s390/perf: extend perf_regs support to include floating-point registers

Extend the perf register support to also export floating-point register
contents for user space tasks.  Floating-point registers might be used
in leaf functions to contain the return address.  Hence, they are required
for proper DWARF unwinding.
Signed-off-by: Hendrik Brueckner <brueckner@linux.vnet.ibm.com>
Reviewed-and-tested-by: Thomas Richter <tmricht@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/include/uapi/asm/perf_regs.h

@@ -18,6 +18,22 @@ enum perf_event_s390_regs {
 	PERF_REG_S390_R13,
 	PERF_REG_S390_R14,
 	PERF_REG_S390_R15,
+	PERF_REG_S390_FP0,
+	PERF_REG_S390_FP1,
+	PERF_REG_S390_FP2,
+	PERF_REG_S390_FP3,
+	PERF_REG_S390_FP4,
+	PERF_REG_S390_FP5,
+	PERF_REG_S390_FP6,
+	PERF_REG_S390_FP7,
+	PERF_REG_S390_FP8,
+	PERF_REG_S390_FP9,
+	PERF_REG_S390_FP10,
+	PERF_REG_S390_FP11,
+	PERF_REG_S390_FP12,
+	PERF_REG_S390_FP13,
+	PERF_REG_S390_FP14,
+	PERF_REG_S390_FP15,
 	PERF_REG_S390_MASK,
 	PERF_REG_S390_PC,
 

arch/s390/kernel/perf_regs.c

@@ -4,12 +4,29 @@
 #include <linux/errno.h>
 #include <linux/bug.h>
 #include <asm/ptrace.h>
+#include <asm/fpu/api.h>
+#include <asm/fpu/types.h>
 
 u64 perf_reg_value(struct pt_regs *regs, int idx)
 {
+	freg_t fp;
+
 	if (WARN_ON_ONCE((u32)idx >= PERF_REG_S390_MAX))
 		return 0;
 
+	if (idx >= PERF_REG_S390_R0 && idx <= PERF_REG_S390_R15)
+		return regs->gprs[idx];
+
+	if (idx >= PERF_REG_S390_FP0 && idx <= PERF_REG_S390_FP15) {
+		if (!user_mode(regs))
+			return 0;
+
+		idx -= PERF_REG_S390_FP0;
+		fp = MACHINE_HAS_VX ? *(freg_t *)(current->thread.fpu.vxrs + idx)
+				    : current->thread.fpu.fprs[idx];
+		return fp.ui;
+	}
+
 	if (idx == PERF_REG_S390_MASK)
 		return regs->psw.mask;
 	if (idx == PERF_REG_S390_PC)
@@ -43,7 +60,11 @@ void perf_get_regs_user(struct perf_regs *regs_user,
 	/*
 	 * Use the regs from the first interruption and let
 	 * perf_sample_regs_intr() handle interrupts (regs == get_irq_regs()).
+	 *
+	 * Also save FPU registers for user-space tasks only.
 	 */
 	regs_user->regs = task_pt_regs(current);
+	if (user_mode(regs_user->regs))
+		save_fpu_regs();
 	regs_user->abi = perf_reg_abi(current);
 }