linux-kernel - [PATCH v2 3/3] x86: call instrumentation hooks from copy

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Date: Wed, 20 Mar 2024 11:18:51 +0100
From: Alexander Potapenko <glider@...gle.com>
To: glider@...gle.com, akpm@...ux-foundation.org
Cc: linux-kernel@...r.kernel.org, linux-mm@...ck.org, 
	kasan-dev@...glegroups.com, tglx@...utronix.de, x86@...nel.org, 
	Linus Torvalds <torvalds@...ux-foundation.org>, Dmitry Vyukov <dvyukov@...gle.com>, 
	Marco Elver <elver@...gle.com>, Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
Subject: [PATCH v2 3/3] x86: call instrumentation hooks from copy_mc.c

Memory accesses in copy_mc_to_kernel() and copy_mc_to_user() are performed
by assembly routines and are invisible to KASAN, KCSAN, and KMSAN.
Add hooks from instrumentation.h to tell the tools these functions have
memcpy/copy_from_user semantics.

The call to copy_mc_fragile() in copy_mc_fragile_handle_tail() is left
intact, because the latter is only called from the assembly implementation
of copy_mc_fragile(), so the memory accesses in it are covered by the
instrumentation in copy_mc_to_kernel() and copy_mc_to_user().

Link: https://lore.kernel.org/all/3b7dbd88-0861-4638-b2d2-911c97a4cadf@I-love.SAKURA.ne.jp/
Suggested-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Alexander Potapenko <glider@...gle.com>
Cc: Dmitry Vyukov <dvyukov@...gle.com>
Cc: Marco Elver <elver@...gle.com>
Cc: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>

---
v2:
 - as requested by Linus Torvalds, move the instrumentation outside the
   uaccess section
---
 arch/x86/lib/copy_mc.c | 21 +++++++++++++++++----
 1 file changed, 17 insertions(+), 4 deletions(-)

diff --git a/arch/x86/lib/copy_mc.c b/arch/x86/lib/copy_mc.c
index 6e8b7e600def5..97e88e58567bf 100644
--- a/arch/x86/lib/copy_mc.c
+++ b/arch/x86/lib/copy_mc.c
@@ -4,6 +4,7 @@
 #include <linux/jump_label.h>
 #include <linux/uaccess.h>
 #include <linux/export.h>
+#include <linux/instrumented.h>
 #include <linux/string.h>
 #include <linux/types.h>
 
@@ -61,10 +62,20 @@ unsigned long copy_mc_enhanced_fast_string(void *dst, const void *src, unsigned
  */
 unsigned long __must_check copy_mc_to_kernel(void *dst, const void *src, unsigned len)
 {
-	if (copy_mc_fragile_enabled)
-		return copy_mc_fragile(dst, src, len);
-	if (static_cpu_has(X86_FEATURE_ERMS))
-		return copy_mc_enhanced_fast_string(dst, src, len);
+	unsigned long ret;
+
+	if (copy_mc_fragile_enabled) {
+		instrument_memcpy_before(dst, src, len);
+		ret = copy_mc_fragile(dst, src, len);
+		instrument_memcpy_after(dst, src, len, ret);
+		return ret;
+	}
+	if (static_cpu_has(X86_FEATURE_ERMS)) {
+		instrument_memcpy_before(dst, src, len);
+		ret = copy_mc_enhanced_fast_string(dst, src, len);
+		instrument_memcpy_after(dst, src, len, ret);
+		return ret;
+	}
 	memcpy(dst, src, len);
 	return 0;
 }
@@ -75,6 +86,7 @@ unsigned long __must_check copy_mc_to_user(void __user *dst, const void *src, un
 	unsigned long ret;
 
 	if (copy_mc_fragile_enabled) {
+		instrument_copy_to_user(dst, src, len);
 		__uaccess_begin();
 		ret = copy_mc_fragile((__force void *)dst, src, len);
 		__uaccess_end();
@@ -82,6 +94,7 @@ unsigned long __must_check copy_mc_to_user(void __user *dst, const void *src, un
 	}
 
 	if (static_cpu_has(X86_FEATURE_ERMS)) {
+		instrument_copy_to_user(dst, src, len);
 		__uaccess_begin();
 		ret = copy_mc_enhanced_fast_string((__force void *)dst, src, len);
 		__uaccess_end();
-- 
2.44.0.291.gc1ea87d7ee-goog