linux.git/arch/um/include/shared/os.h, branch for-next Linux kernel source tree um: remove broken double fault detection 2024-11-07T16:36:31+00:00 Benjamin Berg benjamin.berg@intel.com 2024-11-03T15:05:06+00:00 ce6e85a186c28ab0ca024580cba93fa19147c72b The show_stack function had some code to detect double faults. However, the logic is wrong and it would e.g. trigger if a WARNING happened inside an IRQ. Remove it without trying to add a new logic. The current behaviour, which will just fault repeatedly until the IRQ stack is used up and the host kills UML, seems to be good enough. Signed-off-by: Benjamin Berg <benjamin.berg@intel.com> Link: https://patch.msgid.link/20241103150506.1367695-5-benjamin@sipsolutions.net Signed-off-by: Johannes Berg <johannes.berg@intel.com> 
The show_stack function had some code to detect double faults. However,
the logic is wrong and it would e.g. trigger if a WARNING happened
inside an IRQ.

Remove it without trying to add a new logic. The current behaviour,
which will just fault repeatedly until the IRQ stack is used up and the
host kills UML, seems to be good enough.

Signed-off-by: Benjamin Berg <benjamin.berg@intel.com>
Link: https://patch.msgid.link/20241103150506.1367695-5-benjamin@sipsolutions.net
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
um: remove file sync for stub data 2024-11-07T16:36:30+00:00 Benjamin Berg benjamin.berg@intel.com 2024-11-03T15:05:04+00:00 37c691151e52f7762afa147ffb6e412ee0b5e8ac There is no need to sync the stub code to "disk" for the other process to see the correct memory. Drop the fsync there and remove the helper function. Signed-off-by: Benjamin Berg <benjamin.berg@intel.com> Link: https://patch.msgid.link/20241103150506.1367695-3-benjamin@sipsolutions.net Signed-off-by: Johannes Berg <johannes.berg@intel.com> 
There is no need to sync the stub code to "disk" for the other process
to see the correct memory. Drop the fsync there and remove the helper
function.

Signed-off-by: Benjamin Berg <benjamin.berg@intel.com>
Link: https://patch.msgid.link/20241103150506.1367695-3-benjamin@sipsolutions.net
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
um: Add os_set_pdeathsig helper function 2024-10-25T09:34:54+00:00 Tiwei Bie tiwei.btw@antgroup.com 2024-10-24T14:28:25+00:00 4e5adbe447db382cc76e05613581f96aef4f91d2 This helper can be used to set the parent-death signal of the calling process to SIGKILL to ensure that the process will be killed if the UML kernel dies unexpectedly without proper cleanup. This helper will be used in the follow-up patches. Signed-off-by: Tiwei Bie <tiwei.btw@antgroup.com> Link: https://patch.msgid.link/20241024142828.2612828-2-tiwei.btw@antgroup.com Signed-off-by: Johannes Berg <johannes.berg@intel.com> 
This helper can be used to set the parent-death signal of the calling
process to SIGKILL to ensure that the process will be killed if the
UML kernel dies unexpectedly without proper cleanup. This helper will
be used in the follow-up patches.

Signed-off-by: Tiwei Bie <tiwei.btw@antgroup.com>
Link: https://patch.msgid.link/20241024142828.2612828-2-tiwei.btw@antgroup.com
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
um: Abandon the _PAGE_NEWPROT bit 2024-10-23T07:52:49+00:00 Tiwei Bie tiwei.btw@antgroup.com 2024-10-11T10:23:53+00:00 2717c6b649e1840328c2758a478bf4034a22ac3e When a PTE is updated in the page table, the _PAGE_NEWPAGE bit will always be set. And the corresponding page will always be mapped or unmapped depending on whether the PTE is present or not. The check on the _PAGE_NEWPROT bit is not really reachable. Abandoning it will allow us to simplify the code and remove the unreachable code. Reviewed-by: Benjamin Berg <benjamin.berg@intel.com> Signed-off-by: Tiwei Bie <tiwei.btw@antgroup.com> Link: https://patch.msgid.link/20241011102354.1682626-2-tiwei.btw@antgroup.com Signed-off-by: Johannes Berg <johannes.berg@intel.com> 
When a PTE is updated in the page table, the _PAGE_NEWPAGE bit will
always be set. And the corresponding page will always be mapped or
unmapped depending on whether the PTE is present or not. The check
on the _PAGE_NEWPROT bit is not really reachable. Abandoning it will
allow us to simplify the code and remove the unreachable code.

Reviewed-by: Benjamin Berg <benjamin.berg@intel.com>
Signed-off-by: Tiwei Bie <tiwei.btw@antgroup.com>
Link: https://patch.msgid.link/20241011102354.1682626-2-tiwei.btw@antgroup.com
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
um: Discover host_task_size from envp 2024-10-10T11:37:22+00:00 Benjamin Berg benjamin.berg@intel.com 2024-09-19T12:45:09+00:00 68b9883cc16ec2ce699d832ef60241b1a4e47d33 When loading the UML binary, the host kernel will place the stack at the highest possible address. It will then map the program name and environment variables onto the start of the stack. As such, an easy way to figure out the host_task_size is to use the highest pointer to an environment variable as a reference. Ensure that this works by disabling address layout randomization and re-executing UML in case it was enabled. This increases the available TASK_SIZE for 64 bit UML considerably. Signed-off-by: Benjamin Berg <benjamin.berg@intel.com> Link: https://patch.msgid.link/20240919124511.282088-9-benjamin@sipsolutions.net Signed-off-by: Johannes Berg <johannes.berg@intel.com> 
When loading the UML binary, the host kernel will place the stack at the
highest possible address. It will then map the program name and
environment variables onto the start of the stack.

As such, an easy way to figure out the host_task_size is to use the
highest pointer to an environment variable as a reference.

Ensure that this works by disabling address layout randomization and
re-executing UML in case it was enabled.

This increases the available TASK_SIZE for 64 bit UML considerably.

Signed-off-by: Benjamin Berg <benjamin.berg@intel.com>
Link: https://patch.msgid.link/20240919124511.282088-9-benjamin@sipsolutions.net
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
um: remove auxiliary FP registers 2024-10-10T10:10:30+00:00 Benjamin Berg benjamin.berg@intel.com 2024-10-04T23:38:21+00:00 c6ce72005d1af98b983cc27aaa770afa66a1ca90 We do not need the extra save/restore of the FP registers when getting the fault information. This was originally added in commit 2f56debd77a8 ("uml: fix FP register corruption") but at that time the code was not saving/restoring the FP registers when switching to userspace. This was fixed in commit fbfe9c847edf ("um: Save FPU registers between task switches") and since then the auxiliary registers have not been useful. Signed-off-by: Benjamin Berg <benjamin.berg@intel.com> Link: https://patch.msgid.link/20241004233821.2130874-1-benjamin@sipsolutions.net Signed-off-by: Johannes Berg <johannes.berg@intel.com> 
We do not need the extra save/restore of the FP registers when getting
the fault information. This was originally added in commit 2f56debd77a8
("uml: fix FP register corruption") but at that time the code was not
saving/restoring the FP registers when switching to userspace. This was
fixed in commit fbfe9c847edf ("um: Save FPU registers between task
switches") and since then the auxiliary registers have not been useful.

Signed-off-by: Benjamin Berg <benjamin.berg@intel.com>
Link: https://patch.msgid.link/20241004233821.2130874-1-benjamin@sipsolutions.net
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
um: Remove unused os_getpgrp function 2024-10-10T10:02:04+00:00 Benjamin Berg benjamin.berg@intel.com 2024-09-13T13:44:41+00:00 71fae9dfa7e3a987886c8baf235d5a0b96e5dc15 The function is not used anywhere. Signed-off-by: Benjamin Berg <benjamin.berg@intel.com> Link: https://patch.msgid.link/20240913134442.967599-5-benjamin@sipsolutions.net Signed-off-by: Johannes Berg <johannes.berg@intel.com> 
The function is not used anywhere.

Signed-off-by: Benjamin Berg <benjamin.berg@intel.com>
Link: https://patch.msgid.link/20240913134442.967599-5-benjamin@sipsolutions.net
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
um: Remove unused os_stop_process 2024-10-10T10:02:04+00:00 Benjamin Berg benjamin.berg@intel.com 2024-09-13T13:44:40+00:00 377c23c5588d1f3d572b21d429dd95157bd8b5a9 The function is not used anywhere. Signed-off-by: Benjamin Berg <benjamin.berg@intel.com> Link: https://patch.msgid.link/20240913134442.967599-4-benjamin@sipsolutions.net Signed-off-by: Johannes Berg <johannes.berg@intel.com> 
The function is not used anywhere.

Signed-off-by: Benjamin Berg <benjamin.berg@intel.com>
Link: https://patch.msgid.link/20240913134442.967599-4-benjamin@sipsolutions.net
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
um: Remove unused os_process_parent 2024-10-10T10:02:04+00:00 Benjamin Berg benjamin.berg@intel.com 2024-09-13T13:44:39+00:00 47e174969cbf9244add188635a9590ff717d796e The function is not used anywhere. Signed-off-by: Benjamin Berg <benjamin.berg@intel.com> Link: https://patch.msgid.link/20240913134442.967599-3-benjamin@sipsolutions.net Signed-off-by: Johannes Berg <johannes.berg@intel.com> 
The function is not used anywhere.

Signed-off-by: Benjamin Berg <benjamin.berg@intel.com>
Link: https://patch.msgid.link/20240913134442.967599-3-benjamin@sipsolutions.net
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
um: Remove unused os_process_pc 2024-10-10T10:02:04+00:00 Benjamin Berg benjamin.berg@intel.com 2024-09-13T13:44:38+00:00 7852ee068afe97eec3e955de3c4197aeb4793c52 The function is not used anywhere in the codebase. Signed-off-by: Benjamin Berg <benjamin.berg@intel.com> Link: https://patch.msgid.link/20240913134442.967599-2-benjamin@sipsolutions.net Signed-off-by: Johannes Berg <johannes.berg@intel.com> 
The function is not used anywhere in the codebase.

Signed-off-by: Benjamin Berg <benjamin.berg@intel.com>
Link: https://patch.msgid.link/20240913134442.967599-2-benjamin@sipsolutions.net
Signed-off-by: Johannes Berg <johannes.berg@intel.com>