linux-kernel - [tip: efi/urgent] efi/x86: Fix build with gcc 4

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Message-ID: <159258516173.16989.16252579910825894796.tip-bot2@tip-bot2>
Date:   Fri, 19 Jun 2020 16:46:01 -0000
From:   "tip-bot2 for Arvind Sankar" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     Andrey Ignatov <rdna@...com>,
        Arvind Sankar <nivedita@...m.mit.edu>,
        Ard Biesheuvel <ardb@...nel.org>, x86 <x86@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: [tip: efi/urgent] efi/x86: Fix build with gcc 4

The following commit has been merged into the efi/urgent branch of tip:

Commit-ID:     5435f73d5c4a1b7504356876e69ba52de83f4975
Gitweb:        https://git.kernel.org/tip/5435f73d5c4a1b7504356876e69ba52de83f4975
Author:        Arvind Sankar <nivedita@...m.mit.edu>
AuthorDate:    Fri, 05 Jun 2020 11:06:38 -04:00
Committer:     Ard Biesheuvel <ardb@...nel.org>
CommitterDate: Mon, 15 Jun 2020 11:41:14 +02:00

efi/x86: Fix build with gcc 4

Commit

  bbf8e8b0fe04 ("efi/libstub: Optimize for size instead of speed")

changed the optimization level for the EFI stub to -Os from -O2.

Andrey Ignatov reports that this breaks the build with gcc 4.8.5.

Testing on godbolt.org, the combination of -Os,
-fno-asynchronous-unwind-tables, and ms_abi functions doesn't work,
failing with the error:
  sorry, unimplemented: ms_abi attribute requires
  -maccumulate-outgoing-args or subtarget optimization implying it

This does appear to work with gcc 4.9 onwards.

Add -maccumulate-outgoing-args explicitly to unbreak the build with
pre-4.9 versions of gcc.

Reported-by: Andrey Ignatov <rdna@...com>
Signed-off-by: Arvind Sankar <nivedita@...m.mit.edu>
Link: https://lore.kernel.org/r/20200605150638.1011637-1-nivedita@alum.mit.edu
Signed-off-by: Ard Biesheuvel <ardb@...nel.org>
---
 drivers/firmware/efi/libstub/Makefile | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/firmware/efi/libstub/Makefile b/drivers/firmware/efi/libstub/Makefile
index 75daaf2..4cce372 100644
--- a/drivers/firmware/efi/libstub/Makefile
+++ b/drivers/firmware/efi/libstub/Makefile
@@ -6,7 +6,8 @@
 # enabled, even if doing so doesn't break the build.
 #
 cflags-$(CONFIG_X86_32)		:= -march=i386
-cflags-$(CONFIG_X86_64)		:= -mcmodel=small
+cflags-$(CONFIG_X86_64)		:= -mcmodel=small \
+				   $(call cc-option,-maccumulate-outgoing-args)
 cflags-$(CONFIG_X86)		+= -m$(BITS) -D__KERNEL__ \
 				   -fPIC -fno-strict-aliasing -mno-red-zone \
 				   -mno-mmx -mno-sse -fshort-wchar \