Bug 218825

Summary:	Incorrect thinlto cache directory path in Makefile
Product:	Other	Reporter:	Xu Zhen (xuzhen)
Component:	Other	Assignee:	other_other
Status:	NEW ---
Severity:	normal	CC:	keescook, xuzhen
Priority:	P3
Hardware:	All
OS:	Linux
Kernel Version:		Subsystem:
Regression:	No	Bisected commit-id:

Description Xu Zhen 2024-05-09 15:22:59 UTC

In Makefile, the ld flag `--thinlto-cache-dir' is set to
`$(extmod_prefix).thinlto-cache'. But at that time, the variable extmod_prefix
had not been assigned yet. Therefore, the thinlto cache dir is always created
in the current directory.

Even worse, the cache dir cannot be deleted when executing `make clean'. This
is because its path was written as `$(KBUILD_EXTMOD)/.thinlto-cache' in the
clean: target.

Some users have been troubled by it: https://github.com/dell/dkms/issues/292

This bug was introduced by commit dc5723b02e523b2c4a68667f7e28c65018f7202f