linux-stable.git/arch/mips/kernel/relocate.c, branch linux-rolling-stable

MIPS: Work around LLVM bug when gp is used as global register variable

2026-02-26T22:59:45+00:00

commit 30bfc2d6a1132a89a5f1c3b96c59cf3e4d076ea3 upstream.

On MIPS, __current_thread_info is defined as global register variable
locating in $gp, and is simply assigned with new address during kernel
relocation.

This however is broken with LLVM, which always restores $gp if it finds
$gp is clobbered in any form, including when intentionally through a
global register variable. This is against GCC's documentation[1], which
requires a callee-saved register used as global register variable not to
be restored if it's clobbered.

As a result, $gp will continue to point to the unrelocated kernel after
the epilog of relocate_kernel(), leading to an early crash in init_idle,

[    0.000000] CPU 0 Unable to handle kernel paging request at virtual address 0000000000000000, epc == ffffffff81afada8, ra == ffffffff81afad90
[    0.000000] Oops[#1]:
[    0.000000] CPU: 0 UID: 0 PID: 0 Comm: swapper Tainted: G        W           6.19.0-rc5-00262-gd3eeb99bbc99-dirty #188 VOLUNTARY
[    0.000000] Tainted: [W]=WARN
[    0.000000] Hardware name: loongson,loongson64v-4core-virtio
[    0.000000] $ 0   : 0000000000000000 0000000000000000 0000000000000001 0000000000000000
[    0.000000] $ 4   : ffffffff80b80ec0 ffffffff80b53d48 0000000000000000 00000000000f4240
[    0.000000] $ 8   : 0000000000000100 ffffffff81d82f80 ffffffff81d82f80 0000000000000001
[    0.000000] $12   : 0000000000000000 ffffffff81776f58 00000000000005da 0000000000000002
[    0.000000] $16   : ffffffff80b80e40 0000000000000000 ffffffff80b81614 9800000005dfbe80
[    0.000000] $20   : 00000000540000e0 ffffffff81980000 0000000000000000 ffffffff80f81c80
[    0.000000] $24   : 0000000000000a26 ffffffff8114fb90
[    0.000000] $28   : ffffffff80b50000 ffffffff80b53d40 0000000000000000 ffffffff81afad90
[    0.000000] Hi    : 0000000000000000
[    0.000000] Lo    : 0000000000000000
[    0.000000] epc   : ffffffff81afada8 init_idle+0x130/0x270
[    0.000000] ra    : ffffffff81afad90 init_idle+0x118/0x270
[    0.000000] Status: 540000e2	KX SX UX KERNEL EXL
[    0.000000] Cause : 00000008 (ExcCode 02)
[    0.000000] BadVA : 0000000000000000
[    0.000000] PrId  : 00006305 (ICT Loongson-3)
[    0.000000] Process swapper (pid: 0, threadinfo=(____ptrval____), task=(____ptrval____), tls=0000000000000000)
[    0.000000] Stack : 9800000005dfbf00 ffffffff8178e950 0000000000000000 0000000000000000
[    0.000000]         0000000000000000 ffffffff81970000 000000000000003f ffffffff810a6528
[    0.000000]         0000000000000001 9800000005dfbe80 9800000005dfbf00 ffffffff81980000
[    0.000000]         ffffffff810a6450 ffffffff81afb6c0 0000000000000000 ffffffff810a2258
[    0.000000]         ffffffff81d82ec8 ffffffff8198d010 ffffffff81b67e80 ffffffff8197dd98
[    0.000000]         ffffffff81d81c80 ffffffff81930000 0000000000000040 0000000000000000
[    0.000000]         0000000000000000 0000000000000000 0000000000000000 0000000000000000
[    0.000000]         0000000000000000 000000000000009e ffffffff9fc01000 0000000000000000
[    0.000000]         0000000000000000 0000000000000000 0000000000000000 0000000000000000
[    0.000000]         0000000000000000 ffffffff81ae86dc ffffffff81b3c741 0000000000000002
[    0.000000]         ...
[    0.000000] Call Trace:
[    0.000000] [] init_idle+0x130/0x270
[    0.000000] [] sched_init+0x5c8/0x6c0
[    0.000000] [] start_kernel+0x27c/0x7a8

This bug has been reported to LLVM[2] and affects version from (at
least) 18 to 21. Let's work around this by using inline assembly to
assign $gp before a fix is widely available.

Cc: stable@vger.kernel.org
Link: https://gcc.gnu.org/onlinedocs/gcc-15.2.0/gcc/Global-Register-Variables.html # [1]
Link: https://github.com/llvm/llvm-project/issues/176546 # [2]
Signed-off-by: Yao Zi 
Acked-by: Nathan Chancellor 
Signed-off-by: Thomas Bogendoerfer 
Signed-off-by: Greg Kroah-Hartman

MIPS: Don't use %pK through printk

2025-07-28T07:58:49+00:00

Restricted pointers ("%pK") are not meant to be used through printk().
It can unintentionally expose security sensitive, raw pointer values.

Use regular pointer formatting instead.

Link: https://lore.kernel.org/lkml/20250113171731-dc10e3c1-da64-4af0-b767-7c7070468023@linutronix.de/
Signed-off-by: Thomas Weißschuh 
Signed-off-by: Thomas Bogendoerfer

of/fdt: add dt_phys arg to early_init_dt_scan and early_init_dt_verify

2024-10-29T20:32:45+00:00

 __pa() is only intended to be used for linear map addresses and using
it for initial_boot_params which is in fixmap for arm64 will give an
incorrect value. Hence save the physical address when it is known at
boot time when calling early_init_dt_scan for arm64 and use it at kexec
time instead of converting the virtual address using __pa().

Note that arm64 doesn't need the FDT region reserved in the DT as the
kernel explicitly reserves the passed in FDT. Therefore, only a debug
warning is fixed with this change.

Reported-by: Breno Leitao 
Suggested-by: Mark Rutland 
Signed-off-by: Usama Arif 
Fixes: ac10be5cdbfa ("arm64: Use common of_kexec_alloc_and_setup_fdt()")
Link: https://lore.kernel.org/r/20241023171426.452688-1-usamaarif642@gmail.com
Signed-off-by: Rob Herring (Arm)

MIPS: Fix typos

2024-01-08T09:39:12+00:00

Fix typos, most reported by "codespell arch/mips".  Only touches comments,
no code changes.

Signed-off-by: Bjorn Helgaas 
Cc: linux-mips@vger.kernel.org
Reviewed-by: Randy Dunlap 
Signed-off-by: Thomas Bogendoerfer

MIPS: move from strlcpy with unused retval to strscpy

2022-09-12T13:34:04+00:00

Follow the advice of the below link and prefer 'strscpy' in this
subsystem. Conversion is 1:1 because the return value is not used.
Generated by a coccinelle script.

Link: https://lore.kernel.org/r/CAHk-=wgfRnXz0W3D37d01q3JFkr_i_uTL=V6A6G1oUZcprmknw@mail.gmail.com/
Signed-off-by: Wolfram Sang 
Signed-off-by: Thomas Bogendoerfer

kernel.h: split out panic and oops helpers

2021-07-01T18:06:04+00:00

kernel.h is being used as a dump for all kinds of stuff for a long time.
Here is the attempt to start cleaning it up by splitting out panic and
oops helpers.

There are several purposes of doing this:
- dropping dependency in bug.h
- dropping a loop by moving out panic_notifier.h
- unload kernel.h from something which has its own domain

At the same time convert users tree-wide to use new headers, although for
the time being include new header back to kernel.h to avoid twisted
indirected includes for existing users.

[akpm@linux-foundation.org: thread_info.h needs limits.h]
[andriy.shevchenko@linux.intel.com: ia64 fix]
  Link: https://lkml.kernel.org/r/20210520130557.55277-1-andriy.shevchenko@linux.intel.com

Link: https://lkml.kernel.org/r/20210511074137.33666-1-andriy.shevchenko@linux.intel.com
Signed-off-by: Andy Shevchenko 
Reviewed-by: Bjorn Andersson 
Co-developed-by: Andrew Morton 
Acked-by: Mike Rapoport 
Acked-by: Corey Minyard 
Acked-by: Christian Brauner 
Acked-by: Arnd Bergmann 
Acked-by: Kees Cook 
Acked-by: Wei Liu 
Acked-by: Rasmus Villemoes 
Signed-off-by: Andrew Morton 
Acked-by: Sebastian Reichel 
Acked-by: Luis Chamberlain 
Acked-by: Stephen Boyd 
Acked-by: Thomas Bogendoerfer 
Acked-by: Helge Deller  # parisc
Signed-off-by: Linus Torvalds

Merge tag 'mips_5.12' of git://git.kernel.org/pub/scm/linux/kernel/git/mips/linux

2021-02-21T21:18:26+00:00

Pull MIPS updates from Thomas Bogendoerfer:

 - added support for Nintendo N64

 - added support for Realtek RTL83XX SoCs

 - kaslr support for Loongson64

 - first steps to get rid of set_fs()

 - DMA runtime coherent/non-coherent selection cleanup

 - cleanups and fixes

* tag 'mips_5.12' of git://git.kernel.org/pub/scm/linux/kernel/git/mips/linux: (98 commits)
  Revert "MIPS: Add basic support for ptrace single step"
  vmlinux.lds.h: catch more UBSAN symbols into .data
  MIPS: kernel: Drop kgdb_call_nmi_hook
  MAINTAINERS: Add git tree for KVM/mips
  MIPS: Use common way to parse elfcorehdr
  MIPS: Simplify EVA cache handling
  Revert "MIPS: kernel: {ftrace,kgdb}: Set correct address limit for cache flushes"
  MIPS: remove CONFIG_DMA_PERDEV_COHERENT
  MIPS: remove CONFIG_DMA_MAYBE_COHERENT
  driver core: lift dma_default_coherent into common code
  MIPS: refactor the runtime coherent vs noncoherent DMA indicators
  MIPS/alchemy: factor out the DMA coherent setup
  MIPS/malta: simplify plat_setup_iocoherency
  MIPS: Add basic support for ptrace single step
  MAINTAINERS: replace non-matching patterns for loongson{2,3}
  MIPS: Make check condition for SDBBP consistent with EJTAG spec
  mips: Replace lkml.org links with lore
  Revert "MIPS: microMIPS: Fix the judgment of mm_jr16_op and mm_jalr_op"
  MIPS: crash_dump.c: Simplify copy_oldmem_page()
  Revert "mips: Manually call fdt_init_reserved_mem() method"
  ...

MIPS: relocatable: Use __kaslr_offset in show_kernel_relocation

2021-02-09T09:56:04+00:00

The type of the VMLINUX_LOAD_ADDRESS macro is the (unsigned long long)
in 32bits kernel but (unsigned long) in the 64-bit kernel. Although there
is no error here, avoid using it to calculate kaslr_offset.

Signed-off-by: Jinyang He 
Signed-off-by: Thomas Bogendoerfer

MIPS: relocatable: Provide kaslr_offset() to get the kernel offset

2021-02-09T09:54:29+00:00

Provide kaslr_offset() to get the kernel offset when KASLR is enabled.
Error may occur before update_kaslr_offset(), so put it at the end of
the offset branch.

Fixes: a307a4ce9ecd ("MIPS: Loongson64: Add KASLR support")
Reported-by: kernel test robot 
Signed-off-by: Jinyang He 
Signed-off-by: Thomas Bogendoerfer

MIPS: relocatable: optimize the relocation process

2021-01-18T14:55:29+00:00

For now, vmlinux relocation functions for relocatable kernel are
implemented as an array of handlers of a particular type.

Convert that array into a single switch-case function to:
 - remove unused arguments;
 - change the return type of simple handlers to void;
 - remove the array and don't use any data at all;
 - avoid using indirect calls;
 - allow the compiler to inline and greatly optimize
   the relocation function[s];

and also mark do_relocations() and show_kernel_relocation() static
as they aren't used anywhere else.

The result on MIPS32 R2 with GCC 10.2 -O2 is:

scripts/bloat-o-meter -c arch/mips/kernel/__relocate.o arch/mips/kernel/relocate.o
add/remove: 0/6 grow/shrink: 1/0 up/down: 356/-640 (-284)
Function                                     old     new   delta
relocate_kernel                              852    1208    +356
apply_r_mips_32_rel                           20       -     -20
apply_r_mips_hi16_rel                         40       -     -40
apply_r_mips_64_rel                           44       -     -44
apply_r_mips_26_rel                          144       -    -144
show_kernel_relocation                       164       -    -164
do_relocations                               228       -    -228
Total: Before=1780, After=1496, chg -15.96%
add/remove: 0/1 grow/shrink: 0/0 up/down: 0/-76 (-76)
Data                                         old     new   delta
reloc_handlers_rel                            76       -     -76
Total: Before=92, After=16, chg -82.61%
add/remove: 0/0 grow/shrink: 0/0 up/down: 0/0 (0)
RO Data                                      old     new   delta
Total: Before=0, After=0, chg +0.00%

All functions were collapsed into the main one, relocate_kernel().

Signed-off-by: Alexander Lobakin 
Signed-off-by: Thomas Bogendoerfer