linux-kernel - [PATCH v2] x86/entry: add compatibility with IAS

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Message-Id: <20200714233342.1791530-1-caij2003@gmail.com>
Date:   Tue, 14 Jul 2020 16:33:39 -0700
From:   Jian Cai <caij2003@...il.com>
To:     unlisted-recipients:; (no To-header on input)
Cc:     caij2003@...il.com, jiancai@...gle.com, ndesaulniers@...gle.com,
        manojgupta@...gle.com, sedat.dilek@...il.com,
        Brian Gerst <brgerst@...il.com>,
        Arvind Sankar <nivedita@...m.mit.edu>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Alexandre Chartre <alexandre.chartre@...cle.com>,
        linux-kernel@...r.kernel.org, clang-built-linux@...glegroups.com
Subject: [PATCH v2] x86/entry: add compatibility with IAS

Clang's integrated assembler does not allow symbols with non-absolute
values to be reassigned. This patch allows the affected code to be
compatible with IAS.

Link: https://github.com/ClangBuiltLinux/linux/issues/1043
Reported-by: Nick Desaulniers <ndesaulniers@...gle.com>
Reported-by: Sedat Dilek <sedat.dilek@...il.com>
Suggested-by: Nick Desaulniers <ndesaulniers@...gle.com>
Suggested-by: Brian Gerst <brgerst@...il.com>
Suggested-by: Arvind Sankar <nivedita@...m.mit.edu>
Tested-by: Sedat Dilek <sedat.dilek@...il.com> #
Compile-/Assemble-tested against Linux v5.8-rc5 with LLVM/Clang
v11.0.0-git
Signed-off-by: Jian Cai <caij2003@...il.com>
---

Thanks Nick and Sedat for explaining the process of submitting patches.
Include the changelog as follows,

Changes v1 -> v2:
 Update the patch based on Arvind Sankar <nivedita@...m.mit.edu>'s
 comments. Also include addtional information in the Tested-by tag.

 arch/x86/include/asm/idtentry.h | 14 ++++++--------
 1 file changed, 6 insertions(+), 8 deletions(-)

diff --git a/arch/x86/include/asm/idtentry.h b/arch/x86/include/asm/idtentry.h
index f3d70830bf2a..5efaaed34eda 100644
--- a/arch/x86/include/asm/idtentry.h
+++ b/arch/x86/include/asm/idtentry.h
@@ -469,16 +469,15 @@ __visible noinstr void func(struct pt_regs *regs,			\
 	.align 8
 SYM_CODE_START(irq_entries_start)
     vector=FIRST_EXTERNAL_VECTOR
-    pos = .
     .rept (FIRST_SYSTEM_VECTOR - FIRST_EXTERNAL_VECTOR)
 	UNWIND_HINT_IRET_REGS
+0 :
 	.byte	0x6a, vector
 	jmp	asm_common_interrupt
 	nop
 	/* Ensure that the above is 8 bytes max */
-	. = pos + 8
-    pos=pos+8
-    vector=vector+1
+	. = 0b + 8
+	vector = vector+1
     .endr
 SYM_CODE_END(irq_entries_start)
 
@@ -486,16 +485,15 @@ SYM_CODE_END(irq_entries_start)
 	.align 8
 SYM_CODE_START(spurious_entries_start)
     vector=FIRST_SYSTEM_VECTOR
-    pos = .
     .rept (NR_VECTORS - FIRST_SYSTEM_VECTOR)
 	UNWIND_HINT_IRET_REGS
+0 :
 	.byte	0x6a, vector
 	jmp	asm_spurious_interrupt
 	nop
 	/* Ensure that the above is 8 bytes max */
-	. = pos + 8
-    pos=pos+8
-    vector=vector+1
+	. = 0b + 8
+	vector = vector+1
     .endr
 SYM_CODE_END(spurious_entries_start)
 #endif
-- 
2.27.0.389.gc38d7665816-goog