With GCC 12 allmodconfig prom_init fails to build:

  Error: External symbol 'memset' referenced from prom_init.c
  make[2]: *** [arch/powerpc/kernel/Makefile:204: arch/powerpc/kernel/prom_init_check] Error 1

The allmodconfig build enables KASAN, so all calls to memset in
prom_init should be converted to __memset by the #ifdefs in
asm/string.h, because prom_init must use the non-KASAN instrumented
versions.

The build failure happens because there's a call to memset that hasn't
been caught by the pre-processor and converted to __memset. Typically
that's because it's a memset generated by the compiler itself, and that
is the case here.

With GCC 12, allmodconfig enables CONFIG_INIT_STACK_ALL_PATTERN, which
causes the compiler to emit memset calls to initialise on-stack
variables with a pattern.

Because prom_init is non-user-facing boot-time only code, as a
workaround just disable stack variable initialisation to unbreak the
build.

Reported-by: Sudip Mukherjee <sudipm.mukherjee@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20220718134418.354114-1-mpe@ellerman.id.au

When searching for config options, use the KCONFIG_CONFIG shell variable
so that builds using non-standard config locations work.

Fixes: 26deb04342e3 ("powerpc: prepare string/mem functions for KASAN")
Cc: stable@vger.kernel.org # v5.2+
Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20220624011745.4060795-1-Liam.Howlett@oracle.com

When CONFIG_KASAN is selected, we expect prom_init to use __memset()
because it is too early to use memset().

But with CONFIG_GCC_PLUGIN_STRUCTLEAK_BYREF_ALL, the compiler adds calls
to memset() to clear objects on stack, hence the following failure:

	  PROMCHK arch/powerpc/kernel/prom_init_check
	Error: External symbol 'memset' referenced from prom_init.c
	make[2]: *** [arch/powerpc/kernel/Makefile:204 : arch/powerpc/kernel/prom_init_check] Erreur 1

prom_find_machine_type() is called from prom_init() and is called only
once, so lets put compat[] in BSS instead of stack to avoid that.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/3802811f7cf94f730be44688539c01bba3a3b5c0.1654875808.git.christophe.leroy@csgroup.eu

Add a special case to block_rtas_call() to allow the ibm,platform-dump RTAS
call through the RTAS filter if the buffer address is 0.

According to PAPR, ibm,platform-dump is called with a null buffer address
to notify the platform firmware that processing of a particular dump is
finished.

Without this, on a pseries machine with CONFIG_PPC_RTAS_FILTER enabled, an
application such as rtas_errd that is attempting to retrieve a dump will
encounter an error at the end of the retrieval process.

Fixes: bd59380c5ba4 ("powerpc/rtas: Restrict RTAS requests from userspace")
Cc: stable@vger.kernel.org
Reported-by: Sathvika Vasireddy <sathvika@linux.ibm.com>
Signed-off-by: Andrew Donnellan <ajd@linux.ibm.com>
Reviewed-by: Tyrel Datwyler <tyreld@linux.ibm.com>
Reviewed-by: Nathan Lynch <nathanl@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20220614134952.156010-1-ajd@linux.ibm.com

On execve[at], we are zero'ing out most of the thread register state
including gpr[0], which contains the syscall number. Due to this, we
fail to trigger the syscall exit tracepoint properly. Fix this by
retaining gpr[0] in the thread register state.

Before this patch:
  # tail /sys/kernel/debug/tracing/trace
	       cat-123     [000] .....    61.449351: sys_execve(filename:
  7fffa6b23448, argv: 7fffa6b233e0, envp: 7fffa6b233f8)
	       cat-124     [000] .....    62.428481: sys_execve(filename:
  7fffa6b23448, argv: 7fffa6b233e0, envp: 7fffa6b233f8)
	      echo-125     [000] .....    65.813702: sys_execve(filename:
  7fffa6b23378, argv: 7fffa6b233a0, envp: 7fffa6b233b0)
	      echo-125     [000] .....    65.822214: sys_execveat(fd: 0,
  filename: 1009ac48, argv: 7ffff65d0c98, envp: 7ffff65d0ca8, flags: 0)

After this patch:
  # tail /sys/kernel/debug/tracing/trace
	       cat-127     [000] .....   100.416262: sys_execve(filename:
  7fffa41b3448, argv: 7fffa41b33e0, envp: 7fffa41b33f8)
	       cat-127     [000] .....   100.418203: sys_execve -> 0x0
	      echo-128     [000] .....   103.873968: sys_execve(filename:
  7fffa41b3378, argv: 7fffa41b33a0, envp: 7fffa41b33b0)
	      echo-128     [000] .....   103.875102: sys_execve -> 0x0
	      echo-128     [000] .....   103.882097: sys_execveat(fd: 0,
  filename: 1009ac48, argv: 7fffd10d2148, envp: 7fffd10d2158, flags: 0)
	      echo-128     [000] .....   103.883225: sys_execveat -> 0x0

Cc: stable@vger.kernel.org
Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Tested-by: Sumit Dubey2 <Sumit.Dubey2@ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20220609103328.41306-1-naveen.n.rao@linux.vnet.ibm.com

After commit 11ac3e87ce09 ("mm: cma: use pageblock_order as the single
alignment") there is an error at boot about the KVM CMA reservation
failing, eg:

  kvm_cma_reserve: reserving 6553 MiB for global area
  cma: Failed to reserve 6553 MiB

That makes it impossible to start KVM guests using the hash MMU with
more than 2G of memory, because the VM is unable to allocate a large
enough region for the hash page table, eg:

  $ qemu-system-ppc64 -enable-kvm -M pseries -m 4G ...
  qemu-system-ppc64: Failed to allocate KVM HPT of order 25: Cannot allocate memory

Aneesh pointed out that this happens because when kvm_cma_reserve() is
called, pageblock_order has not been initialised yet, and is still zero,
causing the checks in cma_init_reserved_mem() against
CMA_MIN_ALIGNMENT_PAGES to fail.

Fix it by moving the call to kvm_cma_reserve() after initmem_init(). The
pageblock_order is initialised in sparse_init() which is called from
initmem_init().

Also move the hugetlb CMA reservation.

Fixes: 11ac3e87ce09 ("mm: cma: use pageblock_order as the single alignment")
Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Reviewed-by: Zi Yan <ziy@nvidia.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20220616120033.1976732-1-mpe@ellerman.id.au

Pull powerpc fixes from Michael Ellerman:

 - On 32-bit fix overread/overwrite of thread_struct via ptrace
   PEEK/POKE.

 - Fix softirqs not switching to the softirq stack since we moved
   irq_exit().

 - Force thread size increase when KASAN is enabled to avoid stack
   overflows.

 - On Book3s 64 mark more code as not to be instrumented by KASAN to
   avoid crashes.

 - Exempt __get_wchan() from KASAN checking, as it's inherently racy.

 - Fix a recently introduced crash in the papr_scm driver in some
   configurations.

 - Remove include of <generated/compile.h> which is forbidden.

Thanks to Ariel Miculas, Chen Jingwen, Christophe Leroy, Erhard Furtner,
He Ying, Kees Cook, Masahiro Yamada, Nageswara R Sastry, Paul Mackerras,
Sachin Sant, Vaibhav Jain, and Wanming Hu.

* tag 'powerpc-5.19-2' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux:
  powerpc/32: Fix overread/overwrite of thread_struct via ptrace
  powerpc/book3e: get rid of #include <generated/compile.h>
  powerpc/kasan: Force thread size increase with KASAN
  powerpc/papr_scm: don't requests stats with '0' sized stats buffer
  powerpc: Don't select HAVE_IRQ_EXIT_ON_IRQ_STACK
  powerpc/kasan: Silence KASAN warnings in __get_wchan()
  powerpc/kasan: Mark more real-mode code as not to be instrumented

The ptrace PEEKUSR/POKEUSR (aka PEEKUSER/POKEUSER) API allows a process
to read/write registers of another process.

To get/set a register, the API takes an index into an imaginary address
space called the "USER area", where the registers of the process are
laid out in some fashion.

The kernel then maps that index to a particular register in its own data
structures and gets/sets the value.

The API only allows a single machine-word to be read/written at a time.
So 4 bytes on 32-bit kernels and 8 bytes on 64-bit kernels.

The way floating point registers (FPRs) are addressed is somewhat
complicated, because double precision float values are 64-bit even on
32-bit CPUs. That means on 32-bit kernels each FPR occupies two
word-sized locations in the USER area. On 64-bit kernels each FPR
occupies one word-sized location in the USER area.

Internally the kernel stores the FPRs in an array of u64s, or if VSX is
enabled, an array of pairs of u64s where one half of each pair stores
the FPR. Which half of the pair stores the FPR depends on the kernel's
endianness.

To handle the different layouts of the FPRs depending on VSX/no-VSX and
big/little endian, the TS_FPR() macro was introduced.

Unfortunately the TS_FPR() macro does not take into account the fact
that the addressing of each FPR differs between 32-bit and 64-bit
kernels. It just takes the index into the "USER area" passed from
userspace and indexes into the fp_state.fpr array.

On 32-bit there are 64 indexes that address FPRs, but only 32 entries in
the fp_state.fpr array, meaning the user can read/write 256 bytes past
the end of the array. Because the fp_state sits in the middle of the
thread_struct there are various fields than can be overwritten,
including some pointers. As such it may be exploitable.

It has also been observed to cause systems to hang or otherwise
misbehave when using gdbserver, and is probably the root cause of this
report which could not be easily reproduced:
  https://lore.kernel.org/linuxppc-dev/dc38afe9-6b78-f3f5-666b-986939e40fc6@keymile.com/

Rather than trying to make the TS_FPR() macro even more complicated to
fix the bug, or add more macros, instead add a special-case for 32-bit
kernels. This is more obvious and hopefully avoids a similar bug
happening again in future.

Note that because 32-bit kernels never have VSX enabled the code doesn't
need to consider TS_FPRWIDTH/OFFSET at all. Add a BUILD_BUG_ON() to
ensure that 32-bit && VSX is never enabled.

Fixes: 87fec0514f61 ("powerpc: PTRACE_PEEKUSR/PTRACE_POKEUSER of FPR registers in little endian builds")
Cc: stable@vger.kernel.org # v3.13+
Reported-by: Ariel Miculas <ariel.miculas@belden.com>
Tested-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20220609133245.573565-1-mpe@ellerman.id.au

Pull kthread updates from Eric Biederman:
 "This updates init and user mode helper tasks to be ordinary user mode
  tasks.

  Commit 40966e316f86 ("kthread: Ensure struct kthread is present for
  all kthreads") caused init and the user mode helper threads that call
  kernel_execve to have struct kthread allocated for them. This struct
  kthread going away during execve in turned made a use after free of
  struct kthread possible.

  Here, commit 343f4c49f243 ("kthread: Don't allocate kthread_struct for
  init and umh") is enough to fix the use after free and is simple
  enough to be backportable.

  The rest of the changes pass struct kernel_clone_args to clean things
  up and cause the code to make sense.

  In making init and the user mode helpers tasks purely user mode tasks
  I ran into two complications. The function task_tick_numa was
  detecting tasks without an mm by testing for the presence of
  PF_KTHREAD. The initramfs code in populate_initrd_image was using
  flush_delayed_fput to ensuere the closing of all it's file descriptors
  was complete, and flush_delayed_fput does not work in a userspace
  thread.

  I have looked and looked and more complications and in my code review
  I have not found any, and neither has anyone else with the code
  sitting in linux-next"

* tag 'kthread-cleanups-for-v5.19' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace:
  sched: Update task_tick_numa to ignore tasks without an mm
  fork: Stop allowing kthreads to call execve
  fork: Explicitly set PF_KTHREAD
  init: Deal with the init process being a user mode process
  fork: Generalize PF_IO_WORKER handling
  fork: Explicity test for idle tasks in copy_thread
  fork: Pass struct kernel_clone_args into copy_thread
  kthread: Don't allocate kthread_struct for init and umh

Pull livepatching cleanup from Petr Mladek:

 - Remove duplicated livepatch code [Christophe]

* tag 'livepatching-for-5.19' of git://git.kernel.org/pub/scm/linux/kernel/git/livepatching/livepatching:
  livepatch: Remove klp_arch_set_pc() and asm/livepatch.h