From c6cfcbd8ca43766851a8c952e3b570727147020f Mon Sep 17 00:00:00 2001 From: Josh Poimboeuf Date: Fri, 7 Apr 2023 17:16:41 -0700 Subject: x86/ibt: Convert IBT selftest to asm The following warning is reported when frame pointers and kernel IBT are enabled: vmlinux.o: warning: objtool: ibt_selftest+0x11: sibling call from callable instruction with modified stack frame The problem is that objtool interprets the indirect branch in ibt_selftest() as a sibling call, and GCC inserts a (partial) frame pointer prologue before it: 0000 000000000003f550 : 0000 3f550: f3 0f 1e fa endbr64 0004 3f554: e8 00 00 00 00 call 3f559 3f555: R_X86_64_PLT32 __fentry__-0x4 0009 3f559: 55 push %rbp 000a 3f55a: 48 8d 05 02 00 00 00 lea 0x2(%rip),%rax # 3f563 0011 3f561: ff e0 jmp *%rax Note the inline asm is missing ASM_CALL_CONSTRAINT, so the 'push %rbp' happens before the indirect branch and the 'mov %rsp, %rbp' happens afterwards. Simplify the generated code and make it easier to understand for both tools and humans by moving the selftest to proper asm. Signed-off-by: Josh Poimboeuf Signed-off-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/99a7e16b97bda97bf0a04aa141d6241cd8a839a2.1680912949.git.jpoimboe@kernel.org --- arch/x86/kernel/Makefile | 1 + 1 file changed, 1 insertion(+) (limited to 'arch/x86/kernel/Makefile') diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile index 6b6bf47652ee..eca9784a46fe 100644 --- a/arch/x86/kernel/Makefile +++ b/arch/x86/kernel/Makefile @@ -49,6 +49,7 @@ obj-y += process_$(BITS).o signal.o signal_$(BITS).o obj-y += traps.o idt.o irq.o irq_$(BITS).o dumpstack_$(BITS).o obj-y += time.o ioport.o dumpstack.o nmi.o obj-$(CONFIG_MODIFY_LDT_SYSCALL) += ldt.o +obj-$(CONFIG_X86_KERNEL_IBT) += ibt_selftest.o obj-y += setup.o x86_init.o i8259.o irqinit.o obj-$(CONFIG_JUMP_LABEL) += jump_label.o obj-$(CONFIG_IRQ_WORK) += irq_work.o -- cgit v1.2.3