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MIPS: Support for 64-bit FP with O32 binaries

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CPUs implementing MIPS32 R2 may include a 64-bit FPU, just as MIPS64 CPUs
do. In order to preserve backwards compatibility a 64-bit FPU will act
like a 32-bit FPU (by accessing doubles from the least significant 32
bits of an even-odd pair of FP registers) when the Status.FR bit is
zero, again just like a mips64 CPU. The standard O32 ABI is defined
expecting a 32-bit FPU, however recent toolchains support use of a
64-bit FPU from an O32 MIPS32 executable. When an ELF executable is
built to use a 64-bit FPU a new flag (EF_MIPS_FP64) is set in the ELF
header.

With this patch the kernel will check the EF_MIPS_FP64 flag when
executing an O32 binary, and set Status.FR accordingly. The addition
of O32 64-bit FP support lessens the opportunity for optimisation in
the FPU emulator, so a CONFIG_MIPS_O32_FP64_SUPPORT Kconfig option is
introduced to allow this support to be disabled for those that don't
require it.

Inspired by an earlier patch by Leonid Yegoshin, but implemented more
cleanly & correctly.

Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Cc: linux-mips@linux-mips.org
Cc: Paul Burton <paul.burton@imgtec.com>
Patchwork: https://patchwork.linux-mips.org/patch/6154/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
This commit is contained in:
Paul Burton
2013-11-22 13:12:07 +00:00
committed by Ralf Baechle
parent 56a22d21bf
commit 597ce1723e
19 changed files with 449 additions and 236 deletions
Download Patch File Download Diff File Expand all files Collapse all files

10
arch/mips/kernel/traps.c
View File

@@ -1080,7 +1080,7 @@ asmlinkage void do_cpu(struct pt_regs *regs)
unsigned long old_epc, old31;
unsigned int opcode;
unsigned int cpid;
int status;
int status, err;
unsigned long __maybe_unused flags;
prev_state = exception_enter();
@@ -1153,19 +1153,19 @@ asmlinkage void do_cpu(struct pt_regs *regs)
case 1:
if (used_math()) /* Using the FPU again. */
own_fpu(1);
err = own_fpu(1);
else { /* First time FPU user. */
init_fpu();
err = init_fpu();
set_used_math();
}
if (!raw_cpu_has_fpu) {
if (!raw_cpu_has_fpu || err) {
int sig;
void __user *fault_addr = NULL;
sig = fpu_emulator_cop1Handler(regs,
&current->thread.fpu,
0, &fault_addr);
if (!process_fpemu_return(sig, fault_addr))
if (!process_fpemu_return(sig, fault_addr) && !err)
mt_ase_fp_affinity();
}