[PATCH v4 18/29] arm64: add POE signal support

[Joey Gouly]

Add PKEY support to signals, by saving and restoring POR_EL0 from the 
stackframe.

Signed-off-by: Joey Gouly <joey.go...@arm.com>
Cc: Catalin Marinas <catalin.mari...@arm.com>
Cc: Will Deacon <w...@kernel.org>
Reviewed-by: Mark Brown <broo...@kernel.org>
Acked-by: Szabolcs Nagy <szabolcs.n...@arm.com>
---
 arch/arm64/include/uapi/asm/sigcontext.h |  7 ++++
 arch/arm64/kernel/signal.c               | 52 ++++++++++++++++++++++++
 2 files changed, 59 insertions(+)

diff --git a/arch/arm64/include/uapi/asm/sigcontext.h 
b/arch/arm64/include/uapi/asm/sigcontext.h
index 8a45b7a411e0..e4cba8a6c9a2 100644
--- a/arch/arm64/include/uapi/asm/sigcontext.h
+++ b/arch/arm64/include/uapi/asm/sigcontext.h
@@ -98,6 +98,13 @@ struct esr_context {
        __u64 esr;
 };
 
+#define POE_MAGIC      0x504f4530
+
+struct poe_context {
+       struct _aarch64_ctx head;
+       __u64 por_el0;
+};
+
 /*
  * extra_context: describes extra space in the signal frame for
  * additional structures that don't fit in sigcontext.__reserved[].
diff --git a/arch/arm64/kernel/signal.c b/arch/arm64/kernel/signal.c
index 4a77f4976e11..077436a8bc10 100644
--- a/arch/arm64/kernel/signal.c
+++ b/arch/arm64/kernel/signal.c
@@ -63,6 +63,7 @@ struct rt_sigframe_user_layout {
        unsigned long fpmr_offset;
        unsigned long extra_offset;
        unsigned long end_offset;
+       unsigned long poe_offset;
 };
 
 #define BASE_SIGFRAME_SIZE round_up(sizeof(struct rt_sigframe), 16)
@@ -185,6 +186,8 @@ struct user_ctxs {
        u32 zt_size;
        struct fpmr_context __user *fpmr;
        u32 fpmr_size;
+       struct poe_context __user *poe;
+       u32 poe_size;
 };
 
 static int preserve_fpsimd_context(struct fpsimd_context __user *ctx)
@@ -258,6 +261,21 @@ static int restore_fpmr_context(struct user_ctxs *user)
        return err;
 }
 
+static int restore_poe_context(struct user_ctxs *user)
+{
+       u64 por_el0;
+       int err = 0;
+
+       if (user->poe_size != sizeof(*user->poe))
+               return -EINVAL;
+
+       __get_user_error(por_el0, &(user->poe->por_el0), err);
+       if (!err)
+               write_sysreg_s(por_el0, SYS_POR_EL0);
+
+       return err;
+}
+
 #ifdef CONFIG_ARM64_SVE
 
 static int preserve_sve_context(struct sve_context __user *ctx)
@@ -621,6 +639,7 @@ static int parse_user_sigframe(struct user_ctxs *user,
        user->za = NULL;
        user->zt = NULL;
        user->fpmr = NULL;
+       user->poe = NULL;
 
        if (!IS_ALIGNED((unsigned long)base, 16))
                goto invalid;
@@ -671,6 +690,17 @@ static int parse_user_sigframe(struct user_ctxs *user,
                        /* ignore */
                        break;
 
+               case POE_MAGIC:
+                       if (!system_supports_poe())
+                               goto invalid;
+
+                       if (user->poe)
+                               goto invalid;
+
+                       user->poe = (struct poe_context __user *)head;
+                       user->poe_size = size;
+                       break;
+
                case SVE_MAGIC:
                        if (!system_supports_sve() && !system_supports_sme())
                                goto invalid;
@@ -857,6 +887,9 @@ static int restore_sigframe(struct pt_regs *regs,
        if (err == 0 && system_supports_sme2() && user.zt)
                err = restore_zt_context(&user);
 
+       if (err == 0 && system_supports_poe() && user.poe)
+               err = restore_poe_context(&user);
+
        return err;
 }
 
@@ -980,6 +1013,13 @@ static int setup_sigframe_layout(struct 
rt_sigframe_user_layout *user,
                        return err;
        }
 
+       if (system_supports_poe()) {
+               err = sigframe_alloc(user, &user->poe_offset,
+                                    sizeof(struct poe_context));
+               if (err)
+                       return err;
+       }
+
        return sigframe_alloc_end(user);
 }
 
@@ -1020,6 +1060,15 @@ static int setup_sigframe(struct rt_sigframe_user_layout 
*user,
                __put_user_error(current->thread.fault_code, &esr_ctx->esr, 
err);
        }
 
+       if (system_supports_poe() && err == 0 && user->poe_offset) {
+               struct poe_context __user *poe_ctx =
+                       apply_user_offset(user, user->poe_offset);
+
+               __put_user_error(POE_MAGIC, &poe_ctx->head.magic, err);
+               __put_user_error(sizeof(*poe_ctx), &poe_ctx->head.size, err);
+               __put_user_error(read_sysreg_s(SYS_POR_EL0), &poe_ctx->por_el0, 
err);
+       }
+
        /* Scalable Vector Extension state (including streaming), if present */
        if ((system_supports_sve() || system_supports_sme()) &&
            err == 0 && user->sve_offset) {
@@ -1178,6 +1227,9 @@ static void setup_return(struct pt_regs *regs, struct 
k_sigaction *ka,
                sme_smstop();
        }
 
+       if (system_supports_poe())
+               write_sysreg_s(POR_EL0_INIT, SYS_POR_EL0);
+
        if (ka->sa.sa_flags & SA_RESTORER)
                sigtramp = ka->sa.sa_restorer;
        else
-- 
2.25.1