powerpc: Keep track of emulated instructions

If CONFIG_PPC_EMULATED_STATS is enabled, make available counters for the
various classes of emulated instructions under
/sys/kernel/debug/powerpc/emulated_instructions/ (assumed debugfs is mounted on
/sys/kernel/debug).  Optionally (controlled by
/sys/kernel/debug/powerpc/emulated_instructions/do_warn), rate-limited warnings
can be printed to the console when instructions are emulated.

Signed-off-by: Geert Uytterhoeven <Geert.Uytterhoeven@sonycom.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

1 files changed, 94 insertions, 2 deletions

diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/traps.c
index 678fbff0d206..6a5b2b731f43 100644
--- a/arch/powerpc/kernel/traps.c
+++ b/arch/powerpc/kernel/traps.c
@@ -33,7 +33,9 @@
 #include <linux/backlight.h>
 #include <linux/bug.h>
 #include <linux/kdebug.h>
+#include <linux/debugfs.h>
 
+#include <asm/emulated_ops.h>
 #include <asm/pgtable.h>
 #include <asm/uaccess.h>
 #include <asm/system.h>
@@ -757,36 +759,44 @@ static int emulate_instruction(struct pt_regs *regs)
 
 	/* Emulate the mfspr rD, PVR. */
 	if ((instword & PPC_INST_MFSPR_PVR_MASK) == PPC_INST_MFSPR_PVR) {
+		PPC_WARN_EMULATED(mfpvr);
 		rd = (instword >> 21) & 0x1f;
 		regs->gpr[rd] = mfspr(SPRN_PVR);
 		return 0;
 	}
 
 	/* Emulating the dcba insn is just a no-op.  */
-	if ((instword & PPC_INST_DCBA_MASK) == PPC_INST_DCBA)
+	if ((instword & PPC_INST_DCBA_MASK) == PPC_INST_DCBA) {
+		PPC_WARN_EMULATED(dcba);
 		return 0;
+	}
 
 	/* Emulate the mcrxr insn.  */
 	if ((instword & PPC_INST_MCRXR_MASK) == PPC_INST_MCRXR) {
 		int shift = (instword >> 21) & 0x1c;
 		unsigned long msk = 0xf0000000UL >> shift;
 
+		PPC_WARN_EMULATED(mcrxr);
 		regs->ccr = (regs->ccr & ~msk) | ((regs->xer >> shift) & msk);
 		regs->xer &= ~0xf0000000UL;
 		return 0;
 	}
 
 	/* Emulate load/store string insn. */
-	if ((instword & PPC_INST_STRING_GEN_MASK) == PPC_INST_STRING)
+	if ((instword & PPC_INST_STRING_GEN_MASK) == PPC_INST_STRING) {
+		PPC_WARN_EMULATED(string);
 		return emulate_string_inst(regs, instword);
+	}
 
 	/* Emulate the popcntb (Population Count Bytes) instruction. */
 	if ((instword & PPC_INST_POPCNTB_MASK) == PPC_INST_POPCNTB) {
+		PPC_WARN_EMULATED(popcntb);
 		return emulate_popcntb_inst(regs, instword);
 	}
 
 	/* Emulate isel (Integer Select) instruction */
 	if ((instword & PPC_INST_ISEL_MASK) == PPC_INST_ISEL) {
+		PPC_WARN_EMULATED(isel);
 		return emulate_isel(regs, instword);
 	}
 
@@ -984,6 +994,8 @@ void SoftwareEmulation(struct pt_regs *regs)
 
 #ifdef CONFIG_MATH_EMULATION
 	errcode = do_mathemu(regs);
+	if (errcode >= 0)
+		PPC_WARN_EMULATED(math);
 
 	switch (errcode) {
 	case 0:
@@ -1005,6 +1017,9 @@ void SoftwareEmulation(struct pt_regs *regs)
 
 #elif defined(CONFIG_8XX_MINIMAL_FPEMU)
 	errcode = Soft_emulate_8xx(regs);
+	if (errcode >= 0)
+		PPC_WARN_EMULATED(8xx);
+
 	switch (errcode) {
 	case 0:
 		emulate_single_step(regs);
@@ -1088,6 +1103,7 @@ void altivec_assist_exception(struct pt_regs *regs)
 
 	flush_altivec_to_thread(current);
 
+	PPC_WARN_EMULATED(altivec);
 	err = emulate_altivec(regs);
 	if (err == 0) {
 		regs->nip += 4;		/* skip emulated instruction */
@@ -1286,3 +1302,79 @@ void kernel_bad_stack(struct pt_regs *regs)
 void __init trap_init(void)
 {
 }
+
+
+#ifdef CONFIG_PPC_EMULATED_STATS
+
+#define WARN_EMULATED_SETUP(type)	.type = { .name = #type }
+
+struct ppc_emulated ppc_emulated = {
+#ifdef CONFIG_ALTIVEC
+	WARN_EMULATED_SETUP(altivec),
+#endif
+	WARN_EMULATED_SETUP(dcba),
+	WARN_EMULATED_SETUP(dcbz),
+	WARN_EMULATED_SETUP(fp_pair),
+	WARN_EMULATED_SETUP(isel),
+	WARN_EMULATED_SETUP(mcrxr),
+	WARN_EMULATED_SETUP(mfpvr),
+	WARN_EMULATED_SETUP(multiple),
+	WARN_EMULATED_SETUP(popcntb),
+	WARN_EMULATED_SETUP(spe),
+	WARN_EMULATED_SETUP(string),
+	WARN_EMULATED_SETUP(unaligned),
+#ifdef CONFIG_MATH_EMULATION
+	WARN_EMULATED_SETUP(math),
+#elif defined(CONFIG_8XX_MINIMAL_FPEMU)
+	WARN_EMULATED_SETUP(8xx),
+#endif
+#ifdef CONFIG_VSX
+	WARN_EMULATED_SETUP(vsx),
+#endif
+};
+
+u32 ppc_warn_emulated;
+
+void ppc_warn_emulated_print(const char *type)
+{
+	if (printk_ratelimit())
+		pr_warning("%s used emulated %s instruction\n", current->comm,
+			   type);
+}
+
+static int __init ppc_warn_emulated_init(void)
+{
+	struct dentry *dir, *d;
+	unsigned int i;
+	struct ppc_emulated_entry *entries = (void *)&ppc_emulated;
+
+	if (!powerpc_debugfs_root)
+		return -ENODEV;
+
+	dir = debugfs_create_dir("emulated_instructions",
+				 powerpc_debugfs_root);
+	if (!dir)
+		return -ENOMEM;
+
+	d = debugfs_create_u32("do_warn", S_IRUGO | S_IWUSR, dir,
+			       &ppc_warn_emulated);
+	if (!d)
+		goto fail;
+
+	for (i = 0; i < sizeof(ppc_emulated)/sizeof(*entries); i++) {
+		d = debugfs_create_u32(entries[i].name, S_IRUGO | S_IWUSR, dir,
+				       (u32 *)&entries[i].val.counter);
+		if (!d)
+			goto fail;
+	}
+
+	return 0;
+
+fail:
+	debugfs_remove_recursive(dir);
+	return -ENOMEM;
+}
+
+device_initcall(ppc_warn_emulated_init);
+
+#endif /* CONFIG_PPC_EMULATED_STATS */