disable kernel build waring

hc

2024-05-10 093a6c67005148ae32a5c9e4553491b9f5c2457b

 kernel/tools/perf/util/llvm-utils.c
..
..
@@ -525,14 +525,37 @@
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 	pr_debug("llvm compiling command template: %s\n", template);
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+	/*
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+	 * Below, substitute control characters for values that can cause the
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+	 * echo to misbehave, then substitute the values back.
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+	 */
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 	err = -ENOMEM;
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-	if (asprintf(&command_echo, "echo -n \"%s\"", template) < 0)
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+	if (asprintf(&command_echo, "echo -n \a%s\a", template) < 0)
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 		goto errout;
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+#define SWAP_CHAR(a, b) do { if (*p == a) *p = b; } while (0)
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+	for (char *p = command_echo; *p; p++) {
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+		SWAP_CHAR('<', '\001');
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+		SWAP_CHAR('>', '\002');
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+		SWAP_CHAR('"', '\003');
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+		SWAP_CHAR('\'', '\004');
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+		SWAP_CHAR('|', '\005');
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+		SWAP_CHAR('&', '\006');
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+		SWAP_CHAR('\a', '"');
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+	}
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 	err = read_from_pipe(command_echo, (void **) &command_out, NULL);
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 	if (err)
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 		goto errout;
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+	for (char *p = command_out; *p; p++) {
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+		SWAP_CHAR('\001', '<');
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+		SWAP_CHAR('\002', '>');
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+		SWAP_CHAR('\003', '"');
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+		SWAP_CHAR('\004', '\'');
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+		SWAP_CHAR('\005', '|');
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+		SWAP_CHAR('\006', '&');
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+	}
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+#undef SWAP_CHAR
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 	pr_debug("llvm compiling command : %s\n", command_out);
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 	err = read_from_pipe(template, &obj_buf, &obj_buf_sz);