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authorBorislav Petkov <bp@suse.de>2013-06-09 12:07:32 +0200
committerH. Peter Anvin <hpa@linux.intel.com>2013-06-21 02:37:19 +0200
commit5700f743b597951743da9c7d891d3989aac0486e (patch)
treee0482b8bb6ec72bc1db19bcd853922efb97b36bc /arch/x86/Kconfig.debug
parentx86, cpu: Add a synthetic, always true, cpu feature (diff)
downloadlinux-5700f743b597951743da9c7d891d3989aac0486e.tar.xz
linux-5700f743b597951743da9c7d891d3989aac0486e.zip
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.debug10
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.
+
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