treewide: Replace zero-length arrays with flexible-array member

The current codebase makes use of the zero-length array language
extension to the C90 standard, but the preferred mechanism to declare
variable-length types such as these ones is a flexible array member[1][2],
introduced in C99:

struct foo {
        int stuff;
        struct boo array[];
};

By making use of the mechanism above, we will get a compiler warning
in case the flexible array does not occur last in the structure, which
will help us prevent some kind of undefined behavior bugs from being
unadvertenly introduced[3] to the codebase from now on.

All these instances of code were found with the help of the following
Coccinelle script:

@@
identifier S, member, array;
type T1, T2;
@@

struct S {
  ...
  T1 member;
  T2 array[
- 0
  ];
};

[1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html
[2] KSPP#21
[3] commit 7649773 ("cxgb3/l2t: Fix undefined behaviour")

NOTE: I'll carry this in my -next tree for the v5.6 merge window.

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

arch/m68k/amiga/config.c

@@ -628,7 +628,7 @@ struct savekmsg {
 	unsigned long magic2;		/* SAVEKMSG_MAGIC2 */
 	unsigned long magicptr;		/* address of magic1 */
 	unsigned long size;
-	char data[0];
+	char data[];
 };
 
 static struct savekmsg *savekmsg;

arch/m68k/tools/amiga/dmesg.c

@@ -34,7 +34,7 @@ struct savekmsg {
     u_long magic2;	/* SAVEKMSG_MAGIC2 */
     u_long magicptr;	/* address of magic1 */
     u_long size;
-    char data[0];
+	char data[];
 };
 
 

arch/mips/kernel/signal.c

@@ -52,7 +52,7 @@ struct sigframe {
 	/* Matches struct ucontext from its uc_mcontext field onwards */
 	struct sigcontext sf_sc;
 	sigset_t sf_mask;
-	unsigned long long sf_extcontext[0];
+	unsigned long long sf_extcontext[];
 };
 
 struct rt_sigframe {

arch/powerpc/mm/hugetlbpage.c

@@ -246,7 +246,7 @@ int __init alloc_bootmem_huge_page(struct hstate *h)
 struct hugepd_freelist {
 	struct rcu_head	rcu;
 	unsigned int index;
-	void *ptes[0];
+	void *ptes[];
 };
 
 static DEFINE_PER_CPU(struct hugepd_freelist *, hugepd_freelist_cur);

arch/powerpc/platforms/powermac/nvram.c

@@ -55,7 +55,7 @@ struct chrp_header {
   u8		cksum;
   u16		len;
   char          name[12];
-  u8		data[0];
+	u8		data[];
 };
 
 struct core99_header {

arch/s390/appldata/appldata_os.c

@@ -75,7 +75,7 @@ struct appldata_os_data {
 				   (waiting for I/O)               */
 
 	/* per cpu data */
-	struct appldata_os_per_cpu os_cpu[0];
+	struct appldata_os_per_cpu os_cpu[];
 } __attribute__((packed));
 
 static struct appldata_os_data *appldata_os_data;

arch/sparc/kernel/cpumap.c

@@ -50,7 +50,7 @@ struct cpuinfo_tree {
 
 	/* Offsets into nodes[] for each level of the tree */
 	struct cpuinfo_level level[CPUINFO_LVL_MAX];
-	struct cpuinfo_node  nodes[0];
+	struct cpuinfo_node  nodes[];
 };
 
 

arch/sparc/kernel/ds.c

@@ -87,7 +87,7 @@ struct ds_reg_req {
 	__u64			handle;
 	__u16			major;
 	__u16			minor;
-	char			svc_id[0];
+	char			svc_id[];
 };
 
 struct ds_reg_ack {
@@ -701,12 +701,12 @@ struct ds_var_hdr {
 
 struct ds_var_set_msg {
 	struct ds_var_hdr		hdr;
-	char				name_and_value[0];
+	char				name_and_value[];
 };
 
 struct ds_var_delete_msg {
 	struct ds_var_hdr		hdr;
-	char				name[0];
+	char				name[];
 };
 
 struct ds_var_resp {
@@ -989,7 +989,7 @@ struct ds_queue_entry {
 	struct ds_info			*dp;
 	int				req_len;
 	int				__pad;
-	u64				req[0];
+	u64				req[];
 };
 
 static void process_ds_work(void)

arch/x86/events/intel/bts.c

@@ -58,7 +58,7 @@ struct bts_buffer {
 	local_t		head;
 	unsigned long	end;
 	void		**data_pages;
-	struct bts_phys	buf[0];
+	struct bts_phys	buf[];
 };
 
 static struct pmu bts_pmu;

drivers/amba/tegra-ahb.c

@@ -120,7 +120,7 @@ static const u32 tegra_ahb_gizmo[] = {
 struct tegra_ahb {
 	void __iomem	*regs;
 	struct device	*dev;
-	u32		ctx[0];
+	u32		ctx[];
 };
 
 static inline u32 gizmo_readl(struct tegra_ahb *ahb, u32 offset)

drivers/auxdisplay/charlcd.c

@@ -88,7 +88,7 @@ struct charlcd_priv {
 		int len;
 	} esc_seq;
 
-	unsigned long long drvdata[0];
+	unsigned long long drvdata[];
 };
 
 #define charlcd_to_priv(p)	container_of(p, struct charlcd_priv, lcd)

drivers/block/rsxx/dma.c

@@ -80,7 +80,7 @@ struct dma_tracker {
 struct dma_tracker_list {
 	spinlock_t		lock;
 	int			head;
-	struct dma_tracker	list[0];
+	struct dma_tracker	list[];
 };
 
 

drivers/bluetooth/btintel.c

@@ -376,13 +376,13 @@ struct ibt_cp_reg_access {
 	__le32  addr;
 	__u8    mode;
 	__u8    len;
-	__u8    data[0];
+	__u8    data[];
 } __packed;
 
 struct ibt_rp_reg_access {
 	__u8    status;
 	__le32  addr;
-	__u8    data[0];
+	__u8    data[];
 } __packed;
 
 static int regmap_ibt_read(void *context, const void *addr, size_t reg_size,

drivers/bluetooth/hci_ag6xx.c

@@ -27,7 +27,7 @@ struct ag6xx_data {
 struct pbn_entry {
 	__le32 addr;
 	__le32 plen;
-	__u8 data[0];
+	__u8 data[];
 } __packed;
 
 static int ag6xx_open(struct hci_uart *hu)

drivers/bluetooth/hci_intel.c

@@ -49,7 +49,7 @@
 struct hci_lpm_pkt {
 	__u8 opcode;
 	__u8 dlen;
-	__u8 data[0];
+	__u8 data[];
 } __packed;
 
 struct intel_device {

drivers/char/mspec.c

@@ -75,7 +75,7 @@ struct vma_data {
 	enum mspec_page_type type; /* Type of pages allocated. */
 	unsigned long vm_start;	/* Original (unsplit) base. */
 	unsigned long vm_end;	/* Original (unsplit) end. */
-	unsigned long maddr[0];	/* Array of MSPEC addresses. */
+	unsigned long maddr[];	/* Array of MSPEC addresses. */
 };
 
 /*

drivers/char/virtio_console.c

@@ -112,7 +112,7 @@ struct port_buffer {
 	unsigned int sgpages;
 
 	/* sg is used if spages > 0. sg must be the last in is struct */
-	struct scatterlist sg[0];
+	struct scatterlist sg[];
 };
 
 /*

drivers/crypto/caam/caamalg.c

@@ -895,7 +895,7 @@ struct skcipher_edesc {
 	int sec4_sg_bytes;
 	dma_addr_t sec4_sg_dma;
 	struct sec4_sg_entry *sec4_sg;
-	u32 hw_desc[0];
+	u32 hw_desc[];
 };
 
 static void caam_unmap(struct device *dev, struct scatterlist *src,

drivers/crypto/caam/caamalg_qi.c

@@ -783,7 +783,7 @@ struct aead_edesc {
 	unsigned int assoclen;
 	dma_addr_t assoclen_dma;
 	struct caam_drv_req drv_req;
-	struct qm_sg_entry sgt[0];
+	struct qm_sg_entry sgt[];
 };
 
 /*
@@ -803,7 +803,7 @@ struct skcipher_edesc {
 	int qm_sg_bytes;
 	dma_addr_t qm_sg_dma;
 	struct caam_drv_req drv_req;
-	struct qm_sg_entry sgt[0];
+	struct qm_sg_entry sgt[];
 };
 
 static struct caam_drv_ctx *get_drv_ctx(struct caam_ctx *ctx,

drivers/crypto/caam/caamhash.c

@@ -529,7 +529,7 @@ struct ahash_edesc {
 	int src_nents;
 	int sec4_sg_bytes;
 	u32 hw_desc[DESC_JOB_IO_LEN_MAX / sizeof(u32)] ____cacheline_aligned;
-	struct sec4_sg_entry sec4_sg[0];
+	struct sec4_sg_entry sec4_sg[];
 };
 
 static inline void ahash_unmap(struct device *dev,

drivers/crypto/cavium/nitrox/nitrox_main.c

@@ -71,7 +71,7 @@ struct ucode {
 	char version[VERSION_LEN - 1];
 	__be32 code_size;
 	u8 raz[12];
-	u64 code[0];
+	u64 code[];
 };
 
 /**

drivers/crypto/img-hash.c

@@ -103,7 +103,7 @@ struct img_hash_request_ctx {
 	struct ahash_request	fallback_req;
 
 	/* Zero length buffer must remain last member of struct */
-	u8 buffer[0] __aligned(sizeof(u32));
+	u8 buffer[] __aligned(sizeof(u32));
 };
 
 struct img_hash_ctx {

drivers/crypto/mediatek/mtk-sha.c

@@ -107,7 +107,7 @@ struct mtk_sha_ctx {
 	u8 id;
 	u8 buf[SHA_BUF_SIZE] __aligned(sizeof(u32));
 
-	struct mtk_sha_hmac_ctx	base[0];
+	struct mtk_sha_hmac_ctx	base[];
 };
 
 struct mtk_sha_drv {

drivers/crypto/omap-sham.c

@@ -159,7 +159,7 @@ struct omap_sham_reqctx {
 	int			sg_len;
 	unsigned int		total;	/* total request */
 
-	u8			buffer[0] OMAP_ALIGNED;
+	u8			buffer[] OMAP_ALIGNED;
 };
 
 struct omap_sham_hmac_ctx {
@@ -176,7 +176,7 @@ struct omap_sham_ctx {
 	/* fallback stuff */
 	struct crypto_shash	*fallback;
 
-	struct omap_sham_hmac_ctx base[0];
+	struct omap_sham_hmac_ctx base[];
 };
 
 #define OMAP_SHAM_QUEUE_LENGTH	10

drivers/crypto/s5p-sss.c

@@ -369,7 +369,7 @@ struct s5p_hash_reqctx {
 	bool			error;
 
 	u32			bufcnt;
-	u8			buffer[0];
+	u8			buffer[];
 };
 
 /**

drivers/dma/at_xdmac.c

@@ -212,7 +212,7 @@ struct at_xdmac {
 	struct clk		*clk;
 	u32			save_gim;
 	struct dma_pool		*at_xdmac_desc_pool;
-	struct at_xdmac_chan	chan[0];
+	struct at_xdmac_chan	chan[];
 };
 
 

drivers/dma/bcm-sba-raid.c

@@ -120,7 +120,7 @@ struct sba_request {
 	struct brcm_message msg;
 	struct dma_async_tx_descriptor tx;
 	/* SBA commands */
-	struct brcm_sba_command cmds[0];
+	struct brcm_sba_command cmds[];
 };
 
 enum sba_version {

drivers/dma/ioat/dca.c

@@ -102,7 +102,7 @@ struct ioat_dca_priv {
 	int			 max_requesters;
 	int			 requester_count;
 	u8			 tag_map[IOAT_TAG_MAP_LEN];
-	struct ioat_dca_slot 	 req_slots[0];
+	struct ioat_dca_slot	 req_slots[];
 };
 
 static int ioat_dca_dev_managed(struct dca_provider *dca,

drivers/dma/moxart-dma.c

@@ -127,7 +127,7 @@ struct moxart_desc {
 	unsigned int			dma_cycles;
 	struct virt_dma_desc		vd;
 	uint8_t				es;
-	struct moxart_sg		sg[0];
+	struct moxart_sg		sg[];
 };
 
 struct moxart_chan {

drivers/dma/qcom/bam_dma.c

@@ -74,7 +74,7 @@ struct bam_async_desc {
 	struct list_head desc_node;
 	enum dma_transfer_direction dir;
 	size_t length;
-	struct bam_desc_hw desc[0];
+	struct bam_desc_hw desc[];
 };
 
 enum bam_reg {

drivers/dma/sa11x0-dma.c

@@ -78,7 +78,7 @@ struct sa11x0_dma_desc {
 	bool			cyclic;
 
 	unsigned		sglen;
-	struct sa11x0_dma_sg	sg[0];
+	struct sa11x0_dma_sg	sg[];
 };
 
 struct sa11x0_dma_phy;

drivers/dma/sprd-dma.c

@@ -212,7 +212,7 @@ struct sprd_dma_dev {
 	struct clk		*ashb_clk;
 	int			irq;
 	u32			total_chns;
-	struct sprd_dma_chn	channels[0];
+	struct sprd_dma_chn	channels[];
 };
 
 static void sprd_dma_free_desc(struct virt_dma_desc *vd);

drivers/dma/tegra20-apb-dma.c

@@ -226,7 +226,7 @@ struct tegra_dma {
 	u32				reg_gen;
 
 	/* Last member of the structure */
-	struct tegra_dma_channel channels[0];
+	struct tegra_dma_channel channels[];
 };
 
 static inline void tdma_write(struct tegra_dma *tdma, u32 reg, u32 val)

drivers/dma/tegra210-adma.c

@@ -164,7 +164,7 @@ struct tegra_adma {
 	const struct tegra_adma_chip_data *cdata;
 
 	/* Last member of the structure */
-	struct tegra_adma_chan		channels[0];
+	struct tegra_adma_chan		channels[];
 };
 
 static inline void tdma_write(struct tegra_adma *tdma, u32 reg, u32 val)

drivers/dma/ti/edma.c

@@ -211,7 +211,7 @@ struct edma_desc {
 	u32				residue;
 	u32				residue_stat;
 
-	struct edma_pset		pset[0];
+	struct edma_pset		pset[];
 };
 
 struct edma_cc;

drivers/dma/ti/omap-dma.c

@@ -124,7 +124,7 @@ struct omap_desc {
 	uint32_t csdp;		/* CSDP value */
 
 	unsigned sglen;
-	struct omap_sg sg[0];
+	struct omap_sg sg[];
 };
 
 enum {

drivers/dma/timb_dma.c

@@ -88,7 +88,7 @@ struct timb_dma {
 	struct dma_device	dma;
 	void __iomem		*membase;
 	struct tasklet_struct	tasklet;
-	struct timb_dma_chan	channels[0];
+	struct timb_dma_chan	channels[];
 };
 
 static struct device *chan2dev(struct dma_chan *chan)

drivers/dma/uniphier-mdmac.c

@@ -68,7 +68,7 @@ struct uniphier_mdmac_device {
 	struct dma_device ddev;
 	struct clk *clk;
 	void __iomem *reg_base;
-	struct uniphier_mdmac_chan channels[0];
+	struct uniphier_mdmac_chan channels[];
 };
 
 static struct uniphier_mdmac_chan *

drivers/firewire/core-cdev.c

@@ -117,7 +117,7 @@ struct inbound_transaction_resource {
 struct descriptor_resource {
 	struct client_resource resource;
 	struct fw_descriptor descriptor;
-	u32 data[0];
+	u32 data[];
 };
 
 struct iso_resource {