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powerpc/sstep: Fix kernel crash if VSX is not present 

emulate_step() is not checking runtime VSX feature flag before
emulating an instruction. This is causing kernel crash when kernel
is compiled with CONFIG_VSX=y but running on a machine where VSX
is not supported or disabled. Ex, while running emulate_step tests
on P6 machine:

  Oops: Exception in kernel mode, sig: 4 [#1]
  NIP [c000000000095c24] .load_vsrn+0x28/0x54
  LR [c000000000094bdc] .emulate_loadstore+0x167c/0x17b0
  Call Trace:
    0x40fe240c7ae147ae (unreliable)
    .emulate_loadstore+0x167c/0x17b0
    .emulate_step+0x25c/0x5bc
    .test_lxvd2x_stxvd2x+0x64/0x154
    .test_emulate_step+0x38/0x4c
    .do_one_initcall+0x5c/0x2c0
    .kernel_init_freeable+0x314/0x4cc
    .kernel_init+0x24/0x160
    .ret_from_kernel_thread+0x58/0xb4

With fix:
  emulate_step_test: lxvd2x         : FAIL
  emulate_step_test: stxvd2x        : FAIL

Reported-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Ravi Bangoria <ravi.bangoria@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
Ravi Bangoria 2018-05-21 09:51:07 +05:30 committed by Michael Ellerman
parent e6684d07e4
commit 83afab4ce0
1 changed files with 9 additions and 0 deletions
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9
arch/powerpc/lib/sstep.c
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@ -2545,6 +2545,15 @@ int analyse_instr(struct instruction_op *op, const struct pt_regs *regs,
#endif /* __powerpc64__ */
}
#ifdef CONFIG_VSX
if ((GETTYPE(op->type) == LOAD_VSX ||
GETTYPE(op->type) == STORE_VSX) &&
!cpu_has_feature(CPU_FTR_VSX)) {
return -1;
}
#endif /* CONFIG_VSX */
return 0;
logical_done: