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s390: fix floating pointer register corruption (again)

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There is a tricky interaction between the machine check handler
and the critical sections of load_fpu_regs and save_fpu_regs
functions. If the machine check interrupts one of the two
functions the critical section cleanup will complete the function
before the machine check handler s390_do_machine_check is called.
Trouble is that the machine check handler needs to validate the
floating point registers *before* and not *after* the completion
of load_fpu_regs/save_fpu_regs.

The simplest solution is to rewind the PSW to the start of the
load_fpu_regs/save_fpu_regs and retry the function after the
return from the machine check handler.

Tested-by: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: <stable@vger.kernel.org> # 4.3+
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
This commit is contained in:
Martin Schwidefsky 2016-03-10 09:52:55 +01:00
parent 8f100bb1ff
commit e370e47694
1 changed files with 2 additions and 104 deletions
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106
arch/s390/kernel/entry.S
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@ -1200,114 +1200,12 @@ cleanup_critical:
.quad .Lpsw_idle_lpsw
.Lcleanup_save_fpu_regs:
TSTMSK __LC_CPU_FLAGS,_CIF_FPU
bor %r14
clg %r9,BASED(.Lcleanup_save_fpu_regs_done)
jhe 5f
clg %r9,BASED(.Lcleanup_save_fpu_regs_fp)
jhe 4f
clg %r9,BASED(.Lcleanup_save_fpu_regs_vx_high)
jhe 3f
clg %r9,BASED(.Lcleanup_save_fpu_regs_vx_low)
jhe 2f
clg %r9,BASED(.Lcleanup_save_fpu_fpc_end)
jhe 1f
lg %r2,__LC_CURRENT
aghi %r2,__TASK_thread
0: # Store floating-point controls
stfpc __THREAD_FPU_fpc(%r2)
1: # Load register save area and check if VX is active
lg %r3,__THREAD_FPU_regs(%r2)
TSTMSK __LC_MACHINE_FLAGS,MACHINE_FLAG_VX
jz 4f # no VX -> store FP regs
2: # Store vector registers (V0-V15)
VSTM %v0,%v15,0,%r3 # vstm 0,15,0(3)
3: # Store vector registers (V16-V31)
VSTM %v16,%v31,256,%r3 # vstm 16,31,256(3)
j 5f # -> done, set CIF_FPU flag
4: # Store floating-point registers
std 0,0(%r3)
std 1,8(%r3)
std 2,16(%r3)
std 3,24(%r3)
std 4,32(%r3)
std 5,40(%r3)
std 6,48(%r3)
std 7,56(%r3)
std 8,64(%r3)
std 9,72(%r3)
std 10,80(%r3)
std 11,88(%r3)
std 12,96(%r3)
std 13,104(%r3)
std 14,112(%r3)
std 15,120(%r3)
5: # Set CIF_FPU flag
oi __LC_CPU_FLAGS+7,_CIF_FPU
lg %r9,48(%r11) # return from save_fpu_regs
larl %r9,save_fpu_regs
br %r14
.Lcleanup_save_fpu_fpc_end:
.quad .Lsave_fpu_regs_fpc_end
.Lcleanup_save_fpu_regs_vx_low:
.quad .Lsave_fpu_regs_vx_low
.Lcleanup_save_fpu_regs_vx_high:
.quad .Lsave_fpu_regs_vx_high
.Lcleanup_save_fpu_regs_fp:
.quad .Lsave_fpu_regs_fp
.Lcleanup_save_fpu_regs_done:
.quad .Lsave_fpu_regs_done
.Lcleanup_load_fpu_regs:
TSTMSK __LC_CPU_FLAGS,_CIF_FPU
bnor %r14
clg %r9,BASED(.Lcleanup_load_fpu_regs_done)
jhe 1f
clg %r9,BASED(.Lcleanup_load_fpu_regs_fp)
jhe 2f
clg %r9,BASED(.Lcleanup_load_fpu_regs_vx_high)
jhe 3f
clg %r9,BASED(.Lcleanup_load_fpu_regs_vx)
jhe 4f
lg %r4,__LC_CURRENT
aghi %r4,__TASK_thread
lfpc __THREAD_FPU_fpc(%r4)
TSTMSK __LC_MACHINE_FLAGS,MACHINE_FLAG_VX
lg %r4,__THREAD_FPU_regs(%r4) # %r4 <- reg save area
jz 2f # -> no VX, load FP regs
4: # Load V0 ..V15 registers
VLM %v0,%v15,0,%r4
3: # Load V16..V31 registers
VLM %v16,%v31,256,%r4
j 1f
2: # Load floating-point registers
ld 0,0(%r4)
ld 1,8(%r4)
ld 2,16(%r4)
ld 3,24(%r4)
ld 4,32(%r4)
ld 5,40(%r4)
ld 6,48(%r4)
ld 7,56(%r4)
ld 8,64(%r4)
ld 9,72(%r4)
ld 10,80(%r4)
ld 11,88(%r4)
ld 12,96(%r4)
ld 13,104(%r4)
ld 14,112(%r4)
ld 15,120(%r4)
1: # Clear CIF_FPU bit
ni __LC_CPU_FLAGS+7,255-_CIF_FPU
lg %r9,48(%r11) # return from load_fpu_regs
larl %r9,load_fpu_regs
br %r14
.Lcleanup_load_fpu_regs_vx:
.quad .Lload_fpu_regs_vx
.Lcleanup_load_fpu_regs_vx_high:
.quad .Lload_fpu_regs_vx_high
.Lcleanup_load_fpu_regs_fp:
.quad .Lload_fpu_regs_fp
.Lcleanup_load_fpu_regs_done:
.quad .Lload_fpu_regs_done
/*
* Integer constants