[PATCH 1/3] Revert "kbuild: give the SUBLEVEL more room in KERNEL_VERSION"

[PATCH 1/3] Revert "kbuild: give the SUBLEVEL more room in KERNEL_VERSION"

[Sasha Levin]

This reverts commit 537896fabed11f8d9788886d1aacdb977213c7b3.

This turns out to be a bad idea: userspace has coded the structure of
KERNEL_VERSION on it's own and assumes the 2-1-1 byte split, making it
userspace ABI we can't break.

The reverted patch didn't make it past linux-next, so no userspace was
hurt in the process.

Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 Makefile                                       | 7 ++-----
 drivers/net/ethernet/mellanox/mlx5/core/main.c | 4 ++--
 drivers/usb/core/hcd.c                         | 4 ++--
 drivers/usb/gadget/udc/aspeed-vhub/hub.c       | 4 ++--
 include/linux/usb/composite.h                  | 4 ++--
 kernel/sys.c                                   | 2 +-
 tools/perf/tests/bpf-script-example.c          | 2 +-
 tools/perf/tests/bpf-script-test-kbuild.c      | 2 +-
 tools/perf/tests/bpf-script-test-prologue.c    | 2 +-
 9 files changed, 14 insertions(+), 17 deletions(-)

diff --git a/Makefile b/Makefile
index 28019532e55ac..49ac1b7fe8e99 100644
--- a/Makefile
+++ b/Makefile
@@ -1259,11 +1259,8 @@ endef
 
 define filechk_version.h
 	echo \#define LINUX_VERSION_CODE $(shell                         \
-	expr $(VERSION) \* 16777216 + 0$(PATCHLEVEL) \* 65536 + 0$(SUBLEVEL)); \
-	echo \#define LINUX_VERSION_MAJOR $(VERSION); \
-	echo \#define LINUX_VERSION_PATCHLEVEL $(PATCHLEVEL); \
-	echo \#define LINUX_VERSION_SUBLEVEL $(SUBLEVEL); \
-	echo '#define KERNEL_VERSION(a,b,c) (((a) << 24) + ((b) << 16) + (c))'
+	expr $(VERSION) \* 65536 + 0$(PATCHLEVEL) \* 256 + 0$(SUBLEVEL)); \
+	echo '#define KERNEL_VERSION(a,b,c) (((a) << 16) + ((b) << 8) + (c))'
 endef
 
 $(version_h): FORCE
diff --git a/drivers/net/ethernet/mellanox/mlx5/core/main.c b/drivers/net/ethernet/mellanox/mlx5/core/main.c
index 989f15d9aa7d4..e4c9627485aa5 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/main.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/main.c
@@ -237,8 +237,8 @@ static void mlx5_set_driver_version(struct mlx5_core_dev *dev)
 	remaining_size = max_t(int, 0, driver_ver_sz - strlen(string));
 
 	snprintf(string + strlen(string), remaining_size, "%u.%u.%u",
-		(u8)(LINUX_VERSION_MAJOR), (u8)(LINUX_VERSION_PATCHLEVEL),
-		(u16)(LINUX_VERSION_SUBLEVEL));
+		 (u8)((LINUX_VERSION_CODE >> 16) & 0xff), (u8)((LINUX_VERSION_CODE >> 8) & 0xff),
+		 (u16)(LINUX_VERSION_CODE & 0xffff));
 
 	/*Send the command*/
 	MLX5_SET(set_driver_version_in, in, opcode,
diff --git a/drivers/usb/core/hcd.c b/drivers/usb/core/hcd.c
index 3f0381344221e..ad5a0f405a75c 100644
--- a/drivers/usb/core/hcd.c
+++ b/drivers/usb/core/hcd.c
@@ -111,8 +111,8 @@ DECLARE_WAIT_QUEUE_HEAD(usb_kill_urb_queue);
  */
 
 /*-------------------------------------------------------------------------*/
-#define KERNEL_REL	bin2bcd(LINUX_VERSION_MAJOR)
-#define KERNEL_VER	bin2bcd(LINUX_VERSION_PATCHLEVEL)
+#define KERNEL_REL	bin2bcd(((LINUX_VERSION_CODE >> 16) & 0x0ff))
+#define KERNEL_VER	bin2bcd(((LINUX_VERSION_CODE >> 8) & 0x0ff))
 
 /* usb 3.1 root hub device descriptor */
 static const u8 usb31_rh_dev_descriptor[18] = {
diff --git a/drivers/usb/gadget/udc/aspeed-vhub/hub.c b/drivers/usb/gadget/udc/aspeed-vhub/hub.c
index 5c7dea5e0ff16..bfd8e77788e29 100644
--- a/drivers/usb/gadget/udc/aspeed-vhub/hub.c
+++ b/drivers/usb/gadget/udc/aspeed-vhub/hub.c
@@ -46,8 +46,8 @@
  *    - Make vid/did overridable
  *    - make it look like usb1 if usb1 mode forced
  */
-#define KERNEL_REL	bin2bcd(LINUX_VERSION_MAJOR)
-#define KERNEL_VER	bin2bcd(LINUX_VERSION_PATCHLEVEL)
+#define KERNEL_REL	bin2bcd(((LINUX_VERSION_CODE >> 16) & 0x0ff))
+#define KERNEL_VER	bin2bcd(((LINUX_VERSION_CODE >> 8) & 0x0ff))
 
 enum {
 	AST_VHUB_STR_INDEX_MAX = 4,
diff --git a/include/linux/usb/composite.h b/include/linux/usb/composite.h
index c71150f2c6390..5646dad886e61 100644
--- a/include/linux/usb/composite.h
+++ b/include/linux/usb/composite.h
@@ -575,8 +575,8 @@ static inline u16 get_default_bcdDevice(void)
 {
 	u16 bcdDevice;
 
-	bcdDevice = bin2bcd(LINUX_VERSION_MAJOR) << 8;
-	bcdDevice |= bin2bcd(LINUX_VERSION_PATCHLEVEL);
+	bcdDevice = bin2bcd((LINUX_VERSION_CODE >> 16 & 0xff)) << 8;
+	bcdDevice |= bin2bcd((LINUX_VERSION_CODE >> 8 & 0xff));
 	return bcdDevice;
 }
 
diff --git a/kernel/sys.c b/kernel/sys.c
index b09fe21e88ff5..8bb46e50f02d4 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -1242,7 +1242,7 @@ static int override_release(char __user *release, size_t len)
 				break;
 			rest++;
 		}
-		v = LINUX_VERSION_PATCHLEVEL + 60;
+		v = ((LINUX_VERSION_CODE >> 8) & 0xff) + 60;
 		copy = clamp_t(size_t, len, 1, sizeof(buf));
 		copy = scnprintf(buf, copy, "2.6.%u%s", v, rest);
 		ret = copy_to_user(release, buf, copy + 1);
diff --git a/tools/perf/tests/bpf-script-example.c b/tools/perf/tests/bpf-script-example.c
index a56bf381335e9..ab4b98b3165db 100644
--- a/tools/perf/tests/bpf-script-example.c
+++ b/tools/perf/tests/bpf-script-example.c
@@ -5,7 +5,7 @@
  */
 #ifndef LINUX_VERSION_CODE
 # error Need LINUX_VERSION_CODE
-# error Example: for 4.2 kernel, put 'clang-opt="-DLINUX_VERSION_CODE=0x4020000" into llvm section of ~/.perfconfig'
+# error Example: for 4.2 kernel, put 'clang-opt="-DLINUX_VERSION_CODE=0x40200" into llvm section of ~/.perfconfig'
 #endif
 #define BPF_ANY 0
 #define BPF_MAP_TYPE_ARRAY 2
diff --git a/tools/perf/tests/bpf-script-test-kbuild.c b/tools/perf/tests/bpf-script-test-kbuild.c
index 21663295d5b5a..219673aa278fb 100644
--- a/tools/perf/tests/bpf-script-test-kbuild.c
+++ b/tools/perf/tests/bpf-script-test-kbuild.c
@@ -5,7 +5,7 @@
  */
 #ifndef LINUX_VERSION_CODE
 # error Need LINUX_VERSION_CODE
-# error Example: for 4.2 kernel, put 'clang-opt="-DLINUX_VERSION_CODE=0x4020000" into llvm section of ~/.perfconfig'
+# error Example: for 4.2 kernel, put 'clang-opt="-DLINUX_VERSION_CODE=0x40200" into llvm section of ~/.perfconfig'
 #endif
 #define SEC(NAME) __attribute__((section(NAME), used))
 
diff --git a/tools/perf/tests/bpf-script-test-prologue.c b/tools/perf/tests/bpf-script-test-prologue.c
index 8db19e70813cc..bd83d364cf30d 100644
--- a/tools/perf/tests/bpf-script-test-prologue.c
+++ b/tools/perf/tests/bpf-script-test-prologue.c
@@ -5,7 +5,7 @@
  */
 #ifndef LINUX_VERSION_CODE
 # error Need LINUX_VERSION_CODE
-# error Example: for 4.2 kernel, put 'clang-opt="-DLINUX_VERSION_CODE=0x4020000" into llvm section of ~/.perfconfig'
+# error Example: for 4.2 kernel, put 'clang-opt="-DLINUX_VERSION_CODE=0x40200" into llvm section of ~/.perfconfig'
 #endif
 #define SEC(NAME) __attribute__((section(NAME), used))
 
-- 
2.27.0

[PATCH 2/3] kbuild: clamp SUBLEVEL to 255

[Sasha Levin]

Right now if SUBLEVEL becomes larger than 255 it will overflow into the
territory of PATCHLEVEL, causing havoc in userspace that tests for
specific kernel version.

While userspace code tests for MAJOR and PATCHLEVEL, it doesn't test
SUBLEVEL at any point as ABI changes don't happen in the context of
stable tree.

Thus, to avoid overflows, simply clamp SUBLEVEL to it's maximum value in
the context of LINUX_VERSION_CODE. This does not affect "make
kernelversion" and such.

Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 Makefile | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/Makefile b/Makefile
index 49ac1b7fe8e99..157be50c691e5 100644
--- a/Makefile
+++ b/Makefile
@@ -1258,9 +1258,15 @@ define filechk_utsrelease.h
 endef
 
 define filechk_version.h
-	echo \#define LINUX_VERSION_CODE $(shell                         \
-	expr $(VERSION) \* 65536 + 0$(PATCHLEVEL) \* 256 + 0$(SUBLEVEL)); \
-	echo '#define KERNEL_VERSION(a,b,c) (((a) << 16) + ((b) << 8) + (c))'
+	if [ $(SUBLEVEL) -gt 255 ]; then                                 \
+		echo \#define LINUX_VERSION_CODE $(shell                 \
+		expr $(VERSION) \* 65536 + 0$(PATCHLEVEL) \* 256 + 255); \
+	else                                                             \
+		echo \#define LINUX_VERSION_CODE $(shell                 \
+		expr $(VERSION) \* 65536 + 0$(PATCHLEVEL) \* 256 + $(SUBLEVEL)); \
+	fi;                                                              \
+	echo '#define KERNEL_VERSION(a,b,c) (((a) << 16) + ((b) << 8) +  \
+	((c) > 255 ? 255 : (c)))'
 endef
 
 $(version_h): FORCE
-- 
2.27.0

[PATCH 3/3] kbuild: introduce KERNEL_VERSION2 and LINUX_VERSION_CODE2

[Sasha Levin]

SUBLEVEL only has 8 bits of space, which means that we'll overflow it
once it reaches 256.

Few of the stable branches will imminently overflow SUBLEVEL while
there's no risk of overflowing VERSION.

Thus, give SUBLEVEL 8 more bits which will be stolen from VERSION, this
should create a better balance between the different version numbers we
use.

We can't however use the original KERNEL_VERSION and LINUX_VERSION_CODE
as userspace has created ABI dependency on their structure, and we risk
breaking this userspace by modifying the layout of the version integers.

Cc: stable@kernel.org
Signed-off-by: Sasha Levin <sashal@kernel.org>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 Makefile                                       | 8 +++++++-
 drivers/net/ethernet/mellanox/mlx5/core/main.c | 4 ++--
 drivers/usb/core/hcd.c                         | 4 ++--
 drivers/usb/gadget/udc/aspeed-vhub/hub.c       | 4 ++--
 include/linux/usb/composite.h                  | 4 ++--
 kernel/sys.c                                   | 2 +-
 tools/perf/tests/bpf-script-example.c          | 2 +-
 tools/perf/tests/bpf-script-test-kbuild.c      | 2 +-
 tools/perf/tests/bpf-script-test-prologue.c    | 2 +-
 9 files changed, 19 insertions(+), 13 deletions(-)

diff --git a/Makefile b/Makefile
index 157be50c691e5..2177c548e4c24 100644
--- a/Makefile
+++ b/Makefile
@@ -1266,7 +1266,13 @@ define filechk_version.h
 		expr $(VERSION) \* 65536 + 0$(PATCHLEVEL) \* 256 + $(SUBLEVEL)); \
 	fi;                                                              \
 	echo '#define KERNEL_VERSION(a,b,c) (((a) << 16) + ((b) << 8) +  \
-	((c) > 255 ? 255 : (c)))'
+	((c) > 255 ? 255 : (c)))';                                       \
+	echo \#define LINUX_VERSION_CODE2 $(shell                        \
+	expr $(VERSION) \* 16777216 + 0$(PATCHLEVEL) \* 65536 + 0$(SUBLEVEL)); \
+	echo \#define LINUX_VERSION_MAJOR $(VERSION);                    \
+	echo \#define LINUX_VERSION_PATCHLEVEL $(PATCHLEVEL);            \
+	echo \#define LINUX_VERSION_SUBLEVEL $(SUBLEVEL);                \
+	echo '#define KERNEL_VERSION2(a,b,c) (((a) << 24) + ((b) << 16) + (c))'
 endef
 
 $(version_h): FORCE
diff --git a/drivers/net/ethernet/mellanox/mlx5/core/main.c b/drivers/net/ethernet/mellanox/mlx5/core/main.c
index e4c9627485aa5..989f15d9aa7d4 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/main.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/main.c
@@ -237,8 +237,8 @@ static void mlx5_set_driver_version(struct mlx5_core_dev *dev)
 	remaining_size = max_t(int, 0, driver_ver_sz - strlen(string));
 
 	snprintf(string + strlen(string), remaining_size, "%u.%u.%u",
-		 (u8)((LINUX_VERSION_CODE >> 16) & 0xff), (u8)((LINUX_VERSION_CODE >> 8) & 0xff),
-		 (u16)(LINUX_VERSION_CODE & 0xffff));
+		(u8)(LINUX_VERSION_MAJOR), (u8)(LINUX_VERSION_PATCHLEVEL),
+		(u16)(LINUX_VERSION_SUBLEVEL));
 
 	/*Send the command*/
 	MLX5_SET(set_driver_version_in, in, opcode,
diff --git a/drivers/usb/core/hcd.c b/drivers/usb/core/hcd.c
index ad5a0f405a75c..3f0381344221e 100644
--- a/drivers/usb/core/hcd.c
+++ b/drivers/usb/core/hcd.c
@@ -111,8 +111,8 @@ DECLARE_WAIT_QUEUE_HEAD(usb_kill_urb_queue);
  */
 
 /*-------------------------------------------------------------------------*/
-#define KERNEL_REL	bin2bcd(((LINUX_VERSION_CODE >> 16) & 0x0ff))
-#define KERNEL_VER	bin2bcd(((LINUX_VERSION_CODE >> 8) & 0x0ff))
+#define KERNEL_REL	bin2bcd(LINUX_VERSION_MAJOR)
+#define KERNEL_VER	bin2bcd(LINUX_VERSION_PATCHLEVEL)
 
 /* usb 3.1 root hub device descriptor */
 static const u8 usb31_rh_dev_descriptor[18] = {
diff --git a/drivers/usb/gadget/udc/aspeed-vhub/hub.c b/drivers/usb/gadget/udc/aspeed-vhub/hub.c
index bfd8e77788e29..5c7dea5e0ff16 100644
--- a/drivers/usb/gadget/udc/aspeed-vhub/hub.c
+++ b/drivers/usb/gadget/udc/aspeed-vhub/hub.c
@@ -46,8 +46,8 @@
  *    - Make vid/did overridable
  *    - make it look like usb1 if usb1 mode forced
  */
-#define KERNEL_REL	bin2bcd(((LINUX_VERSION_CODE >> 16) & 0x0ff))
-#define KERNEL_VER	bin2bcd(((LINUX_VERSION_CODE >> 8) & 0x0ff))
+#define KERNEL_REL	bin2bcd(LINUX_VERSION_MAJOR)
+#define KERNEL_VER	bin2bcd(LINUX_VERSION_PATCHLEVEL)
 
 enum {
 	AST_VHUB_STR_INDEX_MAX = 4,
diff --git a/include/linux/usb/composite.h b/include/linux/usb/composite.h
index 5646dad886e61..c71150f2c6390 100644
--- a/include/linux/usb/composite.h
+++ b/include/linux/usb/composite.h
@@ -575,8 +575,8 @@ static inline u16 get_default_bcdDevice(void)
 {
 	u16 bcdDevice;
 
-	bcdDevice = bin2bcd((LINUX_VERSION_CODE >> 16 & 0xff)) << 8;
-	bcdDevice |= bin2bcd((LINUX_VERSION_CODE >> 8 & 0xff));
+	bcdDevice = bin2bcd(LINUX_VERSION_MAJOR) << 8;
+	bcdDevice |= bin2bcd(LINUX_VERSION_PATCHLEVEL);
 	return bcdDevice;
 }
 
diff --git a/kernel/sys.c b/kernel/sys.c
index 8bb46e50f02d4..b09fe21e88ff5 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -1242,7 +1242,7 @@ static int override_release(char __user *release, size_t len)
 				break;
 			rest++;
 		}
-		v = ((LINUX_VERSION_CODE >> 8) & 0xff) + 60;
+		v = LINUX_VERSION_PATCHLEVEL + 60;
 		copy = clamp_t(size_t, len, 1, sizeof(buf));
 		copy = scnprintf(buf, copy, "2.6.%u%s", v, rest);
 		ret = copy_to_user(release, buf, copy + 1);
diff --git a/tools/perf/tests/bpf-script-example.c b/tools/perf/tests/bpf-script-example.c
index ab4b98b3165db..a56bf381335e9 100644
--- a/tools/perf/tests/bpf-script-example.c
+++ b/tools/perf/tests/bpf-script-example.c
@@ -5,7 +5,7 @@
  */
 #ifndef LINUX_VERSION_CODE
 # error Need LINUX_VERSION_CODE
-# error Example: for 4.2 kernel, put 'clang-opt="-DLINUX_VERSION_CODE=0x40200" into llvm section of ~/.perfconfig'
+# error Example: for 4.2 kernel, put 'clang-opt="-DLINUX_VERSION_CODE=0x4020000" into llvm section of ~/.perfconfig'
 #endif
 #define BPF_ANY 0
 #define BPF_MAP_TYPE_ARRAY 2
diff --git a/tools/perf/tests/bpf-script-test-kbuild.c b/tools/perf/tests/bpf-script-test-kbuild.c
index 219673aa278fb..21663295d5b5a 100644
--- a/tools/perf/tests/bpf-script-test-kbuild.c
+++ b/tools/perf/tests/bpf-script-test-kbuild.c
@@ -5,7 +5,7 @@
  */
 #ifndef LINUX_VERSION_CODE
 # error Need LINUX_VERSION_CODE
-# error Example: for 4.2 kernel, put 'clang-opt="-DLINUX_VERSION_CODE=0x40200" into llvm section of ~/.perfconfig'
+# error Example: for 4.2 kernel, put 'clang-opt="-DLINUX_VERSION_CODE=0x4020000" into llvm section of ~/.perfconfig'
 #endif
 #define SEC(NAME) __attribute__((section(NAME), used))
 
diff --git a/tools/perf/tests/bpf-script-test-prologue.c b/tools/perf/tests/bpf-script-test-prologue.c
index bd83d364cf30d..8db19e70813cc 100644
--- a/tools/perf/tests/bpf-script-test-prologue.c
+++ b/tools/perf/tests/bpf-script-test-prologue.c
@@ -5,7 +5,7 @@
  */
 #ifndef LINUX_VERSION_CODE
 # error Need LINUX_VERSION_CODE
-# error Example: for 4.2 kernel, put 'clang-opt="-DLINUX_VERSION_CODE=0x40200" into llvm section of ~/.perfconfig'
+# error Example: for 4.2 kernel, put 'clang-opt="-DLINUX_VERSION_CODE=0x4020000" into llvm section of ~/.perfconfig'
 #endif
 #define SEC(NAME) __attribute__((section(NAME), used))
 
-- 
2.27.0

Re: [PATCH 3/3] kbuild: introduce KERNEL_VERSION2 and LINUX_VERSION_CODE2

[Sasha Levin]

On Fri, Feb 05, 2021 at 10:50:33PM -0500, Sasha Levin wrote:
>SUBLEVEL only has 8 bits of space, which means that we'll overflow it
>once it reaches 256.
>
>Few of the stable branches will imminently overflow SUBLEVEL while
>there's no risk of overflowing VERSION.
>
>Thus, give SUBLEVEL 8 more bits which will be stolen from VERSION, this
>should create a better balance between the different version numbers we
>use.
>
>We can't however use the original KERNEL_VERSION and LINUX_VERSION_CODE
>as userspace has created ABI dependency on their structure, and we risk
>breaking this userspace by modifying the layout of the version integers.
>
>Cc: stable@kernel.org
>Signed-off-by: Sasha Levin <sashal@kernel.org>
>Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
>Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

I wanted to re-use an older commit but forgot to drop the two tags
above. The tags from Masahiro and Greg shouldn't be here, sorry about
that.

-- 
Thanks,
Sasha

Re: [PATCH 1/3] Revert "kbuild: give the SUBLEVEL more room in KERNEL_VERSION"

[Masahiro Yamada]

On Sat, Feb 6, 2021 at 12:50 PM Sasha Levin <sashal@kernel.org> wrote:
>
> This reverts commit 537896fabed11f8d9788886d1aacdb977213c7b3.
>
> This turns out to be a bad idea: userspace has coded the structure of
> KERNEL_VERSION on it's own and assumes the 2-1-1 byte split, making it
> userspace ABI we can't break.

It is unfortunate...

I will drop this from my tree.

This did not hit Linus' tree yet.



> The reverted patch didn't make it past linux-next, so no userspace was
> hurt in the process.
>
> Signed-off-by: Sasha Levin <sashal@kernel.org>
> ---
>  Makefile                                       | 7 ++-----
>  drivers/net/ethernet/mellanox/mlx5/core/main.c | 4 ++--
>  drivers/usb/core/hcd.c                         | 4 ++--
>  drivers/usb/gadget/udc/aspeed-vhub/hub.c       | 4 ++--
>  include/linux/usb/composite.h                  | 4 ++--
>  kernel/sys.c                                   | 2 +-
>  tools/perf/tests/bpf-script-example.c          | 2 +-
>  tools/perf/tests/bpf-script-test-kbuild.c      | 2 +-
>  tools/perf/tests/bpf-script-test-prologue.c    | 2 +-
>  9 files changed, 14 insertions(+), 17 deletions(-)
>
> diff --git a/Makefile b/Makefile
> index 28019532e55ac..49ac1b7fe8e99 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -1259,11 +1259,8 @@ endef
>
>  define filechk_version.h
>         echo \#define LINUX_VERSION_CODE $(shell                         \
> -       expr $(VERSION) \* 16777216 + 0$(PATCHLEVEL) \* 65536 + 0$(SUBLEVEL)); \
> -       echo \#define LINUX_VERSION_MAJOR $(VERSION); \
> -       echo \#define LINUX_VERSION_PATCHLEVEL $(PATCHLEVEL); \
> -       echo \#define LINUX_VERSION_SUBLEVEL $(SUBLEVEL); \
> -       echo '#define KERNEL_VERSION(a,b,c) (((a) << 24) + ((b) << 16) + (c))'
> +       expr $(VERSION) \* 65536 + 0$(PATCHLEVEL) \* 256 + 0$(SUBLEVEL)); \
> +       echo '#define KERNEL_VERSION(a,b,c) (((a) << 16) + ((b) << 8) + (c))'
>  endef
>
>  $(version_h): FORCE
> diff --git a/drivers/net/ethernet/mellanox/mlx5/core/main.c b/drivers/net/ethernet/mellanox/mlx5/core/main.c
> index 989f15d9aa7d4..e4c9627485aa5 100644
> --- a/drivers/net/ethernet/mellanox/mlx5/core/main.c
> +++ b/drivers/net/ethernet/mellanox/mlx5/core/main.c
> @@ -237,8 +237,8 @@ static void mlx5_set_driver_version(struct mlx5_core_dev *dev)
>         remaining_size = max_t(int, 0, driver_ver_sz - strlen(string));
>
>         snprintf(string + strlen(string), remaining_size, "%u.%u.%u",
> -               (u8)(LINUX_VERSION_MAJOR), (u8)(LINUX_VERSION_PATCHLEVEL),
> -               (u16)(LINUX_VERSION_SUBLEVEL));
> +                (u8)((LINUX_VERSION_CODE >> 16) & 0xff), (u8)((LINUX_VERSION_CODE >> 8) & 0xff),
> +                (u16)(LINUX_VERSION_CODE & 0xffff));
>
>         /*Send the command*/
>         MLX5_SET(set_driver_version_in, in, opcode,
> diff --git a/drivers/usb/core/hcd.c b/drivers/usb/core/hcd.c
> index 3f0381344221e..ad5a0f405a75c 100644
> --- a/drivers/usb/core/hcd.c
> +++ b/drivers/usb/core/hcd.c
> @@ -111,8 +111,8 @@ DECLARE_WAIT_QUEUE_HEAD(usb_kill_urb_queue);
>   */
>
>  /*-------------------------------------------------------------------------*/
> -#define KERNEL_REL     bin2bcd(LINUX_VERSION_MAJOR)
> -#define KERNEL_VER     bin2bcd(LINUX_VERSION_PATCHLEVEL)
> +#define KERNEL_REL     bin2bcd(((LINUX_VERSION_CODE >> 16) & 0x0ff))
> +#define KERNEL_VER     bin2bcd(((LINUX_VERSION_CODE >> 8) & 0x0ff))
>
>  /* usb 3.1 root hub device descriptor */
>  static const u8 usb31_rh_dev_descriptor[18] = {
> diff --git a/drivers/usb/gadget/udc/aspeed-vhub/hub.c b/drivers/usb/gadget/udc/aspeed-vhub/hub.c
> index 5c7dea5e0ff16..bfd8e77788e29 100644
> --- a/drivers/usb/gadget/udc/aspeed-vhub/hub.c
> +++ b/drivers/usb/gadget/udc/aspeed-vhub/hub.c
> @@ -46,8 +46,8 @@
>   *    - Make vid/did overridable
>   *    - make it look like usb1 if usb1 mode forced
>   */
> -#define KERNEL_REL     bin2bcd(LINUX_VERSION_MAJOR)
> -#define KERNEL_VER     bin2bcd(LINUX_VERSION_PATCHLEVEL)
> +#define KERNEL_REL     bin2bcd(((LINUX_VERSION_CODE >> 16) & 0x0ff))
> +#define KERNEL_VER     bin2bcd(((LINUX_VERSION_CODE >> 8) & 0x0ff))
>
>  enum {
>         AST_VHUB_STR_INDEX_MAX = 4,
> diff --git a/include/linux/usb/composite.h b/include/linux/usb/composite.h
> index c71150f2c6390..5646dad886e61 100644
> --- a/include/linux/usb/composite.h
> +++ b/include/linux/usb/composite.h
> @@ -575,8 +575,8 @@ static inline u16 get_default_bcdDevice(void)
>  {
>         u16 bcdDevice;
>
> -       bcdDevice = bin2bcd(LINUX_VERSION_MAJOR) << 8;
> -       bcdDevice |= bin2bcd(LINUX_VERSION_PATCHLEVEL);
> +       bcdDevice = bin2bcd((LINUX_VERSION_CODE >> 16 & 0xff)) << 8;
> +       bcdDevice |= bin2bcd((LINUX_VERSION_CODE >> 8 & 0xff));
>         return bcdDevice;
>  }
>
> diff --git a/kernel/sys.c b/kernel/sys.c
> index b09fe21e88ff5..8bb46e50f02d4 100644
> --- a/kernel/sys.c
> +++ b/kernel/sys.c
> @@ -1242,7 +1242,7 @@ static int override_release(char __user *release, size_t len)
>                                 break;
>                         rest++;
>                 }
> -               v = LINUX_VERSION_PATCHLEVEL + 60;
> +               v = ((LINUX_VERSION_CODE >> 8) & 0xff) + 60;
>                 copy = clamp_t(size_t, len, 1, sizeof(buf));
>                 copy = scnprintf(buf, copy, "2.6.%u%s", v, rest);
>                 ret = copy_to_user(release, buf, copy + 1);
> diff --git a/tools/perf/tests/bpf-script-example.c b/tools/perf/tests/bpf-script-example.c
> index a56bf381335e9..ab4b98b3165db 100644
> --- a/tools/perf/tests/bpf-script-example.c
> +++ b/tools/perf/tests/bpf-script-example.c
> @@ -5,7 +5,7 @@
>   */
>  #ifndef LINUX_VERSION_CODE
>  # error Need LINUX_VERSION_CODE
> -# error Example: for 4.2 kernel, put 'clang-opt="-DLINUX_VERSION_CODE=0x4020000" into llvm section of ~/.perfconfig'
> +# error Example: for 4.2 kernel, put 'clang-opt="-DLINUX_VERSION_CODE=0x40200" into llvm section of ~/.perfconfig'
>  #endif
>  #define BPF_ANY 0
>  #define BPF_MAP_TYPE_ARRAY 2
> diff --git a/tools/perf/tests/bpf-script-test-kbuild.c b/tools/perf/tests/bpf-script-test-kbuild.c
> index 21663295d5b5a..219673aa278fb 100644
> --- a/tools/perf/tests/bpf-script-test-kbuild.c
> +++ b/tools/perf/tests/bpf-script-test-kbuild.c
> @@ -5,7 +5,7 @@
>   */
>  #ifndef LINUX_VERSION_CODE
>  # error Need LINUX_VERSION_CODE
> -# error Example: for 4.2 kernel, put 'clang-opt="-DLINUX_VERSION_CODE=0x4020000" into llvm section of ~/.perfconfig'
> +# error Example: for 4.2 kernel, put 'clang-opt="-DLINUX_VERSION_CODE=0x40200" into llvm section of ~/.perfconfig'
>  #endif
>  #define SEC(NAME) __attribute__((section(NAME), used))
>
> diff --git a/tools/perf/tests/bpf-script-test-prologue.c b/tools/perf/tests/bpf-script-test-prologue.c
> index 8db19e70813cc..bd83d364cf30d 100644
> --- a/tools/perf/tests/bpf-script-test-prologue.c
> +++ b/tools/perf/tests/bpf-script-test-prologue.c
> @@ -5,7 +5,7 @@
>   */
>  #ifndef LINUX_VERSION_CODE
>  # error Need LINUX_VERSION_CODE
> -# error Example: for 4.2 kernel, put 'clang-opt="-DLINUX_VERSION_CODE=0x4020000" into llvm section of ~/.perfconfig'
> +# error Example: for 4.2 kernel, put 'clang-opt="-DLINUX_VERSION_CODE=0x40200" into llvm section of ~/.perfconfig'
>  #endif
>  #define SEC(NAME) __attribute__((section(NAME), used))
>
> --
> 2.27.0
>


-- 
Best Regards
Masahiro Yamada

Re: [PATCH 3/3] kbuild: introduce KERNEL_VERSION2 and LINUX_VERSION_CODE2

[Masahiro Yamada]

On Sat, Feb 6, 2021 at 12:50 PM Sasha Levin <sashal@kernel.org> wrote:
>
> SUBLEVEL only has 8 bits of space, which means that we'll overflow it
> once it reaches 256.
>
> Few of the stable branches will imminently overflow SUBLEVEL while
> there's no risk of overflowing VERSION.
>
> Thus, give SUBLEVEL 8 more bits which will be stolen from VERSION, this
> should create a better balance between the different version numbers we
> use.
>
> We can't however use the original KERNEL_VERSION and LINUX_VERSION_CODE
> as userspace has created ABI dependency on their structure, and we risk
> breaking this userspace by modifying the layout of the version integers.
>
> Cc: stable@kernel.org
> Signed-off-by: Sasha Levin <sashal@kernel.org>
> Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
> Signed-off-by: Sasha Levin <sashal@kernel.org>
> ---
>  Makefile                                       | 8 +++++++-
>  drivers/net/ethernet/mellanox/mlx5/core/main.c | 4 ++--
>  drivers/usb/core/hcd.c                         | 4 ++--
>  drivers/usb/gadget/udc/aspeed-vhub/hub.c       | 4 ++--
>  include/linux/usb/composite.h                  | 4 ++--
>  kernel/sys.c                                   | 2 +-
>  tools/perf/tests/bpf-script-example.c          | 2 +-
>  tools/perf/tests/bpf-script-test-kbuild.c      | 2 +-
>  tools/perf/tests/bpf-script-test-prologue.c    | 2 +-
>  9 files changed, 19 insertions(+), 13 deletions(-)
>
> diff --git a/Makefile b/Makefile
> index 157be50c691e5..2177c548e4c24 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -1266,7 +1266,13 @@ define filechk_version.h
>                 expr $(VERSION) \* 65536 + 0$(PATCHLEVEL) \* 256 + $(SUBLEVEL)); \
>         fi;                                                              \
>         echo '#define KERNEL_VERSION(a,b,c) (((a) << 16) + ((b) << 8) +  \
> -       ((c) > 255 ? 255 : (c)))'
> +       ((c) > 255 ? 255 : (c)))';                                       \
> +       echo \#define LINUX_VERSION_CODE2 $(shell                        \
> +       expr $(VERSION) \* 16777216 + 0$(PATCHLEVEL) \* 65536 + 0$(SUBLEVEL)); \


Is this needed?
No one in this patch uses LINUX_VERSION_CODE2.

The in-kernel code can use
LINUX_VERSION_MAJOR/PATCHLEVEL/SUBLEVEL directly.


Userspace does not need LINUX_VERSION_CODE2 either.

Your comment in 2/3 states that
userspace only decodes MAJOR and PATCHLEVEL fields,
so LINUX_VERSION_CODE will still do well.




> index ab4b98b3165db..a56bf381335e9 100644
> --- a/tools/perf/tests/bpf-script-example.c
> +++ b/tools/perf/tests/bpf-script-example.c
> @@ -5,7 +5,7 @@
>   */
>  #ifndef LINUX_VERSION_CODE
>  # error Need LINUX_VERSION_CODE
> -# error Example: for 4.2 kernel, put 'clang-opt="-DLINUX_VERSION_CODE=0x40200" into llvm section of ~/.perfconfig'
> +# error Example: for 4.2 kernel, put 'clang-opt="-DLINUX_VERSION_CODE=0x4020000" into llvm section of ~/.perfconfig'


Is this change needed?




>  #endif
>  #define BPF_ANY 0
>  #define BPF_MAP_TYPE_ARRAY 2
> diff --git a/tools/perf/tests/bpf-script-test-kbuild.c b/tools/perf/tests/bpf-script-test-kbuild.c
> index 219673aa278fb..21663295d5b5a 100644
> --- a/tools/perf/tests/bpf-script-test-kbuild.c
> +++ b/tools/perf/tests/bpf-script-test-kbuild.c
> @@ -5,7 +5,7 @@
>   */
>  #ifndef LINUX_VERSION_CODE
>  # error Need LINUX_VERSION_CODE
> -# error Example: for 4.2 kernel, put 'clang-opt="-DLINUX_VERSION_CODE=0x40200" into llvm section of ~/.perfconfig'
> +# error Example: for 4.2 kernel, put 'clang-opt="-DLINUX_VERSION_CODE=0x4020000" into llvm section of ~/.perfconfig'
>  #endif
>  #define SEC(NAME) __attribute__((section(NAME), used))
>
> diff --git a/tools/perf/tests/bpf-script-test-prologue.c b/tools/perf/tests/bpf-script-test-prologue.c
> index bd83d364cf30d..8db19e70813cc 100644
> --- a/tools/perf/tests/bpf-script-test-prologue.c
> +++ b/tools/perf/tests/bpf-script-test-prologue.c
> @@ -5,7 +5,7 @@
>   */
>  #ifndef LINUX_VERSION_CODE
>  # error Need LINUX_VERSION_CODE
> -# error Example: for 4.2 kernel, put 'clang-opt="-DLINUX_VERSION_CODE=0x40200" into llvm section of ~/.perfconfig'
> +# error Example: for 4.2 kernel, put 'clang-opt="-DLINUX_VERSION_CODE=0x4020000" into llvm section of ~/.perfconfig'
>  #endif
>  #define SEC(NAME) __attribute__((section(NAME), used))
>
> --
> 2.27.0
>


-- 
Best Regards
Masahiro Yamada

Re: [PATCH 2/3] kbuild: clamp SUBLEVEL to 255

[Greg KH]

On Fri, Feb 05, 2021 at 10:50:32PM -0500, Sasha Levin wrote:
> Right now if SUBLEVEL becomes larger than 255 it will overflow into the
> territory of PATCHLEVEL, causing havoc in userspace that tests for
> specific kernel version.
> 
> While userspace code tests for MAJOR and PATCHLEVEL, it doesn't test
> SUBLEVEL at any point as ABI changes don't happen in the context of
> stable tree.
> 
> Thus, to avoid overflows, simply clamp SUBLEVEL to it's maximum value in
> the context of LINUX_VERSION_CODE. This does not affect "make
> kernelversion" and such.
> 
> Signed-off-by: Sasha Levin <sashal@kernel.org>


Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Re: [PATCH 3/3] kbuild: introduce KERNEL_VERSION2 and LINUX_VERSION_CODE2

[Greg KH]

On Fri, Feb 05, 2021 at 10:50:33PM -0500, Sasha Levin wrote:
> SUBLEVEL only has 8 bits of space, which means that we'll overflow it
> once it reaches 256.
> 
> Few of the stable branches will imminently overflow SUBLEVEL while
> there's no risk of overflowing VERSION.
> 
> Thus, give SUBLEVEL 8 more bits which will be stolen from VERSION, this
> should create a better balance between the different version numbers we
> use.
> 
> We can't however use the original KERNEL_VERSION and LINUX_VERSION_CODE
> as userspace has created ABI dependency on their structure, and we risk
> breaking this userspace by modifying the layout of the version integers.
> 
> Cc: stable@kernel.org
> Signed-off-by: Sasha Levin <sashal@kernel.org>
> Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
> Signed-off-by: Sasha Levin <sashal@kernel.org>

Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Re: [PATCH 3/3] kbuild: introduce KERNEL_VERSION2 and LINUX_VERSION_CODE2

[Greg KH]

On Fri, Feb 05, 2021 at 10:50:33PM -0500, Sasha Levin wrote:
> SUBLEVEL only has 8 bits of space, which means that we'll overflow it
> once it reaches 256.
> 
> Few of the stable branches will imminently overflow SUBLEVEL while
> there's no risk of overflowing VERSION.
> 
> Thus, give SUBLEVEL 8 more bits which will be stolen from VERSION, this
> should create a better balance between the different version numbers we
> use.
> 
> We can't however use the original KERNEL_VERSION and LINUX_VERSION_CODE
> as userspace has created ABI dependency on their structure, and we risk
> breaking this userspace by modifying the layout of the version integers.
> 
> Cc: stable@kernel.org
> Signed-off-by: Sasha Levin <sashal@kernel.org>
> Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
> Signed-off-by: Sasha Levin <sashal@kernel.org>
> ---
>  Makefile                                       | 8 +++++++-
>  drivers/net/ethernet/mellanox/mlx5/core/main.c | 4 ++--
>  drivers/usb/core/hcd.c                         | 4 ++--
>  drivers/usb/gadget/udc/aspeed-vhub/hub.c       | 4 ++--
>  include/linux/usb/composite.h                  | 4 ++--
>  kernel/sys.c                                   | 2 +-
>  tools/perf/tests/bpf-script-example.c          | 2 +-
>  tools/perf/tests/bpf-script-test-kbuild.c      | 2 +-
>  tools/perf/tests/bpf-script-test-prologue.c    | 2 +-
>  9 files changed, 19 insertions(+), 13 deletions(-)
> 
> diff --git a/Makefile b/Makefile
> index 157be50c691e5..2177c548e4c24 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -1266,7 +1266,13 @@ define filechk_version.h
>  		expr $(VERSION) \* 65536 + 0$(PATCHLEVEL) \* 256 + $(SUBLEVEL)); \
>  	fi;                                                              \
>  	echo '#define KERNEL_VERSION(a,b,c) (((a) << 16) + ((b) << 8) +  \
> -	((c) > 255 ? 255 : (c)))'
> +	((c) > 255 ? 255 : (c)))';                                       \
> +	echo \#define LINUX_VERSION_CODE2 $(shell                        \

Wait, no, who will use LINUX_VERSION_CODE2()?  Why export something like
this to userspace that no one is asking for?

> +	expr $(VERSION) \* 16777216 + 0$(PATCHLEVEL) \* 65536 + 0$(SUBLEVEL)); \
> +	echo \#define LINUX_VERSION_MAJOR $(VERSION);                    \
> +	echo \#define LINUX_VERSION_PATCHLEVEL $(PATCHLEVEL);            \
> +	echo \#define LINUX_VERSION_SUBLEVEL $(SUBLEVEL);                \

These are good to have, and clean up kernel code.

thanks,

greg k-h

Re: [PATCH 3/3] kbuild: introduce KERNEL_VERSION2 and LINUX_VERSION_CODE2

[Sasha Levin]

On Sat, Feb 06, 2021 at 09:45:44PM +0900, Masahiro Yamada wrote:
>On Sat, Feb 6, 2021 at 12:50 PM Sasha Levin <sashal@kernel.org> wrote:
>> -       ((c) > 255 ? 255 : (c)))'
>> +       ((c) > 255 ? 255 : (c)))';                                       \
>> +       echo \#define LINUX_VERSION_CODE2 $(shell                        \
>> +       expr $(VERSION) \* 16777216 + 0$(PATCHLEVEL) \* 65536 + 0$(SUBLEVEL)); \
>
>
>Is this needed?
>No one in this patch uses LINUX_VERSION_CODE2.
>
>The in-kernel code can use
>LINUX_VERSION_MAJOR/PATCHLEVEL/SUBLEVEL directly.
>
>
>Userspace does not need LINUX_VERSION_CODE2 either.
>
>Your comment in 2/3 states that
>userspace only decodes MAJOR and PATCHLEVEL fields,
>so LINUX_VERSION_CODE will still do well.

Yes, that's fair. I wanted to have that to make it easy for out of tree
code to handle in-kernel ABI changes but as we don't care about such
code there's no strict need for LINUX_VERSION_CODE2. I'll drop it.

>> index ab4b98b3165db..a56bf381335e9 100644
>> --- a/tools/perf/tests/bpf-script-example.c
>> +++ b/tools/perf/tests/bpf-script-example.c
>> @@ -5,7 +5,7 @@
>>   */
>>  #ifndef LINUX_VERSION_CODE
>>  # error Need LINUX_VERSION_CODE
>> -# error Example: for 4.2 kernel, put 'clang-opt="-DLINUX_VERSION_CODE=0x40200" into llvm section of ~/.perfconfig'
>> +# error Example: for 4.2 kernel, put 'clang-opt="-DLINUX_VERSION_CODE=0x4020000" into llvm section of ~/.perfconfig'
>
>
>Is this change needed?

Good point, no. I'll resend.

-- 
Thanks,
Sasha

Re: [PATCH 2/3] kbuild: clamp SUBLEVEL to 255

[Masahiro Yamada]

On Sat, Feb 6, 2021 at 12:50 PM Sasha Levin <sashal@kernel.org> wrote:
>
> Right now if SUBLEVEL becomes larger than 255 it will overflow into the
> territory of PATCHLEVEL, causing havoc in userspace that tests for
> specific kernel version.
>
> While userspace code tests for MAJOR and PATCHLEVEL, it doesn't test
> SUBLEVEL at any point as ABI changes don't happen in the context of
> stable tree.
>
> Thus, to avoid overflows, simply clamp SUBLEVEL to it's maximum value in
> the context of LINUX_VERSION_CODE. This does not affect "make
> kernelversion" and such.
>
> Signed-off-by: Sasha Levin <sashal@kernel.org>


I applied 2/3 to linux-kbuild.

Please resend only 3/3.

Thanks.



> ---
>  Makefile | 12 +++++++++---
>  1 file changed, 9 insertions(+), 3 deletions(-)
>
> diff --git a/Makefile b/Makefile
> index 49ac1b7fe8e99..157be50c691e5 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -1258,9 +1258,15 @@ define filechk_utsrelease.h
>  endef
>
>  define filechk_version.h
> -       echo \#define LINUX_VERSION_CODE $(shell                         \
> -       expr $(VERSION) \* 65536 + 0$(PATCHLEVEL) \* 256 + 0$(SUBLEVEL)); \
> -       echo '#define KERNEL_VERSION(a,b,c) (((a) << 16) + ((b) << 8) + (c))'
> +       if [ $(SUBLEVEL) -gt 255 ]; then                                 \
> +               echo \#define LINUX_VERSION_CODE $(shell                 \
> +               expr $(VERSION) \* 65536 + 0$(PATCHLEVEL) \* 256 + 255); \
> +       else                                                             \
> +               echo \#define LINUX_VERSION_CODE $(shell                 \
> +               expr $(VERSION) \* 65536 + 0$(PATCHLEVEL) \* 256 + $(SUBLEVEL)); \
> +       fi;                                                              \
> +       echo '#define KERNEL_VERSION(a,b,c) (((a) << 16) + ((b) << 8) +  \
> +       ((c) > 255 ? 255 : (c)))'
>  endef
>
>  $(version_h): FORCE
> --
> 2.27.0
>


-- 
Best Regards
Masahiro Yamada

RE: [PATCH 2/3] kbuild: clamp SUBLEVEL to 255

[David Laight]

From: Sasha Levin
> Sent: 06 February 2021 03:51
> 
> Right now if SUBLEVEL becomes larger than 255 it will overflow into the
> territory of PATCHLEVEL, causing havoc in userspace that tests for
> specific kernel version.
> 
> While userspace code tests for MAJOR and PATCHLEVEL, it doesn't test
> SUBLEVEL at any point as ABI changes don't happen in the context of
> stable tree.
> 
> Thus, to avoid overflows, simply clamp SUBLEVEL to it's maximum value in
> the context of LINUX_VERSION_CODE. This does not affect "make
> kernelversion" and such.
> 
> Signed-off-by: Sasha Levin <sashal@kernel.org>
> ---
>  Makefile | 12 +++++++++---
>  1 file changed, 9 insertions(+), 3 deletions(-)
> 
> diff --git a/Makefile b/Makefile
> index 49ac1b7fe8e99..157be50c691e5 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -1258,9 +1258,15 @@ define filechk_utsrelease.h
>  endef
> 
>  define filechk_version.h
> -	echo \#define LINUX_VERSION_CODE $(shell                         \
> -	expr $(VERSION) \* 65536 + 0$(PATCHLEVEL) \* 256 + 0$(SUBLEVEL)); \
> -	echo '#define KERNEL_VERSION(a,b,c) (((a) << 16) + ((b) << 8) + (c))'
> +	if [ $(SUBLEVEL) -gt 255 ]; then                                 \
> +		echo \#define LINUX_VERSION_CODE $(shell                 \
> +		expr $(VERSION) \* 65536 + 0$(PATCHLEVEL) \* 256 + 255); \
> +	else                                                             \
> +		echo \#define LINUX_VERSION_CODE $(shell                 \
> +		expr $(VERSION) \* 65536 + 0$(PATCHLEVEL) \* 256 + $(SUBLEVEL)); \
> +	fi;                                                              \
> +	echo '#define KERNEL_VERSION(a,b,c) (((a) << 16) + ((b) << 8) +  \
> +	((c) > 255 ? 255 : (c)))'
>  endef

Why not use KERNEL_VERSION to define LINUX_VERSION_CODE ?
Basically just:
	echo '#define LINUX_VERSION_CODE KERNEL_VERSION($(VERSION), $(PATCHLEVEL)+0, $(SUBLEVEL)+0)'

If PATCHLEVEL and SUBLEVEL are guaranteed to be non-empty the +0
can be removed.
The patch assumes they are non-empty, the original pre-prended 0
to stop syntax error for empty version strings.

Note that the expr version will process 08 and 09.
gcc will treat them as octal, and may error them.

	David

-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)

Re: [PATCH 2/3] kbuild: clamp SUBLEVEL to 255

[gregkh]

On Mon, Feb 08, 2021 at 01:48:06PM +0000, David Laight wrote:
> From: Sasha Levin
> > Sent: 06 February 2021 03:51
> > 
> > Right now if SUBLEVEL becomes larger than 255 it will overflow into the
> > territory of PATCHLEVEL, causing havoc in userspace that tests for
> > specific kernel version.
> > 
> > While userspace code tests for MAJOR and PATCHLEVEL, it doesn't test
> > SUBLEVEL at any point as ABI changes don't happen in the context of
> > stable tree.
> > 
> > Thus, to avoid overflows, simply clamp SUBLEVEL to it's maximum value in
> > the context of LINUX_VERSION_CODE. This does not affect "make
> > kernelversion" and such.
> > 
> > Signed-off-by: Sasha Levin <sashal@kernel.org>
> > ---
> >  Makefile | 12 +++++++++---
> >  1 file changed, 9 insertions(+), 3 deletions(-)
> > 
> > diff --git a/Makefile b/Makefile
> > index 49ac1b7fe8e99..157be50c691e5 100644
> > --- a/Makefile
> > +++ b/Makefile
> > @@ -1258,9 +1258,15 @@ define filechk_utsrelease.h
> >  endef
> > 
> >  define filechk_version.h
> > -	echo \#define LINUX_VERSION_CODE $(shell                         \
> > -	expr $(VERSION) \* 65536 + 0$(PATCHLEVEL) \* 256 + 0$(SUBLEVEL)); \
> > -	echo '#define KERNEL_VERSION(a,b,c) (((a) << 16) + ((b) << 8) + (c))'
> > +	if [ $(SUBLEVEL) -gt 255 ]; then                                 \
> > +		echo \#define LINUX_VERSION_CODE $(shell                 \
> > +		expr $(VERSION) \* 65536 + 0$(PATCHLEVEL) \* 256 + 255); \
> > +	else                                                             \
> > +		echo \#define LINUX_VERSION_CODE $(shell                 \
> > +		expr $(VERSION) \* 65536 + 0$(PATCHLEVEL) \* 256 + $(SUBLEVEL)); \
> > +	fi;                                                              \
> > +	echo '#define KERNEL_VERSION(a,b,c) (((a) << 16) + ((b) << 8) +  \
> > +	((c) > 255 ? 255 : (c)))'
> >  endef
> 
> Why not use KERNEL_VERSION to define LINUX_VERSION_CODE ?
> Basically just:
> 	echo '#define LINUX_VERSION_CODE KERNEL_VERSION($(VERSION), $(PATCHLEVEL)+0, $(SUBLEVEL)+0)'

Because we are "clamping" LINUX_VERSION_CODE() at a x.y.255, while
KERNEL_VERSION() continues on with the "real" minor number.

thanks,

greg k-h

RE: [PATCH 2/3] kbuild: clamp SUBLEVEL to 255

[David Laight]

From: gregkh@linuxfoundation.org
> Sent: 08 February 2021 14:09
> 
> On Mon, Feb 08, 2021 at 01:48:06PM +0000, David Laight wrote:
> > From: Sasha Levin
> > > Sent: 06 February 2021 03:51
> > >
> > > Right now if SUBLEVEL becomes larger than 255 it will overflow into the
> > > territory of PATCHLEVEL, causing havoc in userspace that tests for
> > > specific kernel version.
> > >
> > > While userspace code tests for MAJOR and PATCHLEVEL, it doesn't test
> > > SUBLEVEL at any point as ABI changes don't happen in the context of
> > > stable tree.
> > >
> > > Thus, to avoid overflows, simply clamp SUBLEVEL to it's maximum value in
> > > the context of LINUX_VERSION_CODE. This does not affect "make
> > > kernelversion" and such.
> > >
> > > Signed-off-by: Sasha Levin <sashal@kernel.org>
> > > ---
> > >  Makefile | 12 +++++++++---
> > >  1 file changed, 9 insertions(+), 3 deletions(-)
> > >
> > > diff --git a/Makefile b/Makefile
> > > index 49ac1b7fe8e99..157be50c691e5 100644
> > > --- a/Makefile
> > > +++ b/Makefile
> > > @@ -1258,9 +1258,15 @@ define filechk_utsrelease.h
> > >  endef
> > >
> > >  define filechk_version.h
> > > -	echo \#define LINUX_VERSION_CODE $(shell                         \
> > > -	expr $(VERSION) \* 65536 + 0$(PATCHLEVEL) \* 256 + 0$(SUBLEVEL)); \
> > > -	echo '#define KERNEL_VERSION(a,b,c) (((a) << 16) + ((b) << 8) + (c))'
> > > +	if [ $(SUBLEVEL) -gt 255 ]; then                                 \
> > > +		echo \#define LINUX_VERSION_CODE $(shell                 \
> > > +		expr $(VERSION) \* 65536 + 0$(PATCHLEVEL) \* 256 + 255); \
> > > +	else                                                             \
> > > +		echo \#define LINUX_VERSION_CODE $(shell                 \
> > > +		expr $(VERSION) \* 65536 + 0$(PATCHLEVEL) \* 256 + $(SUBLEVEL)); \
> > > +	fi;                                                              \
> > > +	echo '#define KERNEL_VERSION(a,b,c) (((a) << 16) + ((b) << 8) +  \
> > > +	((c) > 255 ? 255 : (c)))'
> > >  endef
> >
> > Why not use KERNEL_VERSION to define LINUX_VERSION_CODE ?
> > Basically just:
> > 	echo '#define LINUX_VERSION_CODE KERNEL_VERSION($(VERSION), $(PATCHLEVEL)+0, $(SUBLEVEL)+0)'
> 
> Because we are "clamping" LINUX_VERSION_CODE() at a x.y.255, while
> KERNEL_VERSION() continues on with the "real" minor number.

That particular patch (which I think Sasha applied) clamps both.

I know you (personally) don't care about OOT mudules, but a lot of
people do.
They will contain comparisons of KERNEL_VERSION against LINUX_VERSION_CODE.
They almost certainly don't care about the SUBLEVEL, but using different
encodings will break things.

The only real saving grace is that OOT modules tend to get built
against distro kernels which are likely to be 4.9.4-123456
so not hit whatever broken mapping you use for LTS kernels.

Another strange set of '#ifs' for new kernels is just part of the job.
It keeps me in work.

For a comparison the same driver object will load into windows 7
(and maybe even vista) and the current windows 10 kernel.
(But getting a windows driver signed is hard work.)

	David

-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)

Re: [PATCH 2/3] kbuild: clamp SUBLEVEL to 255

[Masahiro Yamada]

On Mon, Feb 8, 2021 at 10:48 PM David Laight <David.Laight@aculab.com> wrote:
>
> From: Sasha Levin
> > Sent: 06 February 2021 03:51
> >
> > Right now if SUBLEVEL becomes larger than 255 it will overflow into the
> > territory of PATCHLEVEL, causing havoc in userspace that tests for
> > specific kernel version.
> >
> > While userspace code tests for MAJOR and PATCHLEVEL, it doesn't test
> > SUBLEVEL at any point as ABI changes don't happen in the context of
> > stable tree.
> >
> > Thus, to avoid overflows, simply clamp SUBLEVEL to it's maximum value in
> > the context of LINUX_VERSION_CODE. This does not affect "make
> > kernelversion" and such.
> >
> > Signed-off-by: Sasha Levin <sashal@kernel.org>
> > ---
> >  Makefile | 12 +++++++++---
> >  1 file changed, 9 insertions(+), 3 deletions(-)
> >
> > diff --git a/Makefile b/Makefile
> > index 49ac1b7fe8e99..157be50c691e5 100644
> > --- a/Makefile
> > +++ b/Makefile
> > @@ -1258,9 +1258,15 @@ define filechk_utsrelease.h
> >  endef
> >
> >  define filechk_version.h
> > -     echo \#define LINUX_VERSION_CODE $(shell                         \
> > -     expr $(VERSION) \* 65536 + 0$(PATCHLEVEL) \* 256 + 0$(SUBLEVEL)); \
> > -     echo '#define KERNEL_VERSION(a,b,c) (((a) << 16) + ((b) << 8) + (c))'
> > +     if [ $(SUBLEVEL) -gt 255 ]; then                                 \
> > +             echo \#define LINUX_VERSION_CODE $(shell                 \
> > +             expr $(VERSION) \* 65536 + 0$(PATCHLEVEL) \* 256 + 255); \
> > +     else                                                             \
> > +             echo \#define LINUX_VERSION_CODE $(shell                 \
> > +             expr $(VERSION) \* 65536 + 0$(PATCHLEVEL) \* 256 + $(SUBLEVEL)); \
> > +     fi;                                                              \
> > +     echo '#define KERNEL_VERSION(a,b,c) (((a) << 16) + ((b) << 8) +  \
> > +     ((c) > 255 ? 255 : (c)))'
> >  endef
>
> Why not use KERNEL_VERSION to define LINUX_VERSION_CODE ?
> Basically just:
>         echo '#define LINUX_VERSION_CODE KERNEL_VERSION($(VERSION), $(PATCHLEVEL)+0, $(SUBLEVEL)+0)'




It was not possible to macrofy LINUX_VERSION_CODE.
(build error when CONFIG_KALLSYMS is disabled)


Presumably, this restriction will go away
with the following commit in linux-next.



commit e06af0b2ba02fc0cc2219a14c4c04ff0296a6f9f
Author: Masahiro Yamada <masahiroy@kernel.org>
Date:   Thu Jan 28 18:42:30 2021 +1100

    init/version.c: remove Version_<LINUX_VERSION_CODE> symbol





My plan is to refactor LINUX_VERSION_CODE in the next
development cycle.






> If PATCHLEVEL and SUBLEVEL are guaranteed to be non-empty the +0
> can be removed.
> The patch assumes they are non-empty, the original pre-prended 0
> to stop syntax error for empty version strings.
>
> Note that the expr version will process 08 and 09.
> gcc will treat them as octal, and may error them.
>
>         David
>
> -
> Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
> Registration No: 1397386 (Wales)
>
--
Best Regards
Masahiro Yamada