linux-kernel - [PATCH v6 15/37] lib: introduce early boot parameter to avoid page

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20240321163705.3067592-16-surenb@google.com>
Date: Thu, 21 Mar 2024 09:36:37 -0700
From: Suren Baghdasaryan <surenb@...gle.com>
To: akpm@...ux-foundation.org
Cc: kent.overstreet@...ux.dev, mhocko@...e.com, vbabka@...e.cz, 
	hannes@...xchg.org, roman.gushchin@...ux.dev, mgorman@...e.de, 
	dave@...olabs.net, willy@...radead.org, liam.howlett@...cle.com, 
	penguin-kernel@...ove.sakura.ne.jp, corbet@....net, void@...ifault.com, 
	peterz@...radead.org, juri.lelli@...hat.com, catalin.marinas@....com, 
	will@...nel.org, arnd@...db.de, tglx@...utronix.de, mingo@...hat.com, 
	dave.hansen@...ux.intel.com, x86@...nel.org, peterx@...hat.com, 
	david@...hat.com, axboe@...nel.dk, mcgrof@...nel.org, masahiroy@...nel.org, 
	nathan@...nel.org, dennis@...nel.org, jhubbard@...dia.com, tj@...nel.org, 
	muchun.song@...ux.dev, rppt@...nel.org, paulmck@...nel.org, 
	pasha.tatashin@...een.com, yosryahmed@...gle.com, yuzhao@...gle.com, 
	dhowells@...hat.com, hughd@...gle.com, andreyknvl@...il.com, 
	keescook@...omium.org, ndesaulniers@...gle.com, vvvvvv@...gle.com, 
	gregkh@...uxfoundation.org, ebiggers@...gle.com, ytcoode@...il.com, 
	vincent.guittot@...aro.org, dietmar.eggemann@....com, rostedt@...dmis.org, 
	bsegall@...gle.com, bristot@...hat.com, vschneid@...hat.com, cl@...ux.com, 
	penberg@...nel.org, iamjoonsoo.kim@....com, 42.hyeyoo@...il.com, 
	glider@...gle.com, elver@...gle.com, dvyukov@...gle.com, 
	songmuchun@...edance.com, jbaron@...mai.com, aliceryhl@...gle.com, 
	rientjes@...gle.com, minchan@...gle.com, kaleshsingh@...gle.com, 
	surenb@...gle.com, kernel-team@...roid.com, linux-doc@...r.kernel.org, 
	linux-kernel@...r.kernel.org, iommu@...ts.linux.dev, 
	linux-arch@...r.kernel.org, linux-fsdevel@...r.kernel.org, linux-mm@...ck.org, 
	linux-modules@...r.kernel.org, kasan-dev@...glegroups.com, 
	cgroups@...r.kernel.org
Subject: [PATCH v6 15/37] lib: introduce early boot parameter to avoid
 page_ext memory overhead

The highest memory overhead from memory allocation profiling comes from
page_ext objects. This overhead exists even if the feature is disabled
but compiled-in. To avoid it, introduce an early boot parameter that
prevents page_ext object creation. The new boot parameter is a tri-state
with possible values of 0|1|never. When it is set to "never" the
memory allocation profiling support is disabled, and overhead is minimized
(currently no page_ext objects are allocated, in the future more overhead
might be eliminated). As a result we also lose ability to enable memory
allocation profiling at runtime (because there is no space to store
alloctag references). Runtime sysctrl becomes read-only if the early boot
parameter was set to "never". Note that the default value of this boot
parameter depends on the CONFIG_MEM_ALLOC_PROFILING_ENABLED_BY_DEFAULT
configuration. When CONFIG_MEM_ALLOC_PROFILING_ENABLED_BY_DEFAULT=n
the boot parameter is set to "never", therefore eliminating any overhead.
CONFIG_MEM_ALLOC_PROFILING_ENABLED_BY_DEFAULT=y results in boot parameter
being set to 1 (enabled). This allows distributions to avoid any overhead
by setting CONFIG_MEM_ALLOC_PROFILING_ENABLED_BY_DEFAULT=n config and
with no changes to the kernel command line.
We reuse sysctl.vm.mem_profiling boot parameter name in order to avoid
introducing yet another control. This change turns it into a tri-state
early boot parameter.

Signed-off-by: Suren Baghdasaryan <surenb@...gle.com>
Reviewed-by: Vlastimil Babka <vbabka@...e.cz>
---
 lib/alloc_tag.c | 41 ++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 40 insertions(+), 1 deletion(-)

diff --git a/lib/alloc_tag.c b/lib/alloc_tag.c
index cb5adec4b2e2..617c2fbb6673 100644
--- a/lib/alloc_tag.c
+++ b/lib/alloc_tag.c
@@ -116,9 +116,46 @@ static bool alloc_tag_module_unload(struct codetag_type *cttype,
 	return module_unused;
 }
 
+#ifdef CONFIG_MEM_ALLOC_PROFILING_ENABLED_BY_DEFAULT
+static bool mem_profiling_support __meminitdata = true;
+#else
+static bool mem_profiling_support __meminitdata;
+#endif
+
+static int __init setup_early_mem_profiling(char *str)
+{
+	bool enable;
+
+	if (!str || !str[0])
+		return -EINVAL;
+
+	if (!strncmp(str, "never", 5)) {
+		enable = false;
+		mem_profiling_support = false;
+	} else {
+		int res;
+
+		res = kstrtobool(str, &enable);
+		if (res)
+			return res;
+
+		mem_profiling_support = true;
+	}
+
+	if (enable != static_key_enabled(&mem_alloc_profiling_key)) {
+		if (enable)
+			static_branch_enable(&mem_alloc_profiling_key);
+		else
+			static_branch_disable(&mem_alloc_profiling_key);
+	}
+
+	return 0;
+}
+early_param("sysctl.vm.mem_profiling", setup_early_mem_profiling);
+
 static __init bool need_page_alloc_tagging(void)
 {
-	return true;
+	return mem_profiling_support;
 }
 
 static __init void init_page_alloc_tagging(void)
@@ -158,6 +195,8 @@ static int __init alloc_tag_init(void)
 	if (IS_ERR_OR_NULL(alloc_tag_cttype))
 		return PTR_ERR(alloc_tag_cttype);
 
+	if (!mem_profiling_support)
+		memory_allocation_profiling_sysctls[0].mode = 0444;
 	register_sysctl_init("vm", memory_allocation_profiling_sysctls);
 	procfs_init();
 
-- 
2.44.0.291.gc1ea87d7ee-goog