Messages in this thread Patch in this message |  | | Date | Mon, 20 Jul 2015 10:00:32 +0200 | | From | Ingo Molnar <> | | Subject | [PATCH] sched, s390: Fix the fallout of increasing the offset of 'thread_struct' within 'task_struct' |
| |
* Heiko Carstens <heiko.carstens@de.ibm.com> wrote:
> > I've tested it on a number of x86 platforms, and I cross-built it to a handful > > of architectures: > > > > (warns) (warns) > > testing x86-64: -git: pass ( 0), -tip: pass ( 0) > > testing x86-32: -git: pass ( 0), -tip: pass ( 0) > > testing arm: -git: pass ( 1359), -tip: pass ( 1359) > > testing cris: -git: pass ( 1031), -tip: pass ( 1031) > > testing m32r: -git: pass ( 1135), -tip: pass ( 1135) > > testing m68k: -git: pass ( 1471), -tip: pass ( 1471) > > testing mips: -git: pass ( 1162), -tip: pass ( 1162) > > testing mn10300: -git: pass ( 1058), -tip: pass ( 1058) > > testing parisc: -git: pass ( 1846), -tip: pass ( 1846) > > testing sparc: -git: pass ( 1185), -tip: pass ( 1185) > > > > ... so I hope the cross-arch impact 'none', as intended. > > > > (by Dave Hansen) > > Unfortunately not true. It breaks the build on s390 since a couple of > displacements used in asm code now get too large: > > arch/s390/kernel/entry.S:181: Error: operand out of range (0x00000000000018a8 is not between 0x0000000000000000 and 0x0000000000000fff) > arch/s390/kernel/entry.S:191: Error: operand out of range (0x00000000000018a8 is not between 0x0000000000000000 and 0x0000000000000fff) > arch/s390/kernel/entry.S:423: Error: operand out of range (0x0000000000001924 is not between 0x0000000000000000 and 0x0000000000000fff) > arch/s390/kernel/entry.S:437: Error: operand out of range (0x00000000000018e8 is not between 0x0000000000000000 and 0x0000000000000fff) > arch/s390/kernel/entry.S:438: Error: operand out of range (0x00000000000018e0 is not between 0x0000000000000000 and 0x0000000000000fff) > arch/s390/kernel/entry.S:439: Error: operand out of range (0x00000000000018f0 is not between 0x0000000000000000 and 0x0000000000000fff) > make[1]: *** [arch/s390/kernel/entry.o] Error 1 > > Let's see how we can fix this.
There's also a traps.c build breakage reported below - and an RFC fix for it.
Thanks,
Ingo
=========================>
* Guenter <linux@roeck-us.net> 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 0x0000000000000fff) > arch/s390/kernel/traps.c:300: Error: operand out of range > (0x00000000000023e8 is not between 0x0000000000000000 and 0x0000000000000fff)
Yeah, so I'm really out on a limb here as I know next to nothing about s390 assembly, but the build failure appears to be analogous to the arm64 one: the offset of thread_struct fields within task_struct increased due to commit 0c8c0f03e3a2 ("x86/fpu, sched: Dynamically allocate 'struct fpu'"), which increased assembly offsets beyond the limit this instruction can apparently encode.
Does the (untested!) patch below help?
It's an equivalent transformation on the C side, but it might cause GCC to generate different assembly code, because we now have a temporary variable with much smaller offsets.
The code is also a tiny bit cleaner this way, as the 'current->thread.fp_regs' pattern isn't repeated twice.
In case this works:
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Thanks,
Ingo
================>
arch/s390/kernel/traps.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/arch/s390/kernel/traps.c b/arch/s390/kernel/traps.c index 4d96c9f53455..db6f0eec55b5 100644 --- a/arch/s390/kernel/traps.c +++ b/arch/s390/kernel/traps.c @@ -251,6 +251,7 @@ int alloc_vector_registers(struct task_struct *tsk) void vector_exception(struct pt_regs *regs) { + s390_fp_regs *fp_regs = ¤t->thread.fp_regs; int si_code, vic; if (!MACHINE_HAS_VX) { @@ -259,8 +260,9 @@ void vector_exception(struct pt_regs *regs) } /* get vector interrupt code from fpc */ - asm volatile("stfpc %0" : "=m" (current->thread.fp_regs.fpc)); - vic = (current->thread.fp_regs.fpc & 0xf00) >> 8; + asm volatile("stfpc %0" : "=m" (fp_regs->fpc)); + vic = (fp_regs->fpc & 0xf00) >> 8; + switch (vic) { case 1: /* invalid vector operation */ si_code = FPE_FLTINV;
|  |