[RFC PATCH 18/29] arm64/sve: signal: Restore FPSIMD/SVE state in rt_sigreturn

Dave Martin
2016-11-25T19:41:20Z

This patch adds the missing logic to restore the SVE state in
rt_sigreturn.

Because the FPSIMD and SVE state alias, this code replaces the
existing fpsimd restore code when there is SVE state to restore.

For Zn[127:0], the saved FPSIMD state in Vn takes precedence.

Since __task_fpsimd_to_sve() is used to merge the FPSIMD and SVE
state back together, and only for this purpose, we don't want it to
zero out the SVE state -- hence delete the memset() from there.

Signed-off-by: Dave Martin <Dave.Martin@arm.com>
---
arch/arm64/kernel/fpsimd.c | 4 ---
arch/arm64/kernel/signal.c | 87 ++++++++++++++++++++++++++++++++++++++++------
2 files changed, 76 insertions(+), 15 deletions(-)

diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c
index 4ef2e37..b1a8d3e 100644
--- a/arch/arm64/kernel/fpsimd.c
+++ b/arch/arm64/kernel/fpsimd.c
@@ -266,9 +266,6 @@ static void task_sve_to_fpsimd(struct task_struct *task __always_unused) { }

void fpsimd_signal_preserve_current_state(void)
{
- WARN_ONCE(elf_hwcap & HWCAP_SVE,
- "SVE state save/restore around signals doesn't work properly, expect userspace corruption!\n");
-
fpsimd_preserve_current_state();
task_sve_to_fpsimd(current);
}
@@ -301,7 +298,6 @@ static void __task_fpsimd_to_sve(struct task_struct *task, unsigned int vq)
struct fpsimd_state *fst = &task->thread.fpsimd_state;
unsigned int i;

- memset(sst, 0, sizeof(*sst));
for (i = 0; i < 32; ++i)
sst->zregs[i][0] = fst->vregs[i];
}
diff --git a/arch/arm64/kernel/signal.c b/arch/arm64/kernel/signal.c
index 038e7338..2697d09 100644
--- a/arch/arm64/kernel/signal.c
+++ b/arch/arm64/kernel/signal.c
@@ -211,6 +211,11 @@ static int restore_fpsimd_context(struct fpsimd_context __user *ctx)
}

+struct user_ctxs {
+ struct fpsimd_context __user *fpsimd;
+ struct sve_context __user *sve;
+};
+
#ifdef CONFIG_ARM64_SVE

static int preserve_sve_context(struct sve_context __user *ctx)
@@ -240,19 +245,68 @@ static int preserve_sve_context(struct sve_context __user *ctx)
return err ? -EFAULT : 0;
}

+static int __restore_sve_fpsimd_context(struct user_ctxs *user,
+ unsigned int vl, unsigned int vq)
+{
+ int err;
+ struct fpsimd_sve_state(vq) *task_sve_regs =
+ __task_sve_state(current);
+ struct fpsimd_state fpsimd;
+
+ if (vl != sve_get_vl())
+ return -EINVAL;
+
+ BUG_ON(SVE_SIG_REGS_SIZE(vq) > sizeof(*task_sve_regs));
+ BUG_ON(round_up(SVE_SIG_REGS_SIZE(vq), 16) < sizeof(*task_sve_regs));
+ BUG_ON(SVE_SIG_FFR_OFFSET(vq) - SVE_SIG_REGS_OFFSET !=
+ (char *)&task_sve_regs->ffr - (char *)task_sve_regs);
+ err = __copy_from_user(task_sve_regs,
+ (char __user const *)user->sve +
+ SVE_SIG_REGS_OFFSET,
+ SVE_SIG_REGS_SIZE(vq));
+ if (err)
+ return err;
+
+ /* copy the FP and status/control registers */
+ /* restore_sigframe() already checked that user->fpsimd != NULL. */
+ err = __copy_from_user(fpsimd.vregs, user->fpsimd->vregs,
+ sizeof(fpsimd.vregs));
+ __get_user_error(fpsimd.fpsr, &user->fpsimd->fpsr, err);
+ __get_user_error(fpsimd.fpcr, &user->fpsimd->fpcr, err);
+
+ /* load the hardware registers from the fpsimd_state structure */
+ if (!err)
+ fpsimd_update_current_state(&fpsimd);
+
+ return err;
+}
+
+static int restore_sve_fpsimd_context(struct user_ctxs *user)
+{
+ int err;
+ u16 vl, vq;
+
+ err = __get_user(vl, &user->sve->vl);
+ if (err)
+ return err;
+
+ if (!sve_vl_valid(vl))
+ return -EINVAL;
+
+ vq = sve_vq_from_vl(vl);
+
+ return __restore_sve_fpsimd_context(user, vl, vq);
+}
+
#else /* ! CONFIG_ARM64_SVE */

-/* Turn any non-optimised out attempt to use this into a link error: */
+/* Turn any non-optimised out attempts to use these into a link error: */
extern int preserve_sve_context(void __user *ctx);
+extern int restore_sve_fpsimd_context(struct user_ctxs *user);

#endif /* ! CONFIG_ARM64_SVE */

-struct user_ctxs {
- struct fpsimd_context __user *fpsimd;
- struct sve_context __user *sve;
-};
-
static int parse_user_sigframe(struct user_ctxs *user,
struct rt_sigframe __user *sf)
{
@@ -316,6 +370,9 @@ static int parse_user_sigframe(struct user_ctxs *user,
if (!IS_ENABLED(CONFIG_ARM64_SVE))
goto invalid;

+ if (!(elf_hwcap & HWCAP_SVE))
+ goto invalid;
+
if (user->sve)
goto invalid;

@@ -375,9 +432,6 @@ static int parse_user_sigframe(struct user_ctxs *user,
}

done:
- if (!user->fpsimd)
- goto invalid;
-
return 0;

invalid:
@@ -411,8 +465,19 @@ static int restore_sigframe(struct pt_regs *regs,
if (err == 0)
err = parse_user_sigframe(&user, sf);

- if (err == 0)
- err = restore_fpsimd_context(user.fpsimd);
+ if (err == 0) {
+ if (!user.fpsimd)
+ return -EINVAL;
+
+ if (user.sve) {
+ if (!IS_ENABLED(CONFIG_ARM64_SVE) ||
+ !(elf_hwcap & HWCAP_SVE))
+ return -EINVAL;
+
+ err = restore_sve_fpsimd_context(&user);
+ } else
+ err = restore_fpsimd_context(user.fpsimd);
+ }

return err;
}
--
2.1.4