WSL2-Linux-Kernel/arch/mips/math-emu
Paul Burton 1975ed43ce
MIPS: Ensure emulated FP sets PF_USED_MATH
Emulated floating point instructions don't ensure that the PF_USED_MATH
flag is set for the task. This results in a couple of inconsistencies:

  - ptrace will return the default initial state of FP registers rather
    than the values actually stored in struct thread_struct, hiding
    state that has been updated by emulated floating point instructions.

  - If a task migrates to a CPU with an FPU after having emulated
    floating point instructions then its floating point register state
    will be reset to the default ~0 bit pattern, losing state from the
    emulated instructions.

Fix this by calling init_fp_ctx() from fpu_emulator_cop1Handler() to
consistently initialize FP state if it was previously uninitialized,
setting the PF_USED_MATH flag in the process.

All callers of fpu_emulator_cop1Handler() either call lose_fpu(1) before
it in order to save any live FPU registers to struct thread_struct, or
in the case of do_cpu() already know that the task does not own an FPU
so lose_fpu(1) would be a no-op. Since we know that saving FP context
will be unnecessary in the case where FP context was just initialized we
move this call into fpu_emulator_cop1Handler() too, providing
consistency & avoiding needless duplication.

Calls to own_fpu(1) are common after return from
fpu_emulator_cop1Handler() too, but this would not be a no-op in the
do_cpu() case so these are left as-is. A potential future improvement
could be to have fpu_emulator_cop1Handler() restore FPU state
automatically only if it saved it, though this may not be optimal if
some callers are better off without their current calls to own_fpu(1).
One potential example of this could be mipsr2_decoder() which as-is
could end up saving & restoring FP context repeatedly & unnecessarily if
emulating multiple FP instructions.

Signed-off-by: Paul Burton <paul.burton@mips.com>
Patchwork: https://patchwork.linux-mips.org/patch/21003/
Cc: linux-mips@linux-mips.org
2018-11-09 10:23:14 -08:00
..
Makefile License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
cp1emu.c MIPS: Ensure emulated FP sets PF_USED_MATH 2018-11-09 10:23:14 -08:00
dp_2008class.c MIPS: math-emu: Add support for the MIPS R6 CLASS FPU instruction 2015-09-03 12:08:14 +02:00
dp_add.c MIPS: math-emu: Mark fall throughs in switch statements with a comment 2017-12-12 17:20:20 +01:00
dp_cmp.c MIPS: math-emu: Remove redundant code from NaN comparison 2015-04-08 01:09:38 +02:00
dp_div.c MIPS: math-emu: Mark fall throughs in switch statements with a comment 2017-12-12 17:20:20 +01:00
dp_fint.c MIPS: math-emu: Cleanup coding style. 2014-05-23 15:11:15 +02:00
dp_flong.c MIPS: math-emu: Cleanup coding style. 2014-05-23 15:11:15 +02:00
dp_fmax.c MIPS: math-emu: Mark fall throughs in switch statements with a comment 2017-12-12 17:20:20 +01:00
dp_fmin.c MIPS: math-emu: Mark fall throughs in switch statements with a comment 2017-12-12 17:20:20 +01:00
dp_fsp.c MIPS: math-emu: Reinstate sNaN quieting handlers 2015-04-08 01:09:31 +02:00
dp_maddf.c MIPS: math-emu: Mark fall throughs in switch statements with a comment 2017-12-12 17:20:20 +01:00
dp_mul.c MIPS: math-emu: Mark fall throughs in switch statements with a comment 2017-12-12 17:20:20 +01:00
dp_rint.c MIPS: math-emu: RINT.<D|S>: Fix several problems by reimplementation 2017-08-29 15:21:56 +02:00
dp_simple.c MIPS: math-emu: Add IEEE Std 754-2008 ABS.fmt and NEG.fmt emulation 2016-01-20 00:39:20 +01:00
dp_sqrt.c MIPS: math-emu: Mark fall throughs in switch statements with a comment 2017-12-12 17:20:20 +01:00
dp_sub.c MIPS: math-emu: Mark fall throughs in switch statements with a comment 2017-12-12 17:20:20 +01:00
dp_tint.c MIPS: math-emu: Add IEEE Std 754-2008 NaN encoding emulation 2016-01-20 00:39:20 +01:00
dp_tlong.c MIPS: math-emu: Add IEEE Std 754-2008 NaN encoding emulation 2016-01-20 00:39:20 +01:00
dsemul.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
ieee754.c MIPS: math-emu: Add IEEE Std 754-2008 NaN encoding emulation 2016-01-20 00:39:20 +01:00
ieee754.h MIPS: math-emu: Use preferred flavor of unsigned integer declarations 2017-11-07 18:33:16 +00:00
ieee754d.c MIPS: math-emu: Cleanup coding style. 2014-05-23 15:11:15 +02:00
ieee754dp.c MIPS: math-emu: Always propagate sNaN payload in quieting 2016-05-13 14:02:11 +02:00
ieee754dp.h MIPS: math-emu: Avoid definition duplication for macro DPXMULT() 2017-12-12 17:20:19 +01:00
ieee754int.h MIPS: math-emu: Use preferred flavor of unsigned integer declarations 2017-11-07 18:33:16 +00:00
ieee754sp.c MIPS: math-emu: Use preferred flavor of unsigned integer declarations 2017-11-07 18:33:16 +00:00
ieee754sp.h MIPS: math-emu: Use preferred flavor of unsigned integer declarations 2017-11-07 18:33:16 +00:00
me-debugfs.c MIPS: math-emu: Change to use DEFINE_SHOW_ATTRIBUTE macro 2018-11-05 10:13:21 -08:00
sp_2008class.c MIPS: math-emu: Add support for the MIPS R6 CLASS FPU instruction 2015-09-03 12:08:14 +02:00
sp_add.c MIPS: math-emu: Mark fall throughs in switch statements with a comment 2017-12-12 17:20:20 +01:00
sp_cmp.c MIPS: math-emu: Remove redundant code from NaN comparison 2015-04-08 01:09:38 +02:00
sp_div.c MIPS: math-emu: Mark fall throughs in switch statements with a comment 2017-12-12 17:20:20 +01:00
sp_fdp.c MIPS: math-emu: Mark fall throughs in switch statements with a comment 2017-12-12 17:20:20 +01:00
sp_fint.c MIPS: math-emu: Use preferred flavor of unsigned integer declarations 2017-11-07 18:33:16 +00:00
sp_flong.c MIPS: math-emu: Cleanup coding style. 2014-05-23 15:11:15 +02:00
sp_fmax.c MIPS: math-emu: Mark fall throughs in switch statements with a comment 2017-12-12 17:20:20 +01:00
sp_fmin.c MIPS: math-emu: Mark fall throughs in switch statements with a comment 2017-12-12 17:20:20 +01:00
sp_maddf.c MIPS: math-emu: Mark fall throughs in switch statements with a comment 2017-12-12 17:20:20 +01:00
sp_mul.c MIPS: math-emu: Mark fall throughs in switch statements with a comment 2017-12-12 17:20:20 +01:00
sp_rint.c MIPS: math-emu: RINT.<D|S>: Fix several problems by reimplementation 2017-08-29 15:21:56 +02:00
sp_simple.c MIPS: math-emu: Add IEEE Std 754-2008 ABS.fmt and NEG.fmt emulation 2016-01-20 00:39:20 +01:00
sp_sqrt.c MIPS: math-emu: Avoid multiple assignment 2017-12-12 17:20:20 +01:00
sp_sub.c MIPS: math-emu: Mark fall throughs in switch statements with a comment 2017-12-12 17:20:20 +01:00
sp_tint.c MIPS: math-emu: Add IEEE Std 754-2008 NaN encoding emulation 2016-01-20 00:39:20 +01:00
sp_tlong.c MIPS: math-emu: Remove an unnecessary header inclusion 2017-12-12 17:20:19 +01:00