[PATCH] arm64: fix the build with binutils 2.27

[Mark Rutland]

Jon Hunter reports that for some toolchains the build has been broken
since commit:

  4c0bd995d73ed889 ("arm64: alternatives: have callbacks take a cap")

... with a stream of build-time splats of the form:

|   CC      arch/arm64/kvm/hyp/vhe/debug-sr.o
| /tmp/ccY3kbki.s: Assembler messages:
| /tmp/ccY3kbki.s:1600: Error: found 'L', expected: ')'
| /tmp/ccY3kbki.s:1600: Error: found 'L', expected: ')'
| /tmp/ccY3kbki.s:1600: Error: found 'L', expected: ')'
| /tmp/ccY3kbki.s:1600: Error: found 'L', expected: ')'
| /tmp/ccY3kbki.s:1600: Error: junk at end of line, first unrecognized character
| is `L'
| /tmp/ccY3kbki.s:1723: Error: found 'L', expected: ')'
| /tmp/ccY3kbki.s:1723: Error: found 'L', expected: ')'
| /tmp/ccY3kbki.s:1723: Error: found 'L', expected: ')'
| /tmp/ccY3kbki.s:1723: Error: found 'L', expected: ')'
| /tmp/ccY3kbki.s:1723: Error: junk at end of line, first unrecognized character
| is `L'
| scripts/Makefile.build:249: recipe for target
| 'arch/arm64/kvm/hyp/vhe/debug-sr.o' failed

The issue here is that older versions of binutils (up to and including
2.27.0) don't like an 'L' suffix on constants. For plain assembly files,
UL() avoids this suffix, but in C files this gets added, and so for
inline assembly we can't directly use a constant defined with `UL()`.

We could avoid this by passing the constant as an input parameter, but
this isn't practical given the way we use the alternative macros.
Instead, just open code the constant without the `UL` suffix, and for
consistency do this for both the inline assembly macro and the regular
assembly macro.

Signed-off-by: Mark Rutland <mark.rutland at arm.com>
Fixes: 4c0bd995d73ed889 ("arm64: alternatives: have callbacks take a cap")
Reported-by: Jon Hunter <jonathanh at nvidia.com>
Link: https://lore.kernel.org/linux-arm-kernel/3cecc3a5-30b0-f0bd-c3de-9e09bd21909b@nvidia.com/
Tested-by: Jon Hunter <jonathanh at nvidia.com>
Cc: Ard Biesheuvel <ardb at kernel.org>
Cc: Catalin Marinas <catalin.marinas at arm.com>
Cc: Will Deacon <will at kernel.org>
---
 arch/arm64/include/asm/alternative-macros.h | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/include/asm/alternative-macros.h b/arch/arm64/include/asm/alternative-macros.h
index 966767debaa3..b5ac0b85c9bb 100644
--- a/arch/arm64/include/asm/alternative-macros.h
+++ b/arch/arm64/include/asm/alternative-macros.h
@@ -2,12 +2,18 @@
 #ifndef __ASM_ALTERNATIVE_MACROS_H
 #define __ASM_ALTERNATIVE_MACROS_H
 
+#include <linux/bits.h>
 #include <linux/const.h>
 
 #include <asm/cpucaps.h>
 #include <asm/insn-def.h>
 
-#define ARM64_CB_BIT	(UL(1) << 15)
+/*
+ * Binutils 2.27.0 can't handle a 'UL' suffix on constants, so for the assembly
+ * macros below we must use we must use `(1 << ARM64_CB_SHIFT)`.
+ */
+#define ARM64_CB_SHIFT	15
+#define ARM64_CB_BIT	BIT(ARM64_CB_SHIFT)
 
 #if ARM64_NCAPS >= ARM64_CB_BIT
 #error "cpucaps have overflown ARM64_CB_BIT"
@@ -80,7 +86,7 @@
 	__ALTERNATIVE_CFG(oldinstr, newinstr, feature, IS_ENABLED(cfg))
 
 #define ALTERNATIVE_CB(oldinstr, feature, cb) \
-	__ALTERNATIVE_CFG_CB(oldinstr, ARM64_CB_BIT | (feature), 1, cb)
+	__ALTERNATIVE_CFG_CB(oldinstr, (1 << ARM64_CB_SHIFT) | (feature), 1, cb)
 #else
 
 #include <asm/assembler.h>
@@ -150,7 +156,7 @@
 .macro alternative_cb cap, cb
 	.set .Lasm_alt_mode, 0
 	.pushsection .altinstructions, "a"
-	altinstruction_entry 661f, \cb, ARM64_CB_BIT | \cap, 662f-661f, 0
+	altinstruction_entry 661f, \cb, (1 << ARM64_CB_SHIFT) | \cap, 662f-661f, 0
 	.popsection
 661:
 .endm
-- 
2.30.2