powerpc/signal: Don't manage floating point regs when no FPU

There is no point in copying floating point regs when there
is no FPU and MATH_EMULATION is not selected.

Create a new CONFIG_PPC_FPU_REGS bool that is selected by
CONFIG_MATH_EMULATION and CONFIG_PPC_FPU, and use it to
opt out everything related to fp_state in thread_struct.

The asm const used only by fpu.S are opted out with CONFIG_PPC_FPU
as fpu.S build is conditionnal to CONFIG_PPC_FPU.

The following app spends approx 8.1 seconds system time on an 8xx
without the patch, and 7.0 seconds with the patch (13.5% reduction).

On an 832x, it spends approx 2.6 seconds system time without
the patch and 2.1 seconds with the patch (19% reduction).

	void sigusr1(int sig) { }

	int main(int argc, char **argv)
	{
		int i = 100000;

		signal(SIGUSR1, sigusr1);
		for (;i--;)
			raise(SIGUSR1);
		exit(0);
	}

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/7569070083e6cd5b279bb5023da601aba3c06f3c.1597770847.git.christophe.leroy@csgroup.eu

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index aad8532..8d12da2 100644 (file)
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -422,6 +422,7 @@ config HUGETLB_PAGE_SIZE_VARIABLE
 config MATH_EMULATION
        bool "Math emulation"
        depends on 4xx || PPC_8xx || PPC_MPC832x || BOOKE
+       select PPC_FPU_REGS
        help
          Some PowerPC chips designed for embedded applications do not have
          a floating-point unit and therefore do not implement the

diff --git a/arch/powerpc/include/asm/processor.h b/arch/powerpc/include/asm/processor.h
index 333e3b6..0792530 100644 (file)
--- a/arch/powerpc/include/asm/processor.h
+++ b/arch/powerpc/include/asm/processor.h
@@ -164,8 +164,10 @@ struct thread_struct {
 #endif
        /* Debug Registers */
        struct debug_reg debug;
+#ifdef CONFIG_PPC_FPU_REGS
        struct thread_fp_state  fp_state;
        struct thread_fp_state  *fp_save_area;
+#endif
        int             fpexc_mode;     /* floating-point exception mode */
        unsigned int    align_ctl;      /* alignment handling control */
 #ifdef CONFIG_HAVE_HW_BREAKPOINT

diff --git a/arch/powerpc/kernel/asm-offsets.c b/arch/powerpc/kernel/asm-offsets.c
index a2dcb8e..81d6849 100644 (file)
--- a/arch/powerpc/kernel/asm-offsets.c
+++ b/arch/powerpc/kernel/asm-offsets.c
@@ -110,9 +110,11 @@ int main(void)
 #ifdef CONFIG_BOOKE
        OFFSET(THREAD_NORMSAVES, thread_struct, normsave[0]);
 #endif
+#ifdef CONFIG_PPC_FPU
        OFFSET(THREAD_FPEXC_MODE, thread_struct, fpexc_mode);
        OFFSET(THREAD_FPSTATE, thread_struct, fp_state.fpr);
        OFFSET(THREAD_FPSAVEAREA, thread_struct, fp_save_area);
+#endif
        OFFSET(FPSTATE_FPSCR, thread_fp_state, fpscr);
        OFFSET(THREAD_LOAD_FP, thread_struct, load_fp);
 #ifdef CONFIG_ALTIVEC

diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
index d421a2c..ba2c987 100644 (file)
--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c
@@ -1730,7 +1730,9 @@ int copy_thread(unsigned long clone_flags, unsigned long usp,
                p->thread.ptrace_bps[i] = NULL;
 #endif
 
+#ifdef CONFIG_PPC_FPU_REGS
        p->thread.fp_save_area = NULL;
+#endif
 #ifdef CONFIG_ALTIVEC
        p->thread.vr_save_area = NULL;
 #endif
@@ -1855,8 +1857,10 @@ void start_thread(struct pt_regs *regs, unsigned long start, unsigned long sp)
 #endif
        current->thread.load_slb = 0;
        current->thread.load_fp = 0;
+#ifdef CONFIG_PPC_FPU_REGS
        memset(&current->thread.fp_state, 0, sizeof(current->thread.fp_state));
        current->thread.fp_save_area = NULL;
+#endif
 #ifdef CONFIG_ALTIVEC
        memset(&current->thread.vr_state, 0, sizeof(current->thread.vr_state));
        current->thread.vr_state.vscr.u[3] = 0x00010000; /* Java mode disabled */

diff --git a/arch/powerpc/kernel/ptrace/Makefile b/arch/powerpc/kernel/ptrace/Makefile
index 77abd1a..8ebc11d 100644 (file)
--- a/arch/powerpc/kernel/ptrace/Makefile
+++ b/arch/powerpc/kernel/ptrace/Makefile
@@ -6,11 +6,11 @@
 CFLAGS_ptrace-view.o           += -DUTS_MACHINE='"$(UTS_MACHINE)"'
 
 obj-y                          += ptrace.o ptrace-view.o
-obj-y                          += ptrace-fpu.o
+obj-$(CONFIG_PPC_FPU_REGS)     += ptrace-fpu.o
 obj-$(CONFIG_COMPAT)           += ptrace32.o
 obj-$(CONFIG_VSX)              += ptrace-vsx.o
 ifneq ($(CONFIG_VSX),y)
-obj-y                          += ptrace-novsx.o
+obj-$(CONFIG_PPC_FPU_REGS)     += ptrace-novsx.o
 endif
 obj-$(CONFIG_ALTIVEC)          += ptrace-altivec.o
 obj-$(CONFIG_SPE)              += ptrace-spe.o

diff --git a/arch/powerpc/kernel/ptrace/ptrace-decl.h b/arch/powerpc/kernel/ptrace/ptrace-decl.h
index eafe5f0..3487f2c 100644 (file)
--- a/arch/powerpc/kernel/ptrace/ptrace-decl.h
+++ b/arch/powerpc/kernel/ptrace/ptrace-decl.h
@@ -165,8 +165,22 @@ int ptrace_put_reg(struct task_struct *task, int regno, unsigned long data);
 extern const struct user_regset_view user_ppc_native_view;
 
 /* ptrace-fpu */
+#ifdef CONFIG_PPC_FPU_REGS
 int ptrace_get_fpr(struct task_struct *child, int index, unsigned long *data);
 int ptrace_put_fpr(struct task_struct *child, int index, unsigned long data);
+#else
+static inline int
+ptrace_get_fpr(struct task_struct *child, int index, unsigned long *data)
+{
+       return -EIO;
+}
+
+static inline int
+ptrace_put_fpr(struct task_struct *child, int index, unsigned long data)
+{
+       return -EIO;
+}
+#endif
 
 /* ptrace-(no)adv */
 void ppc_gethwdinfo(struct ppc_debug_info *dbginfo);

diff --git a/arch/powerpc/kernel/ptrace/ptrace-view.c b/arch/powerpc/kernel/ptrace/ptrace-view.c
index 142d583..00a765f 100644 (file)
--- a/arch/powerpc/kernel/ptrace/ptrace-view.c
+++ b/arch/powerpc/kernel/ptrace/ptrace-view.c
@@ -521,11 +521,13 @@ static const struct user_regset native_regsets[] = {
                .size = sizeof(long), .align = sizeof(long),
                .regset_get = gpr_get, .set = gpr_set
        },
+#ifdef CONFIG_PPC_FPU_REGS
        [REGSET_FPR] = {
                .core_note_type = NT_PRFPREG, .n = ELF_NFPREG,
                .size = sizeof(double), .align = sizeof(double),
                .regset_get = fpr_get, .set = fpr_set
        },
+#endif
 #ifdef CONFIG_ALTIVEC
        [REGSET_VMX] = {
                .core_note_type = NT_PPC_VMX, .n = 34,

diff --git a/arch/powerpc/kernel/signal.h b/arch/powerpc/kernel/signal.h
index 4626d39..6c2a33a 100644 (file)
--- a/arch/powerpc/kernel/signal.h
+++ b/arch/powerpc/kernel/signal.h
@@ -34,7 +34,7 @@ unsigned long copy_fpr_to_user(void __user *to, struct task_struct *task);
 unsigned long copy_ckfpr_to_user(void __user *to, struct task_struct *task);
 unsigned long copy_fpr_from_user(struct task_struct *task, void __user *from);
 unsigned long copy_ckfpr_from_user(struct task_struct *task, void __user *from);
-#else
+#elif defined(CONFIG_PPC_FPU_REGS)
 static inline unsigned long
 copy_fpr_to_user(void __user *to, struct task_struct *task)
 {
@@ -63,6 +63,18 @@ copy_ckfpr_from_user(struct task_struct *task, void __user *from)
                                ELF_NFPREG * sizeof(double));
 }
 #endif /* CONFIG_PPC_TRANSACTIONAL_MEM */
+#else
+static inline unsigned long
+copy_fpr_to_user(void __user *to, struct task_struct *task)
+{
+       return 0;
+}
+
+static inline unsigned long
+copy_fpr_from_user(struct task_struct *task, void __user *from)
+{
+       return 0;
+}
 #endif
 
 #ifdef CONFIG_PPC64

diff --git a/arch/powerpc/kernel/signal_32.c b/arch/powerpc/kernel/signal_32.c
index 96950f1..7b29170 100644 (file)
--- a/arch/powerpc/kernel/signal_32.c
+++ b/arch/powerpc/kernel/signal_32.c
@@ -814,7 +814,9 @@ int handle_rt_signal32(struct ksignal *ksig, sigset_t *oldset,
        }
        regs->link = tramp;
 
+#ifdef CONFIG_PPC_FPU_REGS
        tsk->thread.fp_state.fpscr = 0; /* turn off all fp exceptions */
+#endif
 
        /* create a stack frame for the caller of the handler */
        newsp = ((unsigned long)rt_sf) - (__SIGNAL_FRAMESIZE + 16);
@@ -1271,7 +1273,9 @@ int handle_signal32(struct ksignal *ksig, sigset_t *oldset,
 
        regs->link = tramp;
 
+#ifdef CONFIG_PPC_FPU_REGS
        tsk->thread.fp_state.fpscr = 0; /* turn off all fp exceptions */
+#endif
 
        /* create a stack frame for the caller of the handler */
        newsp = ((unsigned long)frame) - __SIGNAL_FRAMESIZE;

diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/traps.c
index 5006dcb..5b39baa 100644 (file)
--- a/arch/powerpc/kernel/traps.c
+++ b/arch/powerpc/kernel/traps.c
@@ -1190,7 +1190,9 @@ static void parse_fpe(struct pt_regs *regs)
 
        flush_fp_to_thread(current);
 
+#ifdef CONFIG_PPC_FPU_REGS
        code = __parse_fpscr(current->thread.fp_state.fpscr);
+#endif
 
        _exception(SIGFPE, regs, code, regs->nip);
 }

diff --git a/arch/powerpc/platforms/Kconfig.cputype b/arch/powerpc/platforms/Kconfig.cputype
index c194c4a..3e36e37 100644 (file)
--- a/arch/powerpc/platforms/Kconfig.cputype
+++ b/arch/powerpc/platforms/Kconfig.cputype
@@ -218,9 +218,13 @@ config PPC_E500MC
          such as e5500/e6500), and must be disabled for running on
          e500v1 or e500v2.
 
+config PPC_FPU_REGS
+       bool
+
 config PPC_FPU
        bool
        default y if PPC64
+       select PPC_FPU_REGS
 
 config FSL_EMB_PERFMON
        bool "Freescale Embedded Perfmon"