LinuxLists.cc - [PATCH] lib/siphash.c:: annotate implicit fall throughs

2019-01-14 20:20:47

Subject: [PATCH] lib/siphash.c:: annotate implicit fall throughs

2019-01-14 21:06:29

Subject: Re: [PATCH] lib/siphash.c:: annotate implicit fall throughs

On 1/14/19 2:19 PM, Mathieu Malaterre wrote:
> There is a plan to build the kernel with -Wimplicit-fallthrough and
> these places in the code produced warnings (W=1). Fix them up.
>
> This commit remove the following warnings:
>
> lib/siphash.c:71:12: warning: this statement may fall through [-Wimplicit-fallthrough=]
> lib/siphash.c:72:12: warning: this statement may fall through [-Wimplicit-fallthrough=]
> lib/siphash.c:73:12: warning: this statement may fall through [-Wimplicit-fallthrough=]
> lib/siphash.c:75:12: warning: this statement may fall through [-Wimplicit-fallthrough=]
> lib/siphash.c:434:12: warning: this statement may fall through [-Wimplicit-fallthrough=]
>
> Signed-off-by: Mathieu Malaterre <[email protected]>

Acked-by: Gustavo A. R. Silva <[email protected]>

> ---
> lib/siphash.c | 5 +++++
> 1 file changed, 5 insertions(+)
>
> diff --git a/lib/siphash.c b/lib/siphash.c
> index 3ae58b4edad6..b95624f5aa34 100644
> --- a/lib/siphash.c
> +++ b/lib/siphash.c
> @@ -69,10 +69,14 @@ u64 __siphash_aligned(const void *data, size_t len, const siphash_key_t *key)
> #else
> switch (left) {
> case 7: b |= ((u64)end[6]) << 48;
> + /* fall through */
> case 6: b |= ((u64)end[5]) << 40;
> + /* fall through */
> case 5: b |= ((u64)end[4]) << 32;
> + /* fall through */
> case 4: b |= le32_to_cpup(data); break;
> case 3: b |= ((u64)end[2]) << 16;
> + /* fall through */
> case 2: b |= le16_to_cpup(data); break;
> case 1: b |= end[0];
> }
> @@ -432,6 +436,7 @@ u32 __hsiphash_aligned(const void *data, size_t len, const hsiphash_key_t *key)
> }
> switch (left) {
> case 3: b |= ((u32)end[2]) << 16;
> + /* fall through */
> case 2: b |= le16_to_cpup(data); break;
> case 1: b |= end[0];
> }
>

2019-03-13 20:25:27

by Mathieu Malaterre

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Subject: [PATCH v2] lib/siphash.c: annotate implicit fall throughs

2019-03-13 20:43:39

by Jason A. Donenfeld

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Subject: Re: [PATCH v2] lib/siphash.c: annotate implicit fall throughs

Conceptually this seems pretty reasonable. Though, style-wise, perhaps
you might want to put those breaks on the next line too, i.e. s/;
break;/;\n\t\tbreak;/?

2019-03-13 20:47:19

by Gustavo A. R. Silva

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Subject: Re: [PATCH v2] lib/siphash.c: annotate implicit fall throughs

On 3/13/19 3:34 PM, Jason A. Donenfeld wrote:
> Conceptually this seems pretty reasonable. Though, style-wise, perhaps
> you might want to put those breaks on the next line too, i.e. s/;
> break;/;\n\t\tbreak;/?
>

I agree.

With that, you can add my:

Acked-by: Gustavo A. R. Silva <[email protected]>

Thanks
--
Gustavo

2019-03-13 20:53:51

by Mathieu Malaterre

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Subject: Re: [PATCH v2] lib/siphash.c: annotate implicit fall throughs

On Wed, Mar 13, 2019 at 9:34 PM Jason A. Donenfeld <[email protected]> wrote:
>
> Conceptually this seems pretty reasonable. Though, style-wise, perhaps
> you might want to put those breaks on the next line too, i.e. s/;
> break;/;\n\t\tbreak;/?

Good point. This needs some more love since checkpatch complains now with:

ERROR: trailing statements should be on next line
#42: FILE: lib/siphash.c:77:
+ case 4: b |= le32_to_cpup(data);

Let me merge all that and send a v2.

Thanks

2019-03-13 21:14:03

by Mathieu Malaterre

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Subject: [PATCH v3] lib/siphash.c: annotate implicit fall throughs

There is a plan to build the kernel with -Wimplicit-fallthrough and
these places in the code produced warnings (W=1). Fix them up.

This commit remove the following warnings:

lib/siphash.c:71:12: warning: this statement may fall through [-Wimplicit-fallthrough=]
lib/siphash.c:72:12: warning: this statement may fall through [-Wimplicit-fallthrough=]
lib/siphash.c:73:12: warning: this statement may fall through [-Wimplicit-fallthrough=]
lib/siphash.c:75:12: warning: this statement may fall through [-Wimplicit-fallthrough=]
lib/siphash.c:108:12: warning: this statement may fall through [-Wimplicit-fallthrough=]
lib/siphash.c:109:12: warning: this statement may fall through [-Wimplicit-fallthrough=]
lib/siphash.c:110:12: warning: this statement may fall through [-Wimplicit-fallthrough=]
lib/siphash.c:112:12: warning: this statement may fall through [-Wimplicit-fallthrough=]
lib/siphash.c:434:12: warning: this statement may fall through [-Wimplicit-fallthrough=]
lib/siphash.c:462:12: warning: this statement may fall through [-Wimplicit-fallthrough=]

Move the break statement onto the next line to match the fall-through
comment pattern. Also move the trailing statement onto the next line to
pass checkpatch verification.

Acked-by: "Gustavo A. R. Silva" <[email protected]>
Signed-off-by: Mathieu Malaterre <[email protected]>
---
v3: move break statements onto next line and please checkpatch
v2: some cases were missed in v1, update missing ones

lib/siphash.c | 76 +++++++++++++++++++++++++++++++++++++--------------
1 file changed, 56 insertions(+), 20 deletions(-)

diff --git a/lib/siphash.c b/lib/siphash.c
index 3ae58b4edad6..f459e0f4a14e 100644
--- a/lib/siphash.c
+++ b/lib/siphash.c
@@ -68,13 +68,26 @@ u64 __siphash_aligned(const void *data, size_t len, const siphash_key_t *key)
bytemask_from_count(left)));
#else
switch (left) {
- case 7: b |= ((u64)end[6]) << 48;
- case 6: b |= ((u64)end[5]) << 40;
- case 5: b |= ((u64)end[4]) << 32;
- case 4: b |= le32_to_cpup(data); break;
- case 3: b |= ((u64)end[2]) << 16;
- case 2: b |= le16_to_cpup(data); break;
- case 1: b |= end[0];
+ case 7:
+ b |= ((u64)end[6]) << 48;
+ /* fall through */
+ case 6:
+ b |= ((u64)end[5]) << 40;
+ /* fall through */
+ case 5:
+ b |= ((u64)end[4]) << 32;
+ /* fall through */
+ case 4:
+ b |= le32_to_cpup(data);
+ break;
+ case 3:
+ b |= ((u64)end[2]) << 16;
+ /* fall through */
+ case 2:
+ b |= le16_to_cpup(data);
+ break;
+ case 1:
+ b |= end[0];
}
#endif
POSTAMBLE
@@ -101,13 +114,26 @@ u64 __siphash_unaligned(const void *data, size_t len, const siphash_key_t *key)
bytemask_from_count(left)));
#else
switch (left) {
- case 7: b |= ((u64)end[6]) << 48;
- case 6: b |= ((u64)end[5]) << 40;
- case 5: b |= ((u64)end[4]) << 32;
- case 4: b |= get_unaligned_le32(end); break;
- case 3: b |= ((u64)end[2]) << 16;
- case 2: b |= get_unaligned_le16(end); break;
- case 1: b |= end[0];
+ case 7:
+ b |= ((u64)end[6]) << 48;
+ /* fall through */
+ case 6:
+ b |= ((u64)end[5]) << 40;
+ /* fall through */
+ case 5:
+ b |= ((u64)end[4]) << 32;
+ /* fall through */
+ case 4:
+ b |= get_unaligned_le32(end);
+ break;
+ case 3:
+ b |= ((u64)end[2]) << 16;
+ /* fall through */
+ case 2:
+ b |= get_unaligned_le16(end);
+ break;
+ case 1:
+ b |= end[0];
}
#endif
POSTAMBLE
@@ -431,9 +457,14 @@ u32 __hsiphash_aligned(const void *data, size_t len, const hsiphash_key_t *key)
v0 ^= m;
}
switch (left) {
- case 3: b |= ((u32)end[2]) << 16;
- case 2: b |= le16_to_cpup(data); break;
- case 1: b |= end[0];
+ case 3:
+ b |= ((u32)end[2]) << 16;
+ /* fall through */
+ case 2:
+ b |= le16_to_cpup(data);
+ break;
+ case 1:
+ b |= end[0];
}
HPOSTAMBLE
}
@@ -454,9 +485,14 @@ u32 __hsiphash_unaligned(const void *data, size_t len,
v0 ^= m;
}
switch (left) {
- case 3: b |= ((u32)end[2]) << 16;
- case 2: b |= get_unaligned_le16(end); break;
- case 1: b |= end[0];
+ case 3:
+ b |= ((u32)end[2]) << 16;
+ /* fall through */
+ case 2:
+ b |= get_unaligned_le16(end);
+ break;
+ case 1:
+ b |= end[0];
}
HPOSTAMBLE
}
--
2.20.1

2019-03-14 01:51:47

by Joe Perches

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Subject: Re: [PATCH v3] lib/siphash.c: annotate implicit fall throughs

On Wed, 2019-03-13 at 22:12 +0100, Mathieu Malaterre wrote:
> There is a plan to build the kernel with -Wimplicit-fallthrough and
> these places in the code produced warnings (W=1). Fix them up.
>
> This commit remove the following warnings:
>
> lib/siphash.c:71:12: warning: this statement may fall through [-Wimplicit-fallthrough=]
> lib/siphash.c:72:12: warning: this statement may fall through [-Wimplicit-fallthrough=]
> lib/siphash.c:73:12: warning: this statement may fall through [-Wimplicit-fallthrough=]
> lib/siphash.c:75:12: warning: this statement may fall through [-Wimplicit-fallthrough=]
> lib/siphash.c:108:12: warning: this statement may fall through [-Wimplicit-fallthrough=]
> lib/siphash.c:109:12: warning: this statement may fall through [-Wimplicit-fallthrough=]
> lib/siphash.c:110:12: warning: this statement may fall through [-Wimplicit-fallthrough=]
> lib/siphash.c:112:12: warning: this statement may fall through [-Wimplicit-fallthrough=]
> lib/siphash.c:434:12: warning: this statement may fall through [-Wimplicit-fallthrough=]
> lib/siphash.c:462:12: warning: this statement may fall through [-Wimplicit-fallthrough=]
>
> Move the break statement onto the next line to match the fall-through
> comment pattern. Also move the trailing statement onto the next line to
> pass checkpatch verification.
[]
> diff --git a/lib/siphash.c b/lib/siphash.c
[].
> @@ -68,13 +68,26 @@ u64 __siphash_aligned(const void *data, size_t len, const siphash_key_t *key)
> bytemask_from_count(left)));
> #else
> switch (left) {
> - case 7: b |= ((u64)end[6]) << 48;
> - case 6: b |= ((u64)end[5]) << 40;
> - case 5: b |= ((u64)end[4]) << 32;

It might also be worth not casting to u64 then shift
as that can be
moderately expensive on 32 bit systems
and instead use ((char
*)&b)[<appropriate_index>].

> - case 4: b |= le32_to_cpup(data); break;
> - case 3: b |= ((u64)end[2]) << 16;

Perhaps an unnecessary cast before shift

> - case 2: b |= le16_to_cpup(data); break;
> - case 1: b |= end[0];

[]

> @@ -101,13 +114,26 @@ u64 __siphash_unaligned(const void *data, size_t len, const siphash_key_t *key)
> bytemask_from_count(left)));
> #else
> switch (left) {
> - case 7: b |= ((u64)end[6]) << 48;
> - case 6: b |= ((u64)end[5]) << 40;
> - case 5: b |= ((u64)end[4]) << 32;

etc...

> - case 4: b |= get_unaligned_le32(end); break;
> - case 3: b |= ((u64)end[2]) << 16;
> - case 2: b |= get_unaligned_le16(end); break;
> - case 1: b |= end[0];

2019-03-14 07:02:19

by Jason A. Donenfeld

[permalink] [raw]

Subject: Re: [PATCH v3] lib/siphash.c: annotate implicit fall throughs

Hi Mathieu,

Thanks for getting this v3 into shape.

On Wed, Mar 13, 2019 at 3:12 PM Mathieu Malaterre <[email protected]> wrote:
> There is a plan to build the kernel with -Wimplicit-fallthrough and
> these places in the code produced warnings (W=1). Fix them up.
>
> This commit remove the following warnings:
>
> lib/siphash.c:71:12: warning: this statement may fall through [-Wimplicit-fallthrough=]
> lib/siphash.c:72:12: warning: this statement may fall through [-Wimplicit-fallthrough=]
> lib/siphash.c:73:12: warning: this statement may fall through [-Wimplicit-fallthrough=]
> lib/siphash.c:75:12: warning: this statement may fall through [-Wimplicit-fallthrough=]
> lib/siphash.c:108:12: warning: this statement may fall through [-Wimplicit-fallthrough=]
> lib/siphash.c:109:12: warning: this statement may fall through [-Wimplicit-fallthrough=]
> lib/siphash.c:110:12: warning: this statement may fall through [-Wimplicit-fallthrough=]
> lib/siphash.c:112:12: warning: this statement may fall through [-Wimplicit-fallthrough=]
> lib/siphash.c:434:12: warning: this statement may fall through [-Wimplicit-fallthrough=]
> lib/siphash.c:462:12: warning: this statement may fall through [-Wimplicit-fallthrough=]
>
> Move the break statement onto the next line to match the fall-through
> comment pattern. Also move the trailing statement onto the next line to
> pass checkpatch verification.
>
> Acked-by: "Gustavo A. R. Silva" <[email protected]>
> Signed-off-by: Mathieu Malaterre <[email protected]>
> ---
> v3: move break statements onto next line and please checkpatch
> v2: some cases were missed in v1, update missing ones
>
> lib/siphash.c | 76 +++++++++++++++++++++++++++++++++++++--------------
> 1 file changed, 56 insertions(+), 20 deletions(-)
>
> diff --git a/lib/siphash.c b/lib/siphash.c
> index 3ae58b4edad6..f459e0f4a14e 100644
> --- a/lib/siphash.c
> +++ b/lib/siphash.c
> @@ -68,13 +68,26 @@ u64 __siphash_aligned(const void *data, size_t len, const siphash_key_t *key)
> bytemask_from_count(left)));
> #else
> switch (left) {
> - case 7: b |= ((u64)end[6]) << 48;
> - case 6: b |= ((u64)end[5]) << 40;
> - case 5: b |= ((u64)end[4]) << 32;
> - case 4: b |= le32_to_cpup(data); break;
> - case 3: b |= ((u64)end[2]) << 16;
> - case 2: b |= le16_to_cpup(data); break;
> - case 1: b |= end[0];
> + case 7:
> + b |= ((u64)end[6]) << 48;
> + /* fall through */
> + case 6:
> + b |= ((u64)end[5]) << 40;
> + /* fall through */
> + case 5:
> + b |= ((u64)end[4]) << 32;
> + /* fall through */
> + case 4:
> + b |= le32_to_cpup(data);
> + break;
> + case 3:
> + b |= ((u64)end[2]) << 16;
> + /* fall through */
> + case 2:
> + b |= le16_to_cpup(data);
> + break;
> + case 1:
> + b |= end[0];
> }
> #endif
> POSTAMBLE
> @@ -101,13 +114,26 @@ u64 __siphash_unaligned(const void *data, size_t len, const siphash_key_t *key)
> bytemask_from_count(left)));
> #else
> switch (left) {
> - case 7: b |= ((u64)end[6]) << 48;
> - case 6: b |= ((u64)end[5]) << 40;
> - case 5: b |= ((u64)end[4]) << 32;
> - case 4: b |= get_unaligned_le32(end); break;
> - case 3: b |= ((u64)end[2]) << 16;
> - case 2: b |= get_unaligned_le16(end); break;
> - case 1: b |= end[0];
> + case 7:
> + b |= ((u64)end[6]) << 48;
> + /* fall through */
> + case 6:
> + b |= ((u64)end[5]) << 40;
> + /* fall through */
> + case 5:
> + b |= ((u64)end[4]) << 32;
> + /* fall through */
> + case 4:
> + b |= get_unaligned_le32(end);
> + break;
> + case 3:
> + b |= ((u64)end[2]) << 16;
> + /* fall through */
> + case 2:
> + b |= get_unaligned_le16(end);
> + break;
> + case 1:
> + b |= end[0];
> }
> #endif
> POSTAMBLE
> @@ -431,9 +457,14 @@ u32 __hsiphash_aligned(const void *data, size_t len, const hsiphash_key_t *key)
> v0 ^= m;
> }
> switch (left) {
> - case 3: b |= ((u32)end[2]) << 16;
> - case 2: b |= le16_to_cpup(data); break;
> - case 1: b |= end[0];
> + case 3:
> + b |= ((u32)end[2]) << 16;
> + /* fall through */
> + case 2:
> + b |= le16_to_cpup(data);
> + break;
> + case 1:
> + b |= end[0];
> }
> HPOSTAMBLE
> }
> @@ -454,9 +485,14 @@ u32 __hsiphash_unaligned(const void *data, size_t len,
> v0 ^= m;
> }
> switch (left) {
> - case 3: b |= ((u32)end[2]) << 16;
> - case 2: b |= get_unaligned_le16(end); break;
> - case 1: b |= end[0];
> + case 3:
> + b |= ((u32)end[2]) << 16;
> + /* fall through */
> + case 2:
> + b |= get_unaligned_le16(end);
> + break;
> + case 1:
> + b |= end[0];
> }
> HPOSTAMBLE
> }
> --
> 2.20.1

Reviewed-by: Jason A. Donenfeld <[email protected]>

Greg - would you take this through your tree?

Jason