KVM ARM Archive on lore.kernel.org
 help / color / Atom feed
* [kvm-unit-tests PATCH] arm64: Compile with -mno-outline-atomics for GCC >= 10
@ 2020-07-17 16:47 Alexandru Elisei
  2020-07-18  9:11 ` Andrew Jones
  0 siblings, 1 reply; 7+ messages in thread
From: Alexandru Elisei @ 2020-07-17 16:47 UTC (permalink / raw)
  To: kvm, kvmarm; +Cc: pbonzini

GCC 10.1.0 introduced the -m{,no-}outline-atomics flags which, according to
man 1 gcc:

"Enable or disable calls to out-of-line helpers to implement atomic
operations.  These helpers will, at runtime, determine if the LSE
instructions from ARMv8.1-A can be used; if not, they will use the
load/store-exclusive instructions that are present in the base ARMv8.0 ISA.
[..] This option is on by default."

Unfortunately the option causes the following error at compile time:

aarch64-linux-gnu-ld -nostdlib -pie -n -o arm/spinlock-test.elf -T /path/to/kvm-unit-tests/arm/flat.lds \
	arm/spinlock-test.o arm/cstart64.o lib/libcflat.a lib/libfdt/libfdt.a /usr/lib/gcc/aarch64-linux-gnu/10.1.0/libgcc.a lib/arm/libeabi.a arm/spinlock-test.aux.o
aarch64-linux-gnu-ld: /usr/lib/gcc/aarch64-linux-gnu/10.1.0/libgcc.a(lse-init.o): in function `init_have_lse_atomics':
lse-init.c:(.text.startup+0xc): undefined reference to `__getauxval'

This is happening because we are linking against our own libcflat which
doesn't implement the function __getauxval().

Disable the use of the out-of-line functions by compiling with
-mno-outline-atomics if we detect a GCC version greater than 10.

Signed-off-by: Alexandru Elisei <alexandru.elisei@arm.com>
---

Tested with gcc versions 10.1.0 and 5.4.0 (cross-compilation), 9.3.0
(native).

I've been able to suss out the reason for the build failure from this
rejected gcc patch [1].

[1] https://patches.openembedded.org/patch/172460/

 arm/Makefile.arm64 | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/arm/Makefile.arm64 b/arm/Makefile.arm64
index dfd0c56fe8fb..3223cb966789 100644
--- a/arm/Makefile.arm64
+++ b/arm/Makefile.arm64
@@ -9,6 +9,12 @@ ldarch = elf64-littleaarch64
 arch_LDFLAGS = -pie -n
 CFLAGS += -mstrict-align
 
+# The -mno-outline-atomics flag is only valid for GCC versions 10 and greater.
+GCC_MAJOR_VERSION=$(shell $(CC) -dumpversion 2> /dev/null | cut -f1 -d.)
+ifeq ($(shell expr "$(GCC_MAJOR_VERSION)" ">=" "10"), 1)
+CFLAGS += -mno-outline-atomics
+endif
+
 define arch_elf_check =
 	$(if $(shell ! $(OBJDUMP) -R $(1) >&/dev/null && echo "nok"),
 		$(error $(shell $(OBJDUMP) -R $(1) 2>&1)))
-- 
2.27.0

_______________________________________________
kvmarm mailing list
kvmarm@lists.cs.columbia.edu
https://lists.cs.columbia.edu/mailman/listinfo/kvmarm

^ permalink raw reply	[flat|nested] 7+ messages in thread

* Re: [kvm-unit-tests PATCH] arm64: Compile with -mno-outline-atomics for GCC >= 10
  2020-07-17 16:47 [kvm-unit-tests PATCH] arm64: Compile with -mno-outline-atomics for GCC >= 10 Alexandru Elisei
@ 2020-07-18  9:11 ` Andrew Jones
  2020-07-18 13:50   ` Alexandru Elisei
  0 siblings, 1 reply; 7+ messages in thread
From: Andrew Jones @ 2020-07-18  9:11 UTC (permalink / raw)
  To: Alexandru Elisei; +Cc: pbonzini, kvmarm, kvm

On Fri, Jul 17, 2020 at 05:47:27PM +0100, Alexandru Elisei wrote:
> GCC 10.1.0 introduced the -m{,no-}outline-atomics flags which, according to
> man 1 gcc:
> 
> "Enable or disable calls to out-of-line helpers to implement atomic
> operations.  These helpers will, at runtime, determine if the LSE
> instructions from ARMv8.1-A can be used; if not, they will use the
> load/store-exclusive instructions that are present in the base ARMv8.0 ISA.
> [..] This option is on by default."
> 
> Unfortunately the option causes the following error at compile time:
> 
> aarch64-linux-gnu-ld -nostdlib -pie -n -o arm/spinlock-test.elf -T /path/to/kvm-unit-tests/arm/flat.lds \
> 	arm/spinlock-test.o arm/cstart64.o lib/libcflat.a lib/libfdt/libfdt.a /usr/lib/gcc/aarch64-linux-gnu/10.1.0/libgcc.a lib/arm/libeabi.a arm/spinlock-test.aux.o
> aarch64-linux-gnu-ld: /usr/lib/gcc/aarch64-linux-gnu/10.1.0/libgcc.a(lse-init.o): in function `init_have_lse_atomics':
> lse-init.c:(.text.startup+0xc): undefined reference to `__getauxval'
> 
> This is happening because we are linking against our own libcflat which
> doesn't implement the function __getauxval().
> 
> Disable the use of the out-of-line functions by compiling with
> -mno-outline-atomics if we detect a GCC version greater than 10.
> 
> Signed-off-by: Alexandru Elisei <alexandru.elisei@arm.com>
> ---
> 
> Tested with gcc versions 10.1.0 and 5.4.0 (cross-compilation), 9.3.0
> (native).
> 
> I've been able to suss out the reason for the build failure from this
> rejected gcc patch [1].
> 
> [1] https://patches.openembedded.org/patch/172460/
> 
>  arm/Makefile.arm64 | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/arm/Makefile.arm64 b/arm/Makefile.arm64
> index dfd0c56fe8fb..3223cb966789 100644
> --- a/arm/Makefile.arm64
> +++ b/arm/Makefile.arm64
> @@ -9,6 +9,12 @@ ldarch = elf64-littleaarch64
>  arch_LDFLAGS = -pie -n
>  CFLAGS += -mstrict-align
>  
> +# The -mno-outline-atomics flag is only valid for GCC versions 10 and greater.
> +GCC_MAJOR_VERSION=$(shell $(CC) -dumpversion 2> /dev/null | cut -f1 -d.)
> +ifeq ($(shell expr "$(GCC_MAJOR_VERSION)" ">=" "10"), 1)
> +CFLAGS += -mno-outline-atomics
> +endif

How about this patch instead?

diff --git a/Makefile b/Makefile
index 3ff2f91600f6..0e21a49096ba 100644
--- a/Makefile
+++ b/Makefile
@@ -17,6 +17,11 @@ DESTDIR := $(PREFIX)/share/kvm-unit-tests/
 
 .PHONY: arch_clean clean distclean cscope
 
+# cc-option
+# Usage: OP_CFLAGS+=$(call cc-option, -falign-functions=0, -malign-functions=0)
+cc-option = $(shell if $(CC) -Werror $(1) -S -o /dev/null -xc /dev/null \
+              > /dev/null 2>&1; then echo "$(1)"; else echo "$(2)"; fi ;)
+
 #make sure env CFLAGS variable is not used
 CFLAGS =
 
@@ -43,12 +48,6 @@ OBJDIRS += $(LIBFDT_objdir)
 #include architecture specific make rules
 include $(SRCDIR)/$(TEST_DIR)/Makefile
 
-# cc-option
-# Usage: OP_CFLAGS+=$(call cc-option, -falign-functions=0, -malign-functions=0)
-
-cc-option = $(shell if $(CC) -Werror $(1) -S -o /dev/null -xc /dev/null \
-              > /dev/null 2>&1; then echo "$(1)"; else echo "$(2)"; fi ;)
-
 COMMON_CFLAGS += -g $(autodepend-flags) -fno-strict-aliasing -fno-common
 COMMON_CFLAGS += -Wall -Wwrite-strings -Wempty-body -Wuninitialized
 COMMON_CFLAGS += -Wignored-qualifiers -Werror
diff --git a/arm/Makefile.arm64 b/arm/Makefile.arm64
index dfd0c56fe8fb..dbc7524d3070 100644
--- a/arm/Makefile.arm64
+++ b/arm/Makefile.arm64
@@ -9,6 +9,9 @@ ldarch = elf64-littleaarch64
 arch_LDFLAGS = -pie -n
 CFLAGS += -mstrict-align
 
+mno_outline_atomics := $(call cc-option, -mno-outline-atomics, "")
+CFLAGS += $(mno_outline_atomics)
+
 define arch_elf_check =
 	$(if $(shell ! $(OBJDUMP) -R $(1) >&/dev/null && echo "nok"),
 		$(error $(shell $(OBJDUMP) -R $(1) 2>&1)))


Thanks,
drew

> +
>  define arch_elf_check =
>  	$(if $(shell ! $(OBJDUMP) -R $(1) >&/dev/null && echo "nok"),
>  		$(error $(shell $(OBJDUMP) -R $(1) 2>&1)))
> -- 
> 2.27.0
> 

_______________________________________________
kvmarm mailing list
kvmarm@lists.cs.columbia.edu
https://lists.cs.columbia.edu/mailman/listinfo/kvmarm

^ permalink raw reply	[flat|nested] 7+ messages in thread

* Re: [kvm-unit-tests PATCH] arm64: Compile with -mno-outline-atomics for GCC >= 10
  2020-07-18  9:11 ` Andrew Jones
@ 2020-07-18 13:50   ` Alexandru Elisei
  2020-07-27 12:21     ` Alexandru Elisei
  0 siblings, 1 reply; 7+ messages in thread
From: Alexandru Elisei @ 2020-07-18 13:50 UTC (permalink / raw)
  To: Andrew Jones; +Cc: pbonzini, kvmarm, kvm

Hi,

On 7/18/20 10:11 AM, Andrew Jones wrote:
> On Fri, Jul 17, 2020 at 05:47:27PM +0100, Alexandru Elisei wrote:
>> GCC 10.1.0 introduced the -m{,no-}outline-atomics flags which, according to
>> man 1 gcc:
>>
>> "Enable or disable calls to out-of-line helpers to implement atomic
>> operations.  These helpers will, at runtime, determine if the LSE
>> instructions from ARMv8.1-A can be used; if not, they will use the
>> load/store-exclusive instructions that are present in the base ARMv8.0 ISA.
>> [..] This option is on by default."
>>
>> Unfortunately the option causes the following error at compile time:
>>
>> aarch64-linux-gnu-ld -nostdlib -pie -n -o arm/spinlock-test.elf -T /path/to/kvm-unit-tests/arm/flat.lds \
>> 	arm/spinlock-test.o arm/cstart64.o lib/libcflat.a lib/libfdt/libfdt.a /usr/lib/gcc/aarch64-linux-gnu/10.1.0/libgcc.a lib/arm/libeabi.a arm/spinlock-test.aux.o
>> aarch64-linux-gnu-ld: /usr/lib/gcc/aarch64-linux-gnu/10.1.0/libgcc.a(lse-init.o): in function `init_have_lse_atomics':
>> lse-init.c:(.text.startup+0xc): undefined reference to `__getauxval'
>>
>> This is happening because we are linking against our own libcflat which
>> doesn't implement the function __getauxval().
>>
>> Disable the use of the out-of-line functions by compiling with
>> -mno-outline-atomics if we detect a GCC version greater than 10.
>>
>> Signed-off-by: Alexandru Elisei <alexandru.elisei@arm.com>
>> ---
>>
>> Tested with gcc versions 10.1.0 and 5.4.0 (cross-compilation), 9.3.0
>> (native).
>>
>> I've been able to suss out the reason for the build failure from this
>> rejected gcc patch [1].
>>
>> [1] https://patches.openembedded.org/patch/172460/
>>
>>  arm/Makefile.arm64 | 6 ++++++
>>  1 file changed, 6 insertions(+)
>>
>> diff --git a/arm/Makefile.arm64 b/arm/Makefile.arm64
>> index dfd0c56fe8fb..3223cb966789 100644
>> --- a/arm/Makefile.arm64
>> +++ b/arm/Makefile.arm64
>> @@ -9,6 +9,12 @@ ldarch = elf64-littleaarch64
>>  arch_LDFLAGS = -pie -n
>>  CFLAGS += -mstrict-align
>>  
>> +# The -mno-outline-atomics flag is only valid for GCC versions 10 and greater.
>> +GCC_MAJOR_VERSION=$(shell $(CC) -dumpversion 2> /dev/null | cut -f1 -d.)
>> +ifeq ($(shell expr "$(GCC_MAJOR_VERSION)" ">=" "10"), 1)
>> +CFLAGS += -mno-outline-atomics
>> +endif
> How about this patch instead?
>
> diff --git a/Makefile b/Makefile
> index 3ff2f91600f6..0e21a49096ba 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -17,6 +17,11 @@ DESTDIR := $(PREFIX)/share/kvm-unit-tests/
>  
>  .PHONY: arch_clean clean distclean cscope
>  
> +# cc-option
> +# Usage: OP_CFLAGS+=$(call cc-option, -falign-functions=0, -malign-functions=0)
> +cc-option = $(shell if $(CC) -Werror $(1) -S -o /dev/null -xc /dev/null \
> +              > /dev/null 2>&1; then echo "$(1)"; else echo "$(2)"; fi ;)
> +
>  #make sure env CFLAGS variable is not used
>  CFLAGS =
>  
> @@ -43,12 +48,6 @@ OBJDIRS += $(LIBFDT_objdir)
>  #include architecture specific make rules
>  include $(SRCDIR)/$(TEST_DIR)/Makefile
>  
> -# cc-option
> -# Usage: OP_CFLAGS+=$(call cc-option, -falign-functions=0, -malign-functions=0)
> -
> -cc-option = $(shell if $(CC) -Werror $(1) -S -o /dev/null -xc /dev/null \
> -              > /dev/null 2>&1; then echo "$(1)"; else echo "$(2)"; fi ;)
> -
>  COMMON_CFLAGS += -g $(autodepend-flags) -fno-strict-aliasing -fno-common
>  COMMON_CFLAGS += -Wall -Wwrite-strings -Wempty-body -Wuninitialized
>  COMMON_CFLAGS += -Wignored-qualifiers -Werror
> diff --git a/arm/Makefile.arm64 b/arm/Makefile.arm64
> index dfd0c56fe8fb..dbc7524d3070 100644
> --- a/arm/Makefile.arm64
> +++ b/arm/Makefile.arm64
> @@ -9,6 +9,9 @@ ldarch = elf64-littleaarch64
>  arch_LDFLAGS = -pie -n
>  CFLAGS += -mstrict-align
>  
> +mno_outline_atomics := $(call cc-option, -mno-outline-atomics, "")
> +CFLAGS += $(mno_outline_atomics)
> +
>  define arch_elf_check =
>  	$(if $(shell ! $(OBJDUMP) -R $(1) >&/dev/null && echo "nok"),
>  		$(error $(shell $(OBJDUMP) -R $(1) 2>&1)))
>
>
> Thanks,
> drew

Looks much better than my version. Do you want me to spin a v2 or do you want to
send it as a separate patch? If that's the case, I tested the same way I did my
patch (gcc 10.1.0 and 5.4.0 for cross-compiling, 9.3.0 native):

Tested-by: Alexandru Elisei <alexandru.elisei@arm.com>

Thanks,
Alex
_______________________________________________
kvmarm mailing list
kvmarm@lists.cs.columbia.edu
https://lists.cs.columbia.edu/mailman/listinfo/kvmarm

^ permalink raw reply	[flat|nested] 7+ messages in thread

* Re: [kvm-unit-tests PATCH] arm64: Compile with -mno-outline-atomics for GCC >= 10
  2020-07-18 13:50   ` Alexandru Elisei
@ 2020-07-27 12:21     ` Alexandru Elisei
  2020-07-27 12:30       ` Andrew Jones
  0 siblings, 1 reply; 7+ messages in thread
From: Alexandru Elisei @ 2020-07-27 12:21 UTC (permalink / raw)
  To: Andrew Jones; +Cc: pbonzini, kvmarm, kvm

Hi Drew,

On 7/18/20 2:50 PM, Alexandru Elisei wrote:
> Hi,
>
> On 7/18/20 10:11 AM, Andrew Jones wrote:
>> On Fri, Jul 17, 2020 at 05:47:27PM +0100, Alexandru Elisei wrote:
>>> GCC 10.1.0 introduced the -m{,no-}outline-atomics flags which, according to
>>> man 1 gcc:
>>>
>>> "Enable or disable calls to out-of-line helpers to implement atomic
>>> operations.  These helpers will, at runtime, determine if the LSE
>>> instructions from ARMv8.1-A can be used; if not, they will use the
>>> load/store-exclusive instructions that are present in the base ARMv8.0 ISA.
>>> [..] This option is on by default."
>>>
>>> Unfortunately the option causes the following error at compile time:
>>>
>>> aarch64-linux-gnu-ld -nostdlib -pie -n -o arm/spinlock-test.elf -T /path/to/kvm-unit-tests/arm/flat.lds \
>>> 	arm/spinlock-test.o arm/cstart64.o lib/libcflat.a lib/libfdt/libfdt.a /usr/lib/gcc/aarch64-linux-gnu/10.1.0/libgcc.a lib/arm/libeabi.a arm/spinlock-test.aux.o
>>> aarch64-linux-gnu-ld: /usr/lib/gcc/aarch64-linux-gnu/10.1.0/libgcc.a(lse-init.o): in function `init_have_lse_atomics':
>>> lse-init.c:(.text.startup+0xc): undefined reference to `__getauxval'
>>>
>>> This is happening because we are linking against our own libcflat which
>>> doesn't implement the function __getauxval().
>>>
>>> Disable the use of the out-of-line functions by compiling with
>>> -mno-outline-atomics if we detect a GCC version greater than 10.
>>>
>>> Signed-off-by: Alexandru Elisei <alexandru.elisei@arm.com>
>>> ---
>>>
>>> Tested with gcc versions 10.1.0 and 5.4.0 (cross-compilation), 9.3.0
>>> (native).
>>>
>>> I've been able to suss out the reason for the build failure from this
>>> rejected gcc patch [1].
>>>
>>> [1] https://patches.openembedded.org/patch/172460/
>>>
>>>  arm/Makefile.arm64 | 6 ++++++
>>>  1 file changed, 6 insertions(+)
>>>
>>> diff --git a/arm/Makefile.arm64 b/arm/Makefile.arm64
>>> index dfd0c56fe8fb..3223cb966789 100644
>>> --- a/arm/Makefile.arm64
>>> +++ b/arm/Makefile.arm64
>>> @@ -9,6 +9,12 @@ ldarch = elf64-littleaarch64
>>>  arch_LDFLAGS = -pie -n
>>>  CFLAGS += -mstrict-align
>>>  
>>> +# The -mno-outline-atomics flag is only valid for GCC versions 10 and greater.
>>> +GCC_MAJOR_VERSION=$(shell $(CC) -dumpversion 2> /dev/null | cut -f1 -d.)
>>> +ifeq ($(shell expr "$(GCC_MAJOR_VERSION)" ">=" "10"), 1)
>>> +CFLAGS += -mno-outline-atomics
>>> +endif
>> How about this patch instead?
>>
>> diff --git a/Makefile b/Makefile
>> index 3ff2f91600f6..0e21a49096ba 100644
>> --- a/Makefile
>> +++ b/Makefile
>> @@ -17,6 +17,11 @@ DESTDIR := $(PREFIX)/share/kvm-unit-tests/
>>  
>>  .PHONY: arch_clean clean distclean cscope
>>  
>> +# cc-option
>> +# Usage: OP_CFLAGS+=$(call cc-option, -falign-functions=0, -malign-functions=0)
>> +cc-option = $(shell if $(CC) -Werror $(1) -S -o /dev/null -xc /dev/null \
>> +              > /dev/null 2>&1; then echo "$(1)"; else echo "$(2)"; fi ;)
>> +
>>  #make sure env CFLAGS variable is not used
>>  CFLAGS =
>>  
>> @@ -43,12 +48,6 @@ OBJDIRS += $(LIBFDT_objdir)
>>  #include architecture specific make rules
>>  include $(SRCDIR)/$(TEST_DIR)/Makefile
>>  
>> -# cc-option
>> -# Usage: OP_CFLAGS+=$(call cc-option, -falign-functions=0, -malign-functions=0)
>> -
>> -cc-option = $(shell if $(CC) -Werror $(1) -S -o /dev/null -xc /dev/null \
>> -              > /dev/null 2>&1; then echo "$(1)"; else echo "$(2)"; fi ;)
>> -
>>  COMMON_CFLAGS += -g $(autodepend-flags) -fno-strict-aliasing -fno-common
>>  COMMON_CFLAGS += -Wall -Wwrite-strings -Wempty-body -Wuninitialized
>>  COMMON_CFLAGS += -Wignored-qualifiers -Werror
>> diff --git a/arm/Makefile.arm64 b/arm/Makefile.arm64
>> index dfd0c56fe8fb..dbc7524d3070 100644
>> --- a/arm/Makefile.arm64
>> +++ b/arm/Makefile.arm64
>> @@ -9,6 +9,9 @@ ldarch = elf64-littleaarch64
>>  arch_LDFLAGS = -pie -n
>>  CFLAGS += -mstrict-align
>>  
>> +mno_outline_atomics := $(call cc-option, -mno-outline-atomics, "")
>> +CFLAGS += $(mno_outline_atomics)
>> +
>>  define arch_elf_check =
>>  	$(if $(shell ! $(OBJDUMP) -R $(1) >&/dev/null && echo "nok"),
>>  		$(error $(shell $(OBJDUMP) -R $(1) 2>&1)))
>>
>>
>> Thanks,
>> drew
> Looks much better than my version. Do you want me to spin a v2 or do you want to
> send it as a separate patch? If that's the case, I tested the same way I did my
> patch (gcc 10.1.0 and 5.4.0 for cross-compiling, 9.3.0 native):
>
> Tested-by: Alexandru Elisei <alexandru.elisei@arm.com>

Gentle ping regarding this.

Thanks,
Alex
_______________________________________________
kvmarm mailing list
kvmarm@lists.cs.columbia.edu
https://lists.cs.columbia.edu/mailman/listinfo/kvmarm

^ permalink raw reply	[flat|nested] 7+ messages in thread

* Re: [kvm-unit-tests PATCH] arm64: Compile with -mno-outline-atomics for GCC >= 10
  2020-07-27 12:21     ` Alexandru Elisei
@ 2020-07-27 12:30       ` Andrew Jones
  2020-07-27 12:39         ` Alexandru Elisei
  2020-07-27 17:25         ` Paolo Bonzini
  0 siblings, 2 replies; 7+ messages in thread
From: Andrew Jones @ 2020-07-27 12:30 UTC (permalink / raw)
  To: Alexandru Elisei; +Cc: pbonzini, kvmarm, kvm

On Mon, Jul 27, 2020 at 01:21:03PM +0100, Alexandru Elisei wrote:
> Hi Drew,
> 
> On 7/18/20 2:50 PM, Alexandru Elisei wrote:
> > Hi,
> >
> > On 7/18/20 10:11 AM, Andrew Jones wrote:
> >> On Fri, Jul 17, 2020 at 05:47:27PM +0100, Alexandru Elisei wrote:
> >>> GCC 10.1.0 introduced the -m{,no-}outline-atomics flags which, according to
> >>> man 1 gcc:
> >>>
> >>> "Enable or disable calls to out-of-line helpers to implement atomic
> >>> operations.  These helpers will, at runtime, determine if the LSE
> >>> instructions from ARMv8.1-A can be used; if not, they will use the
> >>> load/store-exclusive instructions that are present in the base ARMv8.0 ISA.
> >>> [..] This option is on by default."
> >>>
> >>> Unfortunately the option causes the following error at compile time:
> >>>
> >>> aarch64-linux-gnu-ld -nostdlib -pie -n -o arm/spinlock-test.elf -T /path/to/kvm-unit-tests/arm/flat.lds \
> >>> 	arm/spinlock-test.o arm/cstart64.o lib/libcflat.a lib/libfdt/libfdt.a /usr/lib/gcc/aarch64-linux-gnu/10.1.0/libgcc.a lib/arm/libeabi.a arm/spinlock-test.aux.o
> >>> aarch64-linux-gnu-ld: /usr/lib/gcc/aarch64-linux-gnu/10.1.0/libgcc.a(lse-init.o): in function `init_have_lse_atomics':
> >>> lse-init.c:(.text.startup+0xc): undefined reference to `__getauxval'
> >>>
> >>> This is happening because we are linking against our own libcflat which
> >>> doesn't implement the function __getauxval().
> >>>
> >>> Disable the use of the out-of-line functions by compiling with
> >>> -mno-outline-atomics if we detect a GCC version greater than 10.
> >>>
> >>> Signed-off-by: Alexandru Elisei <alexandru.elisei@arm.com>
> >>> ---
> >>>
> >>> Tested with gcc versions 10.1.0 and 5.4.0 (cross-compilation), 9.3.0
> >>> (native).
> >>>
> >>> I've been able to suss out the reason for the build failure from this
> >>> rejected gcc patch [1].
> >>>
> >>> [1] https://patches.openembedded.org/patch/172460/
> >>>
> >>>  arm/Makefile.arm64 | 6 ++++++
> >>>  1 file changed, 6 insertions(+)
> >>>
> >>> diff --git a/arm/Makefile.arm64 b/arm/Makefile.arm64
> >>> index dfd0c56fe8fb..3223cb966789 100644
> >>> --- a/arm/Makefile.arm64
> >>> +++ b/arm/Makefile.arm64
> >>> @@ -9,6 +9,12 @@ ldarch = elf64-littleaarch64
> >>>  arch_LDFLAGS = -pie -n
> >>>  CFLAGS += -mstrict-align
> >>>  
> >>> +# The -mno-outline-atomics flag is only valid for GCC versions 10 and greater.
> >>> +GCC_MAJOR_VERSION=$(shell $(CC) -dumpversion 2> /dev/null | cut -f1 -d.)
> >>> +ifeq ($(shell expr "$(GCC_MAJOR_VERSION)" ">=" "10"), 1)
> >>> +CFLAGS += -mno-outline-atomics
> >>> +endif
> >> How about this patch instead?
> >>
> >> diff --git a/Makefile b/Makefile
> >> index 3ff2f91600f6..0e21a49096ba 100644
> >> --- a/Makefile
> >> +++ b/Makefile
> >> @@ -17,6 +17,11 @@ DESTDIR := $(PREFIX)/share/kvm-unit-tests/
> >>  
> >>  .PHONY: arch_clean clean distclean cscope
> >>  
> >> +# cc-option
> >> +# Usage: OP_CFLAGS+=$(call cc-option, -falign-functions=0, -malign-functions=0)
> >> +cc-option = $(shell if $(CC) -Werror $(1) -S -o /dev/null -xc /dev/null \
> >> +              > /dev/null 2>&1; then echo "$(1)"; else echo "$(2)"; fi ;)
> >> +
> >>  #make sure env CFLAGS variable is not used
> >>  CFLAGS =
> >>  
> >> @@ -43,12 +48,6 @@ OBJDIRS += $(LIBFDT_objdir)
> >>  #include architecture specific make rules
> >>  include $(SRCDIR)/$(TEST_DIR)/Makefile
> >>  
> >> -# cc-option
> >> -# Usage: OP_CFLAGS+=$(call cc-option, -falign-functions=0, -malign-functions=0)
> >> -
> >> -cc-option = $(shell if $(CC) -Werror $(1) -S -o /dev/null -xc /dev/null \
> >> -              > /dev/null 2>&1; then echo "$(1)"; else echo "$(2)"; fi ;)
> >> -
> >>  COMMON_CFLAGS += -g $(autodepend-flags) -fno-strict-aliasing -fno-common
> >>  COMMON_CFLAGS += -Wall -Wwrite-strings -Wempty-body -Wuninitialized
> >>  COMMON_CFLAGS += -Wignored-qualifiers -Werror
> >> diff --git a/arm/Makefile.arm64 b/arm/Makefile.arm64
> >> index dfd0c56fe8fb..dbc7524d3070 100644
> >> --- a/arm/Makefile.arm64
> >> +++ b/arm/Makefile.arm64
> >> @@ -9,6 +9,9 @@ ldarch = elf64-littleaarch64
> >>  arch_LDFLAGS = -pie -n
> >>  CFLAGS += -mstrict-align
> >>  
> >> +mno_outline_atomics := $(call cc-option, -mno-outline-atomics, "")
> >> +CFLAGS += $(mno_outline_atomics)
> >> +
> >>  define arch_elf_check =
> >>  	$(if $(shell ! $(OBJDUMP) -R $(1) >&/dev/null && echo "nok"),
> >>  		$(error $(shell $(OBJDUMP) -R $(1) 2>&1)))
> >>
> >>
> >> Thanks,
> >> drew
> > Looks much better than my version. Do you want me to spin a v2 or do you want to
> > send it as a separate patch? If that's the case, I tested the same way I did my
> > patch (gcc 10.1.0 and 5.4.0 for cross-compiling, 9.3.0 native):
> >
> > Tested-by: Alexandru Elisei <alexandru.elisei@arm.com>
> 
> Gentle ping regarding this.
>

Hi Alexandru,

I was on vacation all last week and have been digging myself out of email
today. I'll send this as a proper patch with your T-b later today or
tomorrow.

Thanks,
drew

_______________________________________________
kvmarm mailing list
kvmarm@lists.cs.columbia.edu
https://lists.cs.columbia.edu/mailman/listinfo/kvmarm

^ permalink raw reply	[flat|nested] 7+ messages in thread

* Re: [kvm-unit-tests PATCH] arm64: Compile with -mno-outline-atomics for GCC >= 10
  2020-07-27 12:30       ` Andrew Jones
@ 2020-07-27 12:39         ` Alexandru Elisei
  2020-07-27 17:25         ` Paolo Bonzini
  1 sibling, 0 replies; 7+ messages in thread
From: Alexandru Elisei @ 2020-07-27 12:39 UTC (permalink / raw)
  To: Andrew Jones; +Cc: pbonzini, kvmarm, kvm

Hi Drew,

On 7/27/20 1:30 PM, Andrew Jones wrote:
> On Mon, Jul 27, 2020 at 01:21:03PM +0100, Alexandru Elisei wrote:
>> Hi Drew,
>>
>> On 7/18/20 2:50 PM, Alexandru Elisei wrote:
>>> Hi,
>>>
>>> On 7/18/20 10:11 AM, Andrew Jones wrote:
>>>> On Fri, Jul 17, 2020 at 05:47:27PM +0100, Alexandru Elisei wrote:
>>>>> GCC 10.1.0 introduced the -m{,no-}outline-atomics flags which, according to
>>>>> man 1 gcc:
>>>>>
>>>>> "Enable or disable calls to out-of-line helpers to implement atomic
>>>>> operations.  These helpers will, at runtime, determine if the LSE
>>>>> instructions from ARMv8.1-A can be used; if not, they will use the
>>>>> load/store-exclusive instructions that are present in the base ARMv8.0 ISA.
>>>>> [..] This option is on by default."
>>>>>
>>>>> Unfortunately the option causes the following error at compile time:
>>>>>
>>>>> aarch64-linux-gnu-ld -nostdlib -pie -n -o arm/spinlock-test.elf -T /path/to/kvm-unit-tests/arm/flat.lds \
>>>>> 	arm/spinlock-test.o arm/cstart64.o lib/libcflat.a lib/libfdt/libfdt.a /usr/lib/gcc/aarch64-linux-gnu/10.1.0/libgcc.a lib/arm/libeabi.a arm/spinlock-test.aux.o
>>>>> aarch64-linux-gnu-ld: /usr/lib/gcc/aarch64-linux-gnu/10.1.0/libgcc.a(lse-init.o): in function `init_have_lse_atomics':
>>>>> lse-init.c:(.text.startup+0xc): undefined reference to `__getauxval'
>>>>>
>>>>> This is happening because we are linking against our own libcflat which
>>>>> doesn't implement the function __getauxval().
>>>>>
>>>>> Disable the use of the out-of-line functions by compiling with
>>>>> -mno-outline-atomics if we detect a GCC version greater than 10.
>>>>>
>>>>> Signed-off-by: Alexandru Elisei <alexandru.elisei@arm.com>
>>>>> ---
>>>>>
>>>>> Tested with gcc versions 10.1.0 and 5.4.0 (cross-compilation), 9.3.0
>>>>> (native).
>>>>>
>>>>> I've been able to suss out the reason for the build failure from this
>>>>> rejected gcc patch [1].
>>>>>
>>>>> [1] https://patches.openembedded.org/patch/172460/
>>>>>
>>>>>  arm/Makefile.arm64 | 6 ++++++
>>>>>  1 file changed, 6 insertions(+)
>>>>>
>>>>> diff --git a/arm/Makefile.arm64 b/arm/Makefile.arm64
>>>>> index dfd0c56fe8fb..3223cb966789 100644
>>>>> --- a/arm/Makefile.arm64
>>>>> +++ b/arm/Makefile.arm64
>>>>> @@ -9,6 +9,12 @@ ldarch = elf64-littleaarch64
>>>>>  arch_LDFLAGS = -pie -n
>>>>>  CFLAGS += -mstrict-align
>>>>>  
>>>>> +# The -mno-outline-atomics flag is only valid for GCC versions 10 and greater.
>>>>> +GCC_MAJOR_VERSION=$(shell $(CC) -dumpversion 2> /dev/null | cut -f1 -d.)
>>>>> +ifeq ($(shell expr "$(GCC_MAJOR_VERSION)" ">=" "10"), 1)
>>>>> +CFLAGS += -mno-outline-atomics
>>>>> +endif
>>>> How about this patch instead?
>>>>
>>>> diff --git a/Makefile b/Makefile
>>>> index 3ff2f91600f6..0e21a49096ba 100644
>>>> --- a/Makefile
>>>> +++ b/Makefile
>>>> @@ -17,6 +17,11 @@ DESTDIR := $(PREFIX)/share/kvm-unit-tests/
>>>>  
>>>>  .PHONY: arch_clean clean distclean cscope
>>>>  
>>>> +# cc-option
>>>> +# Usage: OP_CFLAGS+=$(call cc-option, -falign-functions=0, -malign-functions=0)
>>>> +cc-option = $(shell if $(CC) -Werror $(1) -S -o /dev/null -xc /dev/null \
>>>> +              > /dev/null 2>&1; then echo "$(1)"; else echo "$(2)"; fi ;)
>>>> +
>>>>  #make sure env CFLAGS variable is not used
>>>>  CFLAGS =
>>>>  
>>>> @@ -43,12 +48,6 @@ OBJDIRS += $(LIBFDT_objdir)
>>>>  #include architecture specific make rules
>>>>  include $(SRCDIR)/$(TEST_DIR)/Makefile
>>>>  
>>>> -# cc-option
>>>> -# Usage: OP_CFLAGS+=$(call cc-option, -falign-functions=0, -malign-functions=0)
>>>> -
>>>> -cc-option = $(shell if $(CC) -Werror $(1) -S -o /dev/null -xc /dev/null \
>>>> -              > /dev/null 2>&1; then echo "$(1)"; else echo "$(2)"; fi ;)
>>>> -
>>>>  COMMON_CFLAGS += -g $(autodepend-flags) -fno-strict-aliasing -fno-common
>>>>  COMMON_CFLAGS += -Wall -Wwrite-strings -Wempty-body -Wuninitialized
>>>>  COMMON_CFLAGS += -Wignored-qualifiers -Werror
>>>> diff --git a/arm/Makefile.arm64 b/arm/Makefile.arm64
>>>> index dfd0c56fe8fb..dbc7524d3070 100644
>>>> --- a/arm/Makefile.arm64
>>>> +++ b/arm/Makefile.arm64
>>>> @@ -9,6 +9,9 @@ ldarch = elf64-littleaarch64
>>>>  arch_LDFLAGS = -pie -n
>>>>  CFLAGS += -mstrict-align
>>>>  
>>>> +mno_outline_atomics := $(call cc-option, -mno-outline-atomics, "")
>>>> +CFLAGS += $(mno_outline_atomics)
>>>> +
>>>>  define arch_elf_check =
>>>>  	$(if $(shell ! $(OBJDUMP) -R $(1) >&/dev/null && echo "nok"),
>>>>  		$(error $(shell $(OBJDUMP) -R $(1) 2>&1)))
>>>>
>>>>
>>>> Thanks,
>>>> drew
>>> Looks much better than my version. Do you want me to spin a v2 or do you want to
>>> send it as a separate patch? If that's the case, I tested the same way I did my
>>> patch (gcc 10.1.0 and 5.4.0 for cross-compiling, 9.3.0 native):
>>>
>>> Tested-by: Alexandru Elisei <alexandru.elisei@arm.com>
>> Gentle ping regarding this.
>>
> Hi Alexandru,
>
> I was on vacation all last week and have been digging myself out of email
> today. I'll send this as a proper patch with your T-b later today or
> tomorrow.

Great, thanks, I was worried my reply might have slipped by unnoticed.

Thanks,
Alex
>
> Thanks,
> drew
>
_______________________________________________
kvmarm mailing list
kvmarm@lists.cs.columbia.edu
https://lists.cs.columbia.edu/mailman/listinfo/kvmarm

^ permalink raw reply	[flat|nested] 7+ messages in thread

* Re: [kvm-unit-tests PATCH] arm64: Compile with -mno-outline-atomics for GCC >= 10
  2020-07-27 12:30       ` Andrew Jones
  2020-07-27 12:39         ` Alexandru Elisei
@ 2020-07-27 17:25         ` Paolo Bonzini
  1 sibling, 0 replies; 7+ messages in thread
From: Paolo Bonzini @ 2020-07-27 17:25 UTC (permalink / raw)
  To: Andrew Jones, Alexandru Elisei; +Cc: kvmarm, kvm

On 27/07/20 14:30, Andrew Jones wrote:
>>> Looks much better than my version. Do you want me to spin a v2 or do you want to
>>> send it as a separate patch? If that's the case, I tested the same way I did my
>>> patch (gcc 10.1.0 and 5.4.0 for cross-compiling, 9.3.0 native):
>>>
>>> Tested-by: Alexandru Elisei <alexandru.elisei@arm.com>
>> Gentle ping regarding this.
>>
> Hi Alexandru,
> 
> I was on vacation all last week and have been digging myself out of email
> today. I'll send this as a proper patch with your T-b later today or
> tomorrow.

Same here; will wait for Andrew's patch.

Paolo

_______________________________________________
kvmarm mailing list
kvmarm@lists.cs.columbia.edu
https://lists.cs.columbia.edu/mailman/listinfo/kvmarm

^ permalink raw reply	[flat|nested] 7+ messages in thread

end of thread, back to index

Thread overview: 7+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2020-07-17 16:47 [kvm-unit-tests PATCH] arm64: Compile with -mno-outline-atomics for GCC >= 10 Alexandru Elisei
2020-07-18  9:11 ` Andrew Jones
2020-07-18 13:50   ` Alexandru Elisei
2020-07-27 12:21     ` Alexandru Elisei
2020-07-27 12:30       ` Andrew Jones
2020-07-27 12:39         ` Alexandru Elisei
2020-07-27 17:25         ` Paolo Bonzini

KVM ARM Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/kvmarm/0 kvmarm/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 kvmarm kvmarm/ https://lore.kernel.org/kvmarm \
		kvmarm@lists.cs.columbia.edu
	public-inbox-index kvmarm

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/edu.columbia.cs.lists.kvmarm


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git