linux.git/arch/riscv/kernel/patch.c, branch v5.19

riscv: patch_text: Fixup last cpu should be master

2022-04-22T15:29:24+00:00

These patch_text implementations are using stop_machine_cpuslocked
infrastructure with atomic cpu_count. The original idea: When the
master CPU patch_text, the others should wait for it. But current
implementation is using the first CPU as master, which couldn't
guarantee the remaining CPUs are waiting. This patch changes the
last CPU as the master to solve the potential risk.

Signed-off-by: Guo Ren 
Signed-off-by: Guo Ren 
Acked-by: Palmer Dabbelt 
Reviewed-by: Masami Hiramatsu 
Fixes: 043cb41a85de ("riscv: introduce interfaces to patch kernel code")
Cc: stable@vger.kernel.org
Signed-off-by: Palmer Dabbelt

riscv: Fixup compile error BUILD_BUG_ON failed

2021-01-14T23:09:01+00:00

Unfortunately, the current code couldn't be compiled:

  CC      arch/riscv/kernel/patch.o
In file included from ./include/linux/kernel.h:11,
                 from ./include/linux/list.h:9,
                 from ./include/linux/preempt.h:11,
                 from ./include/linux/spinlock.h:51,
                 from arch/riscv/kernel/patch.c:6:
In function ‘fix_to_virt’,
    inlined from ‘patch_map’ at arch/riscv/kernel/patch.c:37:17:
./include/linux/compiler.h:392:38: error: call to ‘__compiletime_assert_205’ declared with attribute error: BUILD_BUG_ON failed: idx >= __end_of_fixed_addresses
  _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
                                      ^
./include/linux/compiler.h:373:4: note: in definition of macro ‘__compiletime_assert’
    prefix ## suffix();    \
    ^~~~~~
./include/linux/compiler.h:392:2: note: in expansion of macro ‘_compiletime_assert’
  _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
  ^~~~~~~~~~~~~~~~~~~
./include/linux/build_bug.h:39:37: note: in expansion of macro ‘compiletime_assert’
 #define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg)
                                     ^~~~~~~~~~~~~~~~~~
./include/linux/build_bug.h:50:2: note: in expansion of macro ‘BUILD_BUG_ON_MSG’
  BUILD_BUG_ON_MSG(condition, "BUILD_BUG_ON failed: " #condition)
  ^~~~~~~~~~~~~~~~
./include/asm-generic/fixmap.h:32:2: note: in expansion of macro ‘BUILD_BUG_ON’
  BUILD_BUG_ON(idx >= __end_of_fixed_addresses);
  ^~~~~~~~~~~~

Because fix_to_virt(, idx) needs a const value, not a dynamic variable of
reg-a0 or BUILD_BUG_ON failed with "idx >= __end_of_fixed_addresses".

Signed-off-by: Guo Ren 
Reviewed-by: Masami Hiramatsu 
Reviewed-by: Pekka Enberg 
Signed-off-by: Palmer Dabbelt

maccess: rename probe_kernel_{read,write} to copy_{from,to}_kernel_nofault

2020-06-17T17:57:41+00:00

Better describe what these functions do.

Suggested-by: Linus Torvalds 
Signed-off-by: Christoph Hellwig 
Signed-off-by: Linus Torvalds

riscv: fix build warning of missing prototypes

2020-06-10T02:11:27+00:00

Add the missing header in file, it was lost in original implementation.

The warning message as follows:
 - no previous prototype for 'patch_text_nosync' [-Wmissing-prototypes]
 - no previous prototype for 'patch_text' [-Wmissing-prototypes]

Changed in v2:
 - Correct the typo of commit message.

Signed-off-by: Zong Li 
Reported-by: kbuild test robot 
Reviewed-by: Atish Patra 
Signed-off-by: Palmer Dabbelt

riscv: Use text_mutex instead of patch_lock

2020-05-18T18:38:16+00:00

We don't need the additional lock protection when patching the text.

There are two patching interfaces here:
 - patch_text: patch code and always synchronize with stop_machine()
 - patch_text_nosync: patch code without synchronization, it's caller's
                      responsibility to synchronize all CPUs if needed.

For the first one, stop_machine() is protected by its own mutex, and
also the irq is already disabled here.

For the second one, in risc-v real case now, it would be used to ftrace
patching the mcount function, since it already running under
kstop_machine(), no other thread will run, so we could use text_mutex
on ftrace side.

Signed-off-by: Zong Li 
Reviewed-by: Masami Hiramatsu 
Reviewed-by: Palmer Dabbelt 
Signed-off-by: Palmer Dabbelt

riscv: Use NOKPROBE_SYMBOL() instead of __krpobes annotation

2020-05-18T18:38:15+00:00

The __kprobes annotation is old style, so change it to NOKPROBE_SYMBOL().

Signed-off-by: Zong Li 
Reviewed-by: Masami Hiramatsu 
Reviewed-by: Palmer Dabbelt 
Signed-off-by: Palmer Dabbelt

riscv: Remove the 'riscv_' prefix of function name

2020-05-18T18:38:13+00:00

Refactor the function name by removing the 'riscv_' prefix, it would be
better unless it could mix up with arch-independent functions.

Signed-off-by: Zong Li 
Reviewed-by: Masami Hiramatsu 
Reviewed-by: Palmer Dabbelt 
Signed-off-by: Palmer Dabbelt

riscv: introduce interfaces to patch kernel code

2020-03-26T16:24:52+00:00

On strict kernel memory permission, we couldn't patch code without
writable permission. Preserve two holes in fixmap area, so we can map
the kernel code temporarily to fixmap area, then patch the instructions.

We need two pages here because we support the compressed instruction, so
the instruction might be align to 2 bytes. When patching the 32-bit
length instruction which is 2 bytes alignment, it will across two pages.

Introduce two interfaces to patch kernel code:
riscv_patch_text_nosync:
 - patch code without synchronization, it's caller's responsibility to
   synchronize all CPUs if needed.
riscv_patch_text:
 - patch code and always synchronize with stop_machine()

Signed-off-by: Zong Li 
Signed-off-by: Palmer Dabbelt