Le 01/09/2021 à 18:54, Nicholas Piggin a écrit :
If a system call is made with a transaction active, the kernel
immediately aborts it and returns. scv system calls disable irqs even
earlier in their interrupt handler, and tabort_syscall does not fix this
up.
This can result in irq soft-mask state being messed up on the next
kernel entry, and crashing at BUG_ON(arch_irq_disabled_regs(regs)) in
the kernel exit handlers, or possibly worse.
Fix this by having tabort_syscall setting irq soft-mask back to enabled
(which requires MSR[EE] be disabled first).
Reported-by: Eirik Fuller <eful...@redhat.com>
Fixes: 7fa95f9adaee7 ("powerpc/64s: system call support for scv/rfscv
instructions")
Signed-off-by: Nicholas Piggin <npig...@gmail.com>
---
Tested the wrong kernel before sending v1 and missed a bug, sorry.
arch/powerpc/kernel/interrupt_64.S | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/arch/powerpc/kernel/interrupt_64.S
b/arch/powerpc/kernel/interrupt_64.S
index d4212d2ff0b5..9c31d65b4851 100644
--- a/arch/powerpc/kernel/interrupt_64.S
+++ b/arch/powerpc/kernel/interrupt_64.S
@@ -428,16 +428,22 @@ RESTART_TABLE(.Lsyscall_rst_start, .Lsyscall_rst_end,
syscall_restart)
#ifdef CONFIG_PPC_TRANSACTIONAL_MEM
tabort_syscall:
_ASM_NOKPROBE_SYMBOL(tabort_syscall)
- /* Firstly we need to enable TM in the kernel */
+ /* We need to enable TM in the kernel, and disable EE (for scv) */
mfmsr r10
li r9, 1
rldimi r10, r9, MSR_TM_LG, 63-MSR_TM_LG
+ LOAD_REG_IMMEDIATE(r9, MSR_EE)
+ andc r10, r10, r9
Why not use 'rlwinm' to mask out MSR_EE ?
Something like
rlwinm r10, r10, 0, ~MSR_EE
mtmsrd r10, 0
/* tabort, this dooms the transaction, nothing else */
li r9, (TM_CAUSE_SYSCALL|TM_CAUSE_PERSISTENT)
TABORT(R9)
+ /* scv has disabled irqs so must re-enable. sc just remains enabled */
+ li r9,IRQS_ENABLED
+ stb r9,PACAIRQSOFTMASK(r13)
+
/*
* Return directly to userspace. We have corrupted user register state,
* but userspace will never see that register state. Execution will
