From 597ce1723e0fa0bdbe2ae4c94f18da6e29b92635 Mon Sep 17 00:00:00 2001 From: Paul Burton Date: Fri, 22 Nov 2013 13:12:07 +0000 Subject: 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 Cc: linux-mips@linux-mips.org Cc: Paul Burton Patchwork: https://patchwork.linux-mips.org/patch/6154/ Signed-off-by: Ralf Baechle --- arch/mips/kernel/process.c | 3 --- 1 file changed, 3 deletions(-) (limited to 'arch/mips/kernel/process.c') diff --git a/arch/mips/kernel/process.c b/arch/mips/kernel/process.c index ddc76103e78c..747a6cfbb709 100644 --- a/arch/mips/kernel/process.c +++ b/arch/mips/kernel/process.c @@ -60,9 +60,6 @@ void start_thread(struct pt_regs * regs, unsigned long pc, unsigned long sp) /* New thread loses kernel privileges. */ status = regs->cp0_status & ~(ST0_CU0|ST0_CU1|ST0_FR|KU_MASK); -#ifdef CONFIG_64BIT - status |= test_thread_flag(TIF_32BIT_REGS) ? 0 : ST0_FR; -#endif status |= KU_USER; regs->cp0_status = status; clear_used_math(); -- cgit v1.2.3