[Qemu-devel] [PATCH 1/7] Add initial x86_64 signal handlers

[Timothy Pearson]

Note that x86_64 systems only offer the _rt signal handler variants,
so the legacy signal handlers remain unimplemented on this platform.

Signed-off-by: Timothy Pearson <address@hidden>
---
 linux-user/signal.c | 302 +++++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 299 insertions(+), 3 deletions(-)

diff --git a/linux-user/signal.c b/linux-user/signal.c
index 61c1145..88d8fd3 100644
--- a/linux-user/signal.c
+++ b/linux-user/signal.c
@@ -26,6 +26,16 @@
 #include "target_signal.h"
 #include "trace.h"
 
+/*
+ * This looks more complex than it should be. But we need to
+ * get the type for the ~ right in round_down (it needs to be
+ * as wide as the result!), and we want to evaluate the macro
+ * arguments just once each.
+ */
+#define __round_mask(x, y) ((__typeof__(x))((y)-1))
+#define round_up(x, y) ((((x)-1) | __round_mask(x, y))+1)
+#define round_down(x, y) ((x) & ~__round_mask(x, y))
+
 static struct target_sigaltstack target_sigaltstack_used = {
     .ss_sp = 0,
     .ss_size = 0,
@@ -256,8 +266,7 @@ int do_sigprocmask(int how, const sigset_t *set, sigset_t 
*oldset)
     return 0;
 }
 
-#if !defined(TARGET_OPENRISC) && !defined(TARGET_UNICORE32) && \
-    !defined(TARGET_X86_64)
+#if !defined(TARGET_OPENRISC) && !defined(TARGET_UNICORE32)
 /* Just set the guest's signal mask to the specified value; the
  * caller is assumed to have called block_signals() already.
  */
@@ -1185,6 +1194,292 @@ badframe:
     return 0;
 }
 
+#elif defined(TARGET_X86_64) && TARGET_ABI_BITS == 64
+
+struct target_fpxreg {
+    uint16_t significand[4];
+    uint16_t exponent;
+    uint16_t padding[3];
+};
+
+struct target_xmmreg {
+    abi_ulong element[4];
+};
+
+struct target_fpstate {
+    unsigned short cwd;
+    unsigned short swd;
+    unsigned short twd;
+
+    unsigned short fop;
+    uint64_t rip;
+    uint64_t rdp;
+    abi_ulong mxcsr;
+    abi_ulong mxcsr_mask;
+    struct target_fpxreg _fxsr_st[8]; /* FXSR FPU reg data is ignored */
+    struct target_xmmreg _xmm[16];
+    __u32 padding[24];
+};
+
+#define X86_FXSR_MAGIC         0x0000
+
+struct target_sigcontext {
+    uint64_t r8;
+    uint64_t r9;
+    uint64_t r10;
+    uint64_t r11;
+    uint64_t r12;
+    uint64_t r13;
+    uint64_t r14;
+    uint64_t r15;
+    uint64_t edi;
+    uint64_t esi;
+    uint64_t ebp;
+    uint64_t ebx;
+    uint64_t edx;
+    uint64_t eax;
+    uint64_t ecx;
+    uint64_t esp;
+    uint64_t eip;
+    uint64_t eflags;
+    uint16_t cs;
+    uint16_t gs;
+    uint16_t fs;
+    uint16_t __pad0;
+    uint64_t err;
+    uint64_t trapno;
+    uint64_t oldmask;
+    uint64_t cr2;
+
+    uint64_t fpstate;
+    uint64_t reserved1[8];
+};
+
+struct target_ucontext {
+    abi_ulong                  tuc_flags;
+    struct target_sigcontext*  tuc_link;
+    target_stack_t             tuc_stack;
+    struct target_sigcontext   tuc_mcontext;
+    target_sigset_t            tuc_sigmask;  /* mask last for extensibility */
+};
+
+struct rt_sigframe
+{
+    char* pretcode;
+    struct target_ucontext uc;
+    struct target_siginfo info;
+    struct target_fpstate fpstate;
+};
+
+/*
+ * Set up a signal frame.
+ */
+
+/* XXX: save x87 state */
+static void setup_sigcontext(struct target_sigcontext *sc,
+        struct target_fpstate *fpstate, CPUX86State *env, abi_ulong mask,
+        abi_ulong fpstate_addr)
+{
+    CPUState *cs = CPU(x86_env_get_cpu(env));
+
+    /* already locked in setup_frame() */
+    __put_user(env->regs[R_EDI], &sc->edi);
+    __put_user(env->regs[R_ESI], &sc->esi);
+    __put_user(env->regs[R_EBP], &sc->ebp);
+    __put_user(env->regs[R_ESP], &sc->esp);
+    __put_user(env->regs[R_EBX], &sc->ebx);
+    __put_user(env->regs[R_EDX], &sc->edx);
+    __put_user(env->regs[R_ECX], &sc->ecx);
+    __put_user(env->regs[R_EAX], &sc->eax);
+    __put_user(env->regs[8], &sc->r8);
+    __put_user(env->regs[9], &sc->r9);
+    __put_user(env->regs[10], &sc->r10);
+    __put_user(env->regs[11], &sc->r11);
+    __put_user(env->regs[12], &sc->r12);
+    __put_user(env->regs[13], &sc->r13);
+    __put_user(env->regs[14], &sc->r14);
+    __put_user(env->regs[15], &sc->r15);
+    __put_user(cs->exception_index, &sc->trapno);
+    __put_user(env->error_code, &sc->err);
+    __put_user(env->eip, &sc->eip);
+    __put_user(env->eflags, &sc->eflags);
+    __put_user(env->segs[R_CS].selector, (unsigned int *)&sc->cs);
+    __put_user(0, &sc->gs);
+    __put_user(0, &sc->fs);
+
+    cpu_x86_fsave(env, fpstate_addr, 1);
+    __put_user(fpstate_addr, &sc->fpstate);
+
+    /* non-iBCS2 extensions.. */
+    __put_user(mask, &sc->oldmask);
+    __put_user(env->cr[2], &sc->cr2);
+}
+
+/*
+ * Determine which stack to use..
+ */
+
+static inline abi_ulong
+get_sigframe(struct target_sigaction *ka, CPUX86State *env, size_t frame_size)
+{
+    unsigned long esp;
+
+    /* Default to using normal stack */
+    esp = env->regs[R_ESP];
+
+    /* redzone */
+    esp -= 128;
+
+    /* This is the X/Open sanctioned signal stack switching.  */
+    if (ka->sa_flags & TARGET_SA_ONSTACK) {
+        if (sas_ss_flags(esp) == 0) {
+            esp = target_sigaltstack_used.ss_sp + 
target_sigaltstack_used.ss_size;
+        }
+    } else {
+
+        /* This is the legacy signal stack switching. */
+        if ((env->segs[R_SS].selector & 0xffff) != __USER_DS &&
+                !(ka->sa_flags & TARGET_SA_RESTORER) &&
+                ka->sa_restorer) {
+            esp = (unsigned long) ka->sa_restorer;
+        }
+    }
+    return round_down(esp - frame_size, 16) - 8;
+}
+
+/* compare linux/arch/i386/kernel/signal.c:setup_rt_frame() */
+static void setup_rt_frame(int sig, struct target_sigaction *ka,
+                           target_siginfo_t *info,
+                           target_sigset_t *set, CPUX86State *env)
+{
+    abi_ulong frame_addr;
+    struct rt_sigframe *frame;
+    int i;
+
+    frame_addr = get_sigframe(ka, env, sizeof(*frame));
+    trace_user_setup_rt_frame(env, frame_addr);
+
+    if (!lock_user_struct(VERIFY_WRITE, frame, frame_addr, 0))
+        goto give_sigsegv;
+
+    __put_user(target_sigaltstack_used.ss_size,
+               &frame->uc.tuc_stack.ss_size);
+
+    /* Create the ucontext.  */
+    __put_user(0, &frame->uc.tuc_flags);
+    __put_user(0, &frame->uc.tuc_link);
+    __put_user(target_sigaltstack_used.ss_sp, &frame->uc.tuc_stack.ss_sp);
+    __put_user(sas_ss_flags(get_sp_from_cpustate(env)),
+               &frame->uc.tuc_stack.ss_flags);
+
+    setup_sigcontext(&frame->uc.tuc_mcontext, &frame->fpstate, env,
+            set->sig[0], frame_addr + offsetof(struct rt_sigframe, fpstate));
+
+    for(i = 0; i < TARGET_NSIG_WORDS; i++) {
+        __put_user(set->sig[i], &frame->uc.tuc_sigmask.sig[i]);
+    }
+
+    /* Set up to return from userspace.  If provided, use a stub
+       already in userspace.  */
+    if (ka->sa_flags & TARGET_SA_RESTORER) {
+        __put_user(ka->sa_restorer, &frame->pretcode);
+    } else {
+        goto give_sigsegv;
+    }
+
+    /* Set up registers for signal handler */
+    env->regs[R_ESP] = frame_addr;
+    env->eip = ka->_sa_handler;
+
+    env->eflags &= ~TF_MASK;
+
+    unlock_user_struct(frame, frame_addr, 1);
+
+    return;
+
+give_sigsegv:
+    if (sig == TARGET_SIGSEGV) {
+        ka->_sa_handler = TARGET_SIG_DFL;
+    }
+    force_sig(TARGET_SIGSEGV /* , current */);
+}
+
+static int
+restore_sigcontext(CPUX86State *env, struct target_sigcontext *sc)
+{
+    unsigned int err = 0;
+    abi_ulong fpstate_addr;
+    unsigned int tmpflags;
+
+    env->regs[R_EDI] = tswapl(sc->edi);
+    env->regs[R_ESI] = tswapl(sc->esi);
+    env->regs[R_EBP] = tswapl(sc->ebp);
+    env->regs[R_ESP] = tswapl(sc->esp);
+    env->regs[R_EBX] = tswapl(sc->ebx);
+    env->regs[R_EDX] = tswapl(sc->edx);
+    env->regs[R_ECX] = tswapl(sc->ecx);
+    env->regs[R_EAX] = tswapl(sc->eax);
+    env->regs[8] = tswapl(sc->r8);
+    env->regs[9] = tswapl(sc->r9);
+    env->regs[10] = tswapl(sc->r10);
+    env->regs[11] = tswapl(sc->r11);
+    env->regs[12] = tswapl(sc->r12);
+    env->regs[13] = tswapl(sc->r13);
+    env->regs[14] = tswapl(sc->r14);
+    env->regs[15] = tswapl(sc->r15);
+
+    env->eip = tswapl(sc->eip);
+
+    cpu_x86_load_seg(env, R_CS, lduw_p(&sc->cs) | 3);
+
+    tmpflags = tswapl(sc->eflags);
+    env->eflags = (env->eflags & ~0x40DD5) | (tmpflags & 0x40DD5);
+    //         regs->orig_eax = -1;            /* disable syscall checks */
+
+    fpstate_addr = tswapl(sc->fpstate);
+    if (fpstate_addr != 0) {
+        if (!access_ok(VERIFY_READ, fpstate_addr,
+                       sizeof(struct target_fpstate)))
+            goto badframe;
+        cpu_x86_frstor(env, fpstate_addr, 1);
+    }
+
+    return err;
+badframe:
+    return 1;
+}
+
+long do_rt_sigreturn(CPUX86State *env)
+{
+    abi_ulong frame_addr;
+    struct rt_sigframe *frame;
+    sigset_t set;
+
+    frame_addr = env->regs[R_ESP] - 8;
+    trace_user_do_rt_sigreturn(env, frame_addr);
+    if (!lock_user_struct(VERIFY_READ, frame, frame_addr, 1))
+        goto badframe;
+    target_to_host_sigset(&set, &frame->uc.tuc_sigmask);
+    set_sigmask(&set);
+
+    if (restore_sigcontext(env, &frame->uc.tuc_mcontext)) {
+        goto badframe;
+    }
+
+    if (do_sigaltstack(frame_addr + offsetof(struct rt_sigframe, 
uc.tuc_stack), 0,
+                       get_sp_from_cpustate(env)) == -EFAULT) {
+        goto badframe;
+    }
+
+    unlock_user_struct(frame, frame_addr, 0);
+    return -TARGET_QEMU_ESIGRETURN;
+
+badframe:
+    unlock_user_struct(frame, frame_addr, 0);
+    force_sig(TARGET_SIGSEGV);
+    return 0;
+}
+
 #elif defined(TARGET_AARCH64)
 
 struct target_sigcontext {
@@ -5883,7 +6178,8 @@ static void handle_pending_signal(CPUArchState *cpu_env, 
int sig)
 #endif
         /* prepare the stack frame of the virtual CPU */
 #if defined(TARGET_ABI_MIPSN32) || defined(TARGET_ABI_MIPSN64) \
-    || defined(TARGET_OPENRISC) || defined(TARGET_TILEGX)
+    || defined(TARGET_OPENRISC) || defined(TARGET_TILEGX) \
+    || defined(TARGET_X86_64)
         /* These targets do not have traditional signals.  */
         setup_rt_frame(sig, sa, &k->info, &target_old_set, cpu_env);
 #else
-- 
2.1.4