linux-user: Save the correct resume address for MIPS signal handling

The current ISA mode needs to be saved in bit 0 of the resume address.
If the current instruction happens to be in a branch delay slot, then
the address of the preceding jump instruction should be stored instead.
exception_resume_pc already does both of these tasks, so it is
made available and reused.

MIPS_HFLAG_BMASK in hflags is cleared, otherwise QEMU may treat the
first instruction of the signal handler as a delay slot instruction.

Signed-off-by: Kwok Cheung Yeung <kcy@codesourcery.com>
Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>

linux-user/signal.c

@@ -2528,7 +2528,8 @@ setup_sigcontext(CPUMIPSState *regs, struct target_sigcontext *sc)
     int err = 0;
     int i;
 
-    err |= __put_user(regs->active_tc.PC, &sc->sc_pc);
+    err |= __put_user(exception_resume_pc(regs), &sc->sc_pc);
+    regs->hflags &= ~MIPS_HFLAG_BMASK;
 
     __put_user(0, &sc->sc_regs[0]);
     for (i = 1; i < 32; ++i) {

target-mips/cpu.h

@@ -668,6 +668,7 @@ void r4k_invalidate_tlb (CPUMIPSState *env, int idx, int use_extra);
 hwaddr cpu_mips_translate_address (CPUMIPSState *env, target_ulong address,
 		                               int rw);
 #endif
+target_ulong exception_resume_pc (CPUMIPSState *env);
 
 static inline void cpu_get_tb_cpu_state(CPUMIPSState *env, target_ulong *pc,
                                         target_ulong *cs_base, int *flags)

target-mips/helper.c

@@ -366,8 +366,7 @@ static const char * const excp_names[EXCP_LAST + 1] = {
     [EXCP_CACHE] = "cache error",
 };
 
-#if !defined(CONFIG_USER_ONLY)
-static target_ulong exception_resume_pc (CPUMIPSState *env)
+target_ulong exception_resume_pc (CPUMIPSState *env)
 {
     target_ulong bad_pc;
     target_ulong isa_mode;
@@ -383,6 +382,7 @@ static target_ulong exception_resume_pc (CPUMIPSState *env)
     return bad_pc;
 }
 
+#if !defined(CONFIG_USER_ONLY)
 static void set_hflags_for_handler (CPUMIPSState *env)
 {
     /* Exception handlers are entered in 32-bit mode.  */