powerpc/ptrace: Enable support for Performance Monitor registers

This patch enables support for Performance monitor registers related
ELF core note NT_PPC_PMU based ptrace requests through
PTRACE_GETREGSET, PTRACE_SETREGSET calls. This is achieved
through adding one new register sets REGSET_PMU in powerpc
corresponding to the ELF core note sections added in this
regard. It also implements the get, set and active functions
for this new register sets added.
Signed-off-by: Anshuman Khandual <khandual@linux.vnet.ibm.com>
Signed-off-by: Simon Guo <wei.guo.simon@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/include/uapi/asm/elf.h

@@ -95,6 +95,7 @@
 #define ELF_NVSX	32	/* includes all VSX registers */
 #define ELF_NTMSPRREG	3	/* include tfhar, tfiar, texasr */
 #define ELF_NEBB	3	/* includes ebbrr, ebbhr, bescr */
+#define ELF_NPMU	5	/* includes siar, sdar, sier, mmcr2, mmcr0 */
 
 typedef unsigned long elf_greg_t64;
 typedef elf_greg_t64 elf_gregset_t64[ELF_NGREG];

arch/powerpc/kernel/ptrace.c

@@ -1824,6 +1824,75 @@ static int ebb_set(struct task_struct *target,
 
 	return ret;
 }
+static int pmu_active(struct task_struct *target,
+			 const struct user_regset *regset)
+{
+	if (!cpu_has_feature(CPU_FTR_ARCH_207S))
+		return -ENODEV;
+
+	return regset->n;
+}
+
+static int pmu_get(struct task_struct *target,
+		      const struct user_regset *regset,
+		      unsigned int pos, unsigned int count,
+		      void *kbuf, void __user *ubuf)
+{
+	/* Build tests */
+	BUILD_BUG_ON(TSO(siar) + sizeof(unsigned long) != TSO(sdar));
+	BUILD_BUG_ON(TSO(sdar) + sizeof(unsigned long) != TSO(sier));
+	BUILD_BUG_ON(TSO(sier) + sizeof(unsigned long) != TSO(mmcr2));
+	BUILD_BUG_ON(TSO(mmcr2) + sizeof(unsigned long) != TSO(mmcr0));
+
+	if (!cpu_has_feature(CPU_FTR_ARCH_207S))
+		return -ENODEV;
+
+	return user_regset_copyout(&pos, &count, &kbuf, &ubuf,
+			&target->thread.siar, 0,
+			5 * sizeof(unsigned long));
+}
+
+static int pmu_set(struct task_struct *target,
+		      const struct user_regset *regset,
+		      unsigned int pos, unsigned int count,
+		      const void *kbuf, const void __user *ubuf)
+{
+	int ret = 0;
+
+	/* Build tests */
+	BUILD_BUG_ON(TSO(siar) + sizeof(unsigned long) != TSO(sdar));
+	BUILD_BUG_ON(TSO(sdar) + sizeof(unsigned long) != TSO(sier));
+	BUILD_BUG_ON(TSO(sier) + sizeof(unsigned long) != TSO(mmcr2));
+	BUILD_BUG_ON(TSO(mmcr2) + sizeof(unsigned long) != TSO(mmcr0));
+
+	if (!cpu_has_feature(CPU_FTR_ARCH_207S))
+		return -ENODEV;
+
+	ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf,
+			&target->thread.siar, 0,
+			sizeof(unsigned long));
+
+	if (!ret)
+		ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf,
+			&target->thread.sdar, sizeof(unsigned long),
+			2 * sizeof(unsigned long));
+
+	if (!ret)
+		ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf,
+			&target->thread.sier, 2 * sizeof(unsigned long),
+			3 * sizeof(unsigned long));
+
+	if (!ret)
+		ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf,
+			&target->thread.mmcr2, 3 * sizeof(unsigned long),
+			4 * sizeof(unsigned long));
+
+	if (!ret)
+		ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf,
+			&target->thread.mmcr0, 4 * sizeof(unsigned long),
+			5 * sizeof(unsigned long));
+	return ret;
+}
 #endif
 /*
  * These are our native regset flavors.
@@ -1857,6 +1926,7 @@ enum powerpc_regset {
 #ifdef CONFIG_PPC_BOOK3S_64
 	REGSET_TAR,		/* TAR register */
 	REGSET_EBB,		/* EBB registers */
+	REGSET_PMR,		/* Performance Monitor Registers */
 #endif
 };
 
@@ -1957,6 +2027,11 @@ static const struct user_regset native_regsets[] = {
 		.size = sizeof(u64), .align = sizeof(u64),
 		.active = ebb_active, .get = ebb_get, .set = ebb_set
 	},
+	[REGSET_PMR] = {
+		.core_note_type = NT_PPC_PMU, .n = ELF_NPMU,
+		.size = sizeof(u64), .align = sizeof(u64),
+		.active = pmu_active, .get = pmu_get, .set = pmu_set
+	},
 #endif
 };