cmd_shipped uses 'cat' instead of 'cp' for copying a file. The reason is explained in the commit [1], but it was in the pre-git era. $ touch a $ chmod -w a $ cp a b $ cp a b cp: cannot create regular file 'b': Permission denied Add comments so that you can see the reason without looking into the history. [1]: https://git.kernel.org/pub/scm/linux/kernel/git/history/history.git/commit/?id=a70dba8086160449cc94c5bdaff78419b6b8e3c8
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| @@ -252,6 +252,9 @@ quiet_cmd_copy = COPY $@ · 251 unmodified lines | ||
| 252 | 252 | |
| 253 | 253 | # Shipped files |
| 254 | 254 | # =========================================================================== |
| 255 | +# 'cp' preserves permissions. If you use it to copy a file in read-only srctree, | |
| 256 | +# the copy would be read-only as well, leading to an error when executing the | |
| 257 | +# rule next time. Use 'cat' instead in order to generate a writable file. | |
| 255 | 258 | |
| 256 | 259 | quiet_cmd_shipped = SHIPPED $@ |
| 257 | 260 | cmd_shipped = cat $< > $@ |