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138 lines
4.1 KiB
Diff
138 lines
4.1 KiB
Diff
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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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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@@ -2892,6 +2892,20 @@ 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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@@ -326,7 +326,7 @@ 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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@@ -230,8 +230,10 @@ static inline int init_fpu(void)
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/* Restore FRE */
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write_c0_config5(config5);
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enable_fpu_hazard();
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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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@@ -179,6 +180,16 @@ do { \
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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 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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+ *fault_addr = NULL;
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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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void force_fcr31_sig(unsigned long fcr31, void __user *fault_addr,
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struct task_struct *tsk);
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int process_fpemu_return(int sig, void __user *fault_addr,
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--- a/arch/mips/include/asm/dsemul.h
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+++ b/arch/mips/include/asm/dsemul.h
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@@ -41,6 +41,7 @@ struct task_struct;
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extern int mips_dsemul(struct pt_regs *regs, mips_instruction ir,
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unsigned long branch_pc, unsigned long cont_pc);
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+#ifdef CONFIG_MIPS_FPU_EMULATOR
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/**
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* do_dsemulret() - Return from a delay slot 'emulation' frame
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* @xcp: User thread register context.
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@@ -88,5 +89,27 @@ extern bool dsemul_thread_rollback(struc
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* before @mm is freed in order to avoid memory leaks.
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*/
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extern void dsemul_mm_cleanup(struct mm_struct *mm);
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+#else
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+static inline bool do_dsemulret(struct pt_regs *xcp)
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+{
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+ return false;
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+}
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+
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+static inline bool dsemul_thread_cleanup(struct task_struct *tsk)
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+{
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+ return false;
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+}
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+
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+static inline bool dsemul_thread_rollback(struct pt_regs *regs)
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+{
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+ return false;
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+}
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+
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+static inline void dsemul_mm_cleanup(struct mm_struct *mm)
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+{
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+
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+}
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+
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+#endif
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#endif /* __MIPS_ASM_DSEMUL_H__ */
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