linux-user/i386: Create init_main_thread

Merge init_thread and target_cpu_copy_regs.
There's no point going through a target_pt_regs intermediate.
Temporarily introduce HAVE_INIT_MAIN_THREAD during conversion.

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

linux-user/elfload.c

@@ -149,17 +149,12 @@ typedef abi_int         target_pid_t;
 
 #ifdef TARGET_I386
 
+#define HAVE_INIT_MAIN_THREAD
+
 #ifdef TARGET_X86_64
 #define ELF_CLASS      ELFCLASS64
 #define ELF_ARCH       EM_X86_64
 
-static inline void init_thread(struct target_pt_regs *regs, struct image_info *infop)
-{
-    regs->rax = 0;
-    regs->rsp = infop->start_stack;
-    regs->rip = infop->entry;
-}
-
 #define ELF_NREG    27
 typedef target_elf_greg_t  target_elf_gregset_t[ELF_NREG];
 
@@ -237,22 +232,6 @@ static bool init_guest_commpage(void)
 
 #define EXSTACK_DEFAULT true
 
-static inline void init_thread(struct target_pt_regs *regs,
-                               struct image_info *infop)
-{
-    regs->esp = infop->start_stack;
-    regs->eip = infop->entry;
-
-    /* SVR4/i386 ABI (pages 3-31, 3-32) says that when the program
-       starts %edx contains a pointer to a function which might be
-       registered using `atexit'.  This provides a mean for the
-       dynamic linker to call DT_FINI functions for shared libraries
-       that have been loaded before the code runs.
-
-       A value of 0 tells we have no such handler.  */
-    regs->edx = 0;
-}
-
 #define ELF_NREG    17
 typedef target_elf_greg_t  target_elf_gregset_t[ELF_NREG];
 
@@ -3621,8 +3600,12 @@ static int elf_core_dump(int signr, const CPUArchState *env)
 
 void do_init_main_thread(CPUState *cs, struct image_info *infop)
 {
+#ifdef HAVE_INIT_MAIN_THREAD
+    init_main_thread(cs, infop);
+#else
     target_pt_regs regs = { };
 
     init_thread(&regs, infop);
     target_cpu_copy_regs(cpu_env(cs), &regs);
+#endif
 }

linux-user/i386/cpu_loop.c

@@ -331,11 +331,10 @@ static void target_cpu_free(void *obj)
     g_free(obj);
 }
 
-void target_cpu_copy_regs(CPUArchState *env, target_pt_regs *regs)
+void init_main_thread(CPUState *cpu, struct image_info *info)
 {
-    CPUState *cpu = env_cpu(env);
+    CPUArchState *env = cpu_env(cpu);
     bool is64 = (env->features[FEAT_8000_0001_EDX] & CPUID_EXT2_LM) != 0;
-    int i;
 
     OBJECT(cpu)->free = target_cpu_free;
     env->cr[0] = CR0_PG_MASK | CR0_WP_MASK | CR0_PE_MASK;
@@ -361,28 +360,25 @@ void target_cpu_copy_regs(CPUArchState *env, target_pt_regs *regs)
     /* flags setup : we activate the IRQs by default as in user mode */
     env->eflags |= IF_MASK;
 
-    /* linux register setup */
-#ifndef TARGET_ABI32
-    env->regs[R_EAX] = regs->rax;
-    env->regs[R_EBX] = regs->rbx;
-    env->regs[R_ECX] = regs->rcx;
-    env->regs[R_EDX] = regs->rdx;
-    env->regs[R_ESI] = regs->rsi;
-    env->regs[R_EDI] = regs->rdi;
-    env->regs[R_EBP] = regs->rbp;
-    env->regs[R_ESP] = regs->rsp;
-    env->eip = regs->rip;
-#else
-    env->regs[R_EAX] = regs->eax;
-    env->regs[R_EBX] = regs->ebx;
-    env->regs[R_ECX] = regs->ecx;
-    env->regs[R_EDX] = regs->edx;
-    env->regs[R_ESI] = regs->esi;
-    env->regs[R_EDI] = regs->edi;
-    env->regs[R_EBP] = regs->ebp;
-    env->regs[R_ESP] = regs->esp;
-    env->eip = regs->eip;
-#endif
+    /*
+     * Linux register setup.
+     *
+     * SVR4/i386 ABI (pages 3-31, 3-32) says that when the program
+     * starts %edx contains a pointer to a function which might be
+     * registered using `atexit'.  This provides a mean for the
+     * dynamic linker to call DT_FINI functions for shared libraries
+     * that have been loaded before the code runs.
+     * A value of 0 tells we have no such handler.
+     *
+     * This applies to x86_64 as well as i386.
+     *
+     * That said, the kernel's ELF_PLAT_INIT simply zeros all of the general
+     * registers.  Note that x86_cpu_reset_hold will set %edx to cpuid_version;
+     * clear all general registers defensively.
+     */
+    memset(env->regs, 0, sizeof(env->regs));
+    env->regs[R_ESP] = info->start_stack;
+    env->eip = info->entry;
 
     /* linux interrupt setup */
 #ifndef TARGET_ABI32
@@ -394,7 +390,7 @@ void target_cpu_copy_regs(CPUArchState *env, target_pt_regs *regs)
                                 PROT_READ|PROT_WRITE,
                                 MAP_ANONYMOUS|MAP_PRIVATE, -1, 0);
     idt_table = g2h_untagged(env->idt.base);
-    for (i = 0; i < 20; i++) {
+    for (int i = 0; i < 20; i++) {
         set_idt(i, 0, is64);
     }
     set_idt(3, 3, is64);

linux-user/qemu.h

@@ -361,5 +361,6 @@ CPUArchState *cpu_copy(CPUArchState *env);
 
 typedef struct target_pt_regs target_pt_regs;
 void target_cpu_copy_regs(CPUArchState *env, target_pt_regs *regs);
+void init_main_thread(CPUState *cs, struct image_info *info);
 
 #endif /* QEMU_H */