Re: [PATCH v5 2/6] alloc_tag: add ioctl filters to /proc/allocinfo

[Suren Baghdasaryan]

On Mon, Jun 15, 2026 at 4:04 PM Abhishek Bapat <abhishekbapat@xxxxxxxxxx> wrote:
>
> Extend the capability of the IOCTL mechanism to filter allocations based
> on tag's module name, function name, file name and line number.
>
> Signed-off-by: Abhishek Bapat <abhishekbapat@xxxxxxxxxx>
> Acked-by: Hao Ge <hao.ge@xxxxxxxxx>

Acked-by: Suren Baghdasaryan <surenb@xxxxxxxxxx>

> ---
>  include/uapi/linux/alloc_tag.h | 26 ++++++++++++-
>  lib/alloc_tag.c                | 68 ++++++++++++++++++++++++++++++++--
>  2 files changed, 89 insertions(+), 5 deletions(-)
>
> diff --git a/include/uapi/linux/alloc_tag.h b/include/uapi/linux/alloc_tag.h
> index 0928e1a48d49..3b11877955b9 100644
> --- a/include/uapi/linux/alloc_tag.h
> +++ b/include/uapi/linux/alloc_tag.h
> @@ -40,8 +40,32 @@ struct allocinfo_tag_data {
>         struct allocinfo_counter counter;
>  };
>
> +enum {
> +       ALLOCINFO_FILTER_MODNAME,
> +       ALLOCINFO_FILTER_FUNCTION,
> +       ALLOCINFO_FILTER_FILENAME,
> +       ALLOCINFO_FILTER_LINENO,
> +       __ALLOCINFO_FILTER_LAST = ALLOCINFO_FILTER_LINENO
> +};
> +
> +#define ALLOCINFO_FILTER_MASK_MODNAME          (1 << ALLOCINFO_FILTER_MODNAME)
> +#define ALLOCINFO_FILTER_MASK_FUNCTION         (1 << ALLOCINFO_FILTER_FUNCTION)
> +#define ALLOCINFO_FILTER_MASK_FILENAME         (1 << ALLOCINFO_FILTER_FILENAME)
> +#define ALLOCINFO_FILTER_MASK_LINENO           (1 << ALLOCINFO_FILTER_LINENO)
> +
> +#define ALLOCINFO_FILTER_MASKS \
> +       ((1 << (__ALLOCINFO_FILTER_LAST + 1)) - 1)
> +
> +struct allocinfo_filter {
> +       __u64 mask; /* bitmask of the filter fields used */
> +       struct allocinfo_tag fields;
> +};
> +
>  struct allocinfo_get_at {
> -       __u64 pos;      /* input */
> +       /* inputs */
> +       __u64 pos;
> +       struct allocinfo_filter filter;
> +       /* output */
>         struct allocinfo_tag_data data;
>  };
>
> diff --git a/lib/alloc_tag.c b/lib/alloc_tag.c
> index 82e3b5f32dff..5feb61d9fb92 100644
> --- a/lib/alloc_tag.c
> +++ b/lib/alloc_tag.c
> @@ -49,6 +49,7 @@ struct allocinfo_private {
>         struct codetag_iterator iter;
>         struct codetag_iterator reported_iter;
>         bool print_header;
> +       struct allocinfo_filter filter;
>         /* ioctl uses a separate iterator not to interfere with reads */
>         struct codetag_iterator ioctl_iter;
>         bool positioned; /* seq_open_private() sets to 0 */
> @@ -188,6 +189,12 @@ static void allocinfo_copy_str(char *dest, const char *src)
>         strscpy_pad(dest, allocinfo_str(src), ALLOCINFO_STR_SIZE);
>  }
>
> +/* Compare two strings and only consider the trimmed suffix if s1 is too long */
> +static int allocinfo_cmp_str(const char *str, const char *template)
> +{
> +       return strncmp(allocinfo_str(str), template, ALLOCINFO_STR_SIZE);
> +}
> +
>  /*
>   * Populates the UAPI allocinfo_tag_data structure with active runtime
>   * profiling counters extracted from the given kernel codetag.
> @@ -227,6 +234,40 @@ static int allocinfo_ioctl_get_content_id(struct seq_file *m, void __user *arg)
>         return 0;
>  }
>
> +/*
> + * Verifies whether a given codetag satisfies the active filtering criteria by
> + * matching its characteristics against the specified filter.
> + */
> +static bool matches_filter(struct codetag *ct, struct allocinfo_filter *filter)
> +{
> +       if (!filter || !filter->mask)
> +               return true;
> +
> +       if (filter->mask & ALLOCINFO_FILTER_MASK_MODNAME) {
> +               /* user wants to filter by modname but ct->modname is NULL */
> +               if (!ct->modname) {
> +                       /* validate if user was attempting to filter for built-in allocations */
> +                       if (filter->fields.modname[0] != '\0')
> +                               return false;
> +               } else if (allocinfo_cmp_str(ct->modname, filter->fields.modname))
> +                       return false;
> +       }
> +
> +       if ((filter->mask & ALLOCINFO_FILTER_MASK_FUNCTION) &&
> +           ct->function && allocinfo_cmp_str(ct->function, filter->fields.function))
> +               return false;
> +
> +       if ((filter->mask & ALLOCINFO_FILTER_MASK_FILENAME) &&
> +           ct->filename && allocinfo_cmp_str(ct->filename, filter->fields.filename))
> +               return false;
> +
> +       if ((filter->mask & ALLOCINFO_FILTER_MASK_LINENO) &&
> +           ct->lineno != filter->fields.lineno)
> +               return false;
> +
> +       return true;
> +}
> +
>  /*
>   * Seeks the ioctl iterator to the specified 0-indexed tag position, reads its
>   * profiling data and returns it to userspace.
> @@ -235,29 +276,46 @@ static int allocinfo_ioctl_get_at(struct seq_file *m, void __user *arg)
>  {
>         struct allocinfo_private *priv;
>         struct codetag *ct;
> -       __u64 pos;
>         struct allocinfo_get_at params = {0};
> +       __u64 skip_count;
>
>         if (copy_from_user(&params, arg, sizeof(params)))
>                 return -EFAULT;
>
> +       if (params.filter.mask & ~ALLOCINFO_FILTER_MASKS)
> +               return -EINVAL;
> +
>         priv = m->private;
> -       pos = params.pos;
>
>         mutex_lock(&priv->ioctl_lock);
>         codetag_lock_module_list(alloc_tag_cttype);
>
> -       if (pos >= codetag_get_count(alloc_tag_cttype)) {
> +       if (params.pos >= codetag_get_count(alloc_tag_cttype)) {
>                 codetag_unlock_module_list(alloc_tag_cttype);
>                 mutex_unlock(&priv->ioctl_lock);
>                 return -ENOENT;
>         }
>
> +       skip_count = params.pos;
> +
> +       if (params.filter.mask)
> +               priv->filter = params.filter;
> +       else
> +               priv->filter.mask = 0;
> +
>         /* Find the codetag */
>         priv->ioctl_iter = codetag_get_ct_iter(alloc_tag_cttype);
>         ct = codetag_next_ct(&priv->ioctl_iter);
> -       while (ct && pos--)
> +
> +       while (ct) {
> +               if (matches_filter(ct, &priv->filter)) {
> +                       if (skip_count == 0)
> +                               break;
> +                       skip_count--;
> +               }
>                 ct = codetag_next_ct(&priv->ioctl_iter);
> +       }
> +
>         if (ct) {
>                 allocinfo_to_params(ct, &params.data);
>                 priv->positioned = true;
> @@ -298,6 +356,8 @@ static int allocinfo_ioctl_get_next(struct seq_file *m, void __user *arg)
>         }
>
>         ct = codetag_next_ct(&priv->ioctl_iter);
> +       while (ct && !matches_filter(ct, &priv->filter))
> +               ct = codetag_next_ct(&priv->ioctl_iter);
>         if (ct)
>                 allocinfo_to_params(ct, &params);
>
> --
> 2.54.0.1136.gdb2ca164c4-goog
>