linux-kernel - [PATCH v1A 1/2] x86/fred: Fix build with clang

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Date: Sun, 28 Jan 2024 22:45:21 -0800
From: Xin Li <xin3.li@...el.com>
To: linux-kernel@...r.kernel.org
Cc: tglx@...utronix.de,
	mingo@...hat.com,
	bp@...en8.de,
	dave.hansen@...ux.intel.com,
	x86@...nel.org,
	hpa@...or.com,
	luto@...nel.org,
	ravi.v.shankar@...el.com,
	andrew.cooper3@...rix.com
Subject: [PATCH v1A 1/2] x86/fred: Fix build with clang

Remove the .fill statement that referneces asm_fred_entrypoint_kernel()
before it's defined, which breaks clang build.

Use the .org directive instead to fill "int3" into the memory between
asm_fred_entrypoint_user() and asm_fred_entrypoint_kernel().

Fixes: 5e0636a41485 ("x86/fred: FRED entry/exit and dispatch code")
Reported-by: Borislav Petkov (AMD) <bp@...en8.de>
Link: https://lore.kernel.org/lkml/20240126100050.GAZbOC0g3Rlr6otZcT@fat_crate.local/
Signed-off-by: Xin Li <xin3.li@...el.com>
---

Change since v1:
* Use ".org ..., 0xcc" to fill "int3" into memory (H. Peter Anvin).
---
 arch/x86/entry/entry_64_fred.S | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/arch/x86/entry/entry_64_fred.S b/arch/x86/entry/entry_64_fred.S
index eedf98de7538..a02bc6f3d2e6 100644
--- a/arch/x86/entry/entry_64_fred.S
+++ b/arch/x86/entry/entry_64_fred.S
@@ -43,14 +43,12 @@ SYM_INNER_LABEL(asm_fred_exit_user, SYM_L_GLOBAL)
 	_ASM_EXTABLE_TYPE(1b, asm_fred_entrypoint_user, EX_TYPE_ERETU)
 SYM_CODE_END(asm_fred_entrypoint_user)
 
-.fill asm_fred_entrypoint_kernel - ., 1, 0xcc
-
 /*
  * The new RIP value that FRED event delivery establishes is
  * (IA32_FRED_CONFIG & ~FFFH) + 256 for events that occur in
  * ring 0, i.e., asm_fred_entrypoint_user + 256.
  */
-	.org asm_fred_entrypoint_user + 256
+	.org asm_fred_entrypoint_user + 256, 0xcc
 SYM_CODE_START_NOALIGN(asm_fred_entrypoint_kernel)
 	FRED_ENTER
 	call	fred_entry_from_kernel
-- 
2.43.0