linux-hardening - [POC][RFC][PATCH 2/2] pstore/ramoops: Add ramoops.mem

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Date: Tue, 09 Apr 2024 17:02:56 -0400
From: Steven Rostedt <rostedt@...dmis.org>
To: linux-kernel@...r.kernel.org,
 linux-trace-kernel@...r.kernel.org
Cc: Masami Hiramatsu <mhiramat@...nel.org>,
 Mark Rutland <mark.rutland@....com>,
 Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
 Andrew Morton <akpm@...ux-foundation.org>,
 "Liam R. Howlett" <Liam.Howlett@...cle.com>,
 Vlastimil Babka <vbabka@...e.cz>,
 Lorenzo Stoakes <lstoakes@...il.com>,
 linux-mm@...ck.org,
 Thomas Gleixner <tglx@...utronix.de>,
 Ingo Molnar <mingo@...hat.com>,
 Borislav Petkov <bp@...en8.de>,
 Dave Hansen <dave.hansen@...ux.intel.com>,
 x86@...nel.org,
 "H. Peter Anvin" <hpa@...or.com>,
 Peter Zijlstra <peterz@...radead.org>,
 Kees Cook <keescook@...omium.org>,
 Tony Luck <tony.luck@...el.com>,
 "Guilherme G. Piccoli" <gpiccoli@...lia.com>,
 linux-hardening@...r.kernel.org,
 Guenter Roeck <linux@...ck-us.net>,
 Ross Zwisler <zwisler@...gle.com>,
 wklin@...gle.com,
 Vineeth Remanan Pillai <vineeth@...byteword.org>,
 Joel Fernandes <joel@...lfernandes.org>,
 Suleiman Souhlal <suleiman@...gle.com>,
 Linus Torvalds <torvalds@...uxfoundation.org>,
 Catalin Marinas <catalin.marinas@....com>,
 Will Deacon <will@...nel.org>
Subject: [POC][RFC][PATCH 2/2] pstore/ramoops: Add ramoops.mem_name= command line option

From: "Steven Rostedt (Google)" <rostedt@...dmis.org>

Add a method to find a region specified by memmap=nn*align:name for
ramoops. Adding a kernel command line parameter:

  memmap=12M*4096:oops ramoops.mem_name=oops

Will use the size and location defined by the memmap parameter where it
finds the memory and labels it "oops". The "oops" in the ramoops option
is used to search for it.

This allows for arbitrary RAM to be used for ramoops if it is known that
the memory is not cleared on kernel crashes or soft reboots.

Signed-off-by: Steven Rostedt (Google) <rostedt@...dmis.org>
---
 fs/pstore/ram.c | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/fs/pstore/ram.c b/fs/pstore/ram.c
index b1a455f42e93..c200388399fb 100644
--- a/fs/pstore/ram.c
+++ b/fs/pstore/ram.c
@@ -50,6 +50,11 @@ module_param_hw(mem_address, ullong, other, 0400);
 MODULE_PARM_DESC(mem_address,
 		"start of reserved RAM used to store oops/panic logs");

+static char *mem_name;
+module_param_named(mem_name, mem_name, charp, 0400);
+MODULE_PARM_DESC(mem_name,
+		"name of kernel param that holds addr (builtin only)");
+
 static ulong mem_size;
 module_param(mem_size, ulong, 0400);
 MODULE_PARM_DESC(mem_size,
@@ -914,6 +919,19 @@ static void __init ramoops_register_dummy(void)
 {
 	struct ramoops_platform_data pdata;

+#ifndef MODULE
+	/* Only allowed when builtin */
+	if (mem_name) {
+		u64 start;
+		u64 size;
+
+		if (memmap_named(mem_name, &start, &size)) {
+			mem_address = start;
+			mem_size = size;
+		}
+	}
+#endif
+
 	/*
 	 * Prepare a dummy platform data structure to carry the module
 	 * parameters. If mem_size isn't set, then there are no module
-- 
2.43.0