linux.git/arch/x86/math-emu, branch master

x86/math-emu: Fix div_Xsig() prototype

2025-11-09T20:01:08+00:00

The third argument of div_Xsig() is the output of the division, but is marked
'const', which means the compiler is not expecting it to be updated and may
generate bad code around the call. clang-21 now warns about the pattern since
an uninitialized variable is passed into two 'const' arguments by reference:

  arch/x86/math-emu/poly_atan.c:93:28: error: variable 'argSignif' is uninitialized \
  when passed as a const pointer argument here [-Werror,-Wuninitialized-const-pointer]
     93 |         div_Xsig(&Numer, &Denom, &argSignif);
        |                                   ^~~~~~~~~
  arch/x86/math-emu/poly_l2.c:195:29: error: variable 'argSignif' is uninitialized \
  when passed as a const pointer argument here [-Werror,-Wuninitialized-const-pointer]
    195 |                 div_Xsig(&Numer, &Denom, &argSignif);
        |                                           ^~~~~~~~~

The implementation is in assembly, so the problem has gone unnoticed since the
code was added in the linux-1.1 days. Remove the 'const' marker here.

Fixes: e19a1bdb835c ("Import 1.1.38")
Signed-off-by: Arnd Bergmann 
Signed-off-by: Borislav Petkov (AMD) 
Link: https://patch.msgid.link/20250807205334.123231-1-arnd@kernel.org

x86/fpu: Convert task_struct::thread.fpu accesses to use x86_task_fpu()

2025-04-14T06:18:29+00:00

This will make the removal of the task_struct::thread.fpu array
easier.

No change in functionality - code generated before and after this
commit is identical on x86-defconfig:

  kepler:~/tip> diff -up vmlinux.before.asm vmlinux.after.asm
  kepler:~/tip>

Signed-off-by: Ingo Molnar 
Cc: Andy Lutomirski 
Cc: Brian Gerst 
Cc: Chang S. Bae 
Cc: H. Peter Anvin 
Cc: Linus Torvalds 
Cc: Oleg Nesterov 
Link: https://lore.kernel.org/r/20250409211127.3544993-3-mingo@kernel.org

x86/headers: Replace ASSEMBLY with ASSEMBLER in non-UAPI headers

2025-03-19T10:47:30+00:00

While the GCC and Clang compilers already define __ASSEMBLER__
automatically when compiling assembly code, __ASSEMBLY__ is a
macro that only gets defined by the Makefiles in the kernel.

This can be very confusing when switching between userspace
and kernelspace coding, or when dealing with UAPI headers that
rather should use __ASSEMBLER__ instead. So let's standardize on
the __ASSEMBLER__ macro that is provided by the compilers now.

This is mostly a mechanical patch (done with a simple "sed -i"
statement), with some manual tweaks in , 
and  that mentioned this macro in comments with some
missing underscores.

Signed-off-by: Thomas Huth 
Signed-off-by: Ingo Molnar 
Cc: Brian Gerst 
Cc: Juergen Gross 
Cc: H. Peter Anvin 
Cc: Kees Cook 
Cc: Linus Torvalds 
Link: https://lore.kernel.org/r/20250314071013.1575167-38-thuth@redhat.com

x86/math-emu: Fix function cast warnings

2024-04-08T14:06:22+00:00

clang-16 warns about casting function pointers with incompatible
prototypes. The x86 math-emu code does this in a number of places
to call some trivial functions that need no arguments:

  arch/x86/math-emu/fpu_etc.c:124:14: error: cast from 'void (*)(void)' to 'FUNC_ST0' \
    (aka 'void (*)(struct fpu__reg *, unsigned char)') converts to incompatible function \
    type [-Werror,-Wcast-function-type-strict]
    124 |         fchs, fabs, (FUNC_ST0) FPU_illegal, (FUNC_ST0) FPU_illegal,
        |                     ^~~~~~~~~~~~~~~~~~~~~~

  arch/x86/math-emu/fpu_trig.c:1634:19: error: cast from 'void (*)(void)' to 'FUNC_ST0' \
    (aka 'void (*)(struct fpu__reg *, unsigned char)') converts to incompatible function \
    type [-Werror,-Wcast-function-type-strict]
   1634 |         fxtract, fprem1, (FUNC_ST0) fdecstp, (FUNC_ST0) fincstp
        |                          ^~~~~~~~~~~~~~~~~~

  arch/x86/math-emu/reg_constant.c:112:53: error: cast from 'void (*)(void)' to 'FUNC_RC' \
  (aka 'void (*)(int)') converts to incompatible function \
  type [-Werror,-Wcast-function-type-strict]
    112 |         fld1, fldl2t, fldl2e, fldpi, fldlg2, fldln2, fldz, (FUNC_RC) FPU_illegal

Change the fdecstp() and fincstp() functions to actually have the correct
prototypes based on the caller, and add wrappers around FPU_illegal() for
adapting those.

Signed-off-by: Arnd Bergmann 
Signed-off-by: Borislav Petkov (AMD) 
Link: https://lore.kernel.org/lkml/20240213095631.454543-1-arnd@kernel.org

x86/fpu: Include asm/fpu/regset.h

2023-05-18T18:56:18+00:00

The fpregs_soft_set/fpregs_soft_get functions are declared in a
header that is not included in the file that defines them, causing
a W=1 warning:

/home/arnd/arm-soc/arch/x86/math-emu/fpu_entry.c:638:5: error: no previous prototype for 'fpregs_soft_set' [-Werror=missing-prototypes]
  638 | int fpregs_soft_set(struct task_struct *target,
      |     ^~~~~~~~~~~~~~~
/home/arnd/arm-soc/arch/x86/math-emu/fpu_entry.c:690:5: error: no previous prototype for 'fpregs_soft_get' [-Werror=missing-prototypes]
  690 | int fpregs_soft_get(struct task_struct *target,

Include the file here to avoid the warning.

Signed-off-by: Arnd Bergmann 
Signed-off-by: Dave Hansen 
Reviewed-by: Alexander Lobakin 
Link: https://lore.kernel.org/all/20230516193549.544673-7-arnd%40kernel.org

x86/32: Remove lazy GS macros

2022-04-14T12:09:43+00:00

GS is always a user segment now.

Signed-off-by: Brian Gerst 
Signed-off-by: Borislav Petkov 
Reviewed-by: Thomas Gleixner 
Acked-by: Andy Lutomirski 
Link: https://lore.kernel.org/r/20220325153953.162643-4-brgerst@gmail.com

x86: Prepare asm files for straight-line-speculation

2021-12-08T11:25:37+00:00

Replace all ret/retq instructions with RET in preparation of making
RET a macro. Since AS is case insensitive it's a big no-op without
RET defined.

  find arch/x86/ -name \*.S | while read file
  do
	sed -i 's/\/RET/' $file
  done

Signed-off-by: Peter Zijlstra (Intel) 
Signed-off-by: Borislav Petkov 
Link: https://lore.kernel.org/r/20211204134907.905503893@infradead.org

x86/math-emu: Convert to fpstate

2021-10-20T21:57:54+00:00

Convert math emulation code to the new register storage
mechanism in preparation for dynamically sized buffers.

No functional change.

Signed-off-by: Thomas Gleixner 
Signed-off-by: Borislav Petkov 
Link: https://lkml.kernel.org/r/20211013145322.711347464@linutronix.de

x86/fpu: Move fpstate functions to api.h

2021-10-20T13:27:28+00:00

Move function declarations which need to be globally available to api.h
where they belong.

Signed-off-by: Thomas Gleixner 
Signed-off-by: Borislav Petkov 
Link: https://lkml.kernel.org/r/20211015011539.792363754@linutronix.de

x86/math-emu: Rename frstor()

2021-06-23T16:16:33+00:00

This is in the way of renaming the low level hardware accessors to match
the instruction name. Prepend it with FPU_ which is consistent vs. the
rest of the emulation code.

No functional change.

  [ bp: Correct the Reported-by: ]

Reported-by: kernel test robot 
Signed-off-by: Thomas Gleixner 
Signed-off-by: Borislav Petkov 
Link: https://lkml.kernel.org/r/20210623121454.111665161@linutronix.de