linux-hardening - [PATCH v3 16/18] firmware: scm: Modify only the download bits in TCSR register

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Message-ID: <1683133352-10046-17-git-send-email-quic_mojha@quicinc.com>
Date:   Wed, 3 May 2023 22:32:30 +0530
From:   Mukesh Ojha <quic_mojha@...cinc.com>
To:     <agross@...nel.org>, <andersson@...nel.org>,
        <konrad.dybcio@...aro.org>, <corbet@....net>,
        <keescook@...omium.org>, <tony.luck@...el.com>,
        <gpiccoli@...lia.com>, <catalin.marinas@....com>,
        <will@...nel.org>, <krzysztof.kozlowski+dt@...aro.org>,
        <robh+dt@...nel.org>, <linus.walleij@...aro.org>,
        <linux-gpio@...r.kernel.org>, <srinivas.kandagatla@...aro.org>
CC:     <linux-arm-msm@...r.kernel.org>,
        <linux-remoteproc@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-hardening@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-doc@...r.kernel.org>,
        "Mukesh Ojha" <quic_mojha@...cinc.com>,
        Poovendhan Selvaraj <quic_poovendh@...cinc.com>
Subject: [PATCH v3 16/18] firmware: scm: Modify only the download bits in TCSR register

CrashDump collection is based on the DLOAD bit of TCSR register.
To retain other bits, we read the register and modify only the
DLOAD bit as the other bits have their own significance.

Signed-off-by: Poovendhan Selvaraj <quic_poovendh@...cinc.com>
Signed-off-by: Mukesh Ojha <quic_mojha@...cinc.com>
---
 drivers/firmware/qcom_scm.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/firmware/qcom_scm.c b/drivers/firmware/qcom_scm.c
index 003cbcb..775ac68 100644
--- a/drivers/firmware/qcom_scm.c
+++ b/drivers/firmware/qcom_scm.c
@@ -30,6 +30,9 @@ module_param(download_mode, bool, 0);
 #define SCM_HAS_IFACE_CLK	BIT(1)
 #define SCM_HAS_BUS_CLK		BIT(2)
 
+#define QCOM_DOWNLOAD_MODE_MASK 0x30
+#define QCOM_DOWNLOAD_FULLDUMP	0x1
+
 struct qcom_scm {
 	struct device *dev;
 	struct clk *core_clk;
@@ -448,8 +451,9 @@ static void qcom_scm_set_download_mode(bool enable)
 	if (avail) {
 		ret = __qcom_scm_set_dload_mode(__scm->dev, enable);
 	} else if (__scm->dload_mode_addr) {
-		ret = qcom_scm_io_writel(__scm->dload_mode_addr,
-				enable ? QCOM_SCM_BOOT_SET_DLOAD_MODE : 0);
+		ret = qcom_scm_io_update_field(__scm->dload_mode_addr,
+				QCOM_DOWNLOAD_MODE_MASK,
+				enable ? QCOM_DOWNLOAD_FULLDUMP : 0);
 	} else {
 		dev_err(__scm->dev,
 			"No available mechanism for setting download mode\n");
-- 
2.7.4