x86/boot: Fix if_changed build flip/flop

PATCH Superseded Kees Cook 3 participants 3 messages Jul 15, 2018 – Jul 18, 2018 x86

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Kees Cook

author

2018-07-15 02:57 UTC #0 lore raw

PATCH 1/1 x86/boot: Fix if_changed build flip/flop

The if_changed kbuild function can only be used once per target. If not it will effectively always trigger, flipping back and forth between the two commands getting recorded. Instead, merge the two commands into a single function to get stable build artifacts (i.e. .vmlinux.cmd).

Reported-by Dirk Gouders <[email protected]>

Fixes 98f78525371b ("x86/boot: Refuse to build with data relocations")

Signed-off-by Kees Cook <[email protected]>

---
 arch/x86/boot/compressed/Makefile | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

arch/x86/boot/compressed/Makefile +6 -2

index fa42f895fdde..169c2feda14a 100644
@@ -106,9 +106,13 @@ define cmd_check_data_rel
 	done
 endef
 
+# We need to run two commands under "if_changed", so merge them into a
+# single invocation.
+quiet_cmd_check-and-link-vmlinux = LD      $@
+      cmd_check-and-link-vmlinux = $(cmd_check_data_rel); $(cmd_ld)
+
 $(obj)/vmlinux: $(vmlinux-objs-y) FORCE
-	$(call if_changed,check_data_rel)
-	$(call if_changed,ld)
+	$(call if_changed,check-and-link-vmlinux)
 
 OBJCOPYFLAGS_vmlinux.bin :=  -R .comment -S
 $(obj)/vmlinux.bin: vmlinux FORCE

Signature · 6 lines

2.17.1


-- 
Kees Cook
Pixel Security

Ingo Molnar

2018-07-15 22:59 UTC #1 lore raw

Quoted 6 lines · Kees Cook

The if_changed kbuild function can only be used once per target. If not it will effectively always trigger, flipping back and forth between the two commands getting recorded. Instead, merge the two commands into a single function to get stable build artifacts (i.e. .vmlinux.cmd).
Reported-by Dirk Gouders <[email protected]>

What actual symptoms does this bug have?

I.e. it would be nice if the changelog started with such an explanation:

Dirk Gouders reported that .... <bad stuff happens during kernel build> ... and bisected it back to:

    98f78525371b ("x86/boot: Refuse to build with data relocations")

The root cause of the bug is that the if_changed kbuild function ...

Or something like that.

Thanks,

Ingo

Masahiro Yamada

Reviewed-by

2018-07-18 05:45 UTC #2 lore raw

2018-07-16 7:58 GMT+09:00 Ingo Molnar <[email protected]>:

Quoted 19 lines · Kees Cook

Quoted 7 lines
The if_changed kbuild function can only be used once per target. If not it will effectively always trigger, flipping back and forth between the two commands getting recorded. Instead, merge the two commands into a single function to get stable build artifacts (i.e. .vmlinux.cmd).
Reported-by Dirk Gouders <[email protected]>
What actual symptoms does this bug have?
I.e. it would be nice if the changelog started with such an explanation:
Dirk Gouders reported that .... <bad stuff happens during kernel build> ... and bisected it back to:
    98f78525371b ("x86/boot: Refuse to build with data relocations")

Quoted 7 lines

The root cause of the bug is that the if_changed kbuild function ...
Or something like that.
Thanks,
Ingo

Anyway, the code diff looks good to me.

Reviewed-by Masahiro Yamada <[email protected]>

Signature · 2 lines

Best Regards
Masahiro Yamada