linux-kernel - [RFC][PATCH v2 20/29] printk: Register information into Kmemdump

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Message-ID: <20250724135512.518487-21-eugen.hristev@linaro.org>
Date: Thu, 24 Jul 2025 16:55:03 +0300
From: Eugen Hristev <eugen.hristev@...aro.org>
To: linux-kernel@...r.kernel.org,
	linux-arm-msm@...r.kernel.org,
	linux-arch@...r.kernel.org,
	linux-mm@...ck.org,
	tglx@...utronix.de,
	andersson@...nel.org,
	pmladek@...e.com
Cc: linux-arm-kernel@...ts.infradead.org,
	linux-hardening@...r.kernel.org,
	eugen.hristev@...aro.org,
	corbet@....net,
	mojha@....qualcomm.com,
	rostedt@...dmis.org,
	jonechou@...gle.com,
	tudor.ambarus@...aro.org
Subject: [RFC][PATCH v2 20/29] printk: Register information into Kmemdump

Annotate vital static information into kmemdump:
 - prb_descs
 - prb_infos
 - prb
 - prb_data
 - printk_rb_static
 - printk_rb_dynamic

Information on these variables is stored into dedicated kmemdump section.

Register dynamic information into kmemdump:
 - new_descs
 - new_infos
 - new_log_buf
In the case when the log buffer is dynamically replaced by a runtime
allocated version, call kmemdump to register the data with a replace
flag to remove the old registered data.

Signed-off-by: Eugen Hristev <eugen.hristev@...aro.org>
---
 kernel/printk/printk.c | 28 +++++++++++++++++++++++-----
 1 file changed, 23 insertions(+), 5 deletions(-)

diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 0efbcdda9aab..f7d60dbe5e5a 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -48,6 +48,7 @@
 #include <linux/sched/clock.h>
 #include <linux/sched/debug.h>
 #include <linux/sched/task_stack.h>
+#include <linux/kmemdump.h>
 
 #include <linux/uaccess.h>
 #include <asm/sections.h>
@@ -540,10 +541,16 @@ static u32 log_buf_len = __LOG_BUF_LEN;
 #endif
 _DEFINE_PRINTKRB(printk_rb_static, CONFIG_LOG_BUF_SHIFT - PRB_AVGBITS,
 		 PRB_AVGBITS, &__log_buf[0]);
+KMEMDUMP_VAR_CORE_NAMED(prb_descs, _printk_rb_static_descs, sizeof(_printk_rb_static_descs));
+KMEMDUMP_VAR_CORE_NAMED(prb_infos, _printk_rb_static_infos, sizeof(_printk_rb_static_infos));
+KMEMDUMP_VAR_CORE_NAMED(prb_data, __log_buf,  __LOG_BUF_LEN);
+KMEMDUMP_VAR_CORE(printk_rb_static, sizeof(printk_rb_static));
 
 static struct printk_ringbuffer printk_rb_dynamic;
+KMEMDUMP_VAR_CORE(printk_rb_dynamic, sizeof(printk_rb_dynamic));
 
 struct printk_ringbuffer *prb = &printk_rb_static;
+KMEMDUMP_VAR_CORE(prb, sizeof(prb));
 
 /*
  * We cannot access per-CPU data (e.g. per-CPU flush irq_work) before
@@ -1211,7 +1218,10 @@ void __init setup_log_buf(int early)
 		goto out;
 	}
 
-	new_log_buf = memblock_alloc(new_log_buf_len, LOG_ALIGN);
+	new_log_buf = kmemdump_alloc_id_size_replace(KMEMDUMP_ID_COREIMAGE_prb_data,
+						     new_log_buf_len,
+						     memblock_alloc,
+						     new_log_buf_len, LOG_ALIGN);
 	if (unlikely(!new_log_buf)) {
 		pr_err("log_buf_len: %lu text bytes not available\n",
 		       new_log_buf_len);
@@ -1219,7 +1229,10 @@ void __init setup_log_buf(int early)
 	}
 
 	new_descs_size = new_descs_count * sizeof(struct prb_desc);
-	new_descs = memblock_alloc(new_descs_size, LOG_ALIGN);
+	new_descs = kmemdump_alloc_id_size_replace(KMEMDUMP_ID_COREIMAGE_prb_descs,
+						   new_descs_size, memblock_alloc,
+						   new_descs_size, LOG_ALIGN);
+
 	if (unlikely(!new_descs)) {
 		pr_err("log_buf_len: %zu desc bytes not available\n",
 		       new_descs_size);
@@ -1227,7 +1240,10 @@ void __init setup_log_buf(int early)
 	}
 
 	new_infos_size = new_descs_count * sizeof(struct printk_info);
-	new_infos = memblock_alloc(new_infos_size, LOG_ALIGN);
+	new_infos = kmemdump_alloc_id_size_replace(KMEMDUMP_ID_COREIMAGE_prb_infos,
+						   new_infos_size, memblock_alloc,
+						   new_infos_size, LOG_ALIGN);
+
 	if (unlikely(!new_infos)) {
 		pr_err("log_buf_len: %zu info bytes not available\n",
 		       new_infos_size);
@@ -1284,9 +1300,11 @@ void __init setup_log_buf(int early)
 	return;
 
 err_free_descs:
-	memblock_free(new_descs, new_descs_size);
+	kmemdump_free_id(KMEMDUMP_ID_COREIMAGE_prb_descs,
+			 memblock_free, new_descs, new_descs_size);
 err_free_log_buf:
-	memblock_free(new_log_buf, new_log_buf_len);
+	kmemdump_free_id(KMEMDUMP_ID_COREIMAGE_prb_data,
+			 memblock_free, new_log_buf, new_log_buf_len);
 out:
 	print_log_buf_usage_stats();
 }
-- 
2.43.0