linux-kernel - Re: [PATCH v9 9/9] liveupdate: kho: Use %pe format specifier for error pointer printing

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Message-ID: <57bbade3-0707-4045-b39b-2053434b0b7c@linux.dev>
Date: Sat, 1 Nov 2025 12:45:59 -0700
From: Zhu Yanjun <yanjun.zhu@...ux.dev>
To: Pasha Tatashin <pasha.tatashin@...een.com>, akpm@...ux-foundation.org,
 brauner@...nel.org, corbet@....net, graf@...zon.com, jgg@...pe.ca,
 linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org,
 linux-mm@...ck.org, masahiroy@...nel.org, ojeda@...nel.org,
 pratyush@...nel.org, rdunlap@...radead.org, rppt@...nel.org, tj@...nel.org
Subject: Re: [PATCH v9 9/9] liveupdate: kho: Use %pe format specifier for
 error pointer printing


在 2025/11/1 7:23, Pasha Tatashin 写道:
> From: Zhu Yanjun <yanjun.zhu@...ux.dev>
>
> Make pr_xxx() call to use the %pe format specifier instead of %d.
> The %pe specifier prints a symbolic error string (e.g., -ENOMEM,
> -EINVAL) when given an error pointer created with ERR_PTR(err).
>
> This change enhances the clarity and diagnostic value of the error
> message by showing a descriptive error name rather than a numeric
> error code.
>
> Note, that some err are still printed by value, as those errors
> might come from libfdt and not regular errnos.
>
> Signed-off-by: Zhu Yanjun <yanjun.zhu@...ux.dev>
> Co-developed-by: Pasha Tatashin <pasha.tatashin@...een.com>
> Signed-off-by: Pasha Tatashin <pasha.tatashin@...een.com>

Appreciate your help, Pasha

Yanjun.Zhu

> Reviewed-by: Simon Horman <horms@...nel.org>
> ---
>   kernel/liveupdate/kexec_handover.c         |  4 ++--
>   kernel/liveupdate/kexec_handover_debugfs.c | 10 ++++++----
>   2 files changed, 8 insertions(+), 6 deletions(-)
>
> diff --git a/kernel/liveupdate/kexec_handover.c b/kernel/liveupdate/kexec_handover.c
> index be945c133a2f..167c761988d3 100644
> --- a/kernel/liveupdate/kexec_handover.c
> +++ b/kernel/liveupdate/kexec_handover.c
> @@ -1448,8 +1448,8 @@ void __init kho_populate(phys_addr_t fdt_phys, u64 fdt_len,
>   		memblock_add(area->addr, size);
>   		err = memblock_mark_kho_scratch(area->addr, size);
>   		if (WARN_ON(err)) {
> -			pr_warn("failed to mark the scratch region 0x%pa+0x%pa: %d",
> -				&area->addr, &size, err);
> +			pr_warn("failed to mark the scratch region 0x%pa+0x%pa: %pe",
> +				&area->addr, &size, ERR_PTR(err));
>   			goto out;
>   		}
>   		pr_debug("Marked 0x%pa+0x%pa as scratch", &area->addr, &size);
> diff --git a/kernel/liveupdate/kexec_handover_debugfs.c b/kernel/liveupdate/kexec_handover_debugfs.c
> index 46e9e6c0791f..ac739d25094d 100644
> --- a/kernel/liveupdate/kexec_handover_debugfs.c
> +++ b/kernel/liveupdate/kexec_handover_debugfs.c
> @@ -150,8 +150,8 @@ __init void kho_in_debugfs_init(struct kho_debugfs *dbg, const void *fdt)
>   		err = __kho_debugfs_fdt_add(&dbg->fdt_list, sub_fdt_dir, name,
>   					    phys_to_virt(*fdt_phys));
>   		if (err) {
> -			pr_warn("failed to add fdt %s to debugfs: %d\n", name,
> -				err);
> +			pr_warn("failed to add fdt %s to debugfs: %pe\n", name,
> +				ERR_PTR(err));
>   			continue;
>   		}
>   	}
> @@ -168,8 +168,10 @@ __init void kho_in_debugfs_init(struct kho_debugfs *dbg, const void *fdt)
>   	 * reviving state from KHO and setting up KHO for the next
>   	 * kexec.
>   	 */
> -	if (err)
> -		pr_err("failed exposing handover FDT in debugfs: %d\n", err);
> +	if (err) {
> +		pr_err("failed exposing handover FDT in debugfs: %pe\n",
> +		       ERR_PTR(err));
> +	}
>   }
>   
>   __init int kho_out_debugfs_init(struct kho_debugfs *dbg)

-- 
Best Regards,
Yanjun.Zhu