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Date: Fri, 12 Apr 2024 13:22:43 -0400
From: Steven Rostedt <rostedt@goodmis.org>
To: "Guilherme G. Piccoli" <gpiccoli@igalia.com>
Cc: "Luck, Tony" <tony.luck@intel.com>, Kees Cook <keescook@chromium.org>,
 Joel Fernandes <joel@joelfernandes.org>, "linux-kernel@vger.kernel.org"
 <linux-kernel@vger.kernel.org>, "linux-trace-kernel@vger.kernel.org"
 <linux-trace-kernel@vger.kernel.org>, Masami Hiramatsu
 <mhiramat@kernel.org>, Mark Rutland <mark.rutland@arm.com>, Mathieu
 Desnoyers <mathieu.desnoyers@efficios.com>, Andrew Morton
 <akpm@linux-foundation.org>, "Liam R. Howlett" <Liam.Howlett@oracle.com>,
 Vlastimil Babka <vbabka@suse.cz>, Lorenzo Stoakes <lstoakes@gmail.com>,
 "linux-mm@kvack.org" <linux-mm@kvack.org>, Thomas Gleixner
 <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>, Borislav Petkov
 <bp@alien8.de>, Dave Hansen <dave.hansen@linux.intel.com>, "x86@kernel.org"
 <x86@kernel.org>, "H. Peter Anvin" <hpa@zytor.com>, Peter Zijlstra
 <peterz@infradead.org>, "linux-hardening@vger.kernel.org"
 <linux-hardening@vger.kernel.org>, Guenter Roeck <linux@roeck-us.net>, Ross
 Zwisler <zwisler@google.com>, "wklin@google.com" <wklin@google.com>,
 Vineeth Remanan Pillai <vineeth@bitbyteword.org>, Suleiman Souhlal
 <suleiman@google.com>, Linus Torvalds <torvalds@linuxfoundation.org>,
 Catalin Marinas <catalin.marinas@arm.com>, Will Deacon <will@kernel.org>
Subject: Re: [POC][RFC][PATCH 0/2] pstore/mm/x86: Add wildcard memmap to map
 pstore consistently
Message-ID: <20240412132243.053ad096@gandalf.local.home>
In-Reply-To: <fa5fa4c6-2b02-f47e-b9ba-65cfd85f57f8@igalia.com>
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	<3391c693-cf54-526b-79a8-d565e7140947@igalia.com>
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On Fri, 12 Apr 2024 09:17:18 -0300
"Guilherme G. Piccoli" <gpiccoli@igalia.com> wrote:

> Thanks Steve, seems a good idea. With that, I could test on kdumpst (the
> tool used on Steam Deck), since it relies on modular pstore/ram.

Something like this could work.

-- Steve

diff --git a/arch/x86/kernel/e820.c b/arch/x86/kernel/e820.c
index a8831ef30c73..878aee8b2399 100644
--- a/arch/x86/kernel/e820.c
+++ b/arch/x86/kernel/e820.c
@@ -16,6 +16,7 @@
 #include <linux/firmware-map.h>
 #include <linux/sort.h>
 #include <linux/memory_hotplug.h>
+#include <linux/mm.h>
 
 #include <asm/e820/api.h>
 #include <asm/setup.h>
@@ -64,61 +65,6 @@ struct e820_table *e820_table __refdata			= &e820_table_init;
 struct e820_table *e820_table_kexec __refdata		= &e820_table_kexec_init;
 struct e820_table *e820_table_firmware __refdata	= &e820_table_firmware_init;
 
-/* For wildcard memory requests, have a table to find them later */
-#define E820_MAX_MAPS		8
-#define E820_MAP_NAME_SIZE	16
-struct e820_mmap_map {
-	char			name[E820_MAP_NAME_SIZE];
-	u64			start;
-	u64			size;
-};
-static struct e820_mmap_map e820_mmap_list[E820_MAX_MAPS] __initdata;
-static int e820_mmap_size				__initdata;
-
-/* Add wildcard region with a lookup name */
-static int __init e820_add_mmap(u64 start, u64 size, const char *name)
-{
-	struct e820_mmap_map *map;
-
-	if (!name || !name[0] || strlen(name) >= E820_MAP_NAME_SIZE)
-		return -EINVAL;
-
-	if (e820_mmap_size >= E820_MAX_MAPS)
-		return -1;
-
-	map = &e820_mmap_list[e820_mmap_size++];
-	map->start = start;
-	map->size = size;
-	strcpy(map->name, name);
-	return 0;
-}
-
-/**
- * memmap_named - Find a wildcard region with a given name
- * @name: The name that is attached to a wildcard region
- * @start: If found, holds the start address
- * @size: If found, holds the size of the address.
- *
- * Returns: 1 if found or 0 if not found.
- */
-int __init memmap_named(const char *name, u64 *start, u64 *size)
-{
-	struct e820_mmap_map *map;
-	int i;
-
-	for (i = 0; i < e820_mmap_size; i++) {
-		map = &e820_mmap_list[i];
-		if (!map->size)
-			continue;
-		if (strcmp(name, map->name) == 0) {
-			*start = map->start;
-			*size = map->size;
-			return 1;
-		}
-	}
-	return 0;
-}
-
 /* For PCI or other memory-mapped resources */
 unsigned long pci_mem_start = 0xaeedbabe;
 #ifdef CONFIG_PCI
@@ -1024,6 +970,8 @@ static int __init parse_memmap_one(char *p)
 		e820__range_add(start_at, mem_size, E820_TYPE_RESERVED);
 	} else if (*p == '*') {
 		u64 align;
+		int ret;
+
 		/* Followed by alignment and ':' then the name */
 		align = memparse(p+1, &p);
 		start_at = e820__region(mem_size, align);
@@ -1032,9 +980,10 @@ static int __init parse_memmap_one(char *p)
 		if (*p != ':')
 			return -EINVAL;
 		p++;
-		e820_add_mmap(start_at, mem_size, p);
+		ret = memmap_add(start_at, mem_size, p);
 		p += strlen(p);
-		e820__range_add(start_at, mem_size, E820_TYPE_RESERVED);
+		if (!ret)
+			e820__range_add(start_at, mem_size, E820_TYPE_RESERVED);
 	} else if (*p == '!') {
 		start_at = memparse(p+1, &p);
 		e820__range_add(start_at, mem_size, E820_TYPE_PRAM);
diff --git a/fs/pstore/ram.c b/fs/pstore/ram.c
index c200388399fb..22d2e2731dc2 100644
--- a/fs/pstore/ram.c
+++ b/fs/pstore/ram.c
@@ -919,7 +919,6 @@ static void __init ramoops_register_dummy(void)
 {
 	struct ramoops_platform_data pdata;
 
-#ifndef MODULE
 	/* Only allowed when builtin */
 	if (mem_name) {
 		u64 start;
@@ -930,7 +929,6 @@ static void __init ramoops_register_dummy(void)
 			mem_size = size;
 		}
 	}
-#endif
 
 	/*
 	 * Prepare a dummy platform data structure to carry the module
diff --git a/include/linux/mm.h b/include/linux/mm.h
index cf9b34454c6f..6ce1c6929d1f 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -4203,5 +4203,6 @@ static inline bool pfn_is_unaccepted_memory(unsigned long pfn)
 }
 
 int memmap_named(const char *name, u64 *start, u64 *size);
+int memmap_add(long start, long size, const char *name);
 
 #endif /* _LINUX_MM_H */
diff --git a/mm/memory.c b/mm/memory.c
index 7a29f17df7c1..fe054e1bb678 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -120,12 +120,6 @@ static bool vmf_orig_pte_uffd_wp(struct vm_fault *vmf)
 	return pte_marker_uffd_wp(vmf->orig_pte);
 }
 
-int __init __weak memmap_named(const char *name, u64 *start, u64 *size)
-{
-	pr_info("Kernel command line: memmap=nn*align:name not supported on this kernel");
-	/* zero means not found */
-	return 0;
-}
 
 /*
  * A number of key systems in x86 including ioremap() rely on the assumption
diff --git a/mm/mm_init.c b/mm/mm_init.c
index 549e76af8f82..e5b729b83fdc 100644
--- a/mm/mm_init.c
+++ b/mm/mm_init.c
@@ -154,6 +154,77 @@ static __init int set_mminit_loglevel(char *str)
 early_param("mminit_loglevel", set_mminit_loglevel);
 #endif /* CONFIG_DEBUG_MEMORY_INIT */
 
+/* For wildcard memory requests, have a table to find them later */
+#define MAX_MAPS		8
+#define MAP_NAME_SIZE	16
+struct mmap_map {
+	char			name[MAP_NAME_SIZE];
+	long			start;
+	long			size;
+};
+static struct mmap_map early_mmap_list[MAX_MAPS] __initdata;
+static int early_mmap_size			__initdata;
+static struct mmap_map *mmap_list;
+
+/* Add wildcard region with a lookup name */
+int memmap_add(long start, long size, const char *name)
+{
+	struct mmap_map *map;
+
+	if (!name || !name[0] || strlen(name) >= MAP_NAME_SIZE)
+		return -EINVAL;
+
+	if (early_mmap_size >= MAX_MAPS)
+		return -1;
+
+	map = &early_mmap_list[early_mmap_size++];
+	map->start = start;
+	map->size = size;
+	strcpy(map->name, name);
+	return 0;
+}
+
+static void __init memmap_copy(void)
+{
+	if (!early_mmap_size)
+		return;
+
+	mmap_list = kcalloc(early_mmap_size + 1, sizeof(mmap_list), GFP_KERNEL);
+	if (!mmap_list)
+		return;
+
+	for (int i = 0; i < early_mmap_size; i++)
+		mmap_list[i] = early_mmap_list[i];
+}
+
+/**
+ * memmap_named - Find a wildcard region with a given name
+ * @name: The name that is attached to a wildcard region
+ * @start: If found, holds the start address
+ * @size: If found, holds the size of the address.
+ *
+ * Returns: 1 if found or 0 if not found.
+ */
+int memmap_named(const char *name, u64 *start, u64 *size)
+{
+	struct mmap_map *map;
+
+	if (!mmap_list)
+		return 0;
+
+	for (int i = 0; mmap_list[i].name[0]; i++) {
+		map = &mmap_list[i];
+		if (!map->size)
+			continue;
+		if (strcmp(name, map->name) == 0) {
+			*start = map->start;
+			*size = map->size;
+			return 1;
+		}
+	}
+	return 0;
+}
+
 struct kobject *mm_kobj;
 
 #ifdef CONFIG_SMP
@@ -2793,4 +2864,5 @@ void __init mm_core_init(void)
 	pti_init();
 	kmsan_init_runtime();
 	mm_cache_init();
+	memmap_copy();
 }