From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Message-ID: <55ACFD1C.8090907@roeck-us.net> Date: Mon, 20 Jul 2015 06:52:28 -0700 From: Guenter Roeck MIME-Version: 1.0 Subject: Re: [PATCH] sched, arm64: Fix the fallout of increasing the offset of 'thread_struct' within 'task_struct' References: <20150718232717.GA3235@groeck-UX31A> <20150718233455.GA3273@groeck-UX31A> <20150720072043.GA7696@gmail.com> In-Reply-To: <20150720072043.GA7696@gmail.com> Content-Type: text/plain; charset="windows-1252"; format="flowed" Content-Transfer-Encoding: quoted-printable Sender: linux-kernel-owner@vger.kernel.org List-Archive: List-Post: To: Ingo Molnar Cc: Dave Hansen , linux-kernel@vger.kernel.org, Martin Schwidefsky , linux-s390@vger.kernel.org, linux390@de.ibm.com, Catalin Marinas , linux-arm-kernel@lists.infradead.org, Linus Torvalds , Stephen Rothwell , Olof Johansson List-ID: On 07/20/2015 12:20 AM, Ingo Molnar wrote: > > * Guenter wrote: > >> On Sat, Jul 18, 2015 at 04:27:17PM -0700, Guenter wrote: >>> Hi, >>> >>> Commit 0c8c0f03e3a2 ("x86/fpu, sched: Dynamically allocate 'struct fpu'= ") >>> causes s390 builds in mainline to fail as follows. >>> >>> arch/s390/kernel/traps.c: Assembler messages: >>> arch/s390/kernel/traps.c:262: Error: operand out of range >>> (0x00000000000023e8 is not between 0x0000000000000000 and 0x0000000000= 000fff) >>> arch/s390/kernel/traps.c:300: Error: operand out of range >>> (0x00000000000023e8 is not between 0x0000000000000000 and 0x0000000000= 000fff) >>> >> >> Also: >> >> arm64:allmodconfig: >> >> arch/arm64/kernel/entry.S: Assembler messages: >> arch/arm64/kernel/entry.S:588: Error: immediate out of range >> arch/arm64/kernel/entry.S:597: Error: immediate out of range >> make[1]: *** [arch/arm64/kernel/entry.o] Error 1 >> >> I didn't bisect that one, but it looks like the cause is the same. > > Hm, it looks like the new, increased offset of 'thread_struct' within > 'task_struct' goes over a limit that these instructions are able to suppo= rt on > arm64: > > arch/arm64/kernel/asm-offsets.c: DEFINE(THREAD_CPU_CONTEXT, offseto= f(struct task_struct, thread.cpu_context)); > arch/arm64/kernel/entry.S: add x8, x0, #THREAD_CPU_CONTEXT > arch/arm64/kernel/entry.S: add x8, x1, #THREAD_CPU_CONTEXT > > If there's no instruction that can support such offset sizes then I suspe= ct the > straightforward fix would be to pass in thread_struct instead - like the = patch > below. That's a tiny bit cleaner for type encapsulation anyway. > Olof submitted a different patch to solve the problem: http://www.spinics.net/lists/kernel/msg2036825.html His patch is passing cpu_context instead of thread_context. > Warning: it's not even build tested, but in case it works: > > Signed-off-by: Ingo Molnar > > Thanks, > > Ingo > > =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D > > arch/arm64/include/asm/processor.h | 4 ++-- > arch/arm64/kernel/asm-offsets.c | 2 +- > arch/arm64/kernel/process.c | 2 +- > 3 files changed, 4 insertions(+), 4 deletions(-) > > diff --git a/arch/arm64/include/asm/processor.h b/arch/arm64/include/asm/= processor.h > index e4c893e54f01..890f84bb3b8c 100644 > --- a/arch/arm64/include/asm/processor.h > +++ b/arch/arm64/include/asm/processor.h > @@ -152,8 +152,8 @@ static inline void cpu_relax(void) > #define cpu_relax_lowlatency() cpu_relax() > > /* Thread switching */ > -extern struct task_struct *cpu_switch_to(struct task_struct *prev, > - struct task_struct *next); > +extern struct task_struct *cpu_switch_to(struct thread_struct *prev, > + struct thread_struct *next); > > #define task_pt_regs(p) \ > ((struct pt_regs *)(THREAD_START_SP + task_stack_page(p)) - 1) > diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offs= ets.c > index c99701a34d7b..3785373c2369 100644 > --- a/arch/arm64/kernel/asm-offsets.c > +++ b/arch/arm64/kernel/asm-offsets.c > @@ -39,7 +39,7 @@ int main(void) > DEFINE(TI_TASK, offsetof(struct thread_info, task)); > DEFINE(TI_CPU, offsetof(struct thread_info, cpu)); > BLANK(); > - DEFINE(THREAD_CPU_CONTEXT, offsetof(struct task_struct, thread.cpu_con= text)); > + DEFINE(THREAD_CPU_CONTEXT, offsetof(struct thread_struct, cpu_context)= ); > BLANK(); > DEFINE(S_X0, offsetof(struct pt_regs, regs[0])); > DEFINE(S_X1, offsetof(struct pt_regs, regs[1])); > diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c > index 223b093c9440..436e95bda1b2 100644 > --- a/arch/arm64/kernel/process.c > +++ b/arch/arm64/kernel/process.c > @@ -325,7 +325,7 @@ struct task_struct *__switch_to(struct task_struct *p= rev, > dsb(ish); > > /* the actual thread switch */ > - last =3D cpu_switch_to(prev, next); > + last =3D cpu_switch_to(&prev.thread, &next.thread); Doesn't compile. arch/arm64/kernel/process.c: In function =91__switch_to=92: arch/arm64/kernel/process.c:328:28: error: request for member =91thread=92 = in something not a structure or union last =3D cpu_switch_to(&prev.thread, &next.thread); ^ arch/arm64/kernel/process.c:328:42: error: request for member =91thread=92 = in something not a structure or union last =3D cpu_switch_to(&prev.thread, &next.thread); It would have to be last =3D cpu_switch_to(&prev->thread, &next->thread); which does compile, but fails to run in qemu. Guenter