[v1,3/7] mm/vmalloc.c: allow vread() to read out vm_map_ram areas
Commit Message
Currently, vread can read out vmalloc areas which is associated with
a vm_struct. While this doesn't work for areas created by vm_map_ram()
interface because it doesn't have an associated vm_struct. Then in vread(),
these areas will be skipped.
Here, add a new function vb_vread() to read out areas managed by
vmap_block specifically. Then recognize vm_map_ram areas via vmap->flags
and handle them respectively.
Signed-off-by: Baoquan He <bhe@redhat.com>
---
mm/vmalloc.c | 61 ++++++++++++++++++++++++++++++++++++++++++++++------
1 file changed, 54 insertions(+), 7 deletions(-)
Comments
Hi Baoquan,
I love your patch! Perhaps something to improve:
[auto build test WARNING on akpm-mm/mm-everything]
url: https://github.com/intel-lab-lkp/linux/commits/Baoquan-He/mm-vmalloc-c-allow-vread-to-read-out-vm_map_ram-areas/20221204-093322
base: https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-everything
patch link: https://lore.kernel.org/r/20221204013046.154960-4-bhe%40redhat.com
patch subject: [PATCH v1 3/7] mm/vmalloc.c: allow vread() to read out vm_map_ram areas
config: arm-randconfig-r046-20221204
compiler: arm-linux-gnueabi-gcc (GCC) 12.1.0
reproduce (this is a W=1 build):
wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
chmod +x ~/bin/make.cross
# https://github.com/intel-lab-lkp/linux/commit/0bcc4ce1e46418b86eb569175879081116649727
git remote add linux-review https://github.com/intel-lab-lkp/linux
git fetch --no-tags linux-review Baoquan-He/mm-vmalloc-c-allow-vread-to-read-out-vm_map_ram-areas/20221204-093322
git checkout 0bcc4ce1e46418b86eb569175879081116649727
# save the config file
mkdir build_dir && cp config build_dir/.config
COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-12.1.0 make.cross W=1 O=build_dir ARCH=arm SHELL=/bin/bash
If you fix the issue, kindly add following tag where applicable
| Reported-by: kernel test robot <lkp@intel.com>
All warnings (new ones prefixed by >>):
mm/vmalloc.c: In function 'vb_vread':
>> mm/vmalloc.c:3540:23: warning: variable 'offset' set but not used [-Wunused-but-set-variable]
3540 | unsigned long offset;
| ^~~~~~
vim +/offset +3540 mm/vmalloc.c
3535
3536 static void vb_vread(char *buf, char *addr, int count)
3537 {
3538 char *start;
3539 struct vmap_block *vb;
> 3540 unsigned long offset;
3541 unsigned int rs, re, n;
3542
3543 offset = ((unsigned long)addr & (VMAP_BLOCK_SIZE - 1)) >> PAGE_SHIFT;
3544 vb = xa_load(&vmap_blocks, addr_to_vb_idx((unsigned long)addr));
3545
3546 spin_lock(&vb->lock);
3547 if (bitmap_empty(vb->used_map, VMAP_BBMAP_BITS)) {
3548 spin_unlock(&vb->lock);
3549 memset(buf, 0, count);
3550 return;
3551 }
3552 for_each_set_bitrange(rs, re, vb->used_map, VMAP_BBMAP_BITS) {
3553 if (!count)
3554 break;
3555 start = vmap_block_vaddr(vb->va->va_start, rs);
3556 if (addr < start) {
3557 if (count == 0)
3558 break;
3559 *buf = '\0';
3560 buf++;
3561 addr++;
3562 count--;
3563 }
3564 n = (re - rs + 1) << PAGE_SHIFT;
3565 if (n > count)
3566 n = count;
3567 aligned_vread(buf, start, n);
3568
3569 buf += n;
3570 addr += n;
3571 count -= n;
3572 }
3573 spin_unlock(&vb->lock);
3574 }
3575
On 12/04/22 at 11:47am, kernel test robot wrote:
> Hi Baoquan,
>
> I love your patch! Perhaps something to improve:
>
> [auto build test WARNING on akpm-mm/mm-everything]
>
> url: https://github.com/intel-lab-lkp/linux/commits/Baoquan-He/mm-vmalloc-c-allow-vread-to-read-out-vm_map_ram-areas/20221204-093322
> base: https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-everything
> patch link: https://lore.kernel.org/r/20221204013046.154960-4-bhe%40redhat.com
> patch subject: [PATCH v1 3/7] mm/vmalloc.c: allow vread() to read out vm_map_ram areas
> config: arm-randconfig-r046-20221204
> compiler: arm-linux-gnueabi-gcc (GCC) 12.1.0
> reproduce (this is a W=1 build):
> wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
> chmod +x ~/bin/make.cross
> # https://github.com/intel-lab-lkp/linux/commit/0bcc4ce1e46418b86eb569175879081116649727
> git remote add linux-review https://github.com/intel-lab-lkp/linux
> git fetch --no-tags linux-review Baoquan-He/mm-vmalloc-c-allow-vread-to-read-out-vm_map_ram-areas/20221204-093322
> git checkout 0bcc4ce1e46418b86eb569175879081116649727
> # save the config file
> mkdir build_dir && cp config build_dir/.config
> COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-12.1.0 make.cross W=1 O=build_dir ARCH=arm SHELL=/bin/bash
>
> If you fix the issue, kindly add following tag where applicable
> | Reported-by: kernel test robot <lkp@intel.com>
>
> All warnings (new ones prefixed by >>):
>
> mm/vmalloc.c: In function 'vb_vread':
> >> mm/vmalloc.c:3540:23: warning: variable 'offset' set but not used [-Wunused-but-set-variable]
> 3540 | unsigned long offset;
> | ^~~~~~
Thanks.
The local variable 'offset' is needed, the handling in vb_vread() need
be improved to cover the case in which reading is started from dirty or
free regions. I will add below change to v2.
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 78cae59170d8..6612914459cf 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -3526,7 +3522,6 @@ static void vb_vread(char *buf, char *addr, int count)
unsigned long offset;
unsigned int rs, re, n;
- offset = ((unsigned long)addr & (VMAP_BLOCK_SIZE - 1)) >> PAGE_SHIFT;
vb = xa_load(&vmap_blocks, addr_to_vb_idx((unsigned long)addr));
spin_lock(&vb->lock);
@@ -3547,16 +3542,22 @@ static void vb_vread(char *buf, char *addr, int count)
addr++;
count--;
}
- n = (re - rs + 1) << PAGE_SHIFT;
+ /*it could start reading from the middle of used region*/
+ offset = offset_in_page(addr);
+ n = (re - rs + 1) << PAGE_SHIFT - offset;
if (n > count)
n = count;
- aligned_vread(buf, start, n);
+ aligned_vread(buf, start+offset, n);
buf += n;
addr += n;
count -= n;
}
spin_unlock(&vb->lock);
+
+ /* zero-fill the left dirty or free regions */
+ if (count)
+ memset(buf, 0, count);
}
/**
@@ -3519,6 +3519,46 @@ static int aligned_vread(char *buf, char *addr, unsigned long count)
return copied;
}
+static void vb_vread(char *buf, char *addr, int count)
+{
+ char *start;
+ struct vmap_block *vb;
+ unsigned long offset;
+ unsigned int rs, re, n;
+
+ offset = ((unsigned long)addr & (VMAP_BLOCK_SIZE - 1)) >> PAGE_SHIFT;
+ vb = xa_load(&vmap_blocks, addr_to_vb_idx((unsigned long)addr));
+
+ spin_lock(&vb->lock);
+ if (bitmap_empty(vb->used_map, VMAP_BBMAP_BITS)) {
+ spin_unlock(&vb->lock);
+ memset(buf, 0, count);
+ return;
+ }
+ for_each_set_bitrange(rs, re, vb->used_map, VMAP_BBMAP_BITS) {
+ if (!count)
+ break;
+ start = vmap_block_vaddr(vb->va->va_start, rs);
+ if (addr < start) {
+ if (count == 0)
+ break;
+ *buf = '\0';
+ buf++;
+ addr++;
+ count--;
+ }
+ n = (re - rs + 1) << PAGE_SHIFT;
+ if (n > count)
+ n = count;
+ aligned_vread(buf, start, n);
+
+ buf += n;
+ addr += n;
+ count -= n;
+ }
+ spin_unlock(&vb->lock);
+}
+
/**
* vread() - read vmalloc area in a safe way.
* @buf: buffer for reading data
@@ -3549,7 +3589,7 @@ long vread(char *buf, char *addr, unsigned long count)
struct vm_struct *vm;
char *vaddr, *buf_start = buf;
unsigned long buflen = count;
- unsigned long n;
+ unsigned long n, size, flags;
addr = kasan_reset_tag(addr);
@@ -3570,12 +3610,16 @@ long vread(char *buf, char *addr, unsigned long count)
if (!count)
break;
- if (!va->vm)
+ vm = va->vm;
+ flags = va->flags & VMAP_FLAGS_MASK;
+
+ if (!vm && !flags)
continue;
- vm = va->vm;
- vaddr = (char *) vm->addr;
- if (addr >= vaddr + get_vm_area_size(vm))
+ vaddr = (char *) va->va_start;
+ size = flags ? va_size(va) : get_vm_area_size(vm);
+
+ if (addr >= vaddr + size)
continue;
while (addr < vaddr) {
if (count == 0)
@@ -3585,10 +3629,13 @@ long vread(char *buf, char *addr, unsigned long count)
addr++;
count--;
}
- n = vaddr + get_vm_area_size(vm) - addr;
+ n = vaddr + size - addr;
if (n > count)
n = count;
- if (!(vm->flags & VM_IOREMAP))
+
+ if ((flags & (VMAP_RAM|VMAP_BLOCK)) == (VMAP_RAM|VMAP_BLOCK))
+ vb_vread(buf, addr, n);
+ else if ((flags & VMAP_RAM) || !(vm->flags & VM_IOREMAP))
aligned_vread(buf, addr, n);
else /* IOREMAP area is treated as memory hole */
memset(buf, 0, n);