From 8708fd888f8a2bd3c68ccc059a579ba7ff41f79d Mon Sep 17 00:00:00 2001
From: Tomohiro Kusumi <kusumi.tomohiro@gmail.com>
Date: Sat, 25 May 2019 04:26:18 +0900
Subject: [PATCH] Linux 2.6.39 compat: Test if kstrtoul() exists

kstrtoul() exists only after torvalds/linux@33ee3b2e2eb9 in 2.6.39.
Use strict_strtoul() if kstrtoul() doesn't exist.
Note that strict_strtoul() has existed as an alias for kstrtoul()
for a while, but removed in torvalds/linux@3db2e9cdc085.

It looks like RHEL6 (2.6.32 based) has backported kstrtoul(),
and this caused build CI to pass compilation test.
It should fail on vanilla < 2.6.39 kernels or distro kernels without
backport as reported in #8760.

--
 # grep "kstrtoul(" /lib/modules/2.6.32-754.12.1.el6.x86_64/build/ \
 include/linux/kernel.h >/dev/null
 # echo $?
 0

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: loli10K <ezomori.nozomu@gmail.com>
Signed-off-by: Tomohiro Kusumi <kusumi.tomohiro@gmail.com>
Closes #8760
Closes #8761
---
 config/kernel-kstrtoul.m4 | 21 +++++++++++++++++++++
 config/kernel.m4          |  1 +
 include/spl/sys/strings.h |  4 ++++
 3 files changed, 26 insertions(+)
 create mode 100644 config/kernel-kstrtoul.m4

diff --git a/config/kernel-kstrtoul.m4 b/config/kernel-kstrtoul.m4
new file mode 100644
index 000000000..5530e0e2d
--- /dev/null
+++ b/config/kernel-kstrtoul.m4
@@ -0,0 +1,21 @@
+dnl #
+dnl # 2.6.39 API change
+dnl #
+dnl # 33ee3b2e2eb9 kstrto*: converting strings to integers done (hopefully) right
+dnl #
+dnl # If kstrtoul() doesn't exist, fallback to use strict_strtoul() which has
+dnl # existed since 2.6.25.
+dnl #
+AC_DEFUN([ZFS_AC_KERNEL_KSTRTOUL], [
+	AC_MSG_CHECKING([whether kstrtoul() exists])
+	ZFS_LINUX_TRY_COMPILE([
+		#include <linux/kernel.h>
+	],[
+		int ret __attribute__ ((unused)) = kstrtoul(NULL, 10, NULL);
+	],[
+		AC_MSG_RESULT(yes)
+		AC_DEFINE(HAVE_KSTRTOUL, 1, [kstrtoul() exists])
+	],[
+		AC_MSG_RESULT(no)
+	])
+])
diff --git a/config/kernel.m4 b/config/kernel.m4
index 54f39164b..6fd0ad5b9 100644
--- a/config/kernel.m4
+++ b/config/kernel.m4
@@ -167,6 +167,7 @@ AC_DEFUN([ZFS_AC_CONFIG_KERNEL], [
 	ZFS_AC_KERNEL_TOTALHIGH_PAGES
 	ZFS_AC_KERNEL_BLK_QUEUE_DISCARD
 	ZFS_AC_KERNEL_BLK_QUEUE_SECURE_ERASE
+	ZFS_AC_KERNEL_KSTRTOUL
 
 	AS_IF([test "$LINUX_OBJ" != "$LINUX"], [
 		KERNEL_MAKE="$KERNEL_MAKE O=$LINUX_OBJ"
diff --git a/include/spl/sys/strings.h b/include/spl/sys/strings.h
index 4fb803206..8b810c9af 100644
--- a/include/spl/sys/strings.h
+++ b/include/spl/sys/strings.h
@@ -28,4 +28,8 @@
 #define	bcopy(src, dest, size)		memmove(dest, src, size)
 #define	bcmp(src, dest, size)		memcmp((src), (dest), (size_t)(size))
 
+#ifndef HAVE_KSTRTOUL
+#define	kstrtoul strict_strtoul
+#endif
+
 #endif	/* _SPL_SYS_STRINGS_H */