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Date: Wed, 16 May 2018 11:10:21 +0530 From: Ravi Bangoria <ravi.bangoria@...ux.ibm.com> To: mpe@...erman.id.au Cc: benh@...nel.crashing.org, paulus@...ba.org, naveen.n.rao@...ux.vnet.ibm.com, anton@...ba.org, cyrilbur@...il.com, matthew.brown.dev@...il.com, sandipan@...ux.vnet.ibm.com, linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org, Ravi Bangoria <ravi.bangoria@...ux.ibm.com> Subject: [RFC] powerpc/emulate_step: Fix kernel crash when VSX is not present emulate_step() is not checking runtime VSX feature flag before emulating an instruction. This can cause kernel oops when kernel is compiled with CONFIG_VSX=y but running on machine where VSX is not supported or disabled. Ex, while running emulate_step tests on P6 machine: ... emulate_step_test: lvx : PASS emulate_step_test: stvx : PASS Oops: Exception in kernel mode, sig: 4 [#1] NIP [c000000000095c24] .load_vsrn+0x28/0x54 LR [c000000000094bdc] .emulate_loadstore+0x167c/0x17b0 Call Trace: [c0000000494c3770] [40fe240c7ae147ae] 0x40fe240c7ae147ae (unreliable) [c0000000494c37f0] [c000000000094bdc] .emulate_loadstore+0x167c/0x17b0 [c0000000494c3900] [c000000000094f6c] .emulate_step+0x25c/0x5bc [c0000000494c39b0] [c000000000ec90dc] .test_lxvd2x_stxvd2x+0x64/0x154 [c0000000494c3b90] [c000000000ec9204] .test_emulate_step+0x38/0x4c [c0000000494c3c00] [c00000000000de2c] .do_one_initcall+0x5c/0x2c0 [c0000000494c3cd0] [c000000000eb4bf8] .kernel_init_freeable+0x314/0x4cc [c0000000494c3db0] [c00000000000e1e4] .kernel_init+0x24/0x160 [c0000000494c3e30] [c00000000000bc24] .ret_from_kernel_thread+0x58/0xb4 With fix: ... emulate_step_test: stvx : PASS emulate_step_test: lxvd2x : FAIL emulate_step_test: stxvd2x : FAIL Fixes: https://github.com/linuxppc/linux/issues/148 Reported-by: Michael Ellerman <mpe@...erman.id.au> Signed-off-by: Ravi Bangoria <ravi.bangoria@...ux.ibm.com> --- Note: VSX was first introduced on P6. But there are many VSX instructions which were introduced in later versions. So ideally, analyse_instr() should check for ISA version along with opcode. arch/powerpc/lib/sstep.c | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/arch/powerpc/lib/sstep.c b/arch/powerpc/lib/sstep.c index 34d68f1b1b40..470942f9c567 100644 --- a/arch/powerpc/lib/sstep.c +++ b/arch/powerpc/lib/sstep.c @@ -1173,6 +1173,7 @@ int analyse_instr(struct instruction_op *op, const struct pt_regs *regs, unsigned long int val, val2; unsigned int mb, me, sh; long ival; + int type; op->type = COMPUTE; @@ -2544,6 +2545,15 @@ int analyse_instr(struct instruction_op *op, const struct pt_regs *regs, #endif /* __powerpc64__ */ } + +#ifdef CONFIG_VSX + type = op->type & INSTR_TYPE_MASK; + if ((type == LOAD_VSX || type == STORE_VSX) && + !cpu_has_feature(CPU_FTR_VSX)) { + return -1; + } +#endif /* CONFIG_VSX */ + return 0; logical_done: -- 2.16.2
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