[PATCH] ptp_qoriq: fix overflow in ptp_qoriq_adjfine() u64 calcalation

Current calculation for diff of TMR_ADD register value may have
64-bit overflow in this code line, when long type scaled_ppm is
large.

adj *= scaled_ppm;

This patch is to resolve it by using mul_u64_u64_div_u64().

Signed-off-by: Yangbo Lu <yangbo.lu@nxp.com>
---
 drivers/ptp/ptp_qoriq.c | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/drivers/ptp/ptp_qoriq.c b/drivers/ptp/ptp_qoriq.c
index 68beb1bd07c0..f7f220700cb5 100644
--- a/drivers/ptp/ptp_qoriq.c
+++ b/drivers/ptp/ptp_qoriq.c

@@ -189,15 +189,16 @@ int ptp_qoriq_adjfine(struct ptp_clock_info *ptp, long scaled_ppm)
 	tmr_add = ptp_qoriq->tmr_add;
 	adj = tmr_add;
 
-	/* calculate diff as adj*(scaled_ppm/65536)/1000000
-	 * and round() to the nearest integer
+	/*
+	 * Calculate diff and round() to the nearest integer
+	 *
+	 * diff = adj * (ppb / 1000000000)
+	 *      = adj * scaled_ppm / 65536000000
 	 */
-	adj *= scaled_ppm;
-	diff = div_u64(adj, 8000000);
-	diff = (diff >> 13) + ((diff >> 12) & 1);
+	diff = mul_u64_u64_div_u64(adj, scaled_ppm, 32768000000);
+	diff = DIV64_U64_ROUND_UP(diff, 2);
 
 	tmr_add = neg_adj ? tmr_add - diff : tmr_add + diff;
-
 	ptp_qoriq->write(&regs->ctrl_regs->tmr_add, tmr_add);
 
 	return 0;

-- 
2.25.1

Hello:

This patch was applied to netdev/net.git (refs/heads/master):

On Tue, 23 Mar 2021 16:02:29 +0800 you wrote:

Current calculation for diff of TMR_ADD register value may have
64-bit overflow in this code line, when long type scaled_ppm is
large.

adj *= scaled_ppm;

This patch is to resolve it by using mul_u64_u64_div_u64().

[...]

Here is the summary with links:
  - ptp_qoriq: fix overflow in ptp_qoriq_adjfine() u64 calcalation
    https://git.kernel.org/netdev/net/c/f51d7bf1dbe5

You are awesome, thank you!
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On Tue, Mar 23, 2021 at 04:02:29PM +0800, Yangbo Lu wrote:

Current calculation for diff of TMR_ADD register value may have
64-bit overflow in this code line, when long type scaled_ppm is
large.

adj *= scaled_ppm;

This patch is to resolve it by using mul_u64_u64_div_u64().

Signed-off-by: Yangbo Lu <yangbo.lu@nxp.com>

Acked-by: Richard Cochran <richardcochran@gmail.com>

On Tue, Mar 23, 2021 at 04:02:29PM +0800, Yangbo Lu wrote:

mul_u64_u64_div_u64() is not exported. As result, every build with
CONFIG_PTP_1588_CLOCK_QORIQ=m (ie every allmodconfig build) fails with:

ERROR: modpost: "mul_u64_u64_div_u64" [drivers/ptp/ptp-qoriq.ko] undefined!

or a similar error.

Guenter

On Thu, Mar 25, 2021 at 03:23:07AM -0700, Guenter Roeck wrote:

On Tue, Mar 23, 2021 at 04:02:29PM +0800, Yangbo Lu wrote:

quoted

Current calculation for diff of TMR_ADD register value may have
64-bit overflow in this code line, when long type scaled_ppm is
large.

adj *= scaled_ppm;

This patch is to resolve it by using mul_u64_u64_div_u64().

Signed-off-by: Yangbo Lu <yangbo.lu@nxp.com>
Acked-by: Richard Cochran <richardcochran@gmail.com>
---
 drivers/ptp/ptp_qoriq.c | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/drivers/ptp/ptp_qoriq.c b/drivers/ptp/ptp_qoriq.c
index 68beb1bd07c0..f7f220700cb5 100644
--- a/drivers/ptp/ptp_qoriq.c
+++ b/drivers/ptp/ptp_qoriq.c

@@ -189,15 +189,16 @@ int ptp_qoriq_adjfine(struct ptp_clock_info *ptp, long scaled_ppm)
 	tmr_add = ptp_qoriq->tmr_add;
 	adj = tmr_add;
 
-	/* calculate diff as adj*(scaled_ppm/65536)/1000000
-	 * and round() to the nearest integer
+	/*
+	 * Calculate diff and round() to the nearest integer
+	 *
+	 * diff = adj * (ppb / 1000000000)
+	 *      = adj * scaled_ppm / 65536000000
 	 */
-	adj *= scaled_ppm;
-	diff = div_u64(adj, 8000000);
-	diff = (diff >> 13) + ((diff >> 12) & 1);
+	diff = mul_u64_u64_div_u64(adj, scaled_ppm, 32768000000);

mul_u64_u64_div_u64() is not exported. As result, every build with
CONFIG_PTP_1588_CLOCK_QORIQ=m (ie every allmodconfig build) fails with:

ERROR: modpost: "mul_u64_u64_div_u64" [drivers/ptp/ptp-qoriq.ko] undefined!

or a similar error.

Ah, never mind. I see this is fixed in mainline (export added).
I see the problem in pending-fixes and in next-20210325.

Sorry for the noise.

Guenter

FYI,

On Tue, 23 Mar 2021 at 13:26, Yangbo Lu [off-list ref] wrote:

While building Linux next 20210325 tag for powerpc architecture ppc6xx_defconfig
failed due to following warnings / errors.

 - powerpc (ppc6xx_defconfig) with gcc-8
 - powerpc (ppc6xx_defconfig) with gcc-9
 - powerpc (ppc6xx_defconfig) with gcc-10

make --silent --keep-going --jobs=8
O=/home/tuxbuild/.cache/tuxmake/builds/1/tmp ARCH=powerpc
CROSS_COMPILE=powerpc64le-linux-gnu- 'CC=sccache
powerpc64le-linux-gnu-gcc' 'HOSTCC=sccache gcc'

INFO: Uncompressed kernel (size 0xd985ec) overlaps the address of the
wrapper(0x400000)
INFO: Fixing the link_address of wrapper to (0xe00000)
INFO: Uncompressed kernel (size 0xd985ec) overlaps the address of the
wrapper(0x400000)
INFO: Fixing the link_address of wrapper to (0xe00000)
INFO: Uncompressed kernel (size 0xd985ec) overlaps the address of the
wrapper(0x400000)
INFO: Fixing the link_address of wrapper to (0xe00000)
ERROR: modpost: "mul_u64_u64_div_u64" [drivers/ptp/ptp-qoriq.ko] undefined!

Reported-by: Naresh Kamboju <redacted>

Steps to reproduce:
-------------------
# TuxMake is a command line tool and Python library that provides
# portable and repeatable Linux kernel builds across a variety of
# architectures, toolchains, kernel configurations, and make targets.
#
# TuxMake supports the concept of runtimes.
# See https://docs.tuxmake.org/runtimes/, for that to work it requires
# that you install podman or docker on your system.
#
# To install tuxmake on your system globally:
# sudo pip3 install -U tuxmake
#
# See https://docs.tuxmake.org/ for complete documentation.


tuxmake --runtime podman --target-arch powerpc --toolchain gcc-8
--kconfig ppc6xx_defconfig

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From: Guenter Roeck <linux@roeck-us.net>
Date: Thu, 25 Mar 2021 03:23:07 -0700

mul_u64_u64_div_u64() is not exported. As result, every build with
CONFIG_PTP_1588_CLOCK_QORIQ=m (ie every allmodconfig build) fails with:

ERROR: modpost: "mul_u64_u64_div_u64" [drivers/ptp/ptp-qoriq.ko] undefined!

or a similar error.

I fixed this with a follow-up commit to export the symbol.