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Subject[PATCH] powerpc: set used_vsr/used_vr/used_spe in sigreturn path when MSR bits are active
Date
From: Simon Guo <wei.guo.simon@gmail.com>

Normally, when MSR[VSX/VR/SPE] bits = 1, the used_vsr/used_vr/used_spe
bit have already been set. However signal frame locates at user space
and it is controlled by user application. It is up to kernel to make
sure used_vsr/used_vr/used_spe(in kernel)=1 and consistent with MSR
bits.

For example, CRIU application, who utilizes sigreturn to restore
checkpointed process, will lead to the case where MSR[VSX] bit is
active in signal frame, but used_vsx bit is not set. (the same applies
to VR/SPE).

This patch will reinforce this at kernel by always setting used_* bit
when MSR related bits are active in signal frame and we are doing
sigreturn.

This patch is based on Ben's Proposal.

Cc: Paul Mackerras <paulus@samba.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Anton Blanchard <anton@samba.org>
Cc: Cyril Bur <cyrilbur@gmail.com>
Cc: Michael Neuling <mikey@neuling.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: "Amanieu d'Antras" <amanieu@gmail.com>
Cc: linuxppc-dev@lists.ozlabs.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Simon Guo <wei.guo.simon@gmail.com>
---
arch/powerpc/kernel/signal_32.c | 6 ++++++
arch/powerpc/kernel/signal_64.c | 11 ++++++++---
2 files changed, 14 insertions(+), 3 deletions(-)

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;
--
1.8.3.1
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