Add some helper macros for asm functions so that they can comply with stackvalidate. The FUNC_ENTER and FUNC_RETURN macros help asm functions save, set up, and restore frame pointers. The RET_NOVALIDATE and FILE_NOVALIDATE macros can be used to whitelist the few locations which need a return instruction outside of a callable function. Signed-off-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx> --- arch/x86/include/asm/func.h | 82 +++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 82 insertions(+) create mode 100644 arch/x86/include/asm/func.h diff --git a/arch/x86/include/asm/func.h b/arch/x86/include/asm/func.h new file mode 100644 index 0000000..ae84196 --- /dev/null +++ b/arch/x86/include/asm/func.h @@ -0,0 +1,82 @@ +#ifndef _ASM_X86_FUNC_H +#define _ASM_X86_FUNC_H + +#include <linux/linkage.h> +#include <asm/dwarf2.h> +#include <asm/asm.h> + +.macro FUNC_ENTER_NO_FP name + ENTRY(\name) + CFI_STARTPROC + CFI_DEF_CFA _ASM_SP, __ASM_SEL(4, 8) +.endm + +.macro FUNC_RETURN_NO_FP name + CFI_DEF_CFA _ASM_SP, __ASM_SEL(4, 8) + __ASM_SIZE(ret) + CFI_ENDPROC + ENDPROC(\name) +.endm + +#ifdef CONFIG_FRAME_POINTER + +.macro FUNC_ENTER_FP name + FUNC_ENTER_NO_FP \name + __ASM_SIZE(push, _cfi) %_ASM_BP + CFI_REL_OFFSET _ASM_BP, 0 + _ASM_MOV %_ASM_SP, %_ASM_BP + CFI_DEF_CFA_REGISTER _ASM_BP +.endm + +.macro FUNC_RETURN_FP name + __ASM_SIZE(pop, _cfi) %_ASM_BP + CFI_RESTORE _ASM_BP + FUNC_RETURN_NO_FP \name +.endm + +/* + * Every callable asm function should be bookended with FUNC_ENTER and + * FUNC_RETURN. They do proper frame pointer and DWARF CFI setups in order to + * achieve more reliable stack traces. + * + * For the sake of simplicity and correct DWARF annotations, use of the macros + * requires that the return instruction comes at the end of the function. + */ +#define FUNC_ENTER(name) FUNC_ENTER_FP name +#define FUNC_RETURN(name) FUNC_RETURN_FP name + +/* + * RET_NOVALIDATE tells the stack validation script to whitelist the return + * instruction immediately after the macro. Only use it if you're completely + * sure you need a return instruction outside of a callable function. + * Otherwise, if the code can be called and you haven't annotated it with + * FUNC_ENTER/FUNC_RETURN, it will break stack trace reliability. + */ +.macro RET_NOVALIDATE + 163: + .pushsection __stackvalidate_whitelist_ret, "ae" + _ASM_ALIGN + .long 163b - . + .popsection +.endm + +/* + * FILE_NOVALIDATE is like RET_NOVALIDATE except it whitelists the entire file. + * Use with extreme caution or you will silently break stack traces. + */ +.macro FILE_NOVALIDATE + .pushsection __stackvalidate_whitelist_file, "ae" + .long 0 + .popsection +.endm + +#else /* !FRAME_POINTER */ + +#define FUNC_ENTER(name) FUNC_ENTER_NO_FP name +#define FUNC_RETURN(name) FUNC_RETURN_NO_FP name +#define RET_NOVALIDATE +#define FILE_NOVALIDATE + +#endif /* FRAME_POINTER */ + +#endif /* _ASM_X86_FUNC_H */ -- 2.1.0 -- To unsubscribe from this list: send the line "unsubscribe live-patching" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
