[PATCH v2 0/3] PPC: Fix -Wimplicit-fallthrough for clang

[PATCH v2 0/3] PPC: Fix -Wimplicit-fallthrough for clang

[Nick Desaulniers]

While cleaning up the last few -Wimplicit-fallthrough warnings in tree
for Clang, I noticed
commit 6a9dc5fd6170d ("lib: Revert use of fallthrough pseudo-keyword in lib/")
which seemed to undo a bunch of fixes in lib/ due to breakage in
arch/powerpc/boot/ not including compiler_types.h.  We don't need
compiler_types.h for the definition of `fallthrough`, simply
compiler_attributes.h.  Include that, revert the revert to lib/, and fix
the last remaining cases I observed for powernv_defconfig.

Changes V1->V2:
* collect tags via b4 (fix Gustavo's tag as per Miguel in patch 2/3).
* reword commit message of patch 1/3 as per Arvind.
* reformat patch 2/3 as per kernel test robot and Gustavo.

Nick Desaulniers (3):
  powerpc: boot: include compiler_attributes.h
  Revert "lib: Revert use of fallthrough pseudo-keyword in lib/"
  powerpc: fix -Wimplicit-fallthrough

 arch/powerpc/boot/Makefile      |  1 +
 arch/powerpc/boot/decompress.c  |  1 -
 arch/powerpc/kernel/prom_init.c |  1 +
 arch/powerpc/kernel/uprobes.c   |  1 +
 arch/powerpc/perf/imc-pmu.c     |  1 +
 lib/asn1_decoder.c              |  4 ++--
 lib/assoc_array.c               |  2 +-
 lib/bootconfig.c                |  4 ++--
 lib/cmdline.c                   | 10 ++++-----
 lib/dim/net_dim.c               |  2 +-
 lib/dim/rdma_dim.c              |  4 ++--
 lib/glob.c                      |  2 +-
 lib/siphash.c                   | 36 ++++++++++++++++-----------------
 lib/ts_fsm.c                    |  2 +-
 lib/vsprintf.c                  | 14 ++++++-------
 lib/xz/xz_dec_lzma2.c           |  4 ++--
 lib/xz/xz_dec_stream.c          | 16 +++++++--------
 lib/zstd/bitstream.h            | 10 ++++-----
 lib/zstd/compress.c             |  2 +-
 lib/zstd/decompress.c           | 12 +++++------
 lib/zstd/huf_compress.c         | 17 +++++++++++-----
 21 files changed, 78 insertions(+), 68 deletions(-)

-- 
2.29.2.299.gdc1121823c-goog

[PATCH v2 1/3] powerpc: boot: include compiler_attributes.h

[Nick Desaulniers]

The kernel uses `-include` to include include/linux/compiler_types.h
into all translation units (see scripts/Makefile.lib), which #includes
compiler_attributes.h.

arch/powerpc/boot/ uses different compiler flags from the rest of the
kernel. As such, it doesn't contain the definitions from these headers,
and redefines a few that it needs.

For the purpose of enabling -Wimplicit-fallthrough for ppc, include
compiler_attributes.h via `-include`.

It was also noted in 6a9dc5fd6170 that we could -D__KERNEL__ and
-include compiler_types.h like the main kernel does, though testing that
produces a whole sea of warnings to cleanup. This approach is minimally
invasive.

Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Tested-by: Nathan Chancellor <natechancellor@gmail.com>
Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>
Acked-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Acked-by: Miguel Ojeda <ojeda@kernel.org>
Acked-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://github.com/ClangBuiltLinux/linux/issues/236
---
 arch/powerpc/boot/Makefile     | 1 +
 arch/powerpc/boot/decompress.c | 1 -
 2 files changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/powerpc/boot/Makefile b/arch/powerpc/boot/Makefile
index f8ce6d2dde7b..1659963a8f1d 100644
--- a/arch/powerpc/boot/Makefile
+++ b/arch/powerpc/boot/Makefile
@@ -31,6 +31,7 @@ endif
 BOOTCFLAGS    := -Wall -Wundef -Wstrict-prototypes -Wno-trigraphs \
 		 -fno-strict-aliasing -O2 -msoft-float -mno-altivec -mno-vsx \
 		 -pipe -fomit-frame-pointer -fno-builtin -fPIC -nostdinc \
+		 -include $(srctree)/include/linux/compiler_attributes.h \
 		 $(LINUXINCLUDE)
 
 ifdef CONFIG_PPC64_BOOT_WRAPPER
diff --git a/arch/powerpc/boot/decompress.c b/arch/powerpc/boot/decompress.c
index 8bf39ef7d2df..6098b879ac97 100644
--- a/arch/powerpc/boot/decompress.c
+++ b/arch/powerpc/boot/decompress.c
@@ -21,7 +21,6 @@
 
 #define STATIC static
 #define INIT
-#define __always_inline inline
 
 /*
  * The build process will copy the required zlib source files and headers
-- 
2.29.2.299.gdc1121823c-goog

[PATCH v2 2/3] Revert "lib: Revert use of fallthrough pseudo-keyword in lib/"

[Nick Desaulniers]

This reverts commit 6a9dc5fd6170 ("lib: Revert use of fallthrough
pseudo-keyword in lib/")

Now that we can build arch/powerpc/boot/ free of -Wimplicit-fallthrough,
re-enable these fixes for lib/.

Reformats HUF_compress1X_usingCTable() in lib/zstd/huf_compress.c to
avoid a smatch warning on "inconsistent indenting" reported by kernel
test robot.

Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Tested-by: Nathan Chancellor <natechancellor@gmail.com>
Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>
Reviewed-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Reviewed-by: Miguel Ojeda <ojeda@kernel.org>
Link: https://github.com/ClangBuiltLinux/linux/issues/236
---
 lib/asn1_decoder.c      |  4 ++--
 lib/assoc_array.c       |  2 +-
 lib/bootconfig.c        |  4 ++--
 lib/cmdline.c           | 10 +++++-----
 lib/dim/net_dim.c       |  2 +-
 lib/dim/rdma_dim.c      |  4 ++--
 lib/glob.c              |  2 +-
 lib/siphash.c           | 36 ++++++++++++++++++------------------
 lib/ts_fsm.c            |  2 +-
 lib/vsprintf.c          | 14 +++++++-------
 lib/xz/xz_dec_lzma2.c   |  4 ++--
 lib/xz/xz_dec_stream.c  | 16 ++++++++--------
 lib/zstd/bitstream.h    | 10 +++++-----
 lib/zstd/compress.c     |  2 +-
 lib/zstd/decompress.c   | 12 ++++++------
 lib/zstd/huf_compress.c | 17 ++++++++++++-----
 16 files changed, 74 insertions(+), 67 deletions(-)

diff --git a/lib/asn1_decoder.c b/lib/asn1_decoder.c
index 58f72b25f8e9..13da529e2e72 100644
--- a/lib/asn1_decoder.c
+++ b/lib/asn1_decoder.c
@@ -381,7 +381,7 @@ int asn1_ber_decoder(const struct asn1_decoder *decoder,
 	case ASN1_OP_END_SET_ACT:
 		if (unlikely(!(flags & FLAG_MATCHED)))
 			goto tag_mismatch;
-		/* fall through */
+		fallthrough;
 
 	case ASN1_OP_END_SEQ:
 	case ASN1_OP_END_SET_OF:
@@ -448,7 +448,7 @@ int asn1_ber_decoder(const struct asn1_decoder *decoder,
 			pc += asn1_op_lengths[op];
 			goto next_op;
 		}
-		/* fall through */
+		fallthrough;
 
 	case ASN1_OP_ACT:
 		ret = actions[machine[pc + 1]](context, hdr, tag, data + tdp, len);
diff --git a/lib/assoc_array.c b/lib/assoc_array.c
index 6f4bcf524554..04c98799c3ba 100644
--- a/lib/assoc_array.c
+++ b/lib/assoc_array.c
@@ -1113,7 +1113,7 @@ struct assoc_array_edit *assoc_array_delete(struct assoc_array *array,
 						index_key))
 				goto found_leaf;
 		}
-		/* fall through */
+		fallthrough;
 	case assoc_array_walk_tree_empty:
 	case assoc_array_walk_found_wrong_shortcut:
 	default:
diff --git a/lib/bootconfig.c b/lib/bootconfig.c
index 649ed44f199c..9f8c70a98fcf 100644
--- a/lib/bootconfig.c
+++ b/lib/bootconfig.c
@@ -827,7 +827,7 @@ int __init xbc_init(char *buf, const char **emsg, int *epos)
 							q - 2);
 				break;
 			}
-			/* fall through */
+			fallthrough;
 		case '=':
 			ret = xbc_parse_kv(&p, q, c);
 			break;
@@ -836,7 +836,7 @@ int __init xbc_init(char *buf, const char **emsg, int *epos)
 			break;
 		case '#':
 			q = skip_comment(q);
-			/* fall through */
+			fallthrough;
 		case ';':
 		case '\n':
 			ret = xbc_parse_key(&p, q);
diff --git a/lib/cmdline.c b/lib/cmdline.c
index 9e186234edc0..46f2cb4ce6d1 100644
--- a/lib/cmdline.c
+++ b/lib/cmdline.c
@@ -144,23 +144,23 @@ unsigned long long memparse(const char *ptr, char **retptr)
 	case 'E':
 	case 'e':
 		ret <<= 10;
-		/* fall through */
+		fallthrough;
 	case 'P':
 	case 'p':
 		ret <<= 10;
-		/* fall through */
+		fallthrough;
 	case 'T':
 	case 't':
 		ret <<= 10;
-		/* fall through */
+		fallthrough;
 	case 'G':
 	case 'g':
 		ret <<= 10;
-		/* fall through */
+		fallthrough;
 	case 'M':
 	case 'm':
 		ret <<= 10;
-		/* fall through */
+		fallthrough;
 	case 'K':
 	case 'k':
 		ret <<= 10;
diff --git a/lib/dim/net_dim.c b/lib/dim/net_dim.c
index a4db51c21266..06811d866775 100644
--- a/lib/dim/net_dim.c
+++ b/lib/dim/net_dim.c
@@ -233,7 +233,7 @@ void net_dim(struct dim *dim, struct dim_sample end_sample)
 			schedule_work(&dim->work);
 			break;
 		}
-		/* fall through */
+		fallthrough;
 	case DIM_START_MEASURE:
 		dim_update_sample(end_sample.event_ctr, end_sample.pkt_ctr,
 				  end_sample.byte_ctr, &dim->start_sample);
diff --git a/lib/dim/rdma_dim.c b/lib/dim/rdma_dim.c
index f7e26c7b4749..15462d54758d 100644
--- a/lib/dim/rdma_dim.c
+++ b/lib/dim/rdma_dim.c
@@ -59,7 +59,7 @@ static bool rdma_dim_decision(struct dim_stats *curr_stats, struct dim *dim)
 			break;
 		case DIM_STATS_WORSE:
 			dim_turn(dim);
-			/* fall through */
+			fallthrough;
 		case DIM_STATS_BETTER:
 			step_res = rdma_dim_step(dim);
 			if (step_res == DIM_ON_EDGE)
@@ -94,7 +94,7 @@ void rdma_dim(struct dim *dim, u64 completions)
 			schedule_work(&dim->work);
 			break;
 		}
-		/* fall through */
+		fallthrough;
 	case DIM_START_MEASURE:
 		dim->state = DIM_MEASURE_IN_PROGRESS;
 		dim_update_sample_with_comps(curr_sample->event_ctr, 0, 0,
diff --git a/lib/glob.c b/lib/glob.c
index 52e3ed7e4a9b..85ecbda45cd8 100644
--- a/lib/glob.c
+++ b/lib/glob.c
@@ -102,7 +102,7 @@ bool __pure glob_match(char const *pat, char const *str)
 			break;
 		case '\\':
 			d = *pat++;
-			/* fall through */
+			fallthrough;
 		default:	/* Literal character */
 literal:
 			if (c == d) {
diff --git a/lib/siphash.c b/lib/siphash.c
index c47bb6ff2149..a90112ee72a1 100644
--- a/lib/siphash.c
+++ b/lib/siphash.c
@@ -68,11 +68,11 @@ 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; /* fall through */
-	case 6: b |= ((u64)end[5]) << 40; /* fall through */
-	case 5: b |= ((u64)end[4]) << 32; /* fall through */
+	case 7: b |= ((u64)end[6]) << 48; fallthrough;
+	case 6: b |= ((u64)end[5]) << 40; fallthrough;
+	case 5: b |= ((u64)end[4]) << 32; fallthrough;
 	case 4: b |= le32_to_cpup(data); break;
-	case 3: b |= ((u64)end[2]) << 16; /* fall through */
+	case 3: b |= ((u64)end[2]) << 16; fallthrough;
 	case 2: b |= le16_to_cpup(data); break;
 	case 1: b |= end[0];
 	}
@@ -101,11 +101,11 @@ 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; /* fall through */
-	case 6: b |= ((u64)end[5]) << 40; /* fall through */
-	case 5: b |= ((u64)end[4]) << 32; /* fall through */
+	case 7: b |= ((u64)end[6]) << 48; fallthrough;
+	case 6: b |= ((u64)end[5]) << 40; fallthrough;
+	case 5: b |= ((u64)end[4]) << 32; fallthrough;
 	case 4: b |= get_unaligned_le32(end); break;
-	case 3: b |= ((u64)end[2]) << 16; /* fall through */
+	case 3: b |= ((u64)end[2]) << 16; fallthrough;
 	case 2: b |= get_unaligned_le16(end); break;
 	case 1: b |= end[0];
 	}
@@ -268,11 +268,11 @@ u32 __hsiphash_aligned(const void *data, size_t len, const hsiphash_key_t *key)
 						  bytemask_from_count(left)));
 #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 7: b |= ((u64)end[6]) << 48; fallthrough;
+	case 6: b |= ((u64)end[5]) << 40; fallthrough;
+	case 5: b |= ((u64)end[4]) << 32; fallthrough;
 	case 4: b |= le32_to_cpup(data); break;
-	case 3: b |= ((u64)end[2]) << 16; /* fall through */
+	case 3: b |= ((u64)end[2]) << 16; fallthrough;
 	case 2: b |= le16_to_cpup(data); break;
 	case 1: b |= end[0];
 	}
@@ -301,11 +301,11 @@ u32 __hsiphash_unaligned(const void *data, size_t len,
 						  bytemask_from_count(left)));
 #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 7: b |= ((u64)end[6]) << 48; fallthrough;
+	case 6: b |= ((u64)end[5]) << 40; fallthrough;
+	case 5: b |= ((u64)end[4]) << 32; fallthrough;
 	case 4: b |= get_unaligned_le32(end); break;
-	case 3: b |= ((u64)end[2]) << 16; /* fall through */
+	case 3: b |= ((u64)end[2]) << 16; fallthrough;
 	case 2: b |= get_unaligned_le16(end); break;
 	case 1: b |= end[0];
 	}
@@ -431,7 +431,7 @@ 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; /* fall through */
+	case 3: b |= ((u32)end[2]) << 16; fallthrough;
 	case 2: b |= le16_to_cpup(data); break;
 	case 1: b |= end[0];
 	}
@@ -454,7 +454,7 @@ u32 __hsiphash_unaligned(const void *data, size_t len,
 		v0 ^= m;
 	}
 	switch (left) {
-	case 3: b |= ((u32)end[2]) << 16; /* fall through */
+	case 3: b |= ((u32)end[2]) << 16; fallthrough;
 	case 2: b |= get_unaligned_le16(end); break;
 	case 1: b |= end[0];
 	}
diff --git a/lib/ts_fsm.c b/lib/ts_fsm.c
index ab749ec10ab5..64fd9015ad80 100644
--- a/lib/ts_fsm.c
+++ b/lib/ts_fsm.c
@@ -193,7 +193,7 @@ static unsigned int fsm_find(struct ts_config *conf, struct ts_state *state)
 				TOKEN_MISMATCH();
 
 			block_idx++;
-			/* fall through */
+			fallthrough;
 
 		case TS_FSM_ANY:
 			if (next == NULL)
diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index 14c9a6af1b23..d3c5c16f391c 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -1265,7 +1265,7 @@ char *mac_address_string(char *buf, char *end, u8 *addr,
 
 	case 'R':
 		reversed = true;
-		/* fall through */
+		fallthrough;
 
 	default:
 		separator = ':';
@@ -1682,7 +1682,7 @@ char *uuid_string(char *buf, char *end, const u8 *addr,
 	switch (*(++fmt)) {
 	case 'L':
 		uc = true;
-		/* fall through */
+		fallthrough;
 	case 'l':
 		index = guid_index;
 		break;
@@ -2219,7 +2219,7 @@ char *pointer(const char *fmt, char *buf, char *end, void *ptr,
 	case 'S':
 	case 's':
 		ptr = dereference_symbol_descriptor(ptr);
-		/* fall through */
+		fallthrough;
 	case 'B':
 		return symbol_string(buf, end, ptr, spec, fmt);
 	case 'R':
@@ -2450,7 +2450,7 @@ int format_decode(const char *fmt, struct printf_spec *spec)
 
 	case 'x':
 		spec->flags |= SMALL;
-		/* fall through */
+		fallthrough;
 
 	case 'X':
 		spec->base = 16;
@@ -2468,7 +2468,7 @@ int format_decode(const char *fmt, struct printf_spec *spec)
 		 * utility, treat it as any other invalid or
 		 * unsupported format specifier.
 		 */
-		/* fall through */
+		fallthrough;
 
 	default:
 		WARN_ONCE(1, "Please remove unsupported %%%c in format string\n", *fmt);
@@ -3411,10 +3411,10 @@ int vsscanf(const char *buf, const char *fmt, va_list args)
 			break;
 		case 'i':
 			base = 0;
-			/* fall through */
+			fallthrough;
 		case 'd':
 			is_sign = true;
-			/* fall through */
+			fallthrough;
 		case 'u':
 			break;
 		case '%':
diff --git a/lib/xz/xz_dec_lzma2.c b/lib/xz/xz_dec_lzma2.c
index 65a1aad8c223..ca2603abee08 100644
--- a/lib/xz/xz_dec_lzma2.c
+++ b/lib/xz/xz_dec_lzma2.c
@@ -1043,7 +1043,7 @@ XZ_EXTERN enum xz_ret xz_dec_lzma2_run(struct xz_dec_lzma2 *s,
 
 			s->lzma2.sequence = SEQ_LZMA_PREPARE;
 
-			/* fall through */
+			fallthrough;
 
 		case SEQ_LZMA_PREPARE:
 			if (s->lzma2.compressed < RC_INIT_BYTES)
@@ -1055,7 +1055,7 @@ XZ_EXTERN enum xz_ret xz_dec_lzma2_run(struct xz_dec_lzma2 *s,
 			s->lzma2.compressed -= RC_INIT_BYTES;
 			s->lzma2.sequence = SEQ_LZMA_RUN;
 
-			/* fall through */
+			fallthrough;
 
 		case SEQ_LZMA_RUN:
 			/*
diff --git a/lib/xz/xz_dec_stream.c b/lib/xz/xz_dec_stream.c
index 32ab2a08b7cb..fea86deaaa01 100644
--- a/lib/xz/xz_dec_stream.c
+++ b/lib/xz/xz_dec_stream.c
@@ -583,7 +583,7 @@ static enum xz_ret dec_main(struct xz_dec *s, struct xz_buf *b)
 			if (ret != XZ_OK)
 				return ret;
 
-			/* fall through */
+			fallthrough;
 
 		case SEQ_BLOCK_START:
 			/* We need one byte of input to continue. */
@@ -608,7 +608,7 @@ static enum xz_ret dec_main(struct xz_dec *s, struct xz_buf *b)
 			s->temp.pos = 0;
 			s->sequence = SEQ_BLOCK_HEADER;
 
-			/* fall through */
+			fallthrough;
 
 		case SEQ_BLOCK_HEADER:
 			if (!fill_temp(s, b))
@@ -620,7 +620,7 @@ static enum xz_ret dec_main(struct xz_dec *s, struct xz_buf *b)
 
 			s->sequence = SEQ_BLOCK_UNCOMPRESS;
 
-			/* fall through */
+			fallthrough;
 
 		case SEQ_BLOCK_UNCOMPRESS:
 			ret = dec_block(s, b);
@@ -629,7 +629,7 @@ static enum xz_ret dec_main(struct xz_dec *s, struct xz_buf *b)
 
 			s->sequence = SEQ_BLOCK_PADDING;
 
-			/* fall through */
+			fallthrough;
 
 		case SEQ_BLOCK_PADDING:
 			/*
@@ -651,7 +651,7 @@ static enum xz_ret dec_main(struct xz_dec *s, struct xz_buf *b)
 
 			s->sequence = SEQ_BLOCK_CHECK;
 
-			/* fall through */
+			fallthrough;
 
 		case SEQ_BLOCK_CHECK:
 			if (s->check_type == XZ_CHECK_CRC32) {
@@ -675,7 +675,7 @@ static enum xz_ret dec_main(struct xz_dec *s, struct xz_buf *b)
 
 			s->sequence = SEQ_INDEX_PADDING;
 
-			/* fall through */
+			fallthrough;
 
 		case SEQ_INDEX_PADDING:
 			while ((s->index.size + (b->in_pos - s->in_start))
@@ -699,7 +699,7 @@ static enum xz_ret dec_main(struct xz_dec *s, struct xz_buf *b)
 
 			s->sequence = SEQ_INDEX_CRC32;
 
-			/* fall through */
+			fallthrough;
 
 		case SEQ_INDEX_CRC32:
 			ret = crc32_validate(s, b);
@@ -709,7 +709,7 @@ static enum xz_ret dec_main(struct xz_dec *s, struct xz_buf *b)
 			s->temp.size = STREAM_HEADER_SIZE;
 			s->sequence = SEQ_STREAM_FOOTER;
 
-			/* fall through */
+			fallthrough;
 
 		case SEQ_STREAM_FOOTER:
 			if (!fill_temp(s, b))
diff --git a/lib/zstd/bitstream.h b/lib/zstd/bitstream.h
index 3a49784d5c61..7c65c66e41fd 100644
--- a/lib/zstd/bitstream.h
+++ b/lib/zstd/bitstream.h
@@ -259,15 +259,15 @@ ZSTD_STATIC size_t BIT_initDStream(BIT_DStream_t *bitD, const void *srcBuffer, s
 		bitD->bitContainer = *(const BYTE *)(bitD->start);
 		switch (srcSize) {
 		case 7: bitD->bitContainer += (size_t)(((const BYTE *)(srcBuffer))[6]) << (sizeof(bitD->bitContainer) * 8 - 16);
-			/* fall through */
+			fallthrough;
 		case 6: bitD->bitContainer += (size_t)(((const BYTE *)(srcBuffer))[5]) << (sizeof(bitD->bitContainer) * 8 - 24);
-			/* fall through */
+			fallthrough;
 		case 5: bitD->bitContainer += (size_t)(((const BYTE *)(srcBuffer))[4]) << (sizeof(bitD->bitContainer) * 8 - 32);
-			/* fall through */
+			fallthrough;
 		case 4: bitD->bitContainer += (size_t)(((const BYTE *)(srcBuffer))[3]) << 24;
-			/* fall through */
+			fallthrough;
 		case 3: bitD->bitContainer += (size_t)(((const BYTE *)(srcBuffer))[2]) << 16;
-			/* fall through */
+			fallthrough;
 		case 2: bitD->bitContainer += (size_t)(((const BYTE *)(srcBuffer))[1]) << 8;
 		default:;
 		}
diff --git a/lib/zstd/compress.c b/lib/zstd/compress.c
index 5e0b67003e55..b080264ed3ad 100644
--- a/lib/zstd/compress.c
+++ b/lib/zstd/compress.c
@@ -3182,7 +3182,7 @@ static size_t ZSTD_compressStream_generic(ZSTD_CStream *zcs, void *dst, size_t *
 				zcs->outBuffFlushedSize = 0;
 				zcs->stage = zcss_flush; /* pass-through to flush stage */
 			}
-			/* fall through */
+			fallthrough;
 
 		case zcss_flush: {
 			size_t const toFlush = zcs->outBuffContentSize - zcs->outBuffFlushedSize;
diff --git a/lib/zstd/decompress.c b/lib/zstd/decompress.c
index db6761ea4deb..66cd487a326a 100644
--- a/lib/zstd/decompress.c
+++ b/lib/zstd/decompress.c
@@ -442,7 +442,7 @@ size_t ZSTD_decodeLiteralsBlock(ZSTD_DCtx *dctx, const void *src, size_t srcSize
 		case set_repeat:
 			if (dctx->litEntropy == 0)
 				return ERROR(dictionary_corrupted);
-			/* fall through */
+			fallthrough;
 		case set_compressed:
 			if (srcSize < 5)
 				return ERROR(corruption_detected); /* srcSize >= MIN_CBLOCK_SIZE == 3; here we need up to 5 for case 3 */
@@ -1768,7 +1768,7 @@ size_t ZSTD_decompressContinue(ZSTD_DCtx *dctx, void *dst, size_t dstCapacity, c
 			return 0;
 		}
 		dctx->expected = 0; /* not necessary to copy more */
-		/* fall through */
+		fallthrough;
 
 	case ZSTDds_decodeFrameHeader:
 		memcpy(dctx->headerBuffer + ZSTD_frameHeaderSize_prefix, src, dctx->expected);
@@ -2309,7 +2309,7 @@ size_t ZSTD_decompressStream(ZSTD_DStream *zds, ZSTD_outBuffer *output, ZSTD_inB
 		switch (zds->stage) {
 		case zdss_init:
 			ZSTD_resetDStream(zds); /* transparent reset on starting decoding a new frame */
-			/* fall through */
+			fallthrough;
 
 		case zdss_loadHeader: {
 			size_t const hSize = ZSTD_getFrameParams(&zds->fParams, zds->headerBuffer, zds->lhSize);
@@ -2376,7 +2376,7 @@ size_t ZSTD_decompressStream(ZSTD_DStream *zds, ZSTD_outBuffer *output, ZSTD_inB
 			}
 			zds->stage = zdss_read;
 		}
-			/* fall through */
+			fallthrough;
 
 		case zdss_read: {
 			size_t const neededInSize = ZSTD_nextSrcSizeToDecompress(zds->dctx);
@@ -2405,7 +2405,7 @@ size_t ZSTD_decompressStream(ZSTD_DStream *zds, ZSTD_outBuffer *output, ZSTD_inB
 			zds->stage = zdss_load;
 			/* pass-through */
 		}
-			/* fall through */
+			fallthrough;
 
 		case zdss_load: {
 			size_t const neededInSize = ZSTD_nextSrcSizeToDecompress(zds->dctx);
@@ -2438,7 +2438,7 @@ size_t ZSTD_decompressStream(ZSTD_DStream *zds, ZSTD_outBuffer *output, ZSTD_inB
 				/* pass-through */
 			}
 		}
-			/* fall through */
+			fallthrough;
 
 		case zdss_flush: {
 			size_t const toFlushSize = zds->outEnd - zds->outStart;
diff --git a/lib/zstd/huf_compress.c b/lib/zstd/huf_compress.c
index e727812d12aa..e23279089293 100644
--- a/lib/zstd/huf_compress.c
+++ b/lib/zstd/huf_compress.c
@@ -555,11 +555,18 @@ size_t HUF_compress1X_usingCTable(void *dst, size_t dstSize, const void *src, si
 
 	n = srcSize & ~3; /* join to mod 4 */
 	switch (srcSize & 3) {
-	case 3: HUF_encodeSymbol(&bitC, ip[n + 2], CTable); HUF_FLUSHBITS_2(&bitC);
-		/* fall through */
-	case 2: HUF_encodeSymbol(&bitC, ip[n + 1], CTable); HUF_FLUSHBITS_1(&bitC);
-		/* fall through */
-	case 1: HUF_encodeSymbol(&bitC, ip[n + 0], CTable); HUF_FLUSHBITS(&bitC);
+	case 3:
+		HUF_encodeSymbol(&bitC, ip[n + 2], CTable);
+		HUF_FLUSHBITS_2(&bitC);
+		fallthrough;
+	case 2:
+		HUF_encodeSymbol(&bitC, ip[n + 1], CTable);
+		HUF_FLUSHBITS_1(&bitC);
+		fallthrough;
+	case 1:
+		HUF_encodeSymbol(&bitC, ip[n + 0], CTable);
+		HUF_FLUSHBITS(&bitC);
+		break;
 	case 0:
 	default:;
 	}
-- 
2.29.2.299.gdc1121823c-goog

[PATCH v2 3/3] powerpc: fix -Wimplicit-fallthrough

[Nick Desaulniers]

The "fallthrough" pseudo-keyword was added as a portable way to denote
intentional fallthrough. Clang will still warn on cases where there is a
fallthrough to an immediate break. Add explicit breaks for those cases.

Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Tested-by: Nathan Chancellor <natechancellor@gmail.com>
Reviewed-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Reviewed-by: Miguel Ojeda <ojeda@kernel.org>
Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>
Acked-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://github.com/ClangBuiltLinux/linux/issues/236
---
 arch/powerpc/kernel/prom_init.c | 1 +
 arch/powerpc/kernel/uprobes.c   | 1 +
 arch/powerpc/perf/imc-pmu.c     | 1 +
 3 files changed, 3 insertions(+)

diff --git a/arch/powerpc/kernel/prom_init.c b/arch/powerpc/kernel/prom_init.c
index 38ae5933d917..e9d4eb6144e1 100644
--- a/arch/powerpc/kernel/prom_init.c
+++ b/arch/powerpc/kernel/prom_init.c
@@ -355,6 +355,7 @@ static int __init prom_strtobool(const char *s, bool *res)
 		default:
 			break;
 		}
+		break;
 	default:
 		break;
 	}
diff --git a/arch/powerpc/kernel/uprobes.c b/arch/powerpc/kernel/uprobes.c
index d200e7df7167..e8a63713e655 100644
--- a/arch/powerpc/kernel/uprobes.c
+++ b/arch/powerpc/kernel/uprobes.c
@@ -141,6 +141,7 @@ int arch_uprobe_exception_notify(struct notifier_block *self,
 	case DIE_SSTEP:
 		if (uprobe_post_sstep_notifier(regs))
 			return NOTIFY_STOP;
+		break;
 	default:
 		break;
 	}
diff --git a/arch/powerpc/perf/imc-pmu.c b/arch/powerpc/perf/imc-pmu.c
index 7b25548ec42b..e106909ff9c3 100644
--- a/arch/powerpc/perf/imc-pmu.c
+++ b/arch/powerpc/perf/imc-pmu.c
@@ -1500,6 +1500,7 @@ static int update_pmu_ops(struct imc_pmu *pmu)
 		pmu->pmu.stop = trace_imc_event_stop;
 		pmu->pmu.read = trace_imc_event_read;
 		pmu->attr_groups[IMC_FORMAT_ATTR] = &trace_imc_format_group;
+		break;
 	default:
 		break;
 	}
-- 
2.29.2.299.gdc1121823c-goog

Re: [PATCH v2 1/3] powerpc: boot: include compiler_attributes.h

[Miguel Ojeda]

On Wed, Nov 18, 2020 at 1:08 AM Nick Desaulniers
<ndesaulniers@google.com> wrote:
>
> It was also noted in 6a9dc5fd6170 that we could -D__KERNEL__ and
> -include compiler_types.h like the main kernel does, though testing that
> produces a whole sea of warnings to cleanup.

(Re; for Gustavo to consider since he took it now): I would add a
comment noting this as a reminder -- it also helps to entice a
cleanup.

Cheers,
Miguel

Re: [PATCH v2 0/3] PPC: Fix -Wimplicit-fallthrough for clang

[Gustavo A. R. Silva]

Nick,

On Tue, Nov 17, 2020 at 04:07:48PM -0800, Nick Desaulniers wrote:
> While cleaning up the last few -Wimplicit-fallthrough warnings in tree
> for Clang, I noticed
> commit 6a9dc5fd6170d ("lib: Revert use of fallthrough pseudo-keyword in lib/")
> which seemed to undo a bunch of fixes in lib/ due to breakage in
> arch/powerpc/boot/ not including compiler_types.h.  We don't need
> compiler_types.h for the definition of `fallthrough`, simply
> compiler_attributes.h.  Include that, revert the revert to lib/, and fix
> the last remaining cases I observed for powernv_defconfig.

I've added the series to my -next tree, together with Miguel's
suggestions.

Thanks for the Acks and comments, Michael.

--
Gustavo