[PULL 4/4] linux-user/xtensa: save/restore FP registers across signal delivery

[Helge Deller <deller@kernel.org>]

From: Matt Turner <mattst88@gmail.com>

Add support for saving and restoring f0-f15 across signal delivery.
The target_xtensa_xtregs_fp struct carries 32-bit f-regs for cores
with XTENSA_OPTION_FP_COPROCESSOR; target_xtensa_xtregs_dfp carries
64-bit f-regs for cores with XTENSA_OPTION_DFP_COPROCESSOR.

Lock the xtregs region via lock_user before reading on sigreturn,
since sc_xtregs is a user-space pointer that may lie outside the
locked sigframe.

Signed-off-by: Matt Turner <mattst88@gmail.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Helge Deller <deller@gmx.de>
---
 linux-user/xtensa/signal.c | 96 ++++++++++++++++++++++++++++++++++----
 1 file changed, 88 insertions(+), 8 deletions(-)

diff --git a/linux-user/xtensa/signal.c b/linux-user/xtensa/signal.c
index ef8b0c3a27..e3f9da322b 100644
--- a/linux-user/xtensa/signal.c
+++ b/linux-user/xtensa/signal.c
@@ -21,6 +21,7 @@
 #include "user-internals.h"
 #include "signal-common.h"
 #include "linux-user/trace.h"
+#include "target/xtensa/cpu.h"
 
 struct target_sigcontext {
     abi_ulong sc_pc;
@@ -43,10 +44,25 @@ struct target_ucontext {
     target_sigset_t tuc_sigmask;
 };
 
+struct target_xtensa_xtregs_fp {
+    uint32_t f[16];
+    uint32_t fcr;
+    uint32_t fsr;
+};
+
+struct target_xtensa_xtregs_dfp {
+    uint64_t f[16];
+    uint32_t fcr;
+    uint32_t fsr;
+};
+
 struct target_rt_sigframe {
     target_siginfo_t info;
     struct target_ucontext uc;
-    /* TODO: xtregs */
+    union {
+        struct target_xtensa_xtregs_fp fp;
+        struct target_xtensa_xtregs_dfp dfp;
+    } xtregs;
     uint8_t retcode[6];
     abi_ulong window[4];
 };
@@ -107,6 +123,7 @@ static int flush_window_regs(CPUXtensaState *env)
 }
 
 static int setup_sigcontext(struct target_rt_sigframe *frame,
+                            abi_ulong frame_addr,
                             CPUXtensaState *env)
 {
     struct target_sigcontext *sc = &frame->uc.tuc_mcontext;
@@ -123,8 +140,25 @@ static int setup_sigcontext(struct target_rt_sigframe *frame,
     for (i = 0; i < 16; ++i) {
         __put_user(env->regs[i], sc->sc_a + i);
     }
-    __put_user(0, &sc->sc_xtregs);
-    /* TODO: xtregs */
+    if (xtensa_option_enabled(env->config, XTENSA_OPTION_DFP_COPROCESSOR)) {
+        for (i = 0; i < 16; ++i) {
+            __put_user(env->fregs[i].f64, &frame->xtregs.dfp.f[i]);
+        }
+        __put_user(env->uregs[FCR], &frame->xtregs.dfp.fcr);
+        __put_user(cpu_get_fsr(env), &frame->xtregs.dfp.fsr);
+        __put_user(frame_addr + offsetof(struct target_rt_sigframe, xtregs),
+                   &sc->sc_xtregs);
+    } else if (xtensa_option_enabled(env->config, XTENSA_OPTION_FP_COPROCESSOR)) {
+        for (i = 0; i < 16; ++i) {
+            __put_user(env->fregs[i].f32[FP_F32_LOW], &frame->xtregs.fp.f[i]);
+        }
+        __put_user(env->uregs[FCR], &frame->xtregs.fp.fcr);
+        __put_user(cpu_get_fsr(env), &frame->xtregs.fp.fsr);
+        __put_user(frame_addr + offsetof(struct target_rt_sigframe, xtregs),
+                   &sc->sc_xtregs);
+    } else {
+        __put_user(0, &sc->sc_xtregs);
+    }
     return 1;
 }
 
@@ -190,7 +224,7 @@ void setup_rt_frame(int sig, struct target_sigaction *ka,
     __put_user(0, &frame->uc.tuc_flags);
     __put_user(0, &frame->uc.tuc_link);
     target_save_altstack(&frame->uc.tuc_stack, env);
-    if (!setup_sigcontext(frame, env)) {
+    if (!setup_sigcontext(frame, frame_addr, env)) {
         unlock_user_struct(frame, frame_addr, 0);
         goto give_sigsegv;
     }
@@ -243,8 +277,8 @@ give_sigsegv:
     force_sigsegv(sig);
 }
 
-static void restore_sigcontext(CPUXtensaState *env,
-                               struct target_rt_sigframe *frame)
+static int restore_sigcontext(CPUXtensaState *env,
+                              struct target_rt_sigframe *frame)
 {
     struct target_sigcontext *sc = &frame->uc.tuc_mcontext;
     uint32_t ps;
@@ -266,7 +300,51 @@ static void restore_sigcontext(CPUXtensaState *env,
     for (i = 0; i < 16; ++i) {
         __get_user(env->regs[i], sc->sc_a + i);
     }
-    /* TODO: xtregs */
+    {
+        abi_ulong xtregs_addr;
+
+        __get_user(xtregs_addr, &sc->sc_xtregs);
+        if (xtregs_addr) {
+            if (xtensa_option_enabled(env->config,
+                                      XTENSA_OPTION_DFP_COPROCESSOR)) {
+                struct target_xtensa_xtregs_dfp *xtregs;
+                uint32_t fcr, fsr;
+
+                xtregs = lock_user(VERIFY_READ, xtregs_addr,
+                                   sizeof(*xtregs), 1);
+                if (!xtregs) {
+                    return 0;
+                }
+                for (i = 0; i < 16; ++i) {
+                    __get_user(env->fregs[i].f64, &xtregs->f[i]);
+                }
+                __get_user(fcr, &xtregs->fcr);
+                __get_user(fsr, &xtregs->fsr);
+                unlock_user(xtregs, xtregs_addr, 0);
+                cpu_set_fcr(env, fcr);
+                cpu_set_fsr(env, fsr);
+            } else if (xtensa_option_enabled(env->config,
+                                             XTENSA_OPTION_FP_COPROCESSOR)) {
+                struct target_xtensa_xtregs_fp *xtregs;
+                uint32_t fcr, fsr;
+
+                xtregs = lock_user(VERIFY_READ, xtregs_addr,
+                                   sizeof(*xtregs), 1);
+                if (!xtregs) {
+                    return 0;
+                }
+                for (i = 0; i < 16; ++i) {
+                    __get_user(env->fregs[i].f32[FP_F32_LOW], &xtregs->f[i]);
+                }
+                __get_user(fcr, &xtregs->fcr);
+                __get_user(fsr, &xtregs->fsr);
+                unlock_user(xtregs, xtregs_addr, 0);
+                cpu_set_fcr(env, fcr);
+                cpu_set_fsr(env, fsr);
+            }
+        }
+    }
+    return 1;
 }
 
 long do_rt_sigreturn(CPUXtensaState *env)
@@ -282,7 +360,9 @@ long do_rt_sigreturn(CPUXtensaState *env)
     target_to_host_sigset(&set, &frame->uc.tuc_sigmask);
     set_sigmask(&set);
 
-    restore_sigcontext(env, frame);
+    if (!restore_sigcontext(env, frame)) {
+        goto badframe;
+    }
     target_restore_altstack(&frame->uc.tuc_stack, env);
 
     unlock_user_struct(frame, frame_addr, 0);
-- 
2.54.0