linux.git/arch/riscv/kernel/patch.c, branch v6.9

riscv: Disable preemption when using patch_map()

2024-04-04T19:33:38+00:00

patch_map() uses fixmap mappings to circumvent the non-writability of
the kernel text mapping.

The __set_fixmap() function only flushes the current cpu tlb, it does
not emit an IPI so we must make sure that while we use a fixmap mapping,
the current task is not migrated on another cpu which could miss the
newly introduced fixmap mapping.

So in order to avoid any task migration, disable the preemption.

Reported-by: Andrea Parri 
Closes: https://lore.kernel.org/all/ZcS+GAaM25LXsBOl@andrea/
Reported-by: Andy Chiu 
Closes: https://lore.kernel.org/linux-riscv/CABgGipUMz3Sffu-CkmeUB1dKVwVQ73+7=sgC45-m0AE9RCjOZg@mail.gmail.com/
Fixes: cad539baa48f ("riscv: implement a memset like function for text")
Fixes: 0ff7c3b33127 ("riscv: Use text_mutex instead of patch_lock")
Co-developed-by: Andy Chiu 
Signed-off-by: Andy Chiu 
Signed-off-by: Alexandre Ghiti 
Acked-by: Puranjay Mohan 
Link: https://lore.kernel.org/r/20240326203017.310422-3-alexghiti@rivosinc.com
Signed-off-by: Palmer Dabbelt

riscv: Check if the code to patch lies in the exit section

2024-01-09T18:58:59+00:00

Otherwise we fall through to vmalloc_to_page() which panics since the
address does not lie in the vmalloc region.

Fixes: 043cb41a85de ("riscv: introduce interfaces to patch kernel code")
Signed-off-by: Alexandre Ghiti 
Reviewed-by: Charlie Jenkins 
Link: https://lore.kernel.org/r/20231214091926.203439-1-alexghiti@rivosinc.com
Signed-off-by: Palmer Dabbelt

riscv: implement a memset like function for text

2023-09-06T13:26:06+00:00

The BPF JIT needs to write invalid instructions to RX regions of memory to
invalidate removed BPF programs. This needs a function like memset() that
can work with RX memory.

Implement patch_text_set_nosync() which is similar to text_poke_set() of
x86.

Signed-off-by: Puranjay Mohan 
Reviewed-by: Pu Lehui 
Acked-by: Björn Töpel 
Tested-by: Björn Töpel 
Acked-by: Daniel Borkmann 
Link: https://lore.kernel.org/r/20230831131229.497941-4-puranjay12@gmail.com
Signed-off-by: Palmer Dabbelt

riscv: extend patch_text_nosync() for multiple pages

2023-09-06T13:26:05+00:00

The patch_insn_write() function currently doesn't work for multiple pages
of instructions, therefore patch_text_nosync() will fail with a page fault
if called with lengths spanning multiple pages.

This commit extends the patch_insn_write() function to support multiple
pages by copying at max 2 pages at a time in a loop. This implementation
is similar to text_poke_copy() function of x86.

Signed-off-by: Puranjay Mohan 
Reviewed-by: Pu Lehui 
Reviewed-by: Björn Töpel 
Tested-by: Björn Töpel 
Acked-by: Daniel Borkmann 
Link: https://lore.kernel.org/r/20230831131229.497941-3-puranjay12@gmail.com
Signed-off-by: Palmer Dabbelt

RISC-V: Don't check text_mutex during stop_machine

2023-03-09T22:58:51+00:00

We're currently using stop_machine() to update ftrace & kprobes, which
means that the thread that takes text_mutex during may not be the same
as the thread that eventually patches the code.  This isn't actually a
race because the lock is still held (preventing any other concurrent
accesses) and there is only one thread running during stop_machine(),
but it does trigger a lockdep failure.

This patch just elides the lockdep check during stop_machine.

Fixes: c15ac4fd60d5 ("riscv/ftrace: Add dynamic function tracer support")
Suggested-by: Steven Rostedt 
Reported-by: Changbin Du 
Signed-off-by: Palmer Dabbelt 
Signed-off-by: Conor Dooley 
Link: https://lore.kernel.org/r/20230303143754.4005217-1-conor.dooley@microchip.com
Signed-off-by: Palmer Dabbelt

riscv: Extend patch_text for multiple instructions

2023-02-17T20:45:30+00:00

Extend patch_text for multiple instructions. This is the preparaiton for
multiple instructions text patching in riscv BPF trampoline, and may be
useful for other scenario.

Signed-off-by: Pu Lehui 
Signed-off-by: Daniel Borkmann 
Tested-by: Björn Töpel 
Reviewed-by: Conor Dooley 
Acked-by: Björn Töpel 
Link: https://lore.kernel.org/bpf/20230215135205.1411105-2-pulehui@huaweicloud.com

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