[v9] liveupdate: Rework KHO for in-kernel users

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

Posted by Pasha Tatashin 1 month, 2 weeks ago

From: Zhu Yanjun <yanjun.zhu@linux.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@linux.dev>
Co-developed-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Reviewed-by: Simon Horman <horms@kernel.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)
-- 
2.51.1.930.gacf6e81ea2-goog

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

Posted by Pratyush Yadav 1 month, 2 weeks ago

On Sat, Nov 01 2025, Pasha Tatashin wrote:

> From: Zhu Yanjun <yanjun.zhu@linux.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.

There is fdt_strerror() that does this for libfdt errnos. Something to
do in a follow up patch I suppose.

>
> Signed-off-by: Zhu Yanjun <yanjun.zhu@linux.dev>
> Co-developed-by: Pasha Tatashin <pasha.tatashin@soleen.com>
> Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
> Reviewed-by: Simon Horman <horms@kernel.org>

Reviewed-by: Pratyush Yadav <pratyush@kernel.org>

[...]

-- 
Regards,
Pratyush Yadav

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

Posted by Mike Rapoport 1 month, 2 weeks ago

On Sat, Nov 01, 2025 at 10:23:25AM -0400, Pasha Tatashin wrote:
> From: Zhu Yanjun <yanjun.zhu@linux.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@linux.dev>
> Co-developed-by: Pasha Tatashin <pasha.tatashin@soleen.com>
> Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
> Reviewed-by: Simon Horman <horms@kernel.org>

Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>

> ---
>  kernel/liveupdate/kexec_handover.c         |  4 ++--
>  kernel/liveupdate/kexec_handover_debugfs.c | 10 ++++++----
>  2 files changed, 8 insertions(+), 6 deletions(-)

-- 
Sincerely yours,
Mike.

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

Posted by Zhu Yanjun 1 month, 2 weeks ago

在 2025/11/1 7:23, Pasha Tatashin 写道:
> From: Zhu Yanjun <yanjun.zhu@linux.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@linux.dev>
> Co-developed-by: Pasha Tatashin <pasha.tatashin@soleen.com>
> Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>

Appreciate your help, Pasha

Yanjun.Zhu

> Reviewed-by: Simon Horman <horms@kernel.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

[PATCH v9 1/9] kho: make debugfs interface optional
[PATCH v9 2/9] kho: drop notifiers
[PATCH v9 3/9] kho: add interfaces to unpreserve folios, page ranges, and vmalloc
[PATCH v9 4/9] memblock: Unpreserve memory in case of error
[PATCH v9 5/9] test_kho: Unpreserve memory in case of error
[PATCH v9 6/9] kho: don't unpreserve memory during abort
[PATCH v9 7/9] liveupdate: kho: move to kernel/liveupdate
[PATCH v9 8/9] MAINTAINERS: update KHO maintainers
[PATCH v9 9/9] liveupdate: kho: Use %pe format specifier for error pointer printing