_mmap(struct file *file, struct vm_area_struct *vma)
 	if ((vma->vm_flags & VM_SHARED) && (vma->vm_flags & VM_MAYWRITE))
 		return -EINVAL;
 
-	vma->vm_ops = &generic_file_vm_ops;
+	fail_reason = "vma is writable";
 	if (vma->vm_flags & VM_WRITE)
-		return 0;
+		goto fail;
 
-	length = vma->vm_end - vma->vm_start;
-	pages = (length + PAGE_SIZE - 1) >> PAGE_SHIFT;
+	vma_pages = (vma->vm_end - vma->vm_start + PAGE_SIZE - 1) >> PAGE_SHIFT;
 	max_pages = (inode->i_size + PAGE_SIZE - 1) >> PAGE_SHIFT;
-	if (vma->vm_pgoff >= max_pages || pages > max_pages - vma->vm_pgoff)
-		return -EINVAL;
+	fail_reason = "beyond file limit";
+	if (vma->vm_pgoff >= max_pages)
+		goto fail;
+	pages = vma_pages;
+	if (pages > max_pages - vma->vm_pgoff)
+		pages = max_pages - vma->vm_pgoff;
 
-	offset = cramfs_get_block_range(inode, vma->vm_pgoff, pages);
+	offset = cramfs_get_block_range(inode, vma->vm_pgoff, &pages);
 	fail_reason = "unsuitable block layout";
 	if (!offset)
 		goto fail;
@@ -351,37 +359,60 @@  static int cramfs_physmem_mmap(struct file *file, struct vm_area_struct *vma)
 	if (!PAGE_ALIGNED(address))
 		goto fail;
 
-	/* Don't map a partial page if it contains some other data */
+	/* Don't map the last page if it contains some other data */
 	if (unlikely(vma->vm_pgoff + pages == max_pages)) {
 		unsigned int partial = offset_in_page(inode->i_size);
 		if (partial) {
 			char *data = sbi->linear_virt_addr + offset;
 			data += (pages - 1) * PAGE_SIZE + partial;
-			fail_reason = "last partial page is shared";
 			while ((unsigned long)data & 7)
 				if (*data++ != 0)
-					goto fail;
+					goto nonzero;
 			while (offset_in_page(data)) {
-				if (*(u64 *)data != 0)
-					goto fail;
+				if (*(u64 *)data != 0) {
+					nonzero:
+					pr_debug("mmap: %s: last page is shared\n",
+						 file_dentry(file)->d_name.name);
+					pages--;
+					break;
+				}
 				data += 8;
 			}
 		}
 	}
-	
-	ret = remap_pfn_range(vma, vma->vm_start, address >> PAGE_SHIFT,
-			      length, vma->vm_page_prot);
-	if (ret)
-		return ret;
-	pr_debug("mapped %s at 0x%08lx, length %lu to vma 0x%08lx, "
+
+	if (pages) {
+		/*
+		 * Split the vma if we can't map it all so normal paging
+		 * will take care of the rest through cramfs_readpage().
+		 */
+		if (pages != vma_pages) {
+			if (1) {
+				fail_reason = "fix me";
+				goto fail;
+			}
+			ret = split_vma(vma->vm_mm, vma,
+					vma->vm_start + pages * PAGE_SIZE, 0);
+			if (ret)
+				return ret;
+		}
+
+		ret = remap_pfn_range(vma, vma->vm_start, address >> PAGE_SHIFT,
+			      	      pages * PAGE_SIZE, vma->vm_page_prot);
+		if (ret)
+			return ret;
+	}
+
+	pr_debug("mapped %s at 0x%08lx, %u/%u pages to vma 0x%08lx, "
 		 "page_prot 0x%llx\n", file_dentry(file)->d_name.name,
-		 address, length, vma->vm_start,
+		 address, pages, vma_pages, vma->vm_start,
 		 (unsigned long long)pgprot_val(vma->vm_page_prot));
 	return 0;
 
 fail:
 	pr_debug("%s: direct mmap failed: %s\n",
 		 file_dentry(file)->d_name.name, fail_reason);
+	vma->vm_ops = &generic_file_vm_ops;
 	return 0;
 }
 
@@ -394,14 +425,15 @@  static unsigned long cramfs_physmem_get_unmapped_area(struct file *file,
 	struct inode *inode = file_inode(file);
 	struct super_block *sb = inode->i_sb;
 	struct cramfs_sb_info *sbi = CRAMFS_SB(sb);
-	unsigned int pages, max_pages, offset;
+	unsigned int pages, block_pages, max_pages, offset;
 
 	pages = (len + PAGE_SIZE - 1) >> PAGE_SHIFT;
 	max_pages = (inode->i_size + PAGE_SIZE - 1) >> PAGE_SHIFT;
 	if (pgoff >= max_pages || pages > max_pages - pgoff)
 		return -EINVAL;
-	offset = cramfs_get_block_range(inode, pgoff, pages);
-	if (!offset)
+	block_pages = pages;
+	offset = cramfs_get_block_range(inode, pgoff, &block_pages);
+	if (!offset || block_pages != pages)
 		return -ENOSYS;
 	addr = sbi->linear_phys_addr + offset;
 	pr_debug("get_unmapped for %s ofs %#lx siz %lu at 0x%08lx\n",