linux-kernel - [PATCH v5] coccinelle: misc: Add field

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-next>] [day] [month] [year] [list]

Message-ID: <20250624-field_modify-v5-1-cd67127030e4@quicinc.com>
Date: Tue, 24 Jun 2025 18:26:59 +0800
From: Luo Jie <quic_luoj@...cinc.com>
To: Yury Norov <yury.norov@...il.com>,
        Rasmus Villemoes
	<linux@...musvillemoes.dk>,
        Julia Lawall <Julia.Lawall@...ia.fr>,
        "Nicolas
 Palix" <nicolas.palix@...g.fr>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>, Marc Zyngier <maz@...nel.org>,
        Oliver Upton
	<oliver.upton@...ux.dev>,
        Joey Gouly <joey.gouly@....com>,
        Suzuki K Poulose
	<suzuki.poulose@....com>,
        Zenghui Yu <yuzenghui@...wei.com>
CC: <linux-kernel@...r.kernel.org>, <cocci@...ia.fr>,
        <linux-arm-kernel@...ts.infradead.org>, <kvmarm@...ts.linux.dev>,
        <andrew@...n.ch>, <quic_kkumarcs@...cinc.com>,
        <quic_linchen@...cinc.com>, <quic_leiwei@...cinc.com>,
        <quic_suruchia@...cinc.com>, <quic_pavir@...cinc.com>,
        <Markus.Elfring@....de>, Luo Jie
	<quic_luoj@...cinc.com>
Subject: [PATCH v5] coccinelle: misc: Add field_modify script

Find and suggest conversions of opencoded field modify patterns with
the wrapper FIELD_MODIFY() API defined in include/linux/bitfield.h
for catching the possible parameter type error in the compile time.

Signed-off-by: Luo Jie <quic_luoj@...cinc.com>
---
Add the helper FIELD_MODIFY() to the FIELD_XXX family of bitfield
macros. It is functionally similar as xxx_replace_bits(), but adds
the compile time checking to catch incorrect parameter type errors.

This series also converts the four instances of opencoded FIELD_MODIFY()
that are found in the core kernel files, to instead use the new
FIELD_MODIFY() macro. This is achieved with Coccinelle, by adding
the script field_modify.cocci.

The changes are validated on IPQ9574 SoC which uses ARM64 architecture.
---
Changes in v5:
- Remove ARM64 patches based on the discussion in v3 and v4 versions of
  this series.
- Simplify the condition selections in coccinelle script.
- Link to v4: https://lore.kernel.org/r/20250612-field_modify-v4-0-ae4f74da45a6@quicinc.com

Changes in v4:
- Add org, report and context mode for coccinelle script.
- Fix other comments on coccinelle script patch.
- Remove the FIELD_MODIFY patch as it is merged.
- Link to v3: https://lore.kernel.org/r/20250417-field_modify-v3-0-6f7992aafcb7@quicinc.com

Changes in v3:
- Correct the order of header files included.
- Add the Coccinelle script field_modify.cocci..
- Convert the opencoded FIELD_MODIFY() variants inside arm64 directory,
  identified by field_modify.cocci.
- Link to v2: https://lore.kernel.org/all/20250410131048.2054791-1-quic_luoj@quicinc.com/

Changes in v2:
- Update the documented example for FIELD_MODIFY().
- Improve the commit message to describe the need for the change.
- Link to v1: https://lore.kernel.org/all/20250318071526.1836194-1-quic_luoj@quicinc.com/
---
 scripts/coccinelle/misc/field_modify.cocci | 60 ++++++++++++++++++++++++++++++
 1 file changed, 60 insertions(+)

diff --git a/scripts/coccinelle/misc/field_modify.cocci b/scripts/coccinelle/misc/field_modify.cocci
new file mode 100644
index 000000000000..7d4858c0a68d
--- /dev/null
+++ b/scripts/coccinelle/misc/field_modify.cocci
@@ -0,0 +1,60 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/// Replace below code with the wrapper FIELD_MODIFY(MASK, &reg, val)
+/// - reg &= ~MASK;
+/// - reg |= FIELD_PREP(MASK, val);
+//
+// Confidence: High
+// Author: Luo Jie <quic_luoj@...cinc.com>
+// Copyright: (C) 2025 Qualcomm Innovation Center, Inc.
+// Keywords: FIELD_PREP, FIELD_MODIFY
+// Options: --include-headers
+
+virtual context
+virtual patch
+virtual org
+virtual report
+
+@...ends on context@
+identifier reg, val;
+constant mask;
+symbol FIELD_PREP;
+@@
+
+*reg &= ~mask;
+*reg |= FIELD_PREP(mask, val);
+
+@...ends on patch@
+identifier reg, val;
+constant mask;
+symbol FIELD_PREP, FIELD_MODIFY;
+@@
+
+-reg &= ~mask;
+-reg |= FIELD_PREP(mask, val);
++FIELD_MODIFY(mask, &reg, val);
+
+@r depends on org || report@
+identifier reg, val;
+constant mask;
+symbol FIELD_PREP;
+position p;
+@@
+
+reg &= ~mask;
+reg |= FIELD_PREP@p(mask, val);
+
+@...ipt:python depends on report@
+p << r.p;
+x << r.reg;
+@@
+
+coccilib.report.print_report(p[0], "WARNING: Consider using FIELD_MODIFY helper on %s" % (x))
+
+@...ipt:python depends on org@
+p << r.p;
+x << r.reg;
+@@
+
+msg="WARNING: Consider using FIELD_MODIFY helper on %s" % (x)
+msg_safe=msg.replace("[","@(").replace("]",")")
+coccilib.org.print_todo(p[0], msg_safe)

---
base-commit: 0bb71d301869446810a0b13d3da290bd455d7c78
change-id: 20250612-field_modify-27139f673881

Best regards,
-- 
Luo Jie <quic_luoj@...cinc.com>