[PATCH] powerpc: Export thread_struct.used_vr/used_vsr to user space

[Simon Guo <wei.guo.simon@gmail.com>]

These 2 fields track whether user process has used Altivec/VSX registers
or not. They are used by kernel to setup signal frame on user stack
correctly regarding vector part.

CRIU(Checkpoint and Restore In User space) builds signal frame for
restored process. It will need this export information to setup signal
frame correctly. And CRIU will need to restore these 2 fields for
the restored process.

Signed-off-by: Simon Guo <wei.guo.simon@gmail.com>
Reviewed-by: Laurent Dufour <ldufour@linux.vnet.ibm.com>
---
 arch/powerpc/include/uapi/asm/ptrace.h | 11 ++++++++++
 arch/powerpc/kernel/ptrace.c           | 39 ++++++++++++++++++++++++++++++++++
 arch/powerpc/kernel/ptrace32.c         |  2 ++
 3 files changed, 52 insertions(+)

diff --git a/arch/powerpc/include/uapi/asm/ptrace.h b/arch/powerpc/include/uapi/asm/ptrace.h
index 8036b38..4456b8f 100644
--- a/arch/powerpc/include/uapi/asm/ptrace.h
+++ b/arch/powerpc/include/uapi/asm/ptrace.h
@@ -176,6 +176,17 @@ struct pt_regs {
 #define PTRACE_GETREGS64	  0x16
 #define PTRACE_SETREGS64	  0x17
 
+/*
+ * Get or set some register used bit.
+ * The flags will be saved in a 32 bit data.
+ * Currently it is only used for VR/VSR usage.
+ */
+#define PTRACE_GET_REGS_USAGE	  0x1e
+#define PTRACE_SET_REGS_USAGE	  0x1f
+
+#define PTRACE_REGS_USAGE_BIT_VR  0x0
+#define PTRACE_REGS_USAGE_BIT_VSR 0x1
+
 /* Calls to trace a 64bit program from a 32bit program */
 #define PPC_PTRACE_PEEKTEXT_3264 0x95
 #define PPC_PTRACE_PEEKDATA_3264 0x94
diff --git a/arch/powerpc/kernel/ptrace.c b/arch/powerpc/kernel/ptrace.c
index 30a03c0..43d3db3b 100644
--- a/arch/powerpc/kernel/ptrace.c
+++ b/arch/powerpc/kernel/ptrace.c
@@ -1755,6 +1755,45 @@ long arch_ptrace(struct task_struct *child, long request,
 					     REGSET_SPE, 0, 35 * sizeof(u32),
 					     datavp);
 #endif
+	case PTRACE_GET_REGS_USAGE:
+		{
+			u32 *u32_datap = (u32 *)datavp;
+			u32 reg_usage = 0;
+
+			if (addr != sizeof(u32))
+				return -EINVAL;
+
+#ifdef CONFIG_ALTIVEC
+			if (child->thread.used_vr)
+				reg_usage |= (1 << PTRACE_REGS_USAGE_BIT_VR);
+#endif
+#ifdef CONFIG_VSX
+			if (child->thread.used_vsr)
+				reg_usage |= (1 << PTRACE_REGS_USAGE_BIT_VSR);
+#endif
+			return put_user(reg_usage, u32_datap);
+		}
+	case PTRACE_SET_REGS_USAGE:
+		{
+			u32 *u32_datap = (u32 *)datavp;
+			u32 reg_usage = 0;
+
+			if (addr != sizeof(u32))
+				return -EINVAL;
+
+			ret = get_user(reg_usage, u32_datap);
+			if (ret)
+				return ret;
+#ifdef CONFIG_ALTIVEC
+			child->thread.used_vr =
+				((reg_usage >> PTRACE_REGS_USAGE_BIT_VR) & 1);
+#endif
+#ifdef CONFIG_VSX
+			child->thread.used_vsr =
+				((reg_usage >> PTRACE_REGS_USAGE_BIT_VSR) & 1);
+#endif
+			break;
+		}
 
 	default:
 		ret = ptrace_request(child, request, addr, data);
diff --git a/arch/powerpc/kernel/ptrace32.c b/arch/powerpc/kernel/ptrace32.c
index f52b7db..ff359a1 100644
--- a/arch/powerpc/kernel/ptrace32.c
+++ b/arch/powerpc/kernel/ptrace32.c
@@ -305,6 +305,8 @@ long compat_arch_ptrace(struct task_struct *child, compat_long_t request,
 	case PPC_PTRACE_GETHWDBGINFO:
 	case PPC_PTRACE_SETHWDEBUG:
 	case PPC_PTRACE_DELHWDEBUG:
+	case PTRACE_GET_REGS_USAGE:
+	case PTRACE_SET_REGS_USAGE:
 		ret = arch_ptrace(child, request, addr, data);
 		break;
 
-- 
2.7.0