ARC, bpf: Fix issues reported by the static analyzers

Also updated couple of comments along the way.

One of the issues reported was indeed a bug in the code:

  memset(ctx, 0, sizeof(ctx))      // original line
  memset(ctx, 0, sizeof(*ctx))     // fixed line

That was a nice catch.
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202405222314.UG5F2NHn-lkp@intel.com/
Closes: https://lore.kernel.org/oe-kbuild-all/202405232036.Xqoc3b0J-lkp@intel.com/Signed-off-by: Shahab Vahedi <shahab@synopsys.com>
Link: https://lore.kernel.org/r/20240525035628.1026-1-list+bpf@vahedi.orgSigned-off-by: Alexei Starovoitov <ast@kernel.org>

arch/arc/net/bpf_jit.h

@@ -39,7 +39,7 @@
 
 /************** Functions that the back-end must provide **************/
 /* Extension for 32-bit operations. */
-inline u8 zext(u8 *buf, u8 rd);
+u8 zext(u8 *buf, u8 rd);
 /***** Moves *****/
 u8 mov_r32(u8 *buf, u8 rd, u8 rs, u8 sign_ext);
 u8 mov_r32_i32(u8 *buf, u8 reg, s32 imm);

arch/arc/net/bpf_jit_arcv2.c

@@ -62,7 +62,7 @@ enum {
  *   If/when we decide to add ARCv2 instructions that do use register pairs,
  *   the mapping, hopefully, doesn't need to be revisited.
  */
-const u8 bpf2arc[][2] = {
+static const u8 bpf2arc[][2] = {
 	/* Return value from in-kernel function, and exit value from eBPF */
 	[BPF_REG_0] = {ARC_R_8, ARC_R_9},
 	/* Arguments from eBPF program to in-kernel function */
@@ -1302,7 +1302,7 @@ static u8 arc_b(u8 *buf, s32 offset)
 
 /************* Packers (Deal with BPF_REGs) **************/
 
-inline u8 zext(u8 *buf, u8 rd)
+u8 zext(u8 *buf, u8 rd)
 {
 	if (rd != BPF_REG_FP)
 		return arc_movi_r(buf, REG_HI(rd), 0);
@@ -2235,6 +2235,7 @@ u8 gen_swap(u8 *buf, u8 rd, u8 size, u8 endian, bool force, bool do_zext)
 			break;
 		default:
 			/* The caller must have handled this. */
+			break;
 		}
 	} else {
 		/*
@@ -2253,6 +2254,7 @@ u8 gen_swap(u8 *buf, u8 rd, u8 size, u8 endian, bool force, bool do_zext)
 			break;
 		default:
 			/* The caller must have handled this. */
+			break;
 		}
 	}
 
@@ -2517,7 +2519,7 @@ u8 arc_epilogue(u8 *buf, u32 usage, u16 frame_size)
 #define JCC64_NR_OF_JMPS 3	/* Number of jumps in jcc64 template. */
 #define JCC64_INSNS_TO_END 3	/* Number of insn. inclusive the 2nd jmp to end. */
 #define JCC64_SKIP_JMP 1	/* Index of the "skip" jump to "end". */
-const struct {
+static const struct {
 	/*
 	 * "jit_off" is common between all "jmp[]" and is coupled with
 	 * "cond" of each "jmp[]" instance. e.g.:
@@ -2883,7 +2885,7 @@ u8 gen_jmp_64(u8 *buf, u8 rd, u8 rs, u8 cond, u32 curr_off, u32 targ_off)
  * The "ARC_CC_SET" becomes "CC_unequal" because of the "tst"
  * instruction that precedes the conditional branch.
  */
-const u8 arcv2_32_jmps[ARC_CC_LAST] = {
+static const u8 arcv2_32_jmps[ARC_CC_LAST] = {
 	[ARC_CC_UGT] = CC_great_u,
 	[ARC_CC_UGE] = CC_great_eq_u,
 	[ARC_CC_ULT] = CC_less_u,

arch/arc/net/bpf_jit_core.c

@@ -159,7 +159,7 @@ static void jit_dump(const struct jit_context *ctx)
 /* Initialise the context so there's no garbage. */
 static int jit_ctx_init(struct jit_context *ctx, struct bpf_prog *prog)
 {
-	memset(ctx, 0, sizeof(ctx));
+	memset(ctx, 0, sizeof(*ctx));
 
 	ctx->orig_prog = prog;
 
@@ -167,7 +167,7 @@ static int jit_ctx_init(struct jit_context *ctx, struct bpf_prog *prog)
 	ctx->prog = bpf_jit_blind_constants(prog);
 	if (IS_ERR(ctx->prog))
 		return PTR_ERR(ctx->prog);
-	ctx->blinded = (ctx->prog == ctx->orig_prog ? false : true);
+	ctx->blinded = (ctx->prog != ctx->orig_prog);
 
 	/* If the verifier doesn't zero-extend, then we have to do it. */
 	ctx->do_zext = !ctx->prog->aux->verifier_zext;
@@ -1182,12 +1182,12 @@ static int jit_prepare(struct jit_context *ctx)
 }
 
 /*
- * All the "handle_*()" functions have been called before by the
- * "jit_prepare()". If there was an error, we would know by now.
- * Therefore, no extra error checking at this point, other than
- * a sanity check at the end that expects the calculated length
- * (jit.len) to be equal to the length of generated instructions
- * (jit.index).
+ * jit_compile() is the real compilation phase. jit_prepare() is
+ * invoked before jit_compile() as a dry-run to make sure everything
+ * will go OK and allocate the necessary memory.
+ *
+ * In the end, jit_compile() checks if it has produced the same number
+ * of instructions as jit_prepare() would.
  */
 static int jit_compile(struct jit_context *ctx)
 {
@@ -1407,9 +1407,9 @@ static struct bpf_prog *do_extra_pass(struct bpf_prog *prog)
 
 /*
  * This function may be invoked twice for the same stream of BPF
- * instructions. The "extra pass" happens, when there are "call"s
- * involved that their addresses are not known during the first
- * invocation.
+ * instructions. The "extra pass" happens, when there are
+ * (re)locations involved that their addresses are not known
+ * during the first run.
  */
 struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog)
 {