diff options
| author | Maciej W. Rozycki | 2018-05-15 23:04:44 +0100 |
|---|---|---|
| committer | James Hogan | 2018-05-24 13:45:13 +0100 |
| commit | 28e4213dd331e944e7fca1954a946829162ed9d4 (patch) | |
| tree | a6cedeaf5a7619682f4bc1449bf72249b5d3e30d /arch | |
| parent | 32795631e67e16141aa5e065c28ba03bf17abb90 (diff) | |
MIPS: prctl: Disallow FRE without FR with PR_SET_FP_MODE requests
Having PR_FP_MODE_FRE (i.e. Config5.FRE) set without PR_FP_MODE_FR (i.e.
Status.FR) is not supported as the lone purpose of Config5.FRE is to
emulate Status.FR=0 handling on FPU hardware that has Status.FR=1
hardwired[1][2]. Also we do not handle this case elsewhere, and assume
throughout our code that TIF_HYBRID_FPREGS and TIF_32BIT_FPREGS cannot
be set both at once for a task, leading to inconsistent behaviour if
this does happen.
Return unsuccessfully then from prctl(2) PR_SET_FP_MODE calls requesting
PR_FP_MODE_FRE to be set with PR_FP_MODE_FR clear. This corresponds to
modes allowed by `mips_set_personality_fp'.
References:
[1] "MIPS Architecture For Programmers, Vol. III: MIPS32 / microMIPS32
Privileged Resource Architecture", Imagination Technologies,
Document Number: MD00090, Revision 6.02, July 10, 2015, Table 9.69
"Config5 Register Field Descriptions", p. 262
[2] "MIPS Architecture For Programmers, Volume III: MIPS64 / microMIPS64
Privileged Resource Architecture", Imagination Technologies,
Document Number: MD00091, Revision 6.03, December 22, 2015, Table
9.72 "Config5 Register Field Descriptions", p. 288
Fixes: 9791554b45a2 ("MIPS,prctl: add PR_[GS]ET_FP_MODE prctl options for MIPS")
Signed-off-by: Maciej W. Rozycki <macro@mips.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Cc: <stable@vger.kernel.org> # 4.0+
Patchwork: https://patchwork.linux-mips.org/patch/19327/
Signed-off-by: James Hogan <jhogan@kernel.org>
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/mips/kernel/process.c | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/arch/mips/kernel/process.c b/arch/mips/kernel/process.c index b9e9bf628849..3775a8d694fb 100644 --- a/arch/mips/kernel/process.c +++ b/arch/mips/kernel/process.c @@ -721,6 +721,10 @@ int mips_set_process_fp_mode(struct task_struct *task, unsigned int value) if (value & ~known_bits) return -EOPNOTSUPP; + /* Setting FRE without FR is not supported. */ + if ((value & (PR_FP_MODE_FR | PR_FP_MODE_FRE)) == PR_FP_MODE_FRE) + return -EOPNOTSUPP; + /* Avoid inadvertently triggering emulation */ if ((value & PR_FP_MODE_FR) && raw_cpu_has_fpu && !(raw_current_cpu_data.fpu_id & MIPS_FPIR_F64)) |