linux.git/arch/um/kernel/skas, branch for-next Linux kernel source tree um: move thread info into task 2024-11-12T13:50:31+00:00 Benjamin Berg benjamin.berg@intel.com 2024-11-11T10:29:10+00:00 2f681ba4b352cdd5658ed2a96062375a12839755 This selects the THREAD_INFO_IN_TASK option for UM and changes the way that the current task is discovered. This is trivial though, as UML already tracks the current task in cpu_tasks[] and this can be used to retrieve it. Also remove the signal handler code that copies the thread information into the IRQ stack. It is obsolete now, which also means that the mentioned race condition cannot happen anymore. Signed-off-by: Benjamin Berg <benjamin.berg@intel.com> Reviewed-by: Hajime Tazaki <thehajime@gmail.com> Link: https://patch.msgid.link/20241111102910.46512-1-benjamin@sipsolutions.net Signed-off-by: Johannes Berg <johannes.berg@intel.com> 
This selects the THREAD_INFO_IN_TASK option for UM and changes the way
that the current task is discovered. This is trivial though, as UML
already tracks the current task in cpu_tasks[] and this can be used to
retrieve it.

Also remove the signal handler code that copies the thread information
into the IRQ stack. It is obsolete now, which also means that the
mentioned race condition cannot happen anymore.

Signed-off-by: Benjamin Berg <benjamin.berg@intel.com>
Reviewed-by: Hajime Tazaki <thehajime@gmail.com>
Link: https://patch.msgid.link/20241111102910.46512-1-benjamin@sipsolutions.net
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
um: Remove double zero check 2024-11-07T16:34:03+00:00 Shaojie Dong quic_shaojied@quicinc.com 2024-10-25T09:02:37+00:00 0b0ad2541d8e465c82b69202bbc2b1efcac6b73d free_pages() performs a parameter null check inside therefore remove double zero check here. Signed-off-by: Shaojie Dong <quic_shaojied@quicinc.com> Link: https://patch.msgid.link/20241025-upstream_branch-v5-1-b8998beb2c64@quicinc.com Signed-off-by: Johannes Berg <johannes.berg@intel.com> 
free_pages() performs a parameter null check inside
therefore remove double zero check here.

Signed-off-by: Shaojie Dong <quic_shaojied@quicinc.com>
Link: https://patch.msgid.link/20241025-upstream_branch-v5-1-b8998beb2c64@quicinc.com
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
um: fix stub exe build with CONFIG_GCOV 2024-10-26T14:06:10+00:00 Johannes Berg johannes.berg@intel.com 2024-10-25T08:27:01+00:00 d3b08e5f3f2829943342b88d3e2b44fb0ccdccab CONFIG_GCOV is special and only in UML since it builds the kernel with a "userspace" option. This is fine, but the stub is even more special and not really a full userspace process, so it then fails to link as reported. Remove the GCOV options from the stub build. For good measure, also remove the GPROF options, even though they don't seem to cause build failures now. To be able to do this, export the specific options (GCOV_OPT and GPROF_OPT) but rename them so there's less chance of any conflicts. Reported-by: kernel test robot <lkp@intel.com> Closes: https://lore.kernel.org/oe-kbuild-all/202410242238.SXhs2kQ4-lkp@intel.com/ Fixes: 32e8eaf263d9 ("um: use execveat to create userspace MMs") Link: https://patch.msgid.link/20241025102700.9fbb9c34473f.I7f1537fe075638f8da64beb52ef6c9e5adc51bc3@changeid Signed-off-by: Johannes Berg <johannes.berg@intel.com> 
CONFIG_GCOV is special and only in UML since it builds the
kernel with a "userspace" option. This is fine, but the stub
is even more special and not really a full userspace process,
so it then fails to link as reported.

Remove the GCOV options from the stub build.

For good measure, also remove the GPROF options, even though
they don't seem to cause build failures now.

To be able to do this, export the specific options (GCOV_OPT
and GPROF_OPT) but rename them so there's less chance of any
conflicts.

Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202410242238.SXhs2kQ4-lkp@intel.com/
Fixes: 32e8eaf263d9 ("um: use execveat to create userspace MMs")
Link: https://patch.msgid.link/20241025102700.9fbb9c34473f.I7f1537fe075638f8da64beb52ef6c9e5adc51bc3@changeid
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: make stub_exe _start() pure inline asm 2024-10-23T07:04:59+00:00 Johannes Berg johannes.berg@intel.com 2024-10-22T12:02:38+00:00 14d4a7b516e993cf3926758a7ede569d8e119855 Since __attribute__((naked)) cannot be used with functions containing C statements, just generate the few instructions it needs in assembly directly. While at it, fix the stack usage ("1 + 2*x - 1" is odd) and document what it must do, and why it must adjust the stack. Fixes: 8508a5e0e9db ("um: Fix misaligned stack in stub_exe") Link: https://lore.kernel.org/linux-um/CABVgOSntH-uoOFMP5HwMXjx_f1osMnVdhgKRKm4uz6DFm2Lb8Q@mail.gmail.com/ Reviewed-by: David Gow <davidgow@google.com> Signed-off-by: Johannes Berg <johannes.berg@intel.com> 
Since __attribute__((naked)) cannot be used with functions
containing C statements, just generate the few instructions
it needs in assembly directly.

While at it, fix the stack usage ("1 + 2*x - 1" is odd) and
document what it must do, and why it must adjust the stack.

Fixes: 8508a5e0e9db ("um: Fix misaligned stack in stub_exe")
Link: https://lore.kernel.org/linux-um/CABVgOSntH-uoOFMP5HwMXjx_f1osMnVdhgKRKm4uz6DFm2Lb8Q@mail.gmail.com/
Reviewed-by: David Gow <davidgow@google.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
um: Fix misaligned stack in stub_exe 2024-10-18T08:37:52+00:00 David Gow davidgow@google.com 2024-10-17T23:10:08+00:00 8508a5e0e9db3932ca43651f86ba1042a1e9f4ca The stub_exe could segfault when built with some compilers (e.g. gcc 13.2.0), as SSE instructions which relied on stack alignment could be generated, but the stack was misaligned. This seems to be due to the __start entry point being run with a 16-byte aligned stack, but the x86_64 SYSV ABI wanting the stack to be so aligned _before_ a function call (so it is misaligned when the function is entered due to the return address being pushed). The function prologue then realigns it. Because the entry point is never _called_, and hence there is no return address, the prologue is therefore actually misaligning it, and causing the generated movaps instructions to SIGSEGV. This results in the following error: start_userspace : expected SIGSTOP, got status = 139 Don't generate this prologue for __start by using __attribute__((naked)), which resolves the issue. Fixes: 32e8eaf263d9 ("um: use execveat to create userspace MMs") Signed-off-by: David Gow <davidgow@google.com> Link: https://lore.kernel.org/linux-um/CABVgOS=boUoG6=LHFFhxEd8H8jDP1zOaPKFEjH+iy2n2Q5S2aQ@mail.gmail.com/ Link: https://patch.msgid.link/20241017231007.1500497-2-davidgow@google.com Signed-off-by: Johannes Berg <johannes.berg@intel.com> 
The stub_exe could segfault when built with some compilers (e.g. gcc
13.2.0), as SSE instructions which relied on stack alignment could be
generated, but the stack was misaligned.

This seems to be due to the __start entry point being run with a 16-byte
aligned stack, but the x86_64 SYSV ABI wanting the stack to be so
aligned _before_ a function call (so it is misaligned when the function
is entered due to the return address being pushed). The function
prologue then realigns it. Because the entry point is never _called_,
and hence there is no return address, the prologue is therefore actually
misaligning it, and causing the generated movaps instructions to
SIGSEGV. This results in the following error:
start_userspace : expected SIGSTOP, got status = 139

Don't generate this prologue for __start by using
__attribute__((naked)), which resolves the issue.

Fixes: 32e8eaf263d9 ("um: use execveat to create userspace MMs")
Signed-off-by: David Gow <davidgow@google.com>
Link: https://lore.kernel.org/linux-um/CABVgOS=boUoG6=LHFFhxEd8H8jDP1zOaPKFEjH+iy2n2Q5S2aQ@mail.gmail.com/
Link: https://patch.msgid.link/20241017231007.1500497-2-davidgow@google.com
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
um: Disable auto variable initialization for stub_exe.c 2024-10-17T08:33:31+00:00 Nathan Chancellor nathan@kernel.org 2024-10-16T21:12:38+00:00 1e3071d629b2e2cd7faeb8de2f88ba31cfd7231a When automatic variable initialization is enabled via CONFIG_INIT_STACK_ALL_{PATTERN,ZERO}, clang will insert a call to memset() to initialize an object created with __builtin_alloca(). This ultimately breaks the build when linking stub_exe because it is a standalone executable that does not include or link against memset(). ld: arch/um/kernel/skas/stub_exe.o: in function `_start': arch/um/kernel/skas/stub_exe.c:83:(.ltext+0x15): undefined reference to `memset' Disable automatic variable initialization for stub_exe.c by passing the default value of 'uninitialized' to '-ftrivial-auto-var-init', which avoids generating the call to memset(). This code is small and runs quickly as it is just designed to set up an environment, so stack variable initialization is unnecessary overhead for little gain. Fixes: 32e8eaf263d9 ("um: use execveat to create userspace MMs") Signed-off-by: Nathan Chancellor <nathan@kernel.org> Link: https://patch.msgid.link/20241016-uml-fix-stub_exe-clang-v1-2-3d6381dc5a78@kernel.org Signed-off-by: Johannes Berg <johannes.berg@intel.com> 
When automatic variable initialization is enabled via
CONFIG_INIT_STACK_ALL_{PATTERN,ZERO}, clang will insert a call to
memset() to initialize an object created with __builtin_alloca(). This
ultimately breaks the build when linking stub_exe because it is a
standalone executable that does not include or link against memset().

  ld: arch/um/kernel/skas/stub_exe.o: in function `_start':
  arch/um/kernel/skas/stub_exe.c:83:(.ltext+0x15): undefined reference to `memset'

Disable automatic variable initialization for stub_exe.c by passing the
default value of 'uninitialized' to '-ftrivial-auto-var-init', which
avoids generating the call to memset(). This code is small and runs
quickly as it is just designed to set up an environment, so stack
variable initialization is unnecessary overhead for little gain.

Fixes: 32e8eaf263d9 ("um: use execveat to create userspace MMs")
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Link: https://patch.msgid.link/20241016-uml-fix-stub_exe-clang-v1-2-3d6381dc5a78@kernel.org
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
um: Fix passing '-n' to linker for stub_exe 2024-10-17T08:33:31+00:00 Nathan Chancellor nathan@kernel.org 2024-10-16T21:12:37+00:00 89350defd1f0eb5a58a7e1155d9e322080f0bf15 When building stub_exe with clang, there is an error because '-n' is not a recognized flag by the clang driver (which is being used to invoke the linker): clang: error: unknown argument: '-n' '-n' should be passed along to the linker, as it is the short flag for '--nmagic', so prefix it with '-Wl,'. Fixes: 32e8eaf263d9 ("um: use execveat to create userspace MMs") Signed-off-by: Nathan Chancellor <nathan@kernel.org> Link: https://patch.msgid.link/20241016-uml-fix-stub_exe-clang-v1-1-3d6381dc5a78@kernel.org Signed-off-by: Johannes Berg <johannes.berg@intel.com> 
When building stub_exe with clang, there is an error because '-n' is not
a recognized flag by the clang driver (which is being used to invoke the
linker):

  clang: error: unknown argument: '-n'

'-n' should be passed along to the linker, as it is the short flag for
'--nmagic', so prefix it with '-Wl,'.

Fixes: 32e8eaf263d9 ("um: use execveat to create userspace MMs")
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Link: https://patch.msgid.link/20241016-uml-fix-stub_exe-clang-v1-1-3d6381dc5a78@kernel.org
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
um: clear all memory in new userspace processes 2024-10-10T11:37:22+00:00 Benjamin Berg benjamin.berg@intel.com 2024-09-19T12:45:10+00:00 e167cc7a95fe01e228e403ac90090f8613e7d8bc With the change to use execve() we can now safely clear the memory up to STUB_START as rseq will not be trying to use memory in that region. Also, on 64 bit the previous changes should mean that there is no usable memory range above the stub. Make the change and remove the comment as it is not needed anymore. Signed-off-by: Benjamin Berg <benjamin.berg@intel.com> Link: https://patch.msgid.link/20240919124511.282088-10-benjamin@sipsolutions.net Signed-off-by: Johannes Berg <johannes.berg@intel.com> 
With the change to use execve() we can now safely clear the memory up to
STUB_START as rseq will not be trying to use memory in that region. Also,
on 64 bit the previous changes should mean that there is no usable
memory range above the stub.

Make the change and remove the comment as it is not needed anymore.

Signed-off-by: Benjamin Berg <benjamin.berg@intel.com>
Link: https://patch.msgid.link/20240919124511.282088-10-benjamin@sipsolutions.net
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
um: Set parent death signal for userspace process 2024-10-10T11:37:21+00:00 Benjamin Berg benjamin.berg@intel.com 2024-09-19T12:45:04+00:00 801e00d3a1b78b7f71675fae79946ff4aa3ee070 Enable PR_SET_PDEATHSIG so that the UML userspace process will be killed when the kernel exits unexpectedly. Signed-off-by: Benjamin Berg <benjamin.berg@intel.com> Link: https://patch.msgid.link/20240919124511.282088-4-benjamin@sipsolutions.net Signed-off-by: Johannes Berg <johannes.berg@intel.com> 
Enable PR_SET_PDEATHSIG so that the UML userspace process will be killed
when the kernel exits unexpectedly.

Signed-off-by: Benjamin Berg <benjamin.berg@intel.com>
Link: https://patch.msgid.link/20240919124511.282088-4-benjamin@sipsolutions.net
Signed-off-by: Johannes Berg <johannes.berg@intel.com>