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1708644f19
Prevents crashes when IRQs arrive when the current kernel stack context already contains deeply nested function calls, e.g. when stacking lots of network devices on top of each other Signed-off-by: Felix Fietkau <nbd@nbd.name>
107 lines
3.5 KiB
Diff
107 lines
3.5 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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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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@@ -2725,6 +2725,20 @@ 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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@@ -285,7 +285,7 @@ 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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@@ -223,8 +223,10 @@ 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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@@ -66,6 +67,21 @@ 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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+ *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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int process_fpemu_return(int sig, void __user *fault_addr,
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unsigned long fcr31);
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int mm_isBranchInstr(struct pt_regs *regs, struct mm_decoded_insn dec_insn,
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