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| author | Nicholas Piggin <npiggin@gmail.com> | 2021-10-28 15:30:43 +0200 |
|---|---|---|
| committer | Michael Ellerman <mpe@ellerman.id.au> | 2021-10-29 14:12:37 +0200 |
| commit | 81291383ffde08b23bce75e7d6b2575ce9d3475c (patch) | |
| tree | cc3b9e03b90f260d7d49fd85be2c0fdb933f4bf0 | |
| parent | powerpc/powernv/prd: Unregister OPAL_MSG_PRD2 notifier during module unload (diff) | |
| download | linux-81291383ffde08b23bce75e7d6b2575ce9d3475c.tar.xz linux-81291383ffde08b23bce75e7d6b2575ce9d3475c.zip | |
powerpc/32e: Ignore ESR in instruction storage interrupt handler
A e5500 machine running a 32-bit kernel sometimes hangs at boot,
seemingly going into an infinite loop of instruction storage interrupts.
The ESR (Exception Syndrome Register) has a value of 0x800000 (store)
when this happens, which is likely set by a previous store. An
instruction TLB miss interrupt would then leave ESR unchanged, and if no
PTE exists it calls directly to the instruction storage interrupt
handler without changing ESR.
access_error() does not cause a segfault due to a store to a read-only
vma because is_exec is true. Most subsequent fault handling does not
check for a write fault on a read-only vma, and might do strange things
like create a writeable PTE or call page_mkwrite on a read only vma or
file. It's not clear what happens here to cause the infinite faulting in
this case, a fault handler failure or low level PTE or TLB handling.
In any case this can be fixed by having the instruction storage
interrupt zero regs->dsisr rather than storing the ESR value to it.
Fixes: a01a3f2ddbcd ("powerpc: remove arguments from fault handler functions")
Cc: stable@vger.kernel.org # v5.12+
Reported-by: Jacques de Laval <jacques.delaval@protonmail.com>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Tested-by: Jacques de Laval <jacques.delaval@protonmail.com>
Reviewed-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20211028133043.4159501-1-npiggin@gmail.com
| -rw-r--r-- | arch/powerpc/kernel/head_booke.h | 15 |
1 files changed, 12 insertions, 3 deletions
diff --git a/arch/powerpc/kernel/head_booke.h b/arch/powerpc/kernel/head_booke.h index e5503420b6c6..ef8d1b1c234e 100644 --- a/arch/powerpc/kernel/head_booke.h +++ b/arch/powerpc/kernel/head_booke.h @@ -465,12 +465,21 @@ label: bl do_page_fault; \ b interrupt_return +/* + * Instruction TLB Error interrupt handlers may call InstructionStorage + * directly without clearing ESR, so the ESR at this point may be left over + * from a prior interrupt. + * + * In any case, do_page_fault for BOOK3E does not use ESR and always expects + * dsisr to be 0. ESR_DST from a prior store in particular would confuse fault + * handling. + */ #define INSTRUCTION_STORAGE_EXCEPTION \ START_EXCEPTION(InstructionStorage) \ - NORMAL_EXCEPTION_PROLOG(0x400, INST_STORAGE); \ - mfspr r5,SPRN_ESR; /* Grab the ESR and save it */ \ + NORMAL_EXCEPTION_PROLOG(0x400, INST_STORAGE); \ + li r5,0; /* Store 0 in regs->esr (dsisr) */ \ stw r5,_ESR(r11); \ - stw r12, _DEAR(r11); /* Pass SRR0 as arg2 */ \ + stw r12, _DEAR(r11); /* Set regs->dear (dar) to SRR0 */ \ prepare_transfer_to_handler; \ bl do_page_fault; \ b interrupt_return |