diff options
| author | Borislav Petkov <bp@suse.de> | 2013-06-09 12:07:32 +0200 |
|---|---|---|
| committer | H. Peter Anvin <hpa@linux.intel.com> | 2013-06-20 17:37:19 -0700 |
| commit | 5700f743b597951743da9c7d891d3989aac0486e (patch) | |
| tree | e0482b8bb6ec72bc1db19bcd853922efb97b36bc /arch/x86/Kconfig.debug | |
| parent | c3b83598c1eeb1507603b461f5843ec2a49e3033 (diff) | |
x86: Sanity-check static_cpu_has usage
static_cpu_has may be used only after alternatives have run. Before that
it always returns false if constant folding with __builtin_constant_p()
doesn't happen. And you don't want that.
This patch is the result of me debugging an issue where I overzealously
put static_cpu_has in code which executed before alternatives have run
and had to spend some time with scratching head and cursing at the
monitor.
So add a jump to a warning which screams loudly when we use this
function too early. The alternatives patch that check away in
conjunction with patching the rest of the kernel image.
[ hpa: factored this into its own configuration option. If we want to
have an overarching option, it should be an option which selects
other options, not as a group option in the source code. ]
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: http://lkml.kernel.org/r/1370772454-6106-4-git-send-email-bp@alien8.de
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Diffstat (limited to 'arch/x86/Kconfig.debug')
| -rw-r--r-- | arch/x86/Kconfig.debug | 10 |
1 files changed, 10 insertions, 0 deletions
diff --git a/arch/x86/Kconfig.debug b/arch/x86/Kconfig.debug index c198b7e13e7b..c6acdf752715 100644 --- a/arch/x86/Kconfig.debug +++ b/arch/x86/Kconfig.debug @@ -304,4 +304,14 @@ config DEBUG_NMI_SELFTEST If unsure, say N. +config X86_DEBUG_STATIC_CPU_HAS + bool "Debug alternatives" + depends on DEBUG_KERNEL + ---help--- + This option causes additional code to be generated which + fails if static_cpu_has() is used before alternatives have + run. + + If unsure, say N. + endmenu |