Makes floating point support a selectable kernel option. Disabling
this option will make the kernel 50kB lighter and kill all float
uses with an illegal instruction exception.
Signed-off-by: Manuel Lauss <manuel.lauss@xxxxxxxxx>
---
v5: now disable float support completely to avoid sudden program crashes
on buggy fpus when the fpu emulator cannot take over (suggested by
Paul Burton).
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 | 11 +++++++++++
arch/mips/include/asm/fpu.h | 20 +++++++++++---------
arch/mips/include/asm/fpu_emulator.h | 15 +++++++++++++++
4 files changed, 38 insertions(+), 10 deletions(-)
diff --git a/arch/mips/Kbuild b/arch/mips/Kbuild
index d2cfe45..730e0a7 100644
--- a/arch/mips/Kbuild
+++ b/arch/mips/Kbuild
@@ -16,7 +16,7 @@ obj- := $(platform-)
obj-y += kernel/
obj-y += mm/
-obj-y += math-emu/
+obj-$(CONFIG_MIPS_FPU_SUPPORT) += math-emu/
ifdef CONFIG_KVM
obj-y += kvm/
diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
index 9b53358..c8040db 100644
--- a/arch/mips/Kconfig
+++ b/arch/mips/Kconfig
@@ -2482,6 +2482,17 @@ config MIPS_O32_FP64_SUPPORT
If unsure, say N.
+config MIPS_FPU_SUPPORT
+ bool "MIPS FPU Support"
+ default y
+ help
+ Support for floating point registers and FP-hardware, and also
+ the in-kernel FPU emulator. Disabling this option will result
+ in all uses of floating point hardware to be killed with an
+ illegal instruction exception, and about a 50kB smaller kernel.
+
+ Say Y.
+
config USE_OF
bool
select OF
diff --git a/arch/mips/include/asm/fpu.h b/arch/mips/include/asm/fpu.h
index 4d86b72..f0ea5ae 100644
--- a/arch/mips/include/asm/fpu.h
+++ b/arch/mips/include/asm/fpu.h
@@ -155,16 +155,18 @@ static inline int init_fpu(void)
{
int ret = 0;
- preempt_disable();
- if (cpu_has_fpu) {
- ret = __own_fpu();
- if (!ret)
- _init_fpu();
- } else {
- fpu_emulator_init_fpu();
- }
+ if (IS_ENABLED(CONFIG_MIPS_FPU_SUPPORT)) {
+ preempt_disable();
+ if (cpu_has_fpu) {
+ ret = __own_fpu();
+ if (!ret)
+ _init_fpu();
+ } else
+ fpu_emulator_init_fpu();
+ preempt_enable();
+ } else
+ ret = SIGILL;
- preempt_enable();
return ret;
}
diff --git a/arch/mips/include/asm/fpu_emulator.h b/arch/mips/include/asm/fpu_emulator.h
index 283e6f3..552a054 100644
--- a/arch/mips/include/asm/fpu_emulator.h
+++ b/arch/mips/include/asm/fpu_emulator.h
@@ -27,6 +27,7 @@
#include <asm/inst.h>
#include <asm/local.h>
+#ifdef CONFIG_MIPS_FPU_SUPPORT
#ifdef CONFIG_DEBUG_FS
struct mips_fpu_emulator_stats {
@@ -57,6 +58,20 @@ extern int do_dsemulret(struct pt_regs *xcp);
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_SUPPORT */
+static inline int do_dsemulret(struct pt_regs *xcp)
+{
+ return 0; /* 0 means error, should never get here anyway */
+}
+
+static inline int fpu_emulator_cop1Handler(struct pt_regs *xcp,
+ struct mips_fpu_struct *ctx, int has_fpu,
+ void *__user *fault_addr)
+{
+ return SIGILL; /* we don't speak MIPS FPU */
+}
+#endif /* CONFIG_MIPS_FPU_SUPPORT */
+
int process_fpemu_return(int sig, void __user *fault_addr);
/*
--
1.9.1
