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authorNadav Amit <namit@vmware.com>2018-10-03 14:30:56 -0700
committerIngo Molnar <mingo@kernel.org>2018-10-04 11:25:00 +0200
commitf81f8ad56fd1c7b99b2ed1c314527f7d9ac447c6 (patch)
tree94a676430a5b92e1c0f551a31700e631bf81d6a4 /include/asm-generic
parent77f48ec28e4ccff94d2e5f4260a83ac27a7f3099 (diff)
x86/bug: Macrofy the BUG table section handling, to work around GCC inlining bugs
As described in: 77b0bf55bc67: ("kbuild/Makefile: Prepare for using macros in inline assembly code to work around asm() related GCC inlining bugs") GCC's inlining heuristics are broken with common asm() patterns used in kernel code, resulting in the effective disabling of inlining. The workaround is to set an assembly macro and call it from the inline assembly block. As a result GCC considers the inline assembly block as a single instruction. (Which it isn't, but that's the best we can get.) This patch increases the kernel size: text data bss dec hex filename 18146889 10225380 2957312 31329581 1de0d2d ./vmlinux before 18147336 10226688 2957312 31331336 1de1408 ./vmlinux after (+1755) But enables more aggressive inlining (and probably better branch decisions). The number of static text symbols in vmlinux is much lower: Before: 40218 After: 40053 (-165) The assembly code gets harder to read due to the extra macro layer. [ mingo: Rewrote the changelog. ] Tested-by: Kees Cook <keescook@chromium.org> Signed-off-by: Nadav Amit <namit@vmware.com> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Borislav Petkov <bp@alien8.de> Cc: Brian Gerst <brgerst@gmail.com> Cc: Denys Vlasenko <dvlasenk@redhat.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/20181003213100.189959-7-namit@vmware.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'include/asm-generic')
-rw-r--r--include/asm-generic/bug.h8
1 files changed, 4 insertions, 4 deletions
diff --git a/include/asm-generic/bug.h b/include/asm-generic/bug.h
index 20561a60db9c..cdafa5edea49 100644
--- a/include/asm-generic/bug.h
+++ b/include/asm-generic/bug.h
@@ -17,10 +17,8 @@
#ifndef __ASSEMBLY__
#include <linux/kernel.h>
-#ifdef CONFIG_BUG
-
-#ifdef CONFIG_GENERIC_BUG
struct bug_entry {
+#ifdef CONFIG_GENERIC_BUG
#ifndef CONFIG_GENERIC_BUG_RELATIVE_POINTERS
unsigned long bug_addr;
#else
@@ -35,8 +33,10 @@ struct bug_entry {
unsigned short line;
#endif
unsigned short flags;
-};
#endif /* CONFIG_GENERIC_BUG */
+};
+
+#ifdef CONFIG_BUG
/*
* Don't use BUG() or BUG_ON() unless there's really no way out; one