linux.git/arch/powerpc/mm, branch v6.2

powerpc/64s/radix: Fix RWX mapping with relocated kernel

2023-01-31T10:37:39+00:00

If a relocatable kernel is loaded at a non-zero address and told not to
relocate to zero (kdump or RELOCATABLE_TEST), the mapping of the
interrupt code at zero is left with RWX permissions.

That is a security weakness, and leads to a warning at boot if
CONFIG_DEBUG_WX is enabled:

  powerpc/mm: Found insecure W+X mapping at address 00000000056435bc/0xc000000000000000
  WARNING: CPU: 1 PID: 1 at arch/powerpc/mm/ptdump/ptdump.c:193 note_page+0x484/0x4c0
  CPU: 1 PID: 1 Comm: swapper/0 Not tainted 6.2.0-rc1-00001-g8ae8e98aea82-dirty #175
  Hardware name: IBM pSeries (emulated by qemu) POWER9 (raw) 0x4e1202 0xf000005 of:SLOF,git-dd0dca hv:linux,kvm pSeries
  NIP:  c0000000004a1c34 LR: c0000000004a1c30 CTR: 0000000000000000
  REGS: c000000003503770 TRAP: 0700   Not tainted  (6.2.0-rc1-00001-g8ae8e98aea82-dirty)
  MSR:  8000000002029033   CR: 24000220  XER: 00000000
  CFAR: c000000000545a58 IRQMASK: 0
  ...
  NIP note_page+0x484/0x4c0
  LR  note_page+0x480/0x4c0
  Call Trace:
    note_page+0x480/0x4c0 (unreliable)
    ptdump_pmd_entry+0xc8/0x100
    walk_pgd_range+0x618/0xab0
    walk_page_range_novma+0x74/0xc0
    ptdump_walk_pgd+0x98/0x170
    ptdump_check_wx+0x94/0x100
    mark_rodata_ro+0x30/0x70
    kernel_init+0x78/0x1a0
    ret_from_kernel_thread+0x5c/0x64

The fix has two parts. Firstly the pages from zero up to the end of
interrupts need to be marked read-only, so that they are left with R-X
permissions. Secondly the mapping logic needs to be taught to ensure
there is a page boundary at the end of the interrupt region, so that the
permission change only applies to the interrupt text, and not the region
following it.

Fixes: c55d7b5e6426 ("powerpc: Remove STRICT_KERNEL_RWX incompatibility with RELOCATABLE")
Reported-by: Sachin Sant 
Tested-by: Sachin Sant 
Signed-off-by: Michael Ellerman 
Link: https://lore.kernel.org/r/20230110124753.1325426-2-mpe@ellerman.id.au

powerpc/64s/radix: Fix crash with unaligned relocated kernel

2023-01-31T10:37:39+00:00

If a relocatable kernel is loaded at an address that is not 2MB aligned
and told not to relocate to zero, the kernel can crash due to
mark_rodata_ro() incorrectly changing some read-write data to read-only.

Scenarios where the misalignment can occur are when the kernel is
loaded by kdump or using the RELOCATABLE_TEST config option.

Example crash with the kernel loaded at 5MB:

  Run /sbin/init as init process
  BUG: Unable to handle kernel data access on write at 0xc000000000452000
  Faulting instruction address: 0xc0000000005b6730
  Oops: Kernel access of bad area, sig: 11 [#1]
  LE PAGE_SIZE=64K MMU=Radix SMP NR_CPUS=2048 NUMA pSeries
  CPU: 1 PID: 1 Comm: init Not tainted 6.2.0-rc1-00011-g349188be4841 #166
  Hardware name: IBM pSeries (emulated by qemu) POWER9 (raw) 0x4e1202 0xf000005 of:SLOF,git-5b4c5a hv:linux,kvm pSeries
  NIP:  c0000000005b6730 LR: c000000000ae9ab8 CTR: 0000000000000380
  REGS: c000000004503250 TRAP: 0300   Not tainted  (6.2.0-rc1-00011-g349188be4841)
  MSR:  8000000000009033   CR: 44288480  XER: 00000000
  CFAR: c0000000005b66ec DAR: c000000000452000 DSISR: 0a000000 IRQMASK: 0
  ...
  NIP memset+0x68/0x104
  LR  zero_user_segments.constprop.0+0xa8/0xf0
  Call Trace:
    ext4_mpage_readpages+0x7f8/0x830
    ext4_readahead+0x48/0x60
    read_pages+0xb8/0x380
    page_cache_ra_unbounded+0x19c/0x250
    filemap_fault+0x58c/0xae0
    __do_fault+0x60/0x100
    __handle_mm_fault+0x1230/0x1a40
    handle_mm_fault+0x120/0x300
    ___do_page_fault+0x20c/0xa80
    do_page_fault+0x30/0xc0
    data_access_common_virt+0x210/0x220

This happens because mark_rodata_ro() tries to change permissions on the
range _stext..__end_rodata, but _stext sits in the middle of the 2MB
page from 4MB to 6MB:

  radix-mmu: Mapped 0x0000000000000000-0x0000000000200000 with 2.00 MiB pages (exec)
  radix-mmu: Mapped 0x0000000000200000-0x0000000000400000 with 2.00 MiB pages
  radix-mmu: Mapped 0x0000000000400000-0x0000000002400000 with 2.00 MiB pages (exec)

The logic that changes the permissions assumes the linear mapping was
split correctly at boot, so it marks the entire 2MB page read-only. That
leads to the write fault above.

To fix it, the boot time mapping logic needs to consider that if the
kernel is running at a non-zero address then _stext is a boundary where
it must split the mapping.

That leads to the mapping being split correctly, allowing the rodata
permission change to take happen correctly, with no spillover:

  radix-mmu: Mapped 0x0000000000000000-0x0000000000200000 with 2.00 MiB pages (exec)
  radix-mmu: Mapped 0x0000000000200000-0x0000000000400000 with 2.00 MiB pages
  radix-mmu: Mapped 0x0000000000400000-0x0000000000500000 with 64.0 KiB pages
  radix-mmu: Mapped 0x0000000000500000-0x0000000000600000 with 64.0 KiB pages (exec)
  radix-mmu: Mapped 0x0000000000600000-0x0000000002400000 with 2.00 MiB pages (exec)

If the kernel is loaded at a 2MB aligned address, the mapping continues
to use 2MB pages as before:

  radix-mmu: Mapped 0x0000000000000000-0x0000000000200000 with 2.00 MiB pages (exec)
  radix-mmu: Mapped 0x0000000000200000-0x0000000000400000 with 2.00 MiB pages
  radix-mmu: Mapped 0x0000000000400000-0x0000000002c00000 with 2.00 MiB pages (exec)
  radix-mmu: Mapped 0x0000000002c00000-0x0000000100000000 with 2.00 MiB pages

Fixes: c55d7b5e6426 ("powerpc: Remove STRICT_KERNEL_RWX incompatibility with RELOCATABLE")
Signed-off-by: Michael Ellerman 
Link: https://lore.kernel.org/r/20230110124753.1325426-1-mpe@ellerman.id.au

powerpc/64s/hash: Make stress_hpt_timer_fn() static

2023-01-11T23:53:37+00:00

stress_hpt_timer_fn() is only used in hash_utils.c, make it static.

Fixes: 6b34a099faa1 ("powerpc/64s/hash: add stress_hpt kernel boot option to increase hash faults")
Signed-off-by: Yang Yingliang 
Signed-off-by: Michael Ellerman 
Link: https://lore.kernel.org/r/20221228093603.3166599-1-yangyingliang@huawei.com

Merge tag 'powerpc-6.2-1' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux

2022-12-19T13:13:33+00:00

Pull powerpc updates from Michael Ellerman:

 - Add powerpc qspinlock implementation optimised for large system
   scalability and paravirt. See the merge message for more details

 - Enable objtool to be built on powerpc to generate mcount locations

 - Use a temporary mm for code patching with the Radix MMU, so the
   writable mapping is restricted to the patching CPU

 - Add an option to build the 64-bit big-endian kernel with the ELFv2
   ABI

 - Sanitise user registers on interrupt entry on 64-bit Book3S

 - Many other small features and fixes

Thanks to Aboorva Devarajan, Angel Iglesias, Benjamin Gray, Bjorn
Helgaas, Bo Liu, Chen Lifu, Christoph Hellwig, Christophe JAILLET,
Christophe Leroy, Christopher M. Riedl, Colin Ian King, Deming Wang,
Disha Goel, Dmitry Torokhov, Finn Thain, Geert Uytterhoeven, Gustavo A.
R. Silva, Haowen Bai, Joel Stanley, Jordan Niethe, Julia Lawall, Kajol
Jain, Laurent Dufour, Li zeming, Miaoqian Lin, Michael Jeanson, Nathan
Lynch, Naveen N. Rao, Nayna Jain, Nicholas Miehlbradt, Nicholas Piggin,
Pali Rohár, Randy Dunlap, Rohan McLure, Russell Currey, Sathvika
Vasireddy, Shaomin Deng, Stephen Kitt, Stephen Rothwell, Thomas
Weißschuh, Tiezhu Yang, Uwe Kleine-König, Xie Shaowen, Xiu Jianfeng,
XueBing Chen, Yang Yingliang, Zhang Jiaming, ruanjinjie, Jessica Yu,
and Wolfram Sang.

* tag 'powerpc-6.2-1' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux: (181 commits)
  powerpc/code-patching: Fix oops with DEBUG_VM enabled
  powerpc/qspinlock: Fix 32-bit build
  powerpc/prom: Fix 32-bit build
  powerpc/rtas: mandate RTAS syscall filtering
  powerpc/rtas: define pr_fmt and convert printk call sites
  powerpc/rtas: clean up includes
  powerpc/rtas: clean up rtas_error_log_max initialization
  powerpc/pseries/eeh: use correct API for error log size
  powerpc/rtas: avoid scheduling in rtas_os_term()
  powerpc/rtas: avoid device tree lookups in rtas_os_term()
  powerpc/rtasd: use correct OF API for event scan rate
  powerpc/rtas: document rtas_call()
  powerpc/pseries: unregister VPA when hot unplugging a CPU
  powerpc/pseries: reset the RCU watchdogs after a LPM
  powerpc: Take in account addition CPU node when building kexec FDT
  powerpc: export the CPU node count
  powerpc/cpuidle: Set CPUIDLE_FLAG_POLLING for snooze state
  powerpc/dts/fsl: Fix pca954x i2c-mux node names
  cxl: Remove unnecessary cxl_pci_window_alignment()
  selftests/powerpc: Fix resource leaks
  ...

powerpc/code-patching: Remove protection against patching init addresses after init

2022-12-02T10:59:57+00:00

Once init section is freed, attempting to patch init code
ends up in the weed.

Commit 51c3c62b58b3 ("powerpc: Avoid code patching freed init sections")
protected patch_instruction() against that, but it is the responsibility
of the caller to ensure that the patched memory is valid.

All callers have now been verified and fixed so the check
can be removed.

This improves ftrace activation by about 2% on 8xx.

Signed-off-by: Christophe Leroy 
Signed-off-by: Michael Ellerman 
Link: https://lore.kernel.org/r/504310828f473d424e2ed229eff57bf075f52796.1669969781.git.christophe.leroy@csgroup.eu

powerpc/64s/hash: add stress_hpt kernel boot option to increase hash faults

2022-12-02T07:04:25+00:00

This option increases the number of hash misses by limiting the number
of kernel HPT entries, by keeping a per-CPU record of the last kernel
HPTEs installed, and removing that from the hash table on the next hash
insertion. A timer round-robins CPUs removing remaining kernel HPTEs and
clearing the TLB (in the case of bare metal) to increase and slightly
randomise kernel fault activity.

Signed-off-by: Nicholas Piggin 
[mpe: Add comment about NR_CPUS usage, fixup whitespace]
Signed-off-by: Michael Ellerman 
Link: https://lore.kernel.org/r/20221024030150.852517-1-npiggin@gmail.com

powerpc/tlb: Add local flush for page given mm_struct and psize

2022-11-30T10:46:49+00:00

Adds a local TLB flush operation that works given an mm_struct, VA to
flush, and page size representation. Most implementations mirror the
surrounding code. The book3s/32/tlbflush.h implementation is left as
a BUILD_BUG because it is more complicated and not required for
anything as yet.

This removes the need to create a vm_area_struct, which the temporary
patching mm work does not need.

Signed-off-by: Benjamin Gray 
Reviewed-by: Christophe Leroy 
Signed-off-by: Michael Ellerman 
Link: https://lore.kernel.org/r/20221109045112.187069-8-bgray@linux.ibm.com

powerpc/book3e: remove #include

2022-11-30T10:46:48+00:00

Commit 7ad4bd887d27 ("powerpc/book3e: get rid of #include ")
removed the usage of the define UTS_RELEASE but forgot to drop the
include.

utsrelease.h is potentially generated on each build. By removing the
unused include we can get rid of some spurious recompilations.

Fixes: 7ad4bd887d27 ("powerpc/book3e: get rid of #include ")
Signed-off-by: Thomas Weißschuh 
Reviewed-by: Masahiro Yamada 
Reviewed-by: Christophe Leroy 
[mpe: Fix typo in change log and add more explanation]
Signed-off-by: Michael Ellerman 
Link: https://lore.kernel.org/r/20221126051002.123199-2-linux@weissschuh.net

Merge branch 'fixes' into next

2022-11-30T10:46:06+00:00

Merge our fixes branch to bring in some changes that are prerequisites
for work in next.

powerpc: Remove find_current_mm_pte()

2022-11-24T12:12:18+00:00

Last usage of find_current_mm_pte() was removed by
commit 15759cb054ef ("powerpc/perf/callchain: Use
__get_user_pages_fast in read_user_stack_slow")

Remove it.

Signed-off-by: Christophe Leroy 
Signed-off-by: Michael Ellerman 
Link: https://lore.kernel.org/r/ec79f462a3bfa8365b7df505e574d5d85246bc68.1646818177.git.christophe.leroy@csgroup.eu