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105 lines
3.4 KiB
105 lines
3.4 KiB
From: Manuel Lauss <manuel.lauss@gmail.com>
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Subject: [RFC PATCH v4 2/2] MIPS: make FPU emulator optional
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Date: Mon, 7 Apr 2014 12:57:04 +0200
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Message-Id: <1396868224-252888-2-git-send-email-manuel.lauss@gmail.com>
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This small patch makes the MIPS FPU emulator optional. The kernel
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kills float-users on systems without a hardware FPU by sending a SIGILL.
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Disabling the emulator shrinks vmlinux by about 54kBytes (32bit,
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optimizing for size).
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Signed-off-by: Manuel Lauss <manuel.lauss@gmail.com>
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---
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v4: rediffed because of patch 1/2, should now work with micromips as well
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v3: updated patch description with size savings.
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v2: incorporated changes suggested by Jonas Gorski
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force the fpu emulator on for micromips: relocating the parts
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of the mmips code in the emulator to other areas would be a
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much larger change; I went the cheap route instead with this.
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arch/mips/Kbuild | 2 +-
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arch/mips/Kconfig | 14 ++++++++++++++
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arch/mips/include/asm/fpu.h | 5 +++--
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arch/mips/include/asm/fpu_emulator.h | 15 +++++++++++++++
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4 files changed, 33 insertions(+), 3 deletions(-)
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--- a/arch/mips/Kconfig
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+++ b/arch/mips/Kconfig
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@@ -2498,6 +2498,20 @@ config MIPS_O32_FP64_SUPPORT
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If unsure, say N.
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+config MIPS_FPU_EMULATOR
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+ bool "MIPS FPU Emulator"
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+ default y
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+ help
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+ This option lets you disable the built-in MIPS FPU (Coprocessor 1)
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+ emulator, which handles floating-point instructions on processors
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+ without a hardware FPU. It is generally a good idea to keep the
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+ emulator built-in, unless you are perfectly sure you have a
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+ complete soft-float environment. With the emulator disabled, all
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+ users of float operations will be killed with an illegal instr-
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+ uction exception.
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+
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+ Say Y, please.
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+
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config USE_OF
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bool
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select OF
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--- a/arch/mips/Makefile
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+++ b/arch/mips/Makefile
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@@ -275,7 +275,7 @@ OBJCOPYFLAGS += --remove-section=.regin
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head-y := arch/mips/kernel/head.o
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libs-y += arch/mips/lib/
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-libs-y += arch/mips/math-emu/
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+libs-$(CONFIG_MIPS_FPU_EMULATOR) += arch/mips/math-emu/
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# See arch/mips/Kbuild for content of core part of the kernel
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core-y += arch/mips/
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--- a/arch/mips/include/asm/fpu.h
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+++ b/arch/mips/include/asm/fpu.h
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@@ -169,8 +169,10 @@ static inline int init_fpu(void)
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ret = __own_fpu();
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if (!ret)
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_init_fpu();
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- } else
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+ } else if (IS_ENABLED(CONFIG_MIPS_FPU_EMULATOR))
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fpu_emulator_init_fpu();
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+ else
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+ ret = SIGILL;
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return ret;
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}
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--- a/arch/mips/include/asm/fpu_emulator.h
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+++ b/arch/mips/include/asm/fpu_emulator.h
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@@ -30,6 +30,7 @@
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#include <asm/local.h>
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#include <asm/processor.h>
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+#ifdef CONFIG_MIPS_FPU_EMULATOR
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#ifdef CONFIG_DEBUG_FS
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struct mips_fpu_emulator_stats {
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@@ -65,6 +66,20 @@ extern int do_dsemulret(struct pt_regs *
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extern int fpu_emulator_cop1Handler(struct pt_regs *xcp,
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struct mips_fpu_struct *ctx, int has_fpu,
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void *__user *fault_addr);
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+#else /* no CONFIG_MIPS_FPU_EMULATOR */
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+static inline int do_dsemulret(struct pt_regs *xcp)
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+{
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+ return 0; /* 0 means error, should never get here anyway */
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+}
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+
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+static inline int fpu_emulator_cop1Handler(struct pt_regs *xcp,
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+ struct mips_fpu_struct *ctx, int has_fpu,
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+ void *__user *fault_addr)
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+{
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+ return SIGILL; /* we don't speak MIPS FPU */
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+}
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+#endif /* CONFIG_MIPS_FPU_EMULATOR */
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+
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int process_fpemu_return(int sig, void __user *fault_addr);
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int mm_isBranchInstr(struct pt_regs *regs, struct mm_decoded_insn dec_insn,
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unsigned long *contpc);
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