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Subject[PATCH V2 1/7] x86/entry: Introduce __entry_text for entry code written in C
Date
From: Lai Jiangshan <jiangshan.ljs@antgroup.com>

Some entry code will be implemented in C files.
Introduce __entry_text to set them in .entry.text section.

The new __entry_text disables instrumentation like noinstr, so
__noinstr_section() is added for noinstr and the new __entry_text.

Note, entry code can not access to %gs before the %gs base is switched
to kernel %gs base, so stack protector can not be used on the C entry
code. But __entry_text doesn't disable stack protector since some
compilers might not support function level granular attribute to
disable stack protector. It will be disabled in C file level.

Cc: Borislav Petkov <bp@alien8.de>
Reviewed-by: Miguel Ojeda <ojeda@kernel.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Suggested-by: Nick Desaulniers <ndesaulniers@google.com>
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Lai Jiangshan <jiangshan.ljs@antgroup.com>
---
arch/x86/include/asm/idtentry.h | 3 +++
include/linux/compiler_types.h | 8 +++++---
2 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/arch/x86/include/asm/idtentry.h b/arch/x86/include/asm/idtentry.h
index 72184b0b2219..acc4c99f801c 100644
--- a/arch/x86/include/asm/idtentry.h
+++ b/arch/x86/include/asm/idtentry.h
@@ -13,6 +13,9 @@

#include <asm/irq_stack.h>

+/* Entry code written in C. */
+#define __entry_text __noinstr_section(".entry.text")
+
/**
* DECLARE_IDTENTRY - Declare functions for simple IDT entry points
* No error code pushed by hardware
diff --git a/include/linux/compiler_types.h b/include/linux/compiler_types.h
index 1c2c33ae1b37..1d6580ccb081 100644
--- a/include/linux/compiler_types.h
+++ b/include/linux/compiler_types.h
@@ -225,9 +225,11 @@ struct ftrace_likely_data {
#endif

/* Section for code which can't be instrumented at all */
-#define noinstr \
- noinline notrace __attribute((__section__(".noinstr.text"))) \
- __no_kcsan __no_sanitize_address __no_profile __no_sanitize_coverage
+#define __noinstr_section(section) \
+ noinline notrace __section(section) __no_kcsan \
+ __no_sanitize_address __no_profile __no_sanitize_coverage
+
+#define noinstr __noinstr_section(".noinstr.text")

#endif /* __KERNEL__ */

--
2.19.1.6.gb485710b
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