[Buildroot] [PATCH 0/2] LTP compilation fixes for buildroot toolchains

[Buildroot] [PATCH 0/2] LTP compilation fixes for buildroot toolchains

[Petr Vorel]

Hi all,

this fixes 2 compilation failures of KVM tests reported some time ago [1].

Kind regards,
Petr

[1] https://lore.kernel.org/buildroot/YofzKdQAUOnR2gSW@pevik/

Petr Vorel (2):
  kvm: Fix compilation on x86
  kvm: Fix undefined reference to __stack_chk_fail()

 testcases/kernel/kvm/Makefile | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

-- 
2.36.1

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[Buildroot] [PATCH 1/2] kvm: Fix compilation on x86

[Petr Vorel]

Buildroot supports i386 pentium toolchains (br-i386-pentium-mmx-musl,
br-i386-pentium4-full) which fail to compile because as is run without --32.

Suggested-by: Martin Doucha <mdoucha@suse.cz>
Signed-off-by: Petr Vorel <petr.vorel@gmail.com>
---
 testcases/kernel/kvm/Makefile | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/testcases/kernel/kvm/Makefile b/testcases/kernel/kvm/Makefile
index adab56952..8d5193d8e 100644
--- a/testcases/kernel/kvm/Makefile
+++ b/testcases/kernel/kvm/Makefile
@@ -17,11 +17,14 @@ FILTER_OUT_MAKE_TARGETS := lib_guest lib_host lib_x86
 ifeq ($(HOST_CPU),x86_64)
 	ifneq (,$(findstring m32,$(CFLAGS)))
 		HOST_CPU = x86
-		GUEST_CFLAGS += -m32
-		ASFLAGS += --32
 	endif
 endif
 
+ifeq ($(HOST_CPU),x86)
+	GUEST_CFLAGS += -m32
+	ASFLAGS += --32
+endif
+
 # Some distros enable -pie by default. That breaks KVM payload linking.
 ifdef LTP_CFLAGS_NOPIE
 	GUEST_CFLAGS += -fno-pie
-- 
2.36.1

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[Buildroot] [PATCH 2/2] kvm: Fix undefined reference to __stack_chk_fail()

[Petr Vorel]

Some x86_64 buildroot toolchains (bootlin-x86-64-glibc,
bootlin-x86-64-musl) try to link to __stack_chk_fail().
-nostdlib is not enough, it requires also -fstack-protector.

x86_64-buildroot-linux-gnu/bin/ld: /tmp/ccgBXEoR.o: in function `handle_page_fault':
kvm_pagefault01.c:(.text+0x5d): undefined reference to `__stack_chk_fail'
collect2: error: ld returned 1 exit status

Signed-off-by: Petr Vorel <petr.vorel@gmail.com>
---
 testcases/kernel/kvm/Makefile | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/testcases/kernel/kvm/Makefile b/testcases/kernel/kvm/Makefile
index 8d5193d8e..bce1a4eb5 100644
--- a/testcases/kernel/kvm/Makefile
+++ b/testcases/kernel/kvm/Makefile
@@ -9,7 +9,7 @@ ASFLAGS =
 CPPFLAGS += -I$(abs_srcdir)/include
 GUEST_CPPFLAGS = $(CPPFLAGS) -DCOMPILE_PAYLOAD
 GUEST_CFLAGS = -ffreestanding -O2 -Wall -fno-asynchronous-unwind-tables -mno-mmx -mno-sse
-GUEST_LDFLAGS = -nostdlib -Wl,--build-id=none
+GUEST_LDFLAGS = -nostdlib -Wl,--build-id=none -fstack-protector
 GUEST_LDLIBS =
 
 FILTER_OUT_MAKE_TARGETS := lib_guest lib_host lib_x86
-- 
2.36.1

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Re: [Buildroot] [PATCH 2/2] kvm: Fix undefined reference to __stack_chk_fail()

[Thomas Petazzoni via buildroot]

On Thu, 9 Jun 2022 10:26:55 +0200
Martin Doucha <mdoucha@suse.cz> wrote:

> > diff --git a/testcases/kernel/kvm/Makefile b/testcases/kernel/kvm/Makefile
> > index 8d5193d8e..bce1a4eb5 100644
> > --- a/testcases/kernel/kvm/Makefile
> > +++ b/testcases/kernel/kvm/Makefile
> > @@ -9,7 +9,7 @@ ASFLAGS =
> >  CPPFLAGS += -I$(abs_srcdir)/include
> >  GUEST_CPPFLAGS = $(CPPFLAGS) -DCOMPILE_PAYLOAD
> >  GUEST_CFLAGS = -ffreestanding -O2 -Wall -fno-asynchronous-unwind-tables -mno-mmx -mno-sse
> > -GUEST_LDFLAGS = -nostdlib -Wl,--build-id=none
> > +GUEST_LDFLAGS = -nostdlib -Wl,--build-id=none -fstack-protector  
> 
> We should use -fno-stack-protector here instead. Your patch probably
> enables linking of libssp despite -nostdlib which we don't want. The GCC
> stack protector may also break tests because bootstrap initializes stack
> manually instead of letting GCC handle it.

I agree. Assuming -nostdlib means you're building freestanding code,
then indeed, -fno-stack-protector is most likely what you want.

Thomas
-- 
Thomas Petazzoni, co-owner and CEO, Bootlin
Embedded Linux and Kernel engineering and training
https://bootlin.com
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Re: [Buildroot] [LTP] [PATCH 2/2] kvm: Fix undefined reference to __stack_chk_fail()

[Petr Vorel]

Hi all,

> Hi,


> Am 6/9/2022 um 10:26 AM schrieb Martin Doucha:
> > On 06. 06. 22 20:43, Petr Vorel wrote:
> >> Some x86_64 buildroot toolchains (bootlin-x86-64-glibc,
> >> bootlin-x86-64-musl) try to link to __stack_chk_fail().
> >> -nostdlib is not enough, it requires also -fstack-protector.

> >> x86_64-buildroot-linux-gnu/bin/ld: /tmp/ccgBXEoR.o: in function `handle_page_fault':
> >> kvm_pagefault01.c:(.text+0x5d): undefined reference to `__stack_chk_fail'
> >> collect2: error: ld returned 1 exit status

> >> Signed-off-by: Petr Vorel <petr.vorel@gmail.com>
> >> ---
> >>  testcases/kernel/kvm/Makefile | 2 +-
> >>  1 file changed, 1 insertion(+), 1 deletion(-)

> >> diff --git a/testcases/kernel/kvm/Makefile b/testcases/kernel/kvm/Makefile
> >> index 8d5193d8e..bce1a4eb5 100644
> >> --- a/testcases/kernel/kvm/Makefile
> >> +++ b/testcases/kernel/kvm/Makefile
> >> @@ -9,7 +9,7 @@ ASFLAGS =
> >>  CPPFLAGS += -I$(abs_srcdir)/include
> >>  GUEST_CPPFLAGS = $(CPPFLAGS) -DCOMPILE_PAYLOAD
> >>  GUEST_CFLAGS = -ffreestanding -O2 -Wall -fno-asynchronous-unwind-tables -mno-mmx -mno-sse
> >> -GUEST_LDFLAGS = -nostdlib -Wl,--build-id=none
> >> +GUEST_LDFLAGS = -nostdlib -Wl,--build-id=none -fstack-protector

> > We should use -fno-stack-protector here instead. Your patch probably
> > enables linking of libssp despite -nostdlib which we don't want. The GCC
> > stack protector may also break tests because bootstrap initializes stack
> > manually instead of letting GCC handle it.
> I can confirm, that adding -fno-stack-protector to GUEST_LDFLAGS fixes
> the linker error.

Thanks a lot for your input. Martin, thanks a lot for testing.
I also verified that -fno-stack-protector fix compilation, thus patchset merged.

Kind regards,
Petr

> >>  GUEST_LDLIBS =

> >>  FILTER_OUT_MAKE_TARGETS := lib_guest lib_host lib_x86



> Joerg
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