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[Qemu-devel] [PATCH v2 6/6] target-i386: Move user-mode exception action

From: Peter Maydell
Subject: [Qemu-devel] [PATCH v2 6/6] target-i386: Move user-mode exception actions out of user-exec.c
Date: Tue, 17 May 2016 15:18:07 +0100

The exception_action() function in user-exec.c is just a call to
cpu_loop_exit() for every target CPU except i386.  Since this
function is only called if the target's handle_mmu_fault() hook has
indicated an MMU fault, and that hook is only called from the
handle_cpu_signal() code path, we can simply move the x86-specific
setup into that hook, which allows us to remove the TARGET_I386
ifdef from user-exec.c.

Of the actions that were done by the call to raise_interrupt_err():
 * cpu_svm_check_intercept_param() is a no-op in user mode
 * check_exception() is a no-op since double faults are impossible
   for user-mode
 * assignments to cs->exception_index and env->error_code are no-ops
 * assigning to env->exception_next_eip is unnecessary because it
   is not used unless env->exception_is_int is true
 * cpu_loop_exit_restore() is equivalent to cpu_loop_exit() since
   pc is 0
which leaves just setting env_>exception_is_int as the action that
needs to be added to x86_cpu_handle_mmu_fault().

Signed-off-by: Peter Maydell <address@hidden>
 target-i386/helper.c |  2 ++
 user-exec.c          | 16 +---------------
 2 files changed, 3 insertions(+), 15 deletions(-)

diff --git a/target-i386/helper.c b/target-i386/helper.c
index bf3e762..81fad6d 100644
--- a/target-i386/helper.c
+++ b/target-i386/helper.c
@@ -700,6 +700,8 @@ int x86_cpu_handle_mmu_fault(CPUState *cs, vaddr addr,
     env->error_code = (is_write << PG_ERROR_W_BIT);
     env->error_code |= PG_ERROR_U_MASK;
     cs->exception_index = EXCP0E_PAGE;
+    env->exception_is_int = 0;
+    env->exception_next_eip = -1;
     return 1;
diff --git a/user-exec.c b/user-exec.c
index ad669f4..439bb37 100644
--- a/user-exec.c
+++ b/user-exec.c
@@ -39,18 +39,6 @@
 //#define DEBUG_SIGNAL
-static void exception_action(CPUState *cpu)
-#if defined(TARGET_I386)
-    X86CPU *x86_cpu = X86_CPU(cpu);
-    CPUX86State *env1 = &x86_cpu->env;
-    raise_exception_err(env1, cpu->exception_index, env1->error_code);
-    cpu_loop_exit(cpu);
 /* exit the current TB from a signal handler. The host registers are
    restored in a state compatible with the CPU emulator
@@ -119,10 +107,8 @@ static inline int handle_cpu_signal(uintptr_t pc, unsigned 
long address,
     /* now we have a real cpu fault */
     cpu_restore_state(cpu, pc);
-    /* we restore the process signal mask as the sigreturn should
-       do it (XXX: use sigsetjmp) */
     sigprocmask(SIG_SETMASK, old_set, NULL);
-    exception_action(cpu);
+    cpu_loop_exit(cpu);
     /* never comes here */
     return 1;

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