Re: [PATCH] arm64: Paper over ARM_SMCCC_ARCH_WORKAROUND_3 Clang issue

Re: [PATCH] arm64: Paper over ARM_SMCCC_ARCH_WORKAROUND_3 Clang issue

[Nathan Chancellor]

[-- Attachment #1: Type: text/plain, Size: 1959 bytes --]

On Wed, Mar 09, 2022 at 03:57:16PM +0000, Marc Zyngier wrote:
> Compiling the arm64 kernel with the BHB workarounds and Clang+LTO
> results in a bunch of:
> 
> <instantiation>:4:2: error: invalid fixup for movz/movk instruction
>  mov w0, #ARM_SMCCC_ARCH_WORKAROUND_3
> 
> when compiling arch/arm64/kernel/entry.S, and makes no sense at all.
> 
> As it turns out, moving a single include line around makes the
> problem disappear. Why, you'd ask? Well, I don't have the faintest
> idea, and I'm running out of patience. So make of that what you want.
> 
> Cc: James Morse <james.morse@arm.com>
> Cc: Nick Desaulniers <ndesaulniers@google.com>
> Cc: Will Deacon <will@kernel.org>
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Signed-off-by: Marc Zyngier <maz@kernel.org>
> ---
>  include/linux/arm-smccc.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/include/linux/arm-smccc.h b/include/linux/arm-smccc.h
> index 220c8c60e021..0a341dd9ff61 100644
> --- a/include/linux/arm-smccc.h
> +++ b/include/linux/arm-smccc.h
> @@ -5,7 +5,6 @@
>  #ifndef __LINUX_ARM_SMCCC_H
>  #define __LINUX_ARM_SMCCC_H
>  
> -#include <linux/init.h>
>  #include <uapi/linux/const.h>
>  
>  /*
> @@ -193,6 +192,7 @@
>  
>  #ifndef __ASSEMBLY__
>  
> +#include <linux/init.h>
>  #include <linux/linkage.h>
>  #include <linux/types.h>
>  
> -- 
> 2.34.1

I am still looking at this but I wanted to post a preliminary finding.
It seems the source of the error is that ARM_SMCCC_ARCH_WORKAROUND_3 is
not getting expanded by the preprocessor. If you preprocess
arch/arm64/kernel/entry.S without LTO then with LTO, it reveals the
attached diff, which shows just "#ARM_SMCCC_ARCH_WORKAROUND_3", rather
than "# (((1) << 31) | ((0) << 30) | (((0) & 0x3F) << 24) | ((0x3fff) & 0xFFFF))".

$ make -skj"$(nproc)" ARCH=arm64 LLVM=1 mrproper defconfig arch/arm64/kernel/entry.s

I'll see if I can figure out what is going wrong in the include chain.

Cheers,
Nathan

[-- Attachment #2: entry.s.diff --]
[-- Type: text/plain, Size: 9597 bytes --]

diff --git a/entry.s.good b/entry.s.bad
index ab98e34..b331cc4 100644
--- a/entry.s.good
+++ b/entry.s.bad
@@ -35,71 +35,17 @@
 # 6 "./include/linux/compiler.h" 2
 # 266 "./include/linux/compiler.h"
 # 1 "./arch/arm64/include/asm/rwonce.h" 1
-# 71 "./arch/arm64/include/asm/rwonce.h"
-# 1 "./include/asm-generic/rwonce.h" 1
-# 72 "./arch/arm64/include/asm/rwonce.h" 2
-# 267 "./include/linux/compiler.h" 2
-# 6 "./include/linux/init.h" 2
-# 1 "./include/linux/types.h" 1
-
-
-
-
-
-# 1 "./include/uapi/linux/types.h" 1
-
-
-
-
-# 1 "./arch/arm64/include/generated/uapi/asm/types.h" 1
-# 1 "./include/uapi/asm-generic/types.h" 1
-
-
-
-
-
-
-# 1 "./include/asm-generic/int-ll64.h" 1
-# 11 "./include/asm-generic/int-ll64.h"
-# 1 "./include/uapi/asm-generic/int-ll64.h" 1
-# 12 "./include/uapi/asm-generic/int-ll64.h"
-# 1 "./arch/arm64/include/uapi/asm/bitsperlong.h" 1
-# 22 "./arch/arm64/include/uapi/asm/bitsperlong.h"
-# 1 "./include/asm-generic/bitsperlong.h" 1
-
-
-
-
-# 1 "./include/uapi/asm-generic/bitsperlong.h" 1
-# 6 "./include/asm-generic/bitsperlong.h" 2
-# 23 "./arch/arm64/include/uapi/asm/bitsperlong.h" 2
-# 13 "./include/uapi/asm-generic/int-ll64.h" 2
-# 12 "./include/asm-generic/int-ll64.h" 2
-# 8 "./include/uapi/asm-generic/types.h" 2
-# 2 "./arch/arm64/include/generated/uapi/asm/types.h" 2
-# 6 "./include/uapi/linux/types.h" 2
-# 7 "./include/linux/types.h" 2
-# 7 "./include/linux/init.h" 2
-# 9 "./include/linux/arm-smccc.h" 2
-# 1 "./include/uapi/linux/const.h" 1
-# 10 "./include/linux/arm-smccc.h" 2
-# 11 "arch/arm64/kernel/entry.S" 2
-
-# 1 "./include/linux/linkage.h" 1
-
-
-
-
-
-# 1 "./include/linux/stringify.h" 1
-# 7 "./include/linux/linkage.h" 2
-# 1 "./include/linux/export.h" 1
-# 8 "./include/linux/linkage.h" 2
-# 1 "./arch/arm64/include/asm/linkage.h" 1
+# 11 "./arch/arm64/include/asm/rwonce.h"
+# 1 "./arch/arm64/include/asm/alternative-macros.h" 1
 
 
 
 
+# 1 "./arch/arm64/include/generated/asm/cpucaps.h" 1
+# 6 "./arch/arm64/include/asm/alternative-macros.h" 2
+# 1 "./arch/arm64/include/asm/insn-def.h" 1
+# 7 "./arch/arm64/include/asm/alternative-macros.h" 2
+# 80 "./arch/arm64/include/asm/alternative-macros.h"
 # 1 "./arch/arm64/include/asm/assembler.h" 1
 # 15 "./arch/arm64/include/asm/assembler.h"
 # 1 "./include/asm-generic/export.h" 1
@@ -141,108 +87,6 @@ __kstrtab_\name:
 
 
 # 1 "./arch/arm64/include/asm/alternative-macros.h" 1
-
-
-
-
-# 1 "./arch/arm64/include/generated/asm/cpucaps.h" 1
-# 6 "./arch/arm64/include/asm/alternative-macros.h" 2
-# 1 "./arch/arm64/include/asm/insn-def.h" 1
-# 7 "./arch/arm64/include/asm/alternative-macros.h" 2
-# 80 "./arch/arm64/include/asm/alternative-macros.h"
-# 1 "./arch/arm64/include/asm/assembler.h" 1
-# 81 "./arch/arm64/include/asm/alternative-macros.h" 2
-
-.macro altinstruction_entry orig_offset alt_offset feature orig_len alt_len
- .word \orig_offset - .
- .word \alt_offset - .
- .hword \feature
- .byte \orig_len
- .byte \alt_len
-.endm
-
-.macro alternative_insn insn1, insn2, cap, enable = 1
- .if \enable
-661: \insn1
-662: .pushsection .altinstructions, "a"
- altinstruction_entry 661b, 663f, \cap, 662b-661b, 664f-663f
- .popsection
- .subsection 1
-663: \insn2
-664: .org . - (664b-663b) + (662b-661b)
- .org . - (662b-661b) + (664b-663b)
- .previous
- .endif
-.endm
-# 126 "./arch/arm64/include/asm/alternative-macros.h"
-.macro alternative_if_not cap
- .set .Lasm_alt_mode, 0
- .pushsection .altinstructions, "a"
- altinstruction_entry 661f, 663f, \cap, 662f-661f, 664f-663f
- .popsection
-661:
-.endm
-
-.macro alternative_if cap
- .set .Lasm_alt_mode, 1
- .pushsection .altinstructions, "a"
- altinstruction_entry 663f, 661f, \cap, 664f-663f, 662f-661f
- .popsection
- .subsection 1
- .align 2
-661:
-.endm
-
-.macro alternative_cb cb
- .set .Lasm_alt_mode, 0
- .pushsection .altinstructions, "a"
- altinstruction_entry 661f, \cb, 71, 662f-661f, 0
- .popsection
-661:
-.endm
-
-
-
-
-.macro alternative_else
-662:
- .if .Lasm_alt_mode==0
- .subsection 1
- .else
- .previous
- .endif
-663:
-.endm
-
-
-
-
-.macro alternative_endif
-664:
- .org . - (664b-663b) + (662b-661b)
- .org . - (662b-661b) + (664b-663b)
- .if .Lasm_alt_mode==0
- .previous
- .endif
-.endm
-
-
-
-
-.macro alternative_cb_end
-662:
-.endm
-
-
-
-
-
-
-.macro alternative_else_nop_endif
-alternative_else
- nops (662b-661b) / 4
-alternative_endif
-.endm
 # 6 "./arch/arm64/include/asm/alternative.h" 2
 # 18 "./arch/arm64/include/asm/assembler.h" 2
 # 1 "./arch/arm64/include/asm/asm-bug.h" 1
@@ -305,12 +149,30 @@ alternative_endif
 
 
 # 1 "./include/vdso/const.h" 1
+
+
+
+
+# 1 "./include/uapi/linux/const.h" 1
+# 6 "./include/vdso/const.h" 2
 # 5 "./include/linux/const.h" 2
 # 6 "./include/linux/bits.h" 2
 # 1 "./include/vdso/bits.h" 1
 # 7 "./include/linux/bits.h" 2
-# 13 "./arch/arm64/include/asm/sysreg.h" 2
+# 1 "./arch/arm64/include/uapi/asm/bitsperlong.h" 1
+# 22 "./arch/arm64/include/uapi/asm/bitsperlong.h"
+# 1 "./include/asm-generic/bitsperlong.h" 1
+
+
 
+
+# 1 "./include/uapi/asm-generic/bitsperlong.h" 1
+# 6 "./include/asm-generic/bitsperlong.h" 2
+# 23 "./arch/arm64/include/uapi/asm/bitsperlong.h" 2
+# 8 "./include/linux/bits.h" 2
+# 13 "./arch/arm64/include/asm/sysreg.h" 2
+# 1 "./include/linux/stringify.h" 1
+# 14 "./arch/arm64/include/asm/sysreg.h" 2
 # 1 "./include/linux/kasan-tags.h" 1
 # 15 "./arch/arm64/include/asm/sysreg.h" 2
 
@@ -365,8 +227,35 @@ alternative_endif
 # 2 "./include/uapi/linux/errno.h" 2
 # 6 "./include/linux/errno.h" 2
 # 9 "./arch/arm64/include/asm/debug-monitors.h" 2
+# 1 "./include/linux/types.h" 1
+
+
+
 
 
+# 1 "./include/uapi/linux/types.h" 1
+
+
+
+
+# 1 "./arch/arm64/include/generated/uapi/asm/types.h" 1
+# 1 "./include/uapi/asm-generic/types.h" 1
+
+
+
+
+
+
+# 1 "./include/asm-generic/int-ll64.h" 1
+# 11 "./include/asm-generic/int-ll64.h"
+# 1 "./include/uapi/asm-generic/int-ll64.h" 1
+# 12 "./include/asm-generic/int-ll64.h" 2
+# 8 "./include/uapi/asm-generic/types.h" 2
+# 2 "./arch/arm64/include/generated/uapi/asm/types.h" 2
+# 6 "./include/uapi/linux/types.h" 2
+# 7 "./include/linux/types.h" 2
+# 10 "./arch/arm64/include/asm/debug-monitors.h" 2
+
 # 1 "./arch/arm64/include/asm/esr.h" 1
 # 10 "./arch/arm64/include/asm/esr.h"
 # 1 "./arch/arm64/include/asm/memory.h" 1
@@ -389,6 +278,12 @@ alternative_endif
 # 1 "./arch/arm64/include/asm/insn.h" 1
 # 10 "./arch/arm64/include/asm/insn.h"
 # 1 "./include/linux/build_bug.h" 1
+
+
+
+
+# 1 "./include/linux/compiler.h" 1
+# 6 "./include/linux/build_bug.h" 2
 # 11 "./arch/arm64/include/asm/insn.h" 2
 # 13 "./arch/arm64/include/asm/debug-monitors.h" 2
 # 1 "./arch/arm64/include/asm/ptrace.h" 1
@@ -409,6 +304,9 @@ alternative_endif
 # 26 "./arch/arm64/include/asm/assembler.h" 2
 
 # 1 "./arch/arm64/include/asm/thread_info.h" 1
+# 11 "./arch/arm64/include/asm/thread_info.h"
+# 1 "./include/linux/compiler.h" 1
+# 12 "./arch/arm64/include/asm/thread_info.h" 2
 # 28 "./arch/arm64/include/asm/assembler.h" 2
 
 
@@ -1089,7 +987,7 @@ alternative_cb_end
 
  stp x0, x1, [sp, #-16]!
  stp x2, x3, [sp, #-16]!
- mov w0, #(((1) << 31) | ((0) << 30) | (((0) & 0x3F) << 24) | ((0x3fff) & 0xFFFF))
+ mov w0, #ARM_SMCCC_ARCH_WORKAROUND_3
 alternative_cb smccc_patch_fw_mitigation_conduit
  nop
 alternative_cb_end
@@ -1097,6 +995,122 @@ alternative_cb_end
  ldp x0, x1, [sp], #16
 
  .endm
+# 81 "./arch/arm64/include/asm/alternative-macros.h" 2
+
+.macro altinstruction_entry orig_offset alt_offset feature orig_len alt_len
+ .word \orig_offset - .
+ .word \alt_offset - .
+ .hword \feature
+ .byte \orig_len
+ .byte \alt_len
+.endm
+
+.macro alternative_insn insn1, insn2, cap, enable = 1
+ .if \enable
+661: \insn1
+662: .pushsection .altinstructions, "a"
+ altinstruction_entry 661b, 663f, \cap, 662b-661b, 664f-663f
+ .popsection
+ .subsection 1
+663: \insn2
+664: .org . - (664b-663b) + (662b-661b)
+ .org . - (662b-661b) + (664b-663b)
+ .previous
+ .endif
+.endm
+# 126 "./arch/arm64/include/asm/alternative-macros.h"
+.macro alternative_if_not cap
+ .set .Lasm_alt_mode, 0
+ .pushsection .altinstructions, "a"
+ altinstruction_entry 661f, 663f, \cap, 662f-661f, 664f-663f
+ .popsection
+661:
+.endm
+
+.macro alternative_if cap
+ .set .Lasm_alt_mode, 1
+ .pushsection .altinstructions, "a"
+ altinstruction_entry 663f, 661f, \cap, 664f-663f, 662f-661f
+ .popsection
+ .subsection 1
+ .align 2
+661:
+.endm
+
+.macro alternative_cb cb
+ .set .Lasm_alt_mode, 0
+ .pushsection .altinstructions, "a"
+ altinstruction_entry 661f, \cb, 71, 662f-661f, 0
+ .popsection
+661:
+.endm
+
+
+
+
+.macro alternative_else
+662:
+ .if .Lasm_alt_mode==0
+ .subsection 1
+ .else
+ .previous
+ .endif
+663:
+.endm
+
+
+
+
+.macro alternative_endif
+664:
+ .org . - (664b-663b) + (662b-661b)
+ .org . - (662b-661b) + (664b-663b)
+ .if .Lasm_alt_mode==0
+ .previous
+ .endif
+.endm
+
+
+
+
+.macro alternative_cb_end
+662:
+.endm
+
+
+
+
+
+
+.macro alternative_else_nop_endif
+alternative_else
+ nops (662b-661b) / 4
+alternative_endif
+.endm
+# 12 "./arch/arm64/include/asm/rwonce.h" 2
+# 71 "./arch/arm64/include/asm/rwonce.h"
+# 1 "./include/asm-generic/rwonce.h" 1
+# 72 "./arch/arm64/include/asm/rwonce.h" 2
+# 267 "./include/linux/compiler.h" 2
+# 6 "./include/linux/init.h" 2
+# 9 "./include/linux/arm-smccc.h" 2
+# 11 "arch/arm64/kernel/entry.S" 2
+
+# 1 "./include/linux/linkage.h" 1
+
+
+
+
+
+
+# 1 "./include/linux/export.h" 1
+# 8 "./include/linux/linkage.h" 2
+# 1 "./arch/arm64/include/asm/linkage.h" 1
+
+
+
+
+# 1 "./arch/arm64/include/asm/assembler.h" 1
 # 6 "./arch/arm64/include/asm/linkage.h" 2
 # 9 "./include/linux/linkage.h" 2
 # 13 "arch/arm64/kernel/entry.S" 2

Re: [PATCH] arm64: Paper over ARM_SMCCC_ARCH_WORKAROUND_3 Clang issue

[Nathan Chancellor]

On Wed, Mar 09, 2022 at 10:11:18AM -0700, Nathan Chancellor wrote:
> On Wed, Mar 09, 2022 at 03:57:16PM +0000, Marc Zyngier wrote:
> > Compiling the arm64 kernel with the BHB workarounds and Clang+LTO
> > results in a bunch of:
> > 
> > <instantiation>:4:2: error: invalid fixup for movz/movk instruction
> >  mov w0, #ARM_SMCCC_ARCH_WORKAROUND_3
> > 
> > when compiling arch/arm64/kernel/entry.S, and makes no sense at all.
> > 
> > As it turns out, moving a single include line around makes the
> > problem disappear. Why, you'd ask? Well, I don't have the faintest
> > idea, and I'm running out of patience. So make of that what you want.
> > 
> > Cc: James Morse <james.morse@arm.com>
> > Cc: Nick Desaulniers <ndesaulniers@google.com>
> > Cc: Will Deacon <will@kernel.org>
> > Cc: Catalin Marinas <catalin.marinas@arm.com>
> > Signed-off-by: Marc Zyngier <maz@kernel.org>
> > ---
> >  include/linux/arm-smccc.h | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/include/linux/arm-smccc.h b/include/linux/arm-smccc.h
> > index 220c8c60e021..0a341dd9ff61 100644
> > --- a/include/linux/arm-smccc.h
> > +++ b/include/linux/arm-smccc.h
> > @@ -5,7 +5,6 @@
> >  #ifndef __LINUX_ARM_SMCCC_H
> >  #define __LINUX_ARM_SMCCC_H
> >  
> > -#include <linux/init.h>
> >  #include <uapi/linux/const.h>
> >  
> >  /*
> > @@ -193,6 +192,7 @@
> >  
> >  #ifndef __ASSEMBLY__
> >  
> > +#include <linux/init.h>
> >  #include <linux/linkage.h>
> >  #include <linux/types.h>
> >  
> > -- 
> > 2.34.1
> 
> I am still looking at this but I wanted to post a preliminary finding.
> It seems the source of the error is that ARM_SMCCC_ARCH_WORKAROUND_3 is
> not getting expanded by the preprocessor. If you preprocess
> arch/arm64/kernel/entry.S without LTO then with LTO, it reveals the
> attached diff, which shows just "#ARM_SMCCC_ARCH_WORKAROUND_3", rather
> than "# (((1) << 31) | ((0) << 30) | (((0) & 0x3F) << 24) | ((0x3fff) & 0xFFFF))".

CONFIG_LTO=y causes the following include chain:

include/linux/arm-smccc.h
include/linux/init.h
include/linux/compiler.h
arch/arm64/include/asm/rwonce.h
arch/arm64/include/asm/alternative-macros.h
arch/arm64/include/asm/assembler.h

assembler.h has the use of ARM_SMCCC_ARCH_WORKAROUND_3 but the init.h
include in arm-smccc.h happens before the definition, so it does not get
expanded. This completely hacky patch proves that, as the error goes
away with it:

diff --git a/include/linux/arm-smccc.h b/include/linux/arm-smccc.h
index 220c8c60e021..6cf6bcf00647 100644
--- a/include/linux/arm-smccc.h
+++ b/include/linux/arm-smccc.h
@@ -5,7 +5,6 @@
 #ifndef __LINUX_ARM_SMCCC_H
 #define __LINUX_ARM_SMCCC_H
 
-#include <linux/init.h>
 #include <uapi/linux/const.h>
 
 /*
@@ -97,6 +96,8 @@
 			   ARM_SMCCC_SMC_32,				\
 			   0, 0x3fff)
 
+#include <linux/init.h>
+
 #define ARM_SMCCC_VENDOR_HYP_CALL_UID_FUNC_ID				\
 	ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL,				\
 			   ARM_SMCCC_SMC_32,				\

This diff seems like a somewhat proper solution, as __READ_ONCE() cannot
be used in assembly, but I am open to other suggestions.

diff --git a/arch/arm64/include/asm/rwonce.h b/arch/arm64/include/asm/rwonce.h
index 1bce62fa908a..56f7b1d4d54b 100644
--- a/arch/arm64/include/asm/rwonce.h
+++ b/arch/arm64/include/asm/rwonce.h
@@ -5,7 +5,7 @@
 #ifndef __ASM_RWONCE_H
 #define __ASM_RWONCE_H
 
-#ifdef CONFIG_LTO
+#if defined(CONFIG_LTO) && !defined(__ASSEMBLY__)
 
 #include <linux/compiler_types.h>
 #include <asm/alternative-macros.h>
@@ -66,7 +66,7 @@
 })
 
 #endif	/* !BUILD_VDSO */
-#endif	/* CONFIG_LTO */
+#endif	/* CONFIG_LTO && !__ASSEMBLY__ */
 
 #include <asm-generic/rwonce.h>
 

Cheers,
Nathan

Re: [PATCH] arm64: Paper over ARM_SMCCC_ARCH_WORKAROUND_3 Clang issue

[James Morse]

Hi Nathan,

On 09/03/2022 17:50, Nathan Chancellor wrote:
> On Wed, Mar 09, 2022 at 10:11:18AM -0700, Nathan Chancellor wrote:
>> On Wed, Mar 09, 2022 at 03:57:16PM +0000, Marc Zyngier wrote:
>>> Compiling the arm64 kernel with the BHB workarounds and Clang+LTO
>>> results in a bunch of:
>>>
>>> <instantiation>:4:2: error: invalid fixup for movz/movk instruction
>>>  mov w0, #ARM_SMCCC_ARCH_WORKAROUND_3
>>>
>>> when compiling arch/arm64/kernel/entry.S, and makes no sense at all.
>>>
>>> As it turns out, moving a single include line around makes the
>>> problem disappear. Why, you'd ask? Well, I don't have the faintest
>>> idea, and I'm running out of patience. So make of that what you want.

[...]

> CONFIG_LTO=y causes the following include chain:
> 
> include/linux/arm-smccc.h
> include/linux/init.h
> include/linux/compiler.h

> arch/arm64/include/asm/rwonce.h

Gah, a header file that does something completely different under LTO!


> arch/arm64/include/asm/alternative-macros.h
> arch/arm64/include/asm/assembler.h
> 
> assembler.h has the use of ARM_SMCCC_ARCH_WORKAROUND_3 but the init.h
> include in arm-smccc.h happens before the definition, so it does not get
> expanded.

Thanks for getting to the bottom of this! The error message had me stumped.

...

> This diff seems like a somewhat proper solution, as __READ_ONCE() cannot
> be used in assembly, but I am open to other suggestions.
> 
> diff --git a/arch/arm64/include/asm/rwonce.h b/arch/arm64/include/asm/rwonce.h
> index 1bce62fa908a..56f7b1d4d54b 100644
> --- a/arch/arm64/include/asm/rwonce.h
> +++ b/arch/arm64/include/asm/rwonce.h
> @@ -5,7 +5,7 @@
>  #ifndef __ASM_RWONCE_H
>  #define __ASM_RWONCE_H
>  
> -#ifdef CONFIG_LTO
> +#if defined(CONFIG_LTO) && !defined(__ASSEMBLY__)
>  
>  #include <linux/compiler_types.h>
>  #include <asm/alternative-macros.h>
> @@ -66,7 +66,7 @@
>  })
>  
>  #endif	/* !BUILD_VDSO */
> -#endif	/* CONFIG_LTO */
> +#endif	/* CONFIG_LTO && !__ASSEMBLY__ */
>  
>  #include <asm-generic/rwonce.h>

This looks like the smallest/cleanest fix.

Acked-by: James Morse <james.morse@arm.com>


I guess ultimately we should split things like arm-smccc.h into multiple files...


Thanks,

James

Re: [PATCH] arm64: Paper over ARM_SMCCC_ARCH_WORKAROUND_3 Clang issue

[Catalin Marinas]

On Wed, Mar 09, 2022 at 10:50:36AM -0700, Nathan Chancellor wrote:
> This diff seems like a somewhat proper solution, as __READ_ONCE() cannot
> be used in assembly, but I am open to other suggestions.
> 
> diff --git a/arch/arm64/include/asm/rwonce.h b/arch/arm64/include/asm/rwonce.h
> index 1bce62fa908a..56f7b1d4d54b 100644
> --- a/arch/arm64/include/asm/rwonce.h
> +++ b/arch/arm64/include/asm/rwonce.h
> @@ -5,7 +5,7 @@
>  #ifndef __ASM_RWONCE_H
>  #define __ASM_RWONCE_H
>  
> -#ifdef CONFIG_LTO
> +#if defined(CONFIG_LTO) && !defined(__ASSEMBLY__)
>  
>  #include <linux/compiler_types.h>
>  #include <asm/alternative-macros.h>
> @@ -66,7 +66,7 @@
>  })
>  
>  #endif	/* !BUILD_VDSO */
> -#endif	/* CONFIG_LTO */
> +#endif	/* CONFIG_LTO && !__ASSEMBLY__ */

Thanks Nathan. Would you please send a proper patch for this? I'd go
with your proposal as it seems more related to LTO than Marc's patch ;).

-- 
Catalin

Re: [PATCH] arm64: Paper over ARM_SMCCC_ARCH_WORKAROUND_3 Clang issue

[Nathan Chancellor]

On Wed, Mar 09, 2022 at 06:45:13PM +0000, Catalin Marinas wrote:
> On Wed, Mar 09, 2022 at 10:50:36AM -0700, Nathan Chancellor wrote:
> > This diff seems like a somewhat proper solution, as __READ_ONCE() cannot
> > be used in assembly, but I am open to other suggestions.
> > 
> > diff --git a/arch/arm64/include/asm/rwonce.h b/arch/arm64/include/asm/rwonce.h
> > index 1bce62fa908a..56f7b1d4d54b 100644
> > --- a/arch/arm64/include/asm/rwonce.h
> > +++ b/arch/arm64/include/asm/rwonce.h
> > @@ -5,7 +5,7 @@
> >  #ifndef __ASM_RWONCE_H
> >  #define __ASM_RWONCE_H
> >  
> > -#ifdef CONFIG_LTO
> > +#if defined(CONFIG_LTO) && !defined(__ASSEMBLY__)
> >  
> >  #include <linux/compiler_types.h>
> >  #include <asm/alternative-macros.h>
> > @@ -66,7 +66,7 @@
> >  })
> >  
> >  #endif	/* !BUILD_VDSO */
> > -#endif	/* CONFIG_LTO */
> > +#endif	/* CONFIG_LTO && !__ASSEMBLY__ */
> 
> Thanks Nathan. Would you please send a proper patch for this? I'd go
> with your proposal as it seems more related to LTO than Marc's patch ;).

Done, thanks Catalin and James for your input!

https://lore.kernel.org/r/20220309191633.2307110-1-nathan@kernel.org/

Cheers,
Nathan