linux-toradex.git/arch/mips/kernel/branch.c, branch v6.19

MIPS: kernel: include probes-common.h header in branch.c

2020-09-21T20:14:24+00:00

arch/mips/kernel/branch.c:876:5: error: no previous prototype for '__insn_is_compact_branch' [-Werror=missing-prototypes]

Signed-off-by: Pujin Shi 
Signed-off-by: Pujin Shi 
Signed-off-by: Thomas Bogendoerfer

MIPS: Use fallthrough for arch/mips

2020-05-07T09:55:47+00:00

Convert the various /* fallthrough */ comments to the pseudo-keyword
fallthrough;

Done via script:
https://lore.kernel.org/lkml/b56602fcf79f849e733e7b521bb0e17895d390fa.1582230379.git.joe@perches.com/

Signed-off-by: Liangliang Huang 
Reviewed-by: Huacai Chen 
Signed-off-by: Thomas Bogendoerfer

MIPS: Don't use bc_false uninitialized in __mm_isBranchInstr

2019-08-12T04:44:24+00:00

clang warns:

arch/mips/kernel/branch.c:148:8: error: variable 'bc_false' is used
uninitialized whenever switch case is taken
[-Werror,-Wsometimes-uninitialized]
                case mm_bc2t_op:
                     ^~~~~~~~~~
arch/mips/kernel/branch.c:157:8: note: uninitialized use occurs here
                        if (bc_false)
                            ^~~~~~~~
arch/mips/kernel/branch.c:149:8: error: variable 'bc_false' is used
uninitialized whenever switch case is taken
[-Werror,-Wsometimes-uninitialized]
                case mm_bc1t_op:
                     ^~~~~~~~~~
arch/mips/kernel/branch.c:157:8: note: uninitialized use occurs here
                        if (bc_false)
                            ^~~~~~~~
arch/mips/kernel/branch.c:142:4: note: variable 'bc_false' is declared
here
                        int bc_false = 0;
                        ^
2 errors generated.

When mm_bc1t_op and mm_bc2t_op are taken, the bc_false initialization
does not happen, which leads to a garbage value upon use, as illustrated
below with a small sample program.

$ mipsel-linux-gnu-gcc --version | head -n1
mipsel-linux-gnu-gcc (Debian 8.3.0-2) 8.3.0

$ clang --version | head -n1
ClangBuiltLinux clang version 9.0.0 (git://github.com/llvm/llvm-project
544315b4197034a3be8acd12cba56a75fb1f08dc) (based on LLVM 9.0.0svn)

$ cat test.c
 #include 

 static void switch_scoped(int opcode)
 {
	 switch (opcode) {
	 case 1:
	 case 2: {
		 int bc_false = 0;

		 bc_false = 4;
	 case 3:
	 case 4:
		 printf("\t* switch scoped bc_false = %d\n", bc_false);
	 }
	 }
 }

 static void function_scoped(int opcode)
 {
	 int bc_false = 0;

	 switch (opcode) {
	 case 1:
	 case 2: {
		 bc_false = 4;
	 case 3:
	 case 4:
		 printf("\t* function scoped bc_false = %d\n", bc_false);
	 }
	 }
 }

 int main(void)
 {
	 int opcode;

	 for (opcode = 1; opcode < 5; opcode++) {
		 printf("opcode = %d:\n", opcode);
		 switch_scoped(opcode);
		 function_scoped(opcode);
		 printf("\n");
	 }

	 return 0;
 }

$ mipsel-linux-gnu-gcc -std=gnu89 -static test.c && \
  qemu-mipsel a.out
opcode = 1:
        * switch scoped bc_false = 4
        * function scoped bc_false = 4

opcode = 2:
        * switch scoped bc_false = 4
        * function scoped bc_false = 4

opcode = 3:
        * switch scoped bc_false = 2147483004
        * function scoped bc_false = 0

opcode = 4:
        * switch scoped bc_false = 2147483004
        * function scoped bc_false = 0

$ clang -std=gnu89 --target=mipsel-linux-gnu -m32 -static test.c && \
  qemu-mipsel a.out
opcode = 1:
        * switch scoped bc_false = 4
        * function scoped bc_false = 4

opcode = 2:
        * switch scoped bc_false = 4
        * function scoped bc_false = 4

opcode = 3:
        * switch scoped bc_false = 2147483004
        * function scoped bc_false = 0

opcode = 4:
        * switch scoped bc_false = 2147483004
        * function scoped bc_false = 0

Move the definition up so that we get the right behavior and mark it
__maybe_unused as it will not be used when CONFIG_MIPS_FP_SUPPORT
isn't enabled.

Fixes: 6a1cc218b9cc ("MIPS: branch: Remove FP branch handling when CONFIG_MIPS_FP_SUPPORT=n")
Link: https://github.com/ClangBuiltLinux/linux/issues/603
Signed-off-by: Nathan Chancellor 
Signed-off-by: Paul Burton 
Cc: Ralf Baechle 
Cc: James Hogan 
Cc: Nick Desaulniers 
Cc: linux-mips@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: clang-built-linux@googlegroups.com

signal: Remove task parameter from force_sig

2019-05-27T14:36:28+00:00

All of the remaining callers pass current into force_sig so
remove the task parameter to make this obvious and to make
misuse more difficult in the future.

This also makes it clear force_sig passes current into force_sig_info.

Signed-off-by: "Eric W. Biederman"

mips: annotate implicit fall throughs

2018-12-03T21:42:38+00:00

There is a plan to build the kernel with -Wimplicit-fallthrough and
these places in the code produced warnings. Fix them up.

This patch produces no change in behaviour, but should be reviewed in
case these are actually bugs not intentional fallthoughs.

Signed-off-by: Mathieu Malaterre 
Signed-off-by: Paul Burton 
Cc: Kees Cook 
Cc: Ralf Baechle 
Cc: James Hogan 
Cc: linux-mips@vger.kernel.org
Cc: linux-kernel@vger.kernel.org

MIPS: branch: Remove FP branch handling when CONFIG_MIPS_FP_SUPPORT=n

2018-11-09T18:23:16+00:00

When CONFIG_MIPS_FP_SUPPORT=n we don't support floating point, so remove
the floating point branch support from __compute_return_epc_for_insn() &
__mm_isBranchInstr(). This code should never be needed & more
importantly relies upon FPU state in struct task_struct which will later
be removed.

Signed-off-by: Paul Burton 
Patchwork: https://patchwork.linux-mips.org/patch/21017/
Cc: linux-mips@linux-mips.org

MIPS: Simplify FP context initialization

2018-11-09T18:23:13+00:00

MIPS has up until now had 3 different ways for a task's floating point
context to be initialized:

  - If the task's first use of FP involves it gaining ownership of an
    FPU then _init_fpu() is used to initialize the FPU's registers such
    that they all contain ~0, and the FPU registers will be stored to
    struct thread_info later (eg. when context switching).

  - If the task first uses FP on a CPU without an associated FPU then
    fpu_emulator_init_fpu() initializes the task's floating point
    register state in struct thread_info such that all floating point
    register contain the bit pattern 0x7ff800007ff80000, different to
    the _init_fpu() behaviour.

  - If a task's floating point context is first accessed via ptrace then
    init_fp_ctx() initializes the floating point register state in
    struct thread_info to ~0, giving equivalent state to _init_fpu().

The _init_fpu() path has 2 separate implementations - one for r2k/r3k
style systems & one for r4k style systems. The _init_fpu() path also
requires that we be careful to clear & restore the value of the
Config5.FRE bit on modern systems in order to avoid inadvertently
triggering floating point exceptions.

None of this code is in a performance critical hot path - it runs only
the first time a task uses floating point. As such it doesn't seem to
warrant the complications of maintaining the _init_fpu() path.

Remove _init_fpu() & fpu_emulator_init_fpu(), instead using
init_fp_ctx() consistently to initialize floating point register state
in struct thread_info. Upon a task's first use of floating point this
will typically mean that we initialize state in memory & then load it
into FPU registers using _restore_fp() just as we would on a context
switch. For other paths such as __compute_return_epc_for_insn() or
mipsr2_decoder() this results in a significant simplification of the
work to be done.

Signed-off-by: Paul Burton 
Patchwork: https://patchwork.linux-mips.org/patch/21002/
Cc: linux-mips@linux-mips.org

MIPS: Use proper kernel-doc Return keyword

2018-01-18T22:29:02+00:00

For reference:
* https://www.kernel.org/doc/html/latest/doc-guide/kernel-doc.html#function-documentation

Fix non-fatal warning:

arch/mips/kernel/branch.c:418: warning: Excess function parameter 'returns' description in '__compute_return_epc_for_insn'

Signed-off-by: Mathieu Malaterre 
Cc: Ralf Baechle 
Cc: Randy Dunlap 
Cc: Maciej W. Rozycki 
Cc: Ingo Molnar 
Cc: Paul Burton 
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/18031/
[jhogan@kernel.org: Expand subject slightly]
Signed-off-by: James Hogan

MIPS: Use `pr_debug' for messages from `__compute_return_epc_for_insn'

2017-06-29T00:42:27+00:00

Reduce the log level for branch emulation error messages issued before
sending SIGILL by `__compute_return_epc_for_insn' as these are triggered
by user software and are not an event that would normally require any
attention.  The same signal sent from elsewhere does not actually leave
any trace in the kernel log at all.

Signed-off-by: Maciej W. Rozycki 
Cc: James Hogan 
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/16402/
Signed-off-by: Ralf Baechle

MIPS: Fix a typo: s/preset/present/ in r2-to-r6 emulation error message

2017-06-29T00:42:27+00:00

This is a user-visible message, so we want it to be spelled correctly.

Fixes: 5f9f41c474be ("MIPS: kernel: Prepare the JR instruction for emulation on MIPS R6")
Signed-off-by: Maciej W. Rozycki 
Cc: James Hogan 
Cc: linux-mips@linux-mips.org
Cc: stable@vger.kernel.org # 3.19+
Patchwork: https://patchwork.linux-mips.org/patch/16400/
Signed-off-by: Ralf Baechle