kernel/git/stable/linux.git/arch/um/drivers, branch linux-5.12.y

um: fix error return code in winch_tramp()

2021-07-20T14:02:18+00:00

[ Upstream commit ccf1236ecac476d9d2704866d9a476c86e387971 ] Fix to return a negative error code from the error handling case instead of 0, as done elsewhere in this function. Fixes: 89df6bfc0405 ("uml: DEBUG_SHIRQ fixes") Reported-by: Hulk Robot Signed-off-by: Zhen Lei Acked-By: anton.ivanov@cambridgegreys.com Signed-off-by: Richard Weinberger Signed-off-by: Sasha Levin

um: fix error return code in slip_open()

2021-07-20T14:02:18+00:00

[ Upstream commit b77e81fbe5f5fb4ad9a61ec80f6d1e30b6da093a ] Fix to return a negative error code from the error handling case instead of 0, as done elsewhere in this function. Fixes: a3c77c67a443 ("[PATCH] uml: slirp and slip driver cleanups and fixes") Reported-by: Hulk Robot Signed-off-by: Zhen Lei Acked-By: anton.ivanov@cambridgegreys.com Signed-off-by: Richard Weinberger Signed-off-by: Sasha Levin

um: Fix stack pointer alignment

2021-07-20T14:02:18+00:00

[ Upstream commit 558f9b2f94dbd2d5c5c8292aa13e081cc11ea7d9 ] GCC assumes that stack is aligned to 16-byte on call sites [1]. Since GCC 8, GCC began using 16-byte aligned SSE instructions to implement assignments to structs on stack. When CC_OPTIMIZE_FOR_PERFORMANCE is enabled, this affects os-Linux/sigio.c, write_sigio_thread: struct pollfds *fds, tmp; tmp = current_poll; Note that struct pollfds is exactly 16 bytes in size. GCC 8+ generates assembly similar to: movdqa (%rdi),%xmm0 movaps %xmm0,-0x50(%rbp) This is an issue, because movaps will #GP if -0x50(%rbp) is not aligned to 16 bytes [2], and how rbp gets assigned to is via glibc clone thread_start, then function prologue, going though execution trace similar to (showing only relevant instructions): sub $0x10,%rsi mov %rcx,0x8(%rsi) mov %rdi,(%rsi) syscall pop %rax pop %rdi callq *%rax push %rbp mov %rsp,%rbp The stack pointer always points to the topmost element on stack, rather then the space right above the topmost. On push, the pointer decrements first before writing to the memory pointed to by it. Therefore, there is no need to have the stack pointer pointer always point to valid memory unless the stack is poped; so the `- sizeof(void *)` in the code is unnecessary. On the other hand, glibc reserves the 16 bytes it needs on stack and pops itself, so by the call instruction the stack pointer is exactly the caller-supplied sp. It then push the 16 bytes of the return address and the saved stack pointer, so the base pointer will be 16-byte aligned if and only if the caller supplied sp is 16-byte aligned. Therefore, the caller must supply a 16-byte aligned pointer, which `stack + UM_KERN_PAGE_SIZE` already satisfies. On a side note, musl is unaffected by this issue because it forces 16 byte alignment via `and $-16,%rsi` in its clone wrapper. Similarly, glibc i386 is also unaffected because it has `andl $0xfffffff0, %ecx`. To reproduce this bug, enable CONFIG_UML_RTC and CC_OPTIMIZE_FOR_PERFORMANCE. uml_rtc will call add_sigio_fd which will then cause write_sigio_thread to either go into segfault loop or panic with "Segfault with no mm". Similarly, signal stacks will be aligned by the host kernel upon signal delivery. `- sizeof(void *)` to sigaltstack is unconventional and extraneous. On a related note, initialization of longjmp buffers do require `- sizeof(void *)`. This is to account for the return address that would have been pushed to the stack at the call site. The reason for uml to respect 16-byte alignment, rather than telling GCC to assume 8-byte alignment like the host kernel since commit d9b0cde91c60 ("x86-64, gcc: Use -mpreferred-stack-boundary=3 if supported"), is because uml links against libc. There is no reason to assume libc is also compiled with that flag and assumes 8-byte alignment rather than 16-byte. [1] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=40838 [2] https://c9x.me/x86/html/file_module_x86_id_180.html Signed-off-by: YiFei Zhu Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Reviewed-by: Johannes Berg Signed-off-by: Richard Weinberger Signed-off-by: Sasha Levin

um: add a pseudo RTC

2021-02-12T20:38:52+00:00

Add a pseudo RTC that simply is able to send an alarm signal waking up the system at a given time in the future. Since apparently timerfd_create() FDs don't support SIGIO, we use the sigio-creating helper thread, which just learned to do suspend/resume properly in the previous patch. For time-travel mode, OTOH, just add an event at the specified time in the future, and that's already sufficient to wake up the system at that point in time since suspend will just be in an "endless wait". For s2idle support also call pm_system_wakeup(). Signed-off-by: Johannes Berg Signed-off-by: Richard Weinberger

um: fix spelling mistake in Kconfig "privleges" -> "privileges"

2021-02-12T20:26:20+00:00

There is a spelling mistake in the Kconfig help text. Fix it. Signed-off-by: Colin Ian King Signed-off-by: Richard Weinberger

um: virtio: allow devices to be configured for wakeup

2021-02-12T20:25:46+00:00

With all the IRQ machinery being in place, we can allow virtio devices to additionally be configured as wakeup sources, in which case basically any interrupt from them wakes us up. Note that this requires a call FD because the VQs are all disabled. Signed-off-by: Johannes Berg Signed-off-by: Richard Weinberger

um: time-travel: rework interrupt handling in ext mode

2021-02-12T20:24:27+00:00

In external time-travel mode, where time is controlled via the controller application socket, interrupt handling is a little tricky. For example on virtio, the following happens: * we receive a message (that requires an ACK) on the vhost-user socket * we add a time-travel event to handle the interrupt (this causes communication on the time socket) * we ACK the original vhost-user message * we then handle the interrupt once the event is triggered This protocol ensures that the sender of the interrupt only continues to run in the simulation when the time-travel event has been added. So far, this was only done in the virtio driver, but it was actually wrong, because only virtqueue interrupts were handled this way, and config change interrupts were handled immediately. Additionally, the messages were actually handled in the real Linux interrupt handler, but Linux interrupt handlers are part of the simulation and shouldn't run while there's no time event. To really do this properly and only handle all kinds of interrupts in the time-travel event when we are scheduled to run in the simulation, rework this to plug in to the lower interrupt layers in UML directly: Add a um_request_irq_tt() function that let's a time-travel aware driver request an interrupt with an additional timetravel_handler() that is called outside of the context of the simulation, to handle the message only. It then adds an event to the time-travel calendar if necessary, and no "real" Linux code runs outside of the time simulation. This also hooks in with suspend/resume properly now, since this new timetravel_handler() can run while Linux is suspended and interrupts are disabled, and decide to wake up (or not) the system based on the message it received. Importantly in this case, it ACKs the message before the system even resumes and interrupts are re-enabled, thus allowing the simulation to progress properly. Signed-off-by: Johannes Berg Signed-off-by: Richard Weinberger

um: virtio: disable VQs during suspend

2021-02-12T20:22:32+00:00

If the system is suspended, the device shouldn't be able to send anything to it. Disable virtqueues in suspend to simulate this, and as we might be only using s2idle (kernel services are still on), prevent sending anything on them as well. Signed-off-by: Johannes Berg Signed-off-by: Richard Weinberger

um: virtio: fix handling of messages without payload

2021-02-12T20:21:52+00:00

If we have a message without payload, we call full_read() with len set to 0, which causes it to return -ECONNRESET. Catch this case and explicitly return 0 for it so we can actually use the zero-size config-changed message. Signed-off-by: Johannes Berg Signed-off-by: Richard Weinberger

um: virtio: clean up a comment

2021-02-12T20:21:17+00:00

There's no 'simtime' device, because implementing that through virtio was just too much complexity. Clean up the comment that still refers to it. Signed-off-by: Johannes Berg Signed-off-by: Richard Weinberger