kernel.git/arch/powerpc/kernel/interrupt_64.S, branch linux-5.16.y

powerpc/64s: Mask SRR0 before checking against the masked NIP

2022-02-01T16:29:13Z

[ Upstream commit aee101d7b95a03078945681dd7f7ea5e4a1e7686 ] Commit 314f6c23dd8d ("powerpc/64s: Mask NIP before checking against SRR0") masked off the low 2 bits of the NIP value in the interrupt stack frame in case they are non-zero and mis-compare against a SRR0 register value of a CPU which always reads back 0 from the 2 low bits which are reserved. This now causes the opposite problem that an implementation which does implement those bits in SRR0 will mis-compare against the masked NIP value in which they have been cleared. QEMU is one such implementation, and this is allowed by the architecture. This can be triggered by sigfuz by setting low bits of PT_NIP in the signal context. Fix this for now by masking the SRR0 bits as well. Cleaner is probably to sanitise these values before putting them in registers or stack, but this is the quick and backportable fix. Fixes: 314f6c23dd8d ("powerpc/64s: Mask NIP before checking against SRR0") Signed-off-by: Nicholas Piggin Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20220117134403.2995059-1-npiggin@gmail.com Signed-off-by: Sasha Levin

powerpc/64s: Use EMIT_WARN_ENTRY for SRR debug warnings

2022-01-27T11:02:08Z

[ Upstream commit fd1eaaaaa6864b5fb8f99880fcefb49760b8fe4e ] When CONFIG_PPC_RFI_SRR_DEBUG=y we check the SRR values before returning from interrupts. This is done in asm using EMIT_BUG_ENTRY, and passing BUGFLAG_WARNING. However that fails to create an exception table entry for the warning, and so do_program_check() fails the exception table search and proceeds to call _exception(), resulting in an oops like: Oops: Exception in kernel mode, sig: 5 [#1] LE PAGE_SIZE=64K MMU=Radix SMP NR_CPUS=2048 NUMA pSeries Modules linked in: CPU: 2 PID: 1204 Comm: sigreturn_unali Tainted: P 5.16.0-rc2-00194-g91ca3d4f77c5 #12 NIP: c00000000000c5b0 LR: 0000000000000000 CTR: 0000000000000000 ... NIP [c00000000000c5b0] system_call_common+0x150/0x268 LR [0000000000000000] 0x0 Call Trace: [c00000000db73e10] [c00000000000c558] system_call_common+0xf8/0x268 (unreliable) ... Instruction dump: 7cc803a6 888d0931 2c240000 4082001c 38800000 988d0931 e8810170 e8a10178 7c9a03a6 7cbb03a6 7d7a02a6 e9810170 <7f0b6088> 7d7b02a6 e9810178 7f0b6088 We should instead use EMIT_WARN_ENTRY, which creates an exception table entry for the warning, allowing the warning to be correctly recognised, and the code to resume after printing the warning. Note however that because this warning is buried deep in the interrupt return path, we are not able to recover from it (due to MSR_RI being clear), so we still end up in die() with an unrecoverable exception. Fixes: 59dc5bfca0cb ("powerpc/64s: avoid reloading (H)SRR registers if they are still valid") Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20211221135101.2085547-2-mpe@ellerman.id.au Signed-off-by: Sasha Levin

powerpc/64s: Mask NIP before checking against SRR0

2022-01-27T11:02:08Z

[ Upstream commit 314f6c23dd8d417281eb9e8a516dd98036f2e7b3 ] When CONFIG_PPC_RFI_SRR_DEBUG=y we check that NIP and SRR0 match when returning from interrupts. This can trigger falsely if NIP has either of its two low bits set via sigreturn or ptrace, while SRR0 has its low two bits masked in hardware. As a quick fix make sure to mask the low bits before doing the check. Fixes: 59dc5bfca0cb ("powerpc/64s: avoid reloading (H)SRR registers if they are still valid") Reported-by: Sachin Sant Signed-off-by: Michael Ellerman Tested-by: Sachin Sant Link: https://lore.kernel.org/r/20211221135101.2085547-1-mpe@ellerman.id.au Signed-off-by: Sasha Levin

powerpc/64s: system call scv tabort fix for corrupt irq soft-mask state

2021-09-13T12:34:11Z

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. This can't easily be fixed in asm because at this point an async irq may have hit, which is soft-masked and marked pending. The pending interrupt has to be replayed before returning to userspace. The fix is to move the tabort_syscall code to C in the main syscall handler, and just skip the system call but otherwise return as usual, which will take care of the pending irqs. This also does a bunch of other things including possible signal delivery to the process, but the doomed transaction should still be aborted when it is eventually returned to. The sc system call path is changed to use the new C function as well to reduce code and path differences. This slows down how quickly system calls are aborted when called while a transaction is active, which could potentially impact TM performance. But making any system call is already bad for performance, and TM is on the way out, so go with simpler over faster. Fixes: 7fa95f9adaee7 ("powerpc/64s: system call support for scv/rfscv instructions") Reported-by: Eirik Fuller Signed-off-by: Nicholas Piggin [mpe: Use #ifdef rather than IS_ENABLED() to fix build error on 32-bit] Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20210903125707.1601269-1-npiggin@gmail.com

powerpc/64e: Fix system call illegal mtmsrd instruction

2021-07-06T09:58:54Z

BookE does not have mtmsrd, switch to use wrteei to enable MSR[EE]. Fixes: dd152f70bdc1 ("powerpc/64s: system call avoid setting MSR[RI] until we set MSR[EE]") Reported-by: Christian Zigotzky Signed-off-by: Nicholas Piggin Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20210706051310.608992-1-npiggin@gmail.com

powerpc/64s: move ret_from_fork etc above __end_soft_masked

2021-06-30T12:21:20Z

Code which runs with interrupts enabled should be moved above __end_soft_masked where possible, because maskable interrupts that hit below that symbol will need to consult the soft mask table, which is an extra cost. Signed-off-by: Nicholas Piggin Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20210630074621.2109197-10-npiggin@gmail.com

powerpc/64s/interrupt: clean up interrupt return labels

2021-06-30T12:21:20Z

Normal kernel-interrupt exits can get interrupt_return_srr_user_restart in their backtrace, which is an unusual and notable function, and it is part of the user-interrupt exit path, which is doubly confusing. Add non-local labels for both user and kernel interrupt exit cases to address this and make the user and kernel cases more symmetric. Also get rid of an unused label. Signed-off-by: Nicholas Piggin Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20210630074621.2109197-9-npiggin@gmail.com

powerpc/64/interrupt: add missing kprobe annotations on interrupt exit symbols

2021-06-30T12:21:20Z

If one interrupt exit symbol must not be kprobed, none of them can be, without more justification for why it's safe. Disallow kprobing on any of the (non-local) labels in the exit paths. Signed-off-by: Nicholas Piggin Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20210630074621.2109197-8-npiggin@gmail.com

powerpc/64s: add a table of implicit soft-masked addresses

2021-06-30T12:21:20Z

Commit 9d1988ca87dd ("powerpc/64: treat low kernel text as irqs soft-masked") ends up catching too much code, including ret_from_fork, and parts of interrupt and syscall return that do not expect to be interrupts to be soft-masked. If an interrupt gets marked pending, and then the code proceeds out of the implicit soft-masked region it will fail to deal with the pending interrupt. Fix this by adding a new table of addresses which explicitly marks the regions of code that are soft masked. This table is only checked for interrupts that below __end_soft_masked, so most kernel interrupts will not have the overhead of the table search. Fixes: 9d1988ca87dd ("powerpc/64: treat low kernel text as irqs soft-masked") Reported-by: Sachin Sant Signed-off-by: Nicholas Piggin Tested-by: Sachin Sant Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20210630074621.2109197-5-npiggin@gmail.com

powerpc/64e: remove implicit soft-masking and interrupt exit restart logic

2021-06-30T12:21:20Z

The implicit soft-masking to speed up interrupt return was going to be used by 64e as well, but it has not been extensively tested on that platform and is not considered ready. It was intended to be disabled before merge. Disable it for now. Most of the restart code is common with 64s, so with more correctness and performance testing this could be re-enabled again by adding the extra soft-mask checks to interrupt handlers and flipping exit_must_hard_disable(). Fixes: 9d1988ca87dd ("powerpc/64: treat low kernel text as irqs soft-masked") Signed-off-by: Nicholas Piggin Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20210630074621.2109197-4-npiggin@gmail.com