hpilo: Replace one-element array with flexible-array member
There is a regular need in the kernel to provide a way to declare having a dynamically sized set of trailing elements in a structure. Kernel code should always use “flexible array members”[1] for these cases. The older style of one-element or zero-length arrays should no longer be used[2]. For this particular case, it is important to notice that the cachelines change from 7 to 6 after the flexible-array conversion: $ pahole -C 'fifo' drivers/misc/hpilo.o struct fifo { u64 nrents; /* 0 8 */ u64 imask; /* 8 8 */ u64 merge; /* 16 8 */ u64 reset; /* 24 8 */ u8 pad_0[96]; /* 32 96 */ /* --- cacheline 2 boundary (128 bytes) --- */ u64 head; /* 128 8 */ u8 pad_1[120]; /* 136 120 */ /* --- cacheline 4 boundary (256 bytes) --- */ u64 tail; /* 256 8 */ u8 pad_2[120]; /* 264 120 */ /* --- cacheline 6 boundary (384 bytes) --- */ u64 fifobar[1]; /* 384 8 */ /* size: 392, cachelines: 7, members: 10 */ /* last cacheline: 8 bytes */ }; $ pahole -C 'fifo' drivers/misc/hpilo.o struct fifo { u64 nrents; /* 0 8 */ u64 imask; /* 8 8 */ u64 merge; /* 16 8 */ u64 reset; /* 24 8 */ u8 pad_0[96]; /* 32 96 */ /* --- cacheline 2 boundary (128 bytes) --- */ u64 head; /* 128 8 */ u8 pad_1[120]; /* 136 120 */ /* --- cacheline 4 boundary (256 bytes) --- */ u64 tail; /* 256 8 */ u8 pad_2[120]; /* 264 120 */ /* --- cacheline 6 boundary (384 bytes) --- */ u64 fifobar[]; /* 384 0 */ /* size: 384, cachelines: 6, members: 10 */ }; Lastly, remove unnecessary parentheses in fifo_sz() and fix the following checkpatch.pl warning for the whole fifo structure: WARNING: please, no spaces at the start of a line [1] https://en.wikipedia.org/wiki/Flexible_array_member [2] https://github.com/KSPP/linux/issues/79 Tested-by: kernel test robot <lkp@intel.com> Link: https://github.com/GustavoARSilva/linux-hardening/blob/master/cii/kernel-ci/hpilo-20200714.md Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org> Link: https://lore.kernel.org/r/20200714154449.GA26153@embeddedor Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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@ -207,7 +207,7 @@ static void ctrl_setup(struct ccb *ccb, int nr_desc, int l2desc_sz)
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static inline int fifo_sz(int nr_entry)
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{
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/* size of a fifo is determined by the number of entries it contains */
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return (nr_entry * sizeof(u64)) + FIFOHANDLESIZE;
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return nr_entry * sizeof(u64) + FIFOHANDLESIZE;
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}
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static void fifo_setup(void *base_addr, int nr_entry)
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@ -160,23 +160,23 @@ struct ccb_data {
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#define ILO_START_ALIGN 4096
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#define ILO_CACHE_SZ 128
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struct fifo {
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u64 nrents; /* user requested number of fifo entries */
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u64 imask; /* mask to extract valid fifo index */
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u64 merge; /* O/C bits to merge in during enqueue operation */
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u64 reset; /* set to non-zero when the target device resets */
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u8 pad_0[ILO_CACHE_SZ - (sizeof(u64) * 4)];
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u64 nrents; /* user requested number of fifo entries */
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u64 imask; /* mask to extract valid fifo index */
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u64 merge; /* O/C bits to merge in during enqueue operation */
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u64 reset; /* set to non-zero when the target device resets */
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u8 pad_0[ILO_CACHE_SZ - (sizeof(u64) * 4)];
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u64 head;
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u8 pad_1[ILO_CACHE_SZ - (sizeof(u64))];
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u64 head;
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u8 pad_1[ILO_CACHE_SZ - (sizeof(u64))];
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u64 tail;
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u8 pad_2[ILO_CACHE_SZ - (sizeof(u64))];
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u64 tail;
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u8 pad_2[ILO_CACHE_SZ - (sizeof(u64))];
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u64 fifobar[1];
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u64 fifobar[];
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};
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/* convert between struct fifo, and the fifobar, which is saved in the ccb */
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#define FIFOHANDLESIZE (sizeof(struct fifo) - sizeof(u64))
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#define FIFOHANDLESIZE (sizeof(struct fifo))
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#define FIFOBARTOHANDLE(_fifo) \
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((struct fifo *)(((char *)(_fifo)) - FIFOHANDLESIZE))
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