linux.git/arch/powerpc/lib, branch v6.4-rc2

powerpc/64: vmlinux support building with PCREL addresing

2023-04-20T02:59:21+00:00

PC-Relative or PCREL addressing is an extension to the ELF ABI which
uses Power ISA v3.1 PC-relative instructions to calculate addresses,
rather than the traditional TOC scheme.

Add an option to build vmlinux using pcrel addressing. Modules continue
to use TOC addressing.

- TOC address helpers and r2 are poisoned with -1 when running vmlinux.
  r2 could be used for something useful once things are ironed out.

- Assembly must call C functions with @notoc annotation, or the linker
  complains aobut a missing nop after the call. This is done with the
  CFUNC macro introduced earlier.

- Boot: with the exception of prom_init, the execution branches to the
  kernel virtual address early in boot, before any addresses are
  generated, which ensures 34-bit pcrel addressing does not miss the
  high PAGE_OFFSET bits. TOC relative addressing has a similar
  requirement. prom_init does not go to the virtual address and its
  addresses should not carry over to the post-prom kernel.

- Ftrace trampolines are converted from TOC addressing to pcrel
  addressing, including module ftrace trampolines that currently use the
  kernel TOC to find ftrace target functions.

- BPF function prologue and function calling generation are converted
  from TOC to pcrel.

- copypage_64.S has an interesting problem, prefixed instructions have
  alignment restrictions so the linker can add padding, which makes the
  assembler treat the difference between two local labels as
  non-constant even if alignment is arranged so padding is not required.
  This may need toolchain help to solve nicely, for now move the prefix
  instruction out of the alternate patch section to work around it.

This reduces kernel text size by about 6%.

Signed-off-by: Nicholas Piggin 
Signed-off-by: Michael Ellerman 
Link: https://msgid.link/20230408021752.862660-6-npiggin@gmail.com

powerpc: add CFUNC assembly label annotation

2023-04-20T02:54:24+00:00

This macro is to be used in assembly where C functions are called.
pcrel addressing mode requires branches to functions with a
localentry value of 1 to have either a trailing nop or @notoc.
This macro permits the latter without changing callers.

Signed-off-by: Nicholas Piggin 
[mpe: Add dummy definitions to fix selftests build]
Signed-off-by: Michael Ellerman 
Link: https://msgid.link/20230408021752.862660-5-npiggin@gmail.com

powerpc: Remove memcpy_page_flushcache()

2023-03-29T12:53:02+00:00

Commit 21b56c847753 ("iov_iter: get rid of separate bvec and xarray
callbacks") removed the calls to memcpy_page_flushcache().

Remove the unnecessary memcpy_page_flushcache() call.

Signed-off-by: Ira Weiny 
Signed-off-by: Michael Ellerman 
Link: https://msgid.link/20221230-kmap-x86-v1-2-15f1ecccab50@intel.com

powerpc/kcsan: Add exclusions from instrumentation

2023-02-10T11:19:56+00:00

Exclude various incompatible compilation units from KCSAN
instrumentation.

Signed-off-by: Rohan McLure 
Signed-off-by: Michael Ellerman 
Link: https://lore.kernel.org/r/20230206021801.105268-2-rmclure@linux.ibm.com

powerpc/code-patching: Fix oops with DEBUG_VM enabled

2022-12-16T12:59:43+00:00

Nathan reported that the new per-cpu mm patching oopses if DEBUG_VM is
enabled:

  ------------[ cut here ]------------
  kernel BUG at arch/powerpc/mm/pgtable.c:333!
  Oops: Exception in kernel mode, sig: 5 [#1]
  LE PAGE_SIZE=64K MMU=Radix SMP NR_CPUS=2048 NUMA PowerNV
  Modules linked in:
  CPU: 0 PID: 1 Comm: swapper/0 Not tainted 6.1.0-rc2+ #1
  Hardware name: IBM PowerNV (emulated by qemu) POWER9 0x4e1200 opal:v7.0 PowerNV
  ...
  NIP assert_pte_locked+0x180/0x1a0
  LR  assert_pte_locked+0x170/0x1a0
  Call Trace:
    0x60000000 (unreliable)
    patch_instruction+0x618/0x6d0
    arch_prepare_kprobe+0xfc/0x2d0
    register_kprobe+0x520/0x7c0
    arch_init_kprobes+0x28/0x3c
    init_kprobes+0x108/0x184
    do_one_initcall+0x60/0x2e0
    kernel_init_freeable+0x1f0/0x3e0
    kernel_init+0x34/0x1d0
    ret_from_kernel_thread+0x5c/0x64

It's caused by the assert_spin_locked() failing in assert_pte_locked().
The assert fails because the PTE was unlocked in text_area_cpu_up_mm(),
and never relocked.

The PTE page shouldn't be freed, the patching_mm is only used for
patching on this CPU, only that single PTE is ever mapped, and it's only
unmapped at CPU offline.

In fact assert_pte_locked() has a special case to ignore init_mm
entirely, and the patching_mm is more-or-less like init_mm, so possibly
the check could be skipped for patching_mm too.

But for now be conservative, and use the proper PTE accessors at
patching time, so that the PTE lock is held while the PTE is used. That
also avoids the warning in assert_pte_locked().

With that it's no longer necessary to save the PTE in
cpu_patching_context for the mm_patch_enabled() case.

Fixes: c28c15b6d28a ("powerpc/code-patching: Use temporary mm for Radix MMU")
Reported-by: Nathan Chancellor 
Signed-off-by: Michael Ellerman 
Link: https://lore.kernel.org/r/20221216125913.990972-1-mpe@ellerman.id.au

powerpc/qspinlock: Fix 32-bit build

2022-12-12T01:34:52+00:00

Some 32-bit configurations don't pull in the spin_begin/end/relax
definitions. Fix is to restore a lost include.

Reported-by: kernel test robot 
Fixes: 84990b169557 ("powerpc/qspinlock: add mcs queueing for contended waiters")
Signed-off-by: Nicholas Piggin 
Signed-off-by: Michael Ellerman 
Link: https://lore.kernel.org/oe-kbuild-all/202212050224.i7uh9fOh-lkp@intel.com
Link: https://lore.kernel.org/r/20221208123225.1566113-1-npiggin@gmail.com

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/feature-fixups: Do not patch init section 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.

In the same spirit as jump_label with its jump_label_can_update()
function, add is_fixup_addr_valid() function to skip patching on
freed init section.

Signed-off-by: Christophe Leroy 
Signed-off-by: Michael Ellerman 
Link: https://lore.kernel.org/r/8e9311fc1b057e4e6a2a3a0701ebcc74b787affe.1669969781.git.christophe.leroy@csgroup.eu

powerpc/feature-fixups: Refactor other fixups patching

2022-12-02T10:59:56+00:00

Several fonctions have the same loop for patching instructions.

Introduce function do_patch_fixups() to refactor those loops.

Signed-off-by: Christophe Leroy 
Signed-off-by: Michael Ellerman 
Link: https://lore.kernel.org/r/58ab36949c18f94d466fc98d6c085783b0cd474f.1669969781.git.christophe.leroy@csgroup.eu

powerpc/feature-fixups: Refactor entry fixups patching

2022-12-02T10:59:56+00:00

Several fonctions have the same loop for patching instructions.

Introduce function do_patch_entry_fixups() to refactor those loops.

Signed-off-by: Christophe Leroy 
Signed-off-by: Michael Ellerman 
Link: https://lore.kernel.org/r/79eeff7b20a98f7136da5f79b1f7c436928f27f3.1669969781.git.christophe.leroy@csgroup.eu