[Skiboot] [PATCH] external/mambo: add helper for machine checks

[Michael Ellerman]

Nicholas Piggin <npiggin at gmail.com> writes:

> Add helpers to construct machine checks with registers set up properly.
> exc_mce raises a machine check exception that can be stepped into. This
> is useful for testing the machine check handler.
>
> Also add a similar exc_sreset for system reset.
>
> inject_mce does the same but runs immediately and stops when the
> instruction reaches the NIP (which can get tangled up if machine check
> re-enters this code). This is useful for testing robustness to
> interleaving machine checks.
>
> inject_mce_step allows injecting MCEs between each instruction and stepping
> over them. inject_mce_step_ri does the same but only when MSR has RI set.
> This can be useful to test correctness of low level code. For example,
> testing system call vs machine check:
>
> systemsim % b 0xC000000000004c00
> systemsim % c
> 0xC000000000004C00 (0x0000000000004C00) Enc:0xA64BB17D : mtspr   HSPRG1,r13
> systemsim % inject_mce_step_ri 100
> 0xC000000000004C04 (0x0000000000004C04) Enc:0xA64AB07D : mfspr   r13,HSPRG0
> 0xC000000000004C08 (0x0000000000004C08) Enc:0x80002DF9 : std     r9,0x80(r13)
> 0xC000000000004C0C (0x0000000000004C0C) Enc:0xA6E2207D : mfspr   r9,PPR
> 0xC000000000004C10 (0x0000000000004C10) Enc:0x7813427C : mr      r2,r2
> 0xC000000000004C14 (0x0000000000004C14) Enc:0x88004DF9 : std     r10,0x88(r13)
> 0xC000000000004C18 (0x0000000000004C18) Enc:0xD8002DF9 : std     r9,0xD8(r13)
> 0xC000000000004C1C (0x0000000000004C1C) Enc:0x2600207D : mfcr    r9
> 0xC000000000004C20 (0x0000000000004C20) Enc:0xE8074D89 : lbz     r10,0x7E8(r13)
> 0xC000000000004C24 (0x0000000000004C24) Enc:0x00000A2C : cmpwi   cr0,r10,0
> 0xC000000000004C28 (0x0000000000004C28) Enc:0xA80F8240 : bne     cr0,$+0xFA8  (bc 0x4,0x2,0xFA8,0,0)
> 0xC000000000004C2C (0x0000000000004C2C) Enc:0xA64AB17D : mfspr   r13,HSPRG1
> 0xC000000000004C30 (0x0000000000004C30) Enc:0xBE1E202C : cmpdi   cr0,r0,7870
> 0xC000000000004C34 (0x0000000000004C34) Enc:0x2000C241 : beq     cr0,$+0x20  (bc 0xE,0x2,0x20,0,0)
> 0xC000000000004C38 (0x0000000000004C38) Enc:0x786BA97D : mr      r9,r13
> 0xC000000000004C3C (0x0000000000004C3C) Enc:0xA64AB07D : mfspr   r13,HSPRG0
> 0xC000000000004C40 (0x0000000000004C40) Enc:0xA6027A7D : mfspr   r11,SRR0
> 0xC000000000004C44 (0x0000000000004C44) Enc:0xA6029B7D : mfspr   r12,SRR1
> 0xC000000000004C48 (0x0000000000004C48) Enc:0x02004039 : li      r10,2
> 0xC000000000004C4C (0x0000000000004C4C) Enc:0x6401417D : mtmsrd  r10,1
> 0xC000000000004C50 (0x0000000000004C50) Enc:0xB0620048 : b       $+0x62B0
> 236380163: (212143620): Disabling lock debugging due to kernel taint
> 0xC000000000004C50 (0x0000000000004C50) Enc:0xB0620048 : b       $+0x62B0
> 0xC00000000000AF00 (0x000000000000AF00) Enc:0xE1F78A79 : rldicl. r10,r12,30,63,63 (0x0000000000000001)
> 0xC00000000000AF00 (0x000000000000AF00) Enc:0xE1F78A79 : rldicl. r10,r12,30,63,63 (0x0000000000000001)
> [...]
>
> Every instruction after 0xC000000000004C4C is getting an interleaving
> MCE, and continuing after this injection the kernel prints a lot of MCE
> reports and continues working properly.
>
> Signed-off-by: Nicholas Piggin <npiggin at gmail.com>


This is really helpful for tripping these otherwise infrequently tested
code paths.

Tested-by: Michael Ellerman <mpe at ellerman.id.au>

cheers