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

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Message-ID: <20251101142325.1326536-10-pasha.tatashin@soleen.com>
Date: Sat,  1 Nov 2025 10:23:25 -0400
From: Pasha Tatashin <pasha.tatashin@...een.com>
To: 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,
	pasha.tatashin@...een.com,
	pratyush@...nel.org,
	rdunlap@...radead.org,
	rppt@...nel.org,
	tj@...nel.org,
	yanjun.zhu@...ux.dev
Subject: [PATCH v9 9/9] liveupdate: kho: Use %pe format specifier for error pointer printing

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>
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)
-- 
2.51.1.930.gacf6e81ea2-goog