Re: [PATCH v2] tools/mm/thpmaps: handle carriage returns and non-UTF-8 filenames

[Ryan Roberts <ryan.roberts@arm.com>]

On 04/11/2026 06:16, Weilin Tong wrote:
> VMAList opens smaps with universal newline handling and strict decoding.
> A carriage return in a mapped filename can split a header into multiple
> records, while non-UTF-8 bytes cause UnicodeDecodeError.
> 
> Read LF-terminated records and use surrogateescape to preserve filename
> bytes. Escape filename characters that stdout cannot encode to avoid
> UnicodeEncodeError when printing mapping names.
> 
> Fixes: 2444172cfde4 ("tools/mm: add thpmaps script to dump THP usage info")
> Suggested-by: Andrew Morton <akpm@linux-foundation.org>
> Link: https://lore.kernel.org/linux-mm/20261101211644.c63a2028bbede0f763f41f80@linux-foundation.org/
> Signed-off-by: Weilin Tong <tongweilin@linux.alibaba.com>

Reviewed-by: Ryan Roberts <ryan.roberts@arm.com>

> ---
> Changes in v2:
> - Escape unencodable mapping names in vma_print() (Sashiko).
> - Rebase onto mm-new.
> 
> Link to v1: https://lore.kernel.org/linux-mm/20261102085419.696232-1-tongweilin@linux.alibaba.com/
> 
>  tools/mm/thpmaps | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/tools/mm/thpmaps b/tools/mm/thpmaps
> index a1a9bc30514f..0e17723515cd 100644
> --- a/tools/mm/thpmaps
> +++ b/tools/mm/thpmaps
> @@ -196,7 +196,8 @@ class VMAList:
>      # instance to receive VMAs.
>      def __init__(self, pid='self', stats=[]):
>          self.vmas = []
> -        with open(f'/proc/{pid}/smaps', 'r') as file:
> +        with open(f'/proc/{pid}/smaps', 'r', newline='\n',
> +                  errors='surrogateescape') as file:
>              for line in file:
>                  elements = line.rstrip('\n').split(maxsplit=5)
>                  if '-' in elements[0]:
> @@ -363,12 +364,14 @@ def cont_parse(vma, order, ranges, anons, heads):
>  def vma_print(vma, pid):
>      # Prints a VMA instance in a format similar to smaps. The main difference is
>      # that the pid is included as the first value.
> +    name = vma.name.encode(sys.stdout.encoding, errors='backslashreplace')
> +    name = name.decode(sys.stdout.encoding)
>      print("{:010d}: {:016x}-{:016x} {}{}{}{} {:08x} {:02x}:{:02x} {:08x} {}"
>          .format(
>              pid, vma.start, vma.end,
>              'r' if vma.read else '-', 'w' if vma.write else '-',
>              'x' if vma.execute else '-', 'p' if vma.private else 's',
> -            vma.pgoff, vma.major, vma.minor, vma.inode, vma.name
> +            vma.pgoff, vma.major, vma.minor, vma.inode, name
>          ))
>  
>  
> 
> base-commit: 74d73ffcffe03804f97e9fb82301dadf75671282