Re: [PATCH] mm: kmemleak: add CONFIG_DEBUG_KMEMLEAK_VERBOSE build option

[Lorenzo Stoakes (Oracle)]

On Mon, Mar 23, 2026 at 04:12:13AM -0700, Breno Leitao wrote:
> Add a Kconfig option to default kmemleak verbose mode on at build time.
> This option depends on DEBUG_KMEMLEAK_AUTO_SCAN since verbose reporting
> is only meaningful when the automatic scanning thread is running.
>
> When enabled, kmemleak prints full details (backtrace, hex dump, address)
> of unreferenced objects to dmesg as they are detected during scanning,
> removing the need to manually read /sys/kernel/debug/kmemleak.
>
> Making this a compile-time option rather than a boot parameter allows
> debug kernel flavors to enable verbose kmemleak reporting by default
> without requiring changes to boot arguments. A machine can simply swap
> to a debug kernel and benefit from kmemleak reporting automatically.
>
> By surfacing leak reports directly in dmesg, they are automatically
> forwarded through any kernel logging infrastructure and can be easily
> captured by log aggregation tooling, making it practical to monitor
> memory leaks across large fleets.
>
> The verbose setting can still be toggled at runtime via
> /sys/module/kmemleak/parameters/verbose.
>
> Signed-off-by: Breno Leitao <leitao@xxxxxxxxxx>

This seems reasonable, so:

Reviewed-by: Lorenzo Stoakes (Oracle) <ljs@xxxxxxxxxx>

Cheers, Lorenzo

> ---
>  mm/Kconfig.debug | 11 +++++++++++
>  mm/kmemleak.c    |  2 +-
>  2 files changed, 12 insertions(+), 1 deletion(-)
>
> diff --git a/mm/Kconfig.debug b/mm/Kconfig.debug
> index 7638d75b27db8..91b3e027b7535 100644
> --- a/mm/Kconfig.debug
> +++ b/mm/Kconfig.debug
> @@ -297,6 +297,17 @@ config DEBUG_KMEMLEAK_AUTO_SCAN
>
>  	  If unsure, say Y.
>
> +config DEBUG_KMEMLEAK_VERBOSE
> +	bool "Default kmemleak to verbose mode"
> +	depends on DEBUG_KMEMLEAK_AUTO_SCAN
> +	help
> +	  Say Y here to have kmemleak print unreferenced object details
> +	  (backtrace, hex dump, address) to dmesg when new memory leaks are
> +	  detected during automatic scanning. This can also be toggled at
> +	  runtime via /sys/module/kmemleak/parameters/verbose.
> +
> +	  If unsure, say N.
> +
>  config PER_VMA_LOCK_STATS
>  	bool "Statistics for per-vma locks"
>  	depends on PER_VMA_LOCK
> diff --git a/mm/kmemleak.c b/mm/kmemleak.c
> index fa8201e232221..2eff0d6b622b6 100644
> --- a/mm/kmemleak.c
> +++ b/mm/kmemleak.c
> @@ -241,7 +241,7 @@ static int kmemleak_skip_disable;
>  /* If there are leaks that can be reported */
>  static bool kmemleak_found_leaks;
>
> -static bool kmemleak_verbose;
> +static bool kmemleak_verbose = IS_ENABLED(CONFIG_DEBUG_KMEMLEAK_VERBOSE);
>  module_param_named(verbose, kmemleak_verbose, bool, 0600);
>
>  static void kmemleak_disable(void);
>
> ---
> base-commit: 785f0eb2f85decbe7c1ef9ae922931f0194ffc2e
> change-id: 20260323-kmemleak_report-a9a103ee0c8c
>
> Best regards,
> --
> Breno Leitao <leitao@xxxxxxxxxx>
>