From a04e134ad1f4271bea2c7b7649b21e35ded91005 Mon Sep 17 00:00:00 2001
From: ths <ths@c046a42c-6fe2-441c-8c8c-71466251a162>
Date: Thu, 27 Sep 2007 13:57:58 +0000
Subject: linux-user sigaltstack() syscall, by Thayne Harbaugh.

git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@3252 c046a42c-6fe2-441c-8c8c-71466251a162
---
 linux-user/alpha/target_signal.h   |  24 ++++++
 linux-user/arm/target_signal.h     |  24 ++++++
 linux-user/i386/target_signal.h    |  24 ++++++
 linux-user/m68k/target_signal.h    |  24 ++++++
 linux-user/mips/target_signal.h    |  24 ++++++
 linux-user/ppc/target_signal.h     |  24 ++++++
 linux-user/ppc64/target_signal.h   |  24 ++++++
 linux-user/qemu.h                  |   4 +
 linux-user/sh4/target_signal.h     |  24 ++++++
 linux-user/signal.c                | 156 +++++++++++++++++++++++++++----------
 linux-user/sparc/target_signal.h   |  24 ++++++
 linux-user/sparc64/target_signal.h |  24 ++++++
 linux-user/syscall.c               |   7 ++
 linux-user/x86_64/target_signal.h  |  24 ++++++
 target-alpha/cpu.h                 |   5 ++
 target-arm/cpu.h                   |   5 ++
 target-i386/cpu.h                  |   5 ++
 target-mips/cpu.h                  |   5 ++
 target-ppc/cpu.h                   |   5 ++
 target-sparc/cpu.h                 |  12 +++
 20 files changed, 425 insertions(+), 43 deletions(-)
 create mode 100644 linux-user/alpha/target_signal.h
 create mode 100644 linux-user/arm/target_signal.h
 create mode 100644 linux-user/i386/target_signal.h
 create mode 100644 linux-user/m68k/target_signal.h
 create mode 100644 linux-user/mips/target_signal.h
 create mode 100644 linux-user/ppc/target_signal.h
 create mode 100644 linux-user/ppc64/target_signal.h
 create mode 100644 linux-user/sh4/target_signal.h
 create mode 100644 linux-user/sparc/target_signal.h
 create mode 100644 linux-user/sparc64/target_signal.h
 create mode 100644 linux-user/x86_64/target_signal.h

diff --git a/linux-user/alpha/target_signal.h b/linux-user/alpha/target_signal.h
new file mode 100644
index 0000000000..bf54ac71d8
--- /dev/null
+++ b/linux-user/alpha/target_signal.h
@@ -0,0 +1,24 @@
+#ifndef TARGET_SIGNAL_H
+#define TARGET_SIGNAL_H
+
+#include "cpu.h"
+
+/* this struct defines a stack used during syscall handling */
+
+typedef struct target_sigaltstack {
+	target_ulong ss_sp;
+	target_long ss_flags;
+	target_ulong ss_size;
+} target_stack_t;
+
+
+/*
+ * sigaltstack controls
+ */
+#define TARGET_SS_ONSTACK	1
+#define TARGET_SS_DISABLE	2
+
+#define TARGET_MINSIGSTKSZ	4096
+#define TARGET_SIGSTKSZ		16384
+
+#endif /* TARGET_SIGNAL_H */
diff --git a/linux-user/arm/target_signal.h b/linux-user/arm/target_signal.h
new file mode 100644
index 0000000000..eb4a0bb12c
--- /dev/null
+++ b/linux-user/arm/target_signal.h
@@ -0,0 +1,24 @@
+#ifndef TARGET_SIGNAL_H
+#define TARGET_SIGNAL_H
+
+#include "cpu.h"
+
+/* this struct defines a stack used during syscall handling */
+
+typedef struct target_sigaltstack {
+	target_ulong ss_sp;
+	target_long ss_flags;
+	target_ulong ss_size;
+} target_stack_t;
+
+
+/*
+ * sigaltstack controls
+ */
+#define TARGET_SS_ONSTACK	1
+#define TARGET_SS_DISABLE	2
+
+#define TARGET_MINSIGSTKSZ	2048
+#define TARGET_SIGSTKSZ		8192
+
+#endif /* TARGET_SIGNAL_H */
diff --git a/linux-user/i386/target_signal.h b/linux-user/i386/target_signal.h
new file mode 100644
index 0000000000..eb4a0bb12c
--- /dev/null
+++ b/linux-user/i386/target_signal.h
@@ -0,0 +1,24 @@
+#ifndef TARGET_SIGNAL_H
+#define TARGET_SIGNAL_H
+
+#include "cpu.h"
+
+/* this struct defines a stack used during syscall handling */
+
+typedef struct target_sigaltstack {
+	target_ulong ss_sp;
+	target_long ss_flags;
+	target_ulong ss_size;
+} target_stack_t;
+
+
+/*
+ * sigaltstack controls
+ */
+#define TARGET_SS_ONSTACK	1
+#define TARGET_SS_DISABLE	2
+
+#define TARGET_MINSIGSTKSZ	2048
+#define TARGET_SIGSTKSZ		8192
+
+#endif /* TARGET_SIGNAL_H */
diff --git a/linux-user/m68k/target_signal.h b/linux-user/m68k/target_signal.h
new file mode 100644
index 0000000000..b481195073
--- /dev/null
+++ b/linux-user/m68k/target_signal.h
@@ -0,0 +1,24 @@
+#ifndef TARGET_SIGNAL_H
+#define TARGET_SIGNAL_H
+
+#include "cpu.h"
+
+/* this struct defines a stack used during syscall handling */
+
+typedef struct target_sigaltstack {
+	target_ulong ss_sp;
+	target_long ss_flags;
+	target_ulong ss_size;
+} target_stack_t;
+
+
+/*
+ * sigaltstack controls
+ */
+#define TARGET_SS_ONSTACK	1
+#define TARGET_SS_DISABLE	2
+
+#define TARGET_MINSIGSTKSZ	2048
+#define TARGET_SIGSTKSZ	8192
+
+#endif /* TARGET_SIGNAL_H */
diff --git a/linux-user/mips/target_signal.h b/linux-user/mips/target_signal.h
new file mode 100644
index 0000000000..c94788497c
--- /dev/null
+++ b/linux-user/mips/target_signal.h
@@ -0,0 +1,24 @@
+#ifndef TARGET_SIGNAL_H
+#define TARGET_SIGNAL_H
+
+#include "cpu.h"
+
+/* this struct defines a stack used during syscall handling */
+
+typedef struct target_sigaltstack {
+	target_ulong ss_sp;
+	target_ulong ss_size;
+	target_long ss_flags;
+} target_stack_t;
+
+
+/*
+ * sigaltstack controls
+ */
+#define TARGET_SS_ONSTACK     1
+#define TARGET_SS_DISABLE     2
+
+#define TARGET_MINSIGSTKSZ    2048
+#define TARGET_SIGSTKSZ       8192
+
+#endif /* TARGET_SIGNAL_H */
diff --git a/linux-user/ppc/target_signal.h b/linux-user/ppc/target_signal.h
new file mode 100644
index 0000000000..e210e7a317
--- /dev/null
+++ b/linux-user/ppc/target_signal.h
@@ -0,0 +1,24 @@
+#ifndef TARGET_SIGNAL_H
+#define TARGET_SIGNAL_H
+
+#include "cpu.h"
+
+/* this struct defines a stack used during syscall handling */
+
+typedef struct target_sigaltstack {
+	target_ulong ss_sp;
+	target_long ss_flags;
+	target_ulong ss_size;
+} target_stack_t;
+
+
+/*
+ * sigaltstack controls
+ */
+#define TARGET_SS_ONSTACK     1
+#define TARGET_SS_DISABLE     2
+
+#define TARGET_MINSIGSTKSZ    2048
+#define TARGET_SIGSTKSZ       8192
+
+#endif /* TARGET_SIGNAL_H */
diff --git a/linux-user/ppc64/target_signal.h b/linux-user/ppc64/target_signal.h
new file mode 100644
index 0000000000..e210e7a317
--- /dev/null
+++ b/linux-user/ppc64/target_signal.h
@@ -0,0 +1,24 @@
+#ifndef TARGET_SIGNAL_H
+#define TARGET_SIGNAL_H
+
+#include "cpu.h"
+
+/* this struct defines a stack used during syscall handling */
+
+typedef struct target_sigaltstack {
+	target_ulong ss_sp;
+	target_long ss_flags;
+	target_ulong ss_size;
+} target_stack_t;
+
+
+/*
+ * sigaltstack controls
+ */
+#define TARGET_SS_ONSTACK     1
+#define TARGET_SS_DISABLE     2
+
+#define TARGET_MINSIGSTKSZ    2048
+#define TARGET_SIGSTKSZ       8192
+
+#endif /* TARGET_SIGNAL_H */
diff --git a/linux-user/qemu.h b/linux-user/qemu.h
index 4b857f3d14..78e9ab34fa 100644
--- a/linux-user/qemu.h
+++ b/linux-user/qemu.h
@@ -9,6 +9,7 @@
 
 #include "cpu.h"
 #include "syscall.h"
+#include "target_signal.h"
 #include "gdbstub.h"
 
 /* This struct is used to hold certain information about the image.
@@ -149,6 +150,9 @@ void host_to_target_siginfo(target_siginfo_t *tinfo, const siginfo_t *info);
 void target_to_host_siginfo(siginfo_t *info, const target_siginfo_t *tinfo);
 long do_sigreturn(CPUState *env);
 long do_rt_sigreturn(CPUState *env);
+int do_sigaltstack(const struct target_sigaltstack *uss,
+                   struct target_sigaltstack *uoss,
+                   target_ulong sp);
 
 #ifdef TARGET_I386
 /* vm86.c */
diff --git a/linux-user/sh4/target_signal.h b/linux-user/sh4/target_signal.h
new file mode 100644
index 0000000000..e210e7a317
--- /dev/null
+++ b/linux-user/sh4/target_signal.h
@@ -0,0 +1,24 @@
+#ifndef TARGET_SIGNAL_H
+#define TARGET_SIGNAL_H
+
+#include "cpu.h"
+
+/* this struct defines a stack used during syscall handling */
+
+typedef struct target_sigaltstack {
+	target_ulong ss_sp;
+	target_long ss_flags;
+	target_ulong ss_size;
+} target_stack_t;
+
+
+/*
+ * sigaltstack controls
+ */
+#define TARGET_SS_ONSTACK     1
+#define TARGET_SS_DISABLE     2
+
+#define TARGET_MINSIGSTKSZ    2048
+#define TARGET_SIGSTKSZ       8192
+
+#endif /* TARGET_SIGNAL_H */
diff --git a/linux-user/signal.c b/linux-user/signal.c
index 97f10957d4..945dd14e0c 100644
--- a/linux-user/signal.c
+++ b/linux-user/signal.c
@@ -26,6 +26,7 @@
 #include <errno.h>
 #include <sys/ucontext.h>
 
+#include "target_signal.h"
 #include "qemu.h"
 
 //#define DEBUG_SIGNAL
@@ -45,6 +46,12 @@ struct emulated_sigaction {
                              first signal, we put it here */
 };
 
+struct target_sigaltstack target_sigaltstack_used = {
+    .ss_sp = 0,
+    .ss_size = 0,
+    .ss_flags = TARGET_SS_DISABLE,
+};
+
 static struct emulated_sigaction sigact_table[TARGET_NSIG];
 static struct sigqueue sigqueue_table[MAX_SIGQUEUE_SIZE]; /* siginfo queue */
 static struct sigqueue *first_free; /* first free siginfo queue entry */
@@ -92,6 +99,18 @@ static uint8_t host_to_target_signal_table[65] = {
 };
 static uint8_t target_to_host_signal_table[65];
 
+static inline int on_sig_stack(unsigned long sp)
+{
+    return (sp - target_sigaltstack_used.ss_sp
+            < target_sigaltstack_used.ss_size);
+}
+
+static inline int sas_ss_flags(unsigned long sp)
+{
+    return (target_sigaltstack_used.ss_size == 0 ? SS_DISABLE
+            : on_sig_stack(sp) ? SS_ONSTACK : 0);
+}
+
 static inline int host_to_target_signal(int sig)
 {
     return host_to_target_signal_table[sig];
@@ -419,6 +438,67 @@ static void host_signal_handler(int host_signum, siginfo_t *info,
     }
 }
 
+int do_sigaltstack(const struct target_sigaltstack *uss,
+                   struct target_sigaltstack *uoss,
+                   target_ulong sp)
+{
+    int ret;
+    struct target_sigaltstack oss;
+
+    /* XXX: test errors */
+    if(uoss)
+    {
+        __put_user(target_sigaltstack_used.ss_sp, &oss.ss_sp);
+        __put_user(target_sigaltstack_used.ss_size, &oss.ss_size);
+        __put_user(sas_ss_flags(sp), &oss.ss_flags);
+    }
+
+    if(uss)
+    {
+	struct target_sigaltstack ss;
+
+	ret = -EFAULT;
+	if (!access_ok(VERIFY_READ, uss, sizeof(*uss))
+	    || __get_user(ss.ss_sp, &uss->ss_sp)
+	    || __get_user(ss.ss_size, &uss->ss_size)
+	    || __get_user(ss.ss_flags, &uss->ss_flags))
+            goto out;
+
+	ret = -EPERM;
+	if (on_sig_stack(sp))
+            goto out;
+
+	ret = -EINVAL;
+	if (ss.ss_flags != TARGET_SS_DISABLE
+            && ss.ss_flags != TARGET_SS_ONSTACK
+            && ss.ss_flags != 0)
+            goto out;
+
+	if (ss.ss_flags == TARGET_SS_DISABLE) {
+            ss.ss_size = 0;
+            ss.ss_sp = 0;
+	} else {
+            ret = -ENOMEM;
+            if (ss.ss_size < MINSIGSTKSZ)
+                goto out;
+	}
+
+        target_sigaltstack_used.ss_sp = ss.ss_sp;
+        target_sigaltstack_used.ss_size = ss.ss_size;
+    }
+
+    if (uoss) {
+        ret = -EFAULT;
+        if (!access_ok(VERIFY_WRITE, uoss, sizeof(oss)))
+            goto out;
+        memcpy(uoss, &oss, sizeof(oss));
+    }
+
+    ret = 0;
+out:
+    return ret;
+}
+
 int do_sigaction(int sig, const struct target_sigaction *act,
                  struct target_sigaction *oact)
 {
@@ -551,12 +631,6 @@ struct target_sigcontext {
 	target_ulong cr2;
 };
 
-typedef struct target_sigaltstack {
-	target_ulong ss_sp;
-	int ss_flags;
-	target_ulong ss_size;
-} target_stack_t;
-
 struct target_ucontext {
         target_ulong	  tuc_flags;
 	target_ulong      tuc_link;
@@ -640,16 +714,14 @@ get_sigframe(struct emulated_sigaction *ka, CPUX86State *env, size_t frame_size)
 
 	/* Default to using normal stack */
 	esp = env->regs[R_ESP];
-#if 0
 	/* This is the X/Open sanctioned signal stack switching.  */
-	if (ka->sa.sa_flags & SA_ONSTACK) {
-		if (sas_ss_flags(esp) == 0)
-			esp = current->sas_ss_sp + current->sas_ss_size;
-	}
+        if (ka->sa.sa_flags & TARGET_SA_ONSTACK) {
+            if (sas_ss_flags(esp) == 0)
+                esp = target_sigaltstack_used.ss_sp + target_sigaltstack_used.ss_size;
+        }
 
 	/* This is the legacy signal stack switching. */
 	else
-#endif
         if ((env->segs[R_SS].selector & 0xffff) != __USER_DS &&
             !(ka->sa.sa_flags & TARGET_SA_RESTORER) &&
             ka->sa.sa_restorer) {
@@ -750,11 +822,11 @@ static void setup_rt_frame(int sig, struct emulated_sigaction *ka,
 	/* Create the ucontext.  */
 	err |= __put_user(0, &frame->uc.tuc_flags);
 	err |= __put_user(0, &frame->uc.tuc_link);
-	err |= __put_user(/*current->sas_ss_sp*/ 0,
+	err |= __put_user(target_sigaltstack_used.ss_sp,
 			  &frame->uc.tuc_stack.ss_sp);
-	err |= __put_user(/* sas_ss_flags(regs->esp) */ 0,
+	err |= __put_user(sas_ss_flags(get_sp_from_cpustate(env)),
 			  &frame->uc.tuc_stack.ss_flags);
-	err |= __put_user(/* current->sas_ss_size */ 0,
+	err |= __put_user(target_sigaltstack_used.ss_size,
 			  &frame->uc.tuc_stack.ss_size);
 	err |= setup_sigcontext(&frame->uc.tuc_mcontext, &frame->fpstate,
 			        env, set->sig[0]);
@@ -880,7 +952,6 @@ long do_rt_sigreturn(CPUX86State *env)
 {
 	struct rt_sigframe *frame = (struct rt_sigframe *)g2h(env->regs[R_ESP] - 4);
         sigset_t set;
-        //	stack_t st;
 	int eax;
 
 #if 0
@@ -893,13 +964,9 @@ long do_rt_sigreturn(CPUX86State *env)
 	if (restore_sigcontext(env, &frame->uc.tuc_mcontext, &eax))
 		goto badframe;
 
-#if 0
-	if (__copy_from_user(&st, &frame->uc.tuc_stack, sizeof(st)))
+	if (do_sigaltstack(&frame->uc.tuc_stack, NULL, get_sp_from_cpustate(env)) == -EFAULT)
 		goto badframe;
-	/* It is more difficult to avoid calling this function than to
-	   call it and ignore errors.  */
-	do_sigaltstack(&st, NULL, regs->esp);
-#endif
+
 	return eax;
 
 badframe:
@@ -933,12 +1000,6 @@ struct target_sigcontext {
 	target_ulong fault_address;
 };
 
-typedef struct target_sigaltstack {
-	target_ulong ss_sp;
-	int ss_flags;
-	target_ulong ss_size;
-} target_stack_t;
-
 struct target_ucontext {
     target_ulong tuc_flags;
     target_ulong tuc_link;
@@ -1031,13 +1092,11 @@ get_sigframe(struct emulated_sigaction *ka, CPUState *regs, int framesize)
 {
 	unsigned long sp = regs->regs[13];
 
-#if 0
 	/*
 	 * This is the X/Open sanctioned signal stack switching.
 	 */
-	if ((ka->sa.sa_flags & SA_ONSTACK) && !sas_ss_flags(sp))
-		sp = current->sas_ss_sp + current->sas_ss_size;
-#endif
+	if ((ka->sa.sa_flags & TARGET_SA_ONSTACK) && !sas_ss_flags(sp))
+            sp = target_sigaltstack_used.ss_sp + target_sigaltstack_used.ss_size;
 	/*
 	 * ATPCS B01 mandates 8-byte alignment
 	 */
@@ -1074,8 +1133,8 @@ setup_return(CPUState *env, struct emulated_sigaction *ka,
 		else
 			cpsr &= ~T_BIT;
 	}
-#endif
-#endif
+#endif /* CONFIG_ARM_THUMB */
+#endif /* 0 */
 #endif /* TARGET_CONFIG_CPU_32 */
 
 	if (ka->sa.sa_flags & TARGET_SA_RESTORER) {
@@ -1132,6 +1191,7 @@ static void setup_rt_frame(int usig, struct emulated_sigaction *ka,
 			   target_sigset_t *set, CPUState *env)
 {
 	struct rt_sigframe *frame = get_sigframe(ka, env, sizeof(*frame));
+	struct target_sigaltstack stack;
 	int i, err = 0;
 
 	if (!access_ok(VERIFY_WRITE, frame, sizeof (*frame)))
@@ -1144,6 +1204,15 @@ static void setup_rt_frame(int usig, struct emulated_sigaction *ka,
 	/* Clear all the bits of the ucontext we don't use.  */
 	memset(&frame->uc, 0, offsetof(struct target_ucontext, tuc_mcontext));
 
+        memset(&stack, 0, sizeof(stack));
+        __put_user(target_sigaltstack_used.ss_sp, &stack.ss_sp);
+        __put_user(target_sigaltstack_used.ss_size, &stack.ss_size);
+        __put_user(sas_ss_flags(get_sp_from_cpustate(env)), &stack.ss_flags);
+        if (!access_ok(VERIFY_WRITE, &frame->uc.tuc_stack, sizeof(stack)))
+            err = 1;
+        else
+            memcpy(&frame->uc.tuc_stack, &stack, sizeof(stack));
+
 	err |= setup_sigcontext(&frame->uc.tuc_mcontext, /*&frame->fpstate,*/
 				env, set->sig[0]);
         for(i = 0; i < TARGET_NSIG_WORDS; i++) {
@@ -1270,6 +1339,9 @@ long do_rt_sigreturn(CPUState *env)
 	if (restore_sigcontext(env, &frame->uc.tuc_mcontext))
 		goto badframe;
 
+	if (do_sigaltstack(&frame->uc.tuc_stack, NULL, get_sp_from_cpustate(env)) == -EFAULT)
+		goto badframe;
+
 #if 0
 	/* Send SIGTRAP if we're single-stepping */
 	if (ptrace_cancel_bpt(current))
@@ -1382,14 +1454,13 @@ static inline void *get_sigframe(struct emulated_sigaction *sa, CPUState *env, u
 	unsigned long sp;
 
 	sp = env->regwptr[UREG_FP];
-#if 0
 
 	/* This is the X/Open sanctioned signal stack switching.  */
-	if (sa->sa_flags & TARGET_SA_ONSTACK) {
-		if (!on_sig_stack(sp) && !((current->sas_ss_sp + current->sas_ss_size) & 7))
-			sp = current->sas_ss_sp + current->sas_ss_size;
+	if (sa->sa.sa_flags & TARGET_SA_ONSTACK) {
+            if (!on_sig_stack(sp)
+                && !((target_sigaltstack_used.ss_sp + target_sigaltstack_used.ss_size) & 7))
+                sp = target_sigaltstack_used.ss_sp + target_sigaltstack_used.ss_size;
 	}
-#endif
 	return g2h(sp - framesize);
 }
 
@@ -1842,11 +1913,10 @@ get_sigframe(struct emulated_sigaction *ka, CPUState *regs, size_t frame_size)
      */
     sp -= 32;
 
-#if 0
     /* This is the X/Open sanctioned signal stack switching.  */
-    if ((ka->sa.sa_flags & SA_ONSTACK) && (sas_ss_flags (sp) == 0))
-	sp = current->sas_ss_sp + current->sas_ss_size;
-#endif
+    if ((ka->sa.sa_flags & TARGET_SA_ONSTACK) && (sas_ss_flags (sp) == 0)) {
+        sp = target_sigaltstack_used.ss_sp + target_sigaltstack_used.ss_size;
+    }
 
     return g2h((sp - frame_size) & ~7);
 }
diff --git a/linux-user/sparc/target_signal.h b/linux-user/sparc/target_signal.h
new file mode 100644
index 0000000000..bf54ac71d8
--- /dev/null
+++ b/linux-user/sparc/target_signal.h
@@ -0,0 +1,24 @@
+#ifndef TARGET_SIGNAL_H
+#define TARGET_SIGNAL_H
+
+#include "cpu.h"
+
+/* this struct defines a stack used during syscall handling */
+
+typedef struct target_sigaltstack {
+	target_ulong ss_sp;
+	target_long ss_flags;
+	target_ulong ss_size;
+} target_stack_t;
+
+
+/*
+ * sigaltstack controls
+ */
+#define TARGET_SS_ONSTACK	1
+#define TARGET_SS_DISABLE	2
+
+#define TARGET_MINSIGSTKSZ	4096
+#define TARGET_SIGSTKSZ		16384
+
+#endif /* TARGET_SIGNAL_H */
diff --git a/linux-user/sparc64/target_signal.h b/linux-user/sparc64/target_signal.h
new file mode 100644
index 0000000000..bf54ac71d8
--- /dev/null
+++ b/linux-user/sparc64/target_signal.h
@@ -0,0 +1,24 @@
+#ifndef TARGET_SIGNAL_H
+#define TARGET_SIGNAL_H
+
+#include "cpu.h"
+
+/* this struct defines a stack used during syscall handling */
+
+typedef struct target_sigaltstack {
+	target_ulong ss_sp;
+	target_long ss_flags;
+	target_ulong ss_size;
+} target_stack_t;
+
+
+/*
+ * sigaltstack controls
+ */
+#define TARGET_SS_ONSTACK	1
+#define TARGET_SS_DISABLE	2
+
+#define TARGET_MINSIGSTKSZ	4096
+#define TARGET_SIGSTKSZ		16384
+
+#endif /* TARGET_SIGNAL_H */
diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index 41d58da14f..5f1c804aaa 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -4318,7 +4318,14 @@ target_long do_syscall(void *cpu_env, int num, target_long arg1,
     case TARGET_NR_capset:
         goto unimplemented;
     case TARGET_NR_sigaltstack:
+#if defined(TARGET_I386) || defined(TARGET_ARM) || defined(TARGET_SPARC)
+        ret = do_sigaltstack((struct target_sigaltstack *)arg1,
+                             (struct target_sigaltstack *)arg2,
+                             get_sp_from_cpustate((CPUState *)cpu_env));
+        break;
+#else
         goto unimplemented;
+#endif
     case TARGET_NR_sendfile:
         goto unimplemented;
 #ifdef TARGET_NR_getpmsg
diff --git a/linux-user/x86_64/target_signal.h b/linux-user/x86_64/target_signal.h
new file mode 100644
index 0000000000..eb4a0bb12c
--- /dev/null
+++ b/linux-user/x86_64/target_signal.h
@@ -0,0 +1,24 @@
+#ifndef TARGET_SIGNAL_H
+#define TARGET_SIGNAL_H
+
+#include "cpu.h"
+
+/* this struct defines a stack used during syscall handling */
+
+typedef struct target_sigaltstack {
+	target_ulong ss_sp;
+	target_long ss_flags;
+	target_ulong ss_size;
+} target_stack_t;
+
+
+/*
+ * sigaltstack controls
+ */
+#define TARGET_SS_ONSTACK	1
+#define TARGET_SS_DISABLE	2
+
+#define TARGET_MINSIGSTKSZ	2048
+#define TARGET_SIGSTKSZ		8192
+
+#endif /* TARGET_SIGNAL_H */
diff --git a/target-alpha/cpu.h b/target-alpha/cpu.h
index 3f517e67b6..ef61d87483 100644
--- a/target-alpha/cpu.h
+++ b/target-alpha/cpu.h
@@ -397,4 +397,9 @@ void cpu_loop_exit (void);
 void pal_init (CPUState *env);
 void call_pal (CPUState *env, int palcode);
 
+static inline target_ulong get_sp_from_cpustate(CPUAlphaState *state)
+{
+    return state->ir[IR_SP];
+}
+
 #endif /* !defined (__CPU_ALPHA_H__) */
diff --git a/target-arm/cpu.h b/target-arm/cpu.h
index 76fdbb26bf..926aa2a32a 100644
--- a/target-arm/cpu.h
+++ b/target-arm/cpu.h
@@ -300,6 +300,11 @@ void cpu_arm_set_cp_io(CPUARMState *env, int cpnum,
 #define cpu_gen_code cpu_arm_gen_code
 #define cpu_signal_handler cpu_arm_signal_handler
 
+static inline target_ulong get_sp_from_cpustate(CPUARMState *state)
+{
+   return state->regs[13];
+}
+
 #include "cpu-all.h"
 
 #endif
diff --git a/target-i386/cpu.h b/target-i386/cpu.h
index 2cc7d64e95..4f454c6e9e 100644
--- a/target-i386/cpu.h
+++ b/target-i386/cpu.h
@@ -688,6 +688,11 @@ static inline int cpu_get_time_fast(void)
 #define cpu_gen_code cpu_x86_gen_code
 #define cpu_signal_handler cpu_x86_signal_handler
 
+static inline target_ulong get_sp_from_cpustate(CPUX86State *state)
+{
+    return state->regs[R_ESP];
+}
+
 #include "cpu-all.h"
 
 #include "svm.h"
diff --git a/target-mips/cpu.h b/target-mips/cpu.h
index 569f9325bf..dd8388152a 100644
--- a/target-mips/cpu.h
+++ b/target-mips/cpu.h
@@ -548,4 +548,9 @@ CPUMIPSState *cpu_mips_init(void);
 uint32_t cpu_mips_get_clock (void);
 int cpu_mips_signal_handler(int host_signum, void *pinfo, void *puc);
 
+static inline target_ulong get_sp_from_cpustate(CPUMIPSState *state)
+{
+    return state->gpr[29][state->current_tc];
+}
+
 #endif /* !defined (__MIPS_CPU_H__) */
diff --git a/target-ppc/cpu.h b/target-ppc/cpu.h
index f1df741e1e..e428f70f16 100644
--- a/target-ppc/cpu.h
+++ b/target-ppc/cpu.h
@@ -1146,4 +1146,9 @@ enum {
 
 /*****************************************************************************/
 
+static inline target_ulong get_sp_from_cpustate(CPUPPCState *state)
+{
+    return state->gpr[1];
+}
+
 #endif /* !defined (__CPU_PPC_H__) */
diff --git a/target-sparc/cpu.h b/target-sparc/cpu.h
index 5c8c49ab63..cb672717f4 100644
--- a/target-sparc/cpu.h
+++ b/target-sparc/cpu.h
@@ -316,6 +316,18 @@ void cpu_check_irqs(CPUSPARCState *env);
 #define cpu_gen_code cpu_sparc_gen_code
 #define cpu_signal_handler cpu_sparc_signal_handler
 
+#ifndef UREG_I6
+#define UREG_I6        6
+#endif
+#ifndef UREG_FP
+#define UREG_FP        UREG_I6
+#endif
+
+static inline target_ulong get_sp_from_cpustate(CPUSPARCState *state)
+{
+    return state->regwptr[UREG_FP];
+}
+
 #include "cpu-all.h"
 
 #endif
-- 
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