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-rw-r--r--target/linux/generic/pending-4.9/304-mips_disable_fpu.patch137
1 files changed, 137 insertions, 0 deletions
diff --git a/target/linux/generic/pending-4.9/304-mips_disable_fpu.patch b/target/linux/generic/pending-4.9/304-mips_disable_fpu.patch
new file mode 100644
index 0000000000..aac9c79da8
--- /dev/null
+++ b/target/linux/generic/pending-4.9/304-mips_disable_fpu.patch
@@ -0,0 +1,137 @@
+From: Manuel Lauss <manuel.lauss@gmail.com>
+Subject: [RFC PATCH v4 2/2] MIPS: make FPU emulator optional
+
+This small patch makes the MIPS FPU emulator optional. The kernel
+kills float-users on systems without a hardware FPU by sending a SIGILL.
+
+Disabling the emulator shrinks vmlinux by about 54kBytes (32bit,
+optimizing for size).
+
+Signed-off-by: Manuel Lauss <manuel.lauss@gmail.com>
+---
+v4: rediffed because of patch 1/2, should now work with micromips as well
+v3: updated patch description with size savings.
+v2: incorporated changes suggested by Jonas Gorski
+ force the fpu emulator on for micromips: relocating the parts
+ of the mmips code in the emulator to other areas would be a
+ much larger change; I went the cheap route instead with this.
+
+ arch/mips/Kbuild | 2 +-
+ arch/mips/Kconfig | 14 ++++++++++++++
+ arch/mips/include/asm/fpu.h | 5 +++--
+ arch/mips/include/asm/fpu_emulator.h | 15 +++++++++++++++
+ 4 files changed, 33 insertions(+), 3 deletions(-)
+
+--- a/arch/mips/Kconfig
++++ b/arch/mips/Kconfig
+@@ -2892,6 +2892,20 @@ config MIPS_O32_FP64_SUPPORT
+
+ If unsure, say N.
+
++config MIPS_FPU_EMULATOR
++ bool "MIPS FPU Emulator"
++ default y
++ help
++ This option lets you disable the built-in MIPS FPU (Coprocessor 1)
++ emulator, which handles floating-point instructions on processors
++ without a hardware FPU. It is generally a good idea to keep the
++ emulator built-in, unless you are perfectly sure you have a
++ complete soft-float environment. With the emulator disabled, all
++ users of float operations will be killed with an illegal instr-
++ uction exception.
++
++ Say Y, please.
++
+ config USE_OF
+ bool
+ select OF
+--- a/arch/mips/Makefile
++++ b/arch/mips/Makefile
+@@ -287,7 +287,7 @@ OBJCOPYFLAGS += --remove-section=.regin
+ head-y := arch/mips/kernel/head.o
+
+ libs-y += arch/mips/lib/
+-libs-y += arch/mips/math-emu/
++libs-$(CONFIG_MIPS_FPU_EMULATOR) += arch/mips/math-emu/
+
+ # See arch/mips/Kbuild for content of core part of the kernel
+ core-y += arch/mips/
+--- a/arch/mips/include/asm/fpu.h
++++ b/arch/mips/include/asm/fpu.h
+@@ -227,8 +227,10 @@ static inline int init_fpu(void)
+ /* Restore FRE */
+ write_c0_config5(config5);
+ enable_fpu_hazard();
+- } else
++ } else if (IS_ENABLED(CONFIG_MIPS_FPU_EMULATOR))
+ fpu_emulator_init_fpu();
++ else
++ ret = SIGILL;
+
+ return ret;
+ }
+--- a/arch/mips/include/asm/fpu_emulator.h
++++ b/arch/mips/include/asm/fpu_emulator.h
+@@ -30,6 +30,7 @@
+ #include <asm/local.h>
+ #include <asm/processor.h>
+
++#ifdef CONFIG_MIPS_FPU_EMULATOR
+ #ifdef CONFIG_DEBUG_FS
+
+ struct mips_fpu_emulator_stats {
+@@ -63,6 +64,16 @@ do { \
+ extern int fpu_emulator_cop1Handler(struct pt_regs *xcp,
+ struct mips_fpu_struct *ctx, int has_fpu,
+ void *__user *fault_addr);
++#else /* no CONFIG_MIPS_FPU_EMULATOR */
++static inline int fpu_emulator_cop1Handler(struct pt_regs *xcp,
++ struct mips_fpu_struct *ctx, int has_fpu,
++ void *__user *fault_addr)
++{
++ *fault_addr = NULL;
++ return SIGILL; /* we don't speak MIPS FPU */
++}
++#endif /* CONFIG_MIPS_FPU_EMULATOR */
++
+ void force_fcr31_sig(unsigned long fcr31, void __user *fault_addr,
+ struct task_struct *tsk);
+ int process_fpemu_return(int sig, void __user *fault_addr,
+--- a/arch/mips/include/asm/dsemul.h
++++ b/arch/mips/include/asm/dsemul.h
+@@ -41,6 +41,7 @@ struct task_struct;
+ extern int mips_dsemul(struct pt_regs *regs, mips_instruction ir,
+ unsigned long branch_pc, unsigned long cont_pc);
+
++#ifdef CONFIG_MIPS_FPU_EMULATOR
+ /**
+ * do_dsemulret() - Return from a delay slot 'emulation' frame
+ * @xcp: User thread register context.
+@@ -88,5 +89,27 @@ extern bool dsemul_thread_rollback(struc
+ * before @mm is freed in order to avoid memory leaks.
+ */
+ extern void dsemul_mm_cleanup(struct mm_struct *mm);
++#else
++static inline bool do_dsemulret(struct pt_regs *xcp)
++{
++ return false;
++}
++
++static inline bool dsemul_thread_cleanup(struct task_struct *tsk)
++{
++ return false;
++}
++
++static inline bool dsemul_thread_rollback(struct pt_regs *regs)
++{
++ return false;
++}
++
++static inline void dsemul_mm_cleanup(struct mm_struct *mm)
++{
++
++}
++
++#endif
+
+ #endif /* __MIPS_ASM_DSEMUL_H__ */