diff options
| author | Alan Kao <alankao@andestech.com> | 2018-10-09 10:18:34 +0800 |
|---|---|---|
| committer | Palmer Dabbelt <palmer@sifive.com> | 2018-10-22 17:02:23 -0700 |
| commit | 9411ec60c23d868124d9c1b1d491937aebe07afa (patch) | |
| tree | b099a760ac5b284dd79281ded728e35ec30d2e77 /arch/riscv/kernel | |
| parent | 9671f7061433e2c58b9894093eada1898595b85d (diff) | |
| download | linux-rt-9411ec60c23d868124d9c1b1d491937aebe07afa.tar.gz | |
Auto-detect whether a FPU exists
We expect that a kernel with CONFIG_FPU=y can still support no-FPU
machines. To do so, the kernel should first examine the existence of a
FPU, then do nothing if a FPU does exist; otherwise, it should
disable/bypass all FPU-related functions.
In this patch, a new global variable, has_fpu, is created and determined
when parsing the hardware capability from device tree during booting.
This variable is used in those FPU-related functions.
Signed-off-by: Alan Kao <alankao@andestech.com>
Cc: Greentime Hu <greentime@andestech.com>
Cc: Vincent Chen <vincentc@andestech.com>
Cc: Zong Li <zong@andestech.com>
Cc: Nick Hu <nickhu@andestech.com>
Signed-off-by: Palmer Dabbelt <palmer@sifive.com>
Diffstat (limited to 'arch/riscv/kernel')
| -rw-r--r-- | arch/riscv/kernel/cpufeature.c | 8 | ||||
| -rw-r--r-- | arch/riscv/kernel/process.c | 4 | ||||
| -rw-r--r-- | arch/riscv/kernel/signal.c | 6 |
3 files changed, 15 insertions, 3 deletions
diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c index 17011a870044..46942e635266 100644 --- a/arch/riscv/kernel/cpufeature.c +++ b/arch/riscv/kernel/cpufeature.c @@ -22,6 +22,9 @@ #include <asm/hwcap.h> unsigned long elf_hwcap __read_mostly; +#ifdef CONFIG_FPU +bool has_fpu __read_mostly; +#endif void riscv_fill_hwcap(void) { @@ -58,4 +61,9 @@ void riscv_fill_hwcap(void) elf_hwcap |= isa2hwcap[(unsigned char)(isa[i])]; pr_info("elf_hwcap is 0x%lx", elf_hwcap); + +#ifdef CONFIG_FPU + if (elf_hwcap & (COMPAT_HWCAP_ISA_F | COMPAT_HWCAP_ISA_D)) + has_fpu = true; +#endif } diff --git a/arch/riscv/kernel/process.c b/arch/riscv/kernel/process.c index 07d515655aa9..bef19993ea92 100644 --- a/arch/riscv/kernel/process.c +++ b/arch/riscv/kernel/process.c @@ -76,7 +76,9 @@ void show_regs(struct pt_regs *regs) void start_thread(struct pt_regs *regs, unsigned long pc, unsigned long sp) { - regs->sstatus = DEFAULT_SSTATUS; + regs->sstatus = SR_SPIE; + if (has_fpu) + regs->sstatus |= SR_FS_INITIAL; regs->sepc = pc; regs->sp = sp; set_fs(USER_DS); diff --git a/arch/riscv/kernel/signal.c b/arch/riscv/kernel/signal.c index 2450b824d799..f9b5e7e352ef 100644 --- a/arch/riscv/kernel/signal.c +++ b/arch/riscv/kernel/signal.c @@ -98,7 +98,8 @@ static long restore_sigcontext(struct pt_regs *regs, /* sc_regs is structured the same as the start of pt_regs */ err = __copy_from_user(regs, &sc->sc_regs, sizeof(sc->sc_regs)); /* Restore the floating-point state. */ - err |= restore_fp_state(regs, &sc->sc_fpregs); + if (has_fpu) + err |= restore_fp_state(regs, &sc->sc_fpregs); return err; } @@ -150,7 +151,8 @@ static long setup_sigcontext(struct rt_sigframe __user *frame, /* sc_regs is structured the same as the start of pt_regs */ err = __copy_to_user(&sc->sc_regs, regs, sizeof(sc->sc_regs)); /* Save the floating-point state. */ - err |= save_fp_state(regs, &sc->sc_fpregs); + if (has_fpu) + err |= save_fp_state(regs, &sc->sc_fpregs); return err; } |