diff options
| author | Paul Burton <paul.burton@imgtec.com> | 2013-11-22 13:12:07 +0000 |
|---|---|---|
| committer | Ralf Baechle <ralf@linux-mips.org> | 2014-01-13 23:40:56 +0100 |
| commit | 597ce1723e0fa0bdbe2ae4c94f18da6e29b92635 (patch) | |
| tree | 21f67268915b8457dd305c6bcf7ac905772fd0ee /arch/mips/math-emu | |
| parent | 56a22d21bf9744315f56b2bbd6416170f27b7765 (diff) | |
MIPS: Support for 64-bit FP with O32 binaries
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>
Diffstat (limited to 'arch/mips/math-emu')
| -rw-r--r-- | arch/mips/math-emu/cp1emu.c | 10 | ||||
| -rw-r--r-- | arch/mips/math-emu/kernel_linkage.c | 6 |
2 files changed, 9 insertions, 7 deletions
diff --git a/arch/mips/math-emu/cp1emu.c b/arch/mips/math-emu/cp1emu.c index 0e47ae2aa96b..506925b2c3f3 100644 --- a/arch/mips/math-emu/cp1emu.c +++ b/arch/mips/math-emu/cp1emu.c @@ -859,20 +859,20 @@ static int isBranchInstr(struct pt_regs *regs, struct mm_decoded_insn dec_insn, * In the Linux kernel, we support selection of FPR format on the * basis of the Status.FR bit. If an FPU is not present, the FR bit * is hardwired to zero, which would imply a 32-bit FPU even for - * 64-bit CPUs so we rather look at TIF_32BIT_REGS. + * 64-bit CPUs so we rather look at TIF_32BIT_FPREGS. * FPU emu is slow and bulky and optimizing this function offers fairly * sizeable benefits so we try to be clever and make this function return * a constant whenever possible, that is on 64-bit kernels without O32 - * compatibility enabled and on 32-bit kernels. + * compatibility enabled and on 32-bit without 64-bit FPU support. */ static inline int cop1_64bit(struct pt_regs *xcp) { #if defined(CONFIG_64BIT) && !defined(CONFIG_MIPS32_O32) return 1; -#elif defined(CONFIG_64BIT) && defined(CONFIG_MIPS32_O32) - return !test_thread_flag(TIF_32BIT_REGS); -#else +#elif defined(CONFIG_32BIT) && !defined(CONFIG_MIPS_O32_FP64_SUPPORT) return 0; +#else + return !test_thread_flag(TIF_32BIT_FPREGS); #endif } diff --git a/arch/mips/math-emu/kernel_linkage.c b/arch/mips/math-emu/kernel_linkage.c index 1c586575fe17..3aeae07ed5b8 100644 --- a/arch/mips/math-emu/kernel_linkage.c +++ b/arch/mips/math-emu/kernel_linkage.c @@ -89,8 +89,9 @@ int fpu_emulator_save_context32(struct sigcontext32 __user *sc) { int i; int err = 0; + int inc = test_thread_flag(TIF_32BIT_FPREGS) ? 2 : 1; - for (i = 0; i < 32; i+=2) { + for (i = 0; i < 32; i += inc) { err |= __put_user(current->thread.fpu.fpr[i], &sc->sc_fpregs[i]); } @@ -103,8 +104,9 @@ int fpu_emulator_restore_context32(struct sigcontext32 __user *sc) { int i; int err = 0; + int inc = test_thread_flag(TIF_32BIT_FPREGS) ? 2 : 1; - for (i = 0; i < 32; i+=2) { + for (i = 0; i < 32; i += inc) { err |= __get_user(current->thread.fpu.fpr[i], &sc->sc_fpregs[i]); } |