Subject: Re: [v4] powerpc: Export thread_struct.used_vr/used_vsr to user space

From: Benjamin Herrenschmidt <[email-masked]>
Date: Thu, 07 Jul 2016 23:29:27 +1000

On Thu, 2016-07-07 at 23:21 +1000, Benjamin Herrenschmidt wrote:
> 
> I think the right fix is that if a restore_sigcontext() has the MSR
> bits set,
> it should set the corresponding used_* flag.

Something like this:

(totally untested)

diff --git a/arch/powerpc/kernel/signal_32.c b/arch/powerpc/kernel/signal_32.c
index b6aa378..1bf074e 100644
--- a/arch/powerpc/kernel/signal_32.c
+++ b/arch/powerpc/kernel/signal_32.c
@@ -698,6 +698,7 @@ static long restore_user_regs(struct pt_regs *regs,
 		if (__copy_from_user(&current->thread.vr_state, &sr->mc_vregs,
 				     sizeof(sr->mc_vregs)))
 			return 1;
+		current->thread.used_vr = true;
 	} else if (current->thread.used_vr)
 		memset(&current->thread.vr_state, 0,
 		       ELF_NVRREG * sizeof(vector128));
@@ -724,6 +725,7 @@ static long restore_user_regs(struct pt_regs *regs,
 		 */
 		if (copy_vsx_from_user(current, &sr->mc_vsregs))
 			return 1;
+		current->thread.used_vsr = true;
 	} else if (current->thread.used_vsr)
 		for (i = 0; i < 32 ; i++)
 			current->thread.fp_state.fpr[i][TS_VSRLOWOFFSET] = 0;
@@ -743,6 +745,7 @@ static long restore_user_regs(struct pt_regs *regs,
 		if (__copy_from_user(current->thread.evr, &sr->mc_vregs,
 				     ELF_NEVRREG * sizeof(u32)))
 			return 1;
+		current->thread.used_spe = true;
 	} else if (current->thread.used_spe)
 		memset(current->thread.evr, 0, ELF_NEVRREG * sizeof(u32));
 
@@ -799,6 +802,7 @@ static long restore_tm_user_regs(struct pt_regs *regs,
 				     &tm_sr->mc_vregs,
 				     sizeof(sr->mc_vregs)))
 			return 1;
+		current->thread.used_vr = true;
 	} else if (current->thread.used_vr) {
 		memset(&current->thread.vr_state, 0,
 		       ELF_NVRREG * sizeof(vector128));
@@ -832,6 +836,7 @@ static long restore_tm_user_regs(struct pt_regs *regs,
 		if (copy_vsx_from_user(current, &sr->mc_vsregs) ||
 		    copy_transact_vsx_from_user(current, &tm_sr->mc_vsregs))
 			return 1;
+		current->thread.used_vsr = true;
 	} else if (current->thread.used_vsr)
 		for (i = 0; i < 32 ; i++) {
 			current->thread.fp_state.fpr[i][TS_VSRLOWOFFSET] = 0;
@@ -848,6 +853,7 @@ static long restore_tm_user_regs(struct pt_regs *regs,
 		if (__copy_from_user(current->thread.evr, &sr->mc_vregs,
 				     ELF_NEVRREG * sizeof(u32)))
 			return 1;
+		current->thread.used_spe = true;
 	} else if (current->thread.used_spe)
 		memset(current->thread.evr, 0, ELF_NEVRREG * sizeof(u32));
 
diff --git a/arch/powerpc/kernel/signal_64.c b/arch/powerpc/kernel/signal_64.c
index 2552079..8704269 100644
--- a/arch/powerpc/kernel/signal_64.c
+++ b/arch/powerpc/kernel/signal_64.c
@@ -363,9 +363,11 @@ static long restore_sigcontext(struct pt_regs *regs, sigset_t *set, int sig,
 	if (v_regs && !access_ok(VERIFY_READ, v_regs, 34 * sizeof(vector128)))
 		return -EFAULT;
 	/* Copy 33 vec registers (vr0..31 and vscr) from the stack */
-	if (v_regs != NULL && (msr & MSR_VEC) != 0)
+	if (v_regs != NULL && (msr & MSR_VEC) != 0) {
 		err |= __copy_from_user(&current->thread.vr_state, v_regs,
 					33 * sizeof(vector128));
+		current->thread.used_vr = true;
+	}
 	else if (current->thread.used_vr)
 		memset(&current->thread.vr_state, 0, 33 * sizeof(vector128));
 	/* Always get VRSAVE back */
@@ -385,9 +387,10 @@ static long restore_sigcontext(struct pt_regs *regs, sigset_t *set, int sig,
 	 * buffer for formatting, then into the taskstruct.
 	 */
 	v_regs += ELF_NVRREG;
-	if ((msr & MSR_VSX) != 0)
+	if ((msr & MSR_VSX) != 0) {
 		err |= copy_vsx_from_user(current, v_regs);
-	else
+		current->thread.used_vsr = true;
+	} else
 		for (i = 0; i < 32 ; i++)
 			current->thread.fp_state.fpr[i][TS_VSRLOWOFFSET] = 0;
 #endif
@@ -482,6 +485,7 @@ static long restore_tm_sigcontexts(struct pt_regs *regs,
 					33 * sizeof(vector128));
 		err |= __copy_from_user(&current->thread.transact_vr, tm_v_regs,
 					33 * sizeof(vector128));
+		current->thread.used_vr = true;
 	}
 	else if (current->thread.used_vr) {
 		memset(&current->thread.vr_state, 0, 33 * sizeof(vector128));
@@ -515,6 +519,7 @@ static long restore_tm_sigcontexts(struct pt_regs *regs,
 		tm_v_regs += ELF_NVRREG;
 		err |= copy_vsx_from_user(current, v_regs);
 		err |= copy_transact_vsx_from_user(current, tm_v_regs);
+		current->thread.used_vsr = true;
 	} else {
 		for (i = 0; i < 32 ; i++) {
 			current->thread.fp_state.fpr[i][TS_VSRLOWOFFSET] = 0;