Messages in this thread Patch in this message | | | Date | Tue, 28 Apr 2020 17:48:38 -0500 | From | Josh Poimboeuf <> | Subject | Re: Remaining randconfig objtool warnings, linux-next-20200428 |
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On Wed, Apr 29, 2020 at 12:33:27AM +0200, Peter Zijlstra wrote: > On Tue, Apr 28, 2020 at 05:03:53PM -0500, Josh Poimboeuf wrote: > > On Tue, Apr 28, 2020 at 11:55:54PM +0200, Peter Zijlstra wrote: > > > > binutils.git/gas/configure/tc-i386.c:i386_generate_nops > > > > > > When there's too many NOPs (as here) it generates a JMP across the NOPS. > > > It makes some sort of sense, at some point executing NOPs is going to be > > > more expensive than a branch.. But shees.. > > > > Urgh. Even if I tell it specifically to pad with NOPs, it still does > > this "trick". I have no idea how to deal with this in objtool. > > This is horrible... but it _might_ just work.
HAHA, nice.
This seems to work:
diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S index 3063aa9090f9..afdf43c9bac1 100644 --- a/arch/x86/entry/entry_64.S +++ b/arch/x86/entry/entry_64.S @@ -597,8 +597,13 @@ SYM_CODE_START_LOCAL(common_spurious) SYM_CODE_END(common_spurious) _ASM_NOKPROBE(common_spurious) +.macro P2ALIGN_NOPS shift + .p2align \shift-1 + .p2align \shift +.endm + /* common_interrupt is a hotpath. Align it */ - .p2align CONFIG_X86_L1_CACHE_SHIFT +P2ALIGN_NOPS shift=CONFIG_X86_L1_CACHE_SHIFT SYM_CODE_START_LOCAL(common_interrupt) addq $-0x80, (%rsp) /* Adjust vector to [-256, -1] range */ call interrupt_entry
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