[Qemu-devel] [PATCH v3 10/13] linux-user: Clean up handling of clone() argument order

[Peter Maydell]

Linux manages to have three separate orderings of the arguments to
the clone() syscall on different architectures. In the kernel these
are selected via CONFIG_CLONE_BACKWARDS and CONFIG_CLONE_BACKWARDS2.
Clean up our implementation of this to use similar #define names
rather than a TARGET_* ifdef ladder.

This includes behaviour changes fixing bugs on cris, x86-64, m68k,
openrisc and unicore32.  cris had explicit but wrong handling; the
others were just incorrectly using QEMU's default, which happened
to be the equivalent of CONFIG_CLONE_BACKWARDS. (unicore32 appears
to be broken in the mainline kernel in that it tries to use arg3 for
both parent_tidptr and newtls simultaneously -- we don't attempt
to emulate this bug...)

Signed-off-by: Peter Maydell <address@hidden>
---
 linux-user/arm/syscall.h        |    2 ++
 linux-user/cris/syscall.h       |    2 ++
 linux-user/i386/syscall.h       |    2 ++
 linux-user/microblaze/syscall.h |    2 ++
 linux-user/mips/syscall.h       |    2 ++
 linux-user/mips64/syscall.h     |    2 ++
 linux-user/ppc/syscall.h        |    2 ++
 linux-user/s390x/syscall.h      |    2 ++
 linux-user/sparc/syscall.h      |    7 +++++++
 linux-user/sparc64/syscall.h    |    7 +++++++
 linux-user/syscall.c            |   18 +++++++++++-------
 11 files changed, 41 insertions(+), 7 deletions(-)

diff --git a/linux-user/arm/syscall.h b/linux-user/arm/syscall.h
index 003d424..73f2931 100644
--- a/linux-user/arm/syscall.h
+++ b/linux-user/arm/syscall.h
@@ -40,3 +40,5 @@ struct target_pt_regs {
 #else
 #define UNAME_MACHINE "armv5tel"
 #endif
+
+#define TARGET_CLONE_BACKWARDS
diff --git a/linux-user/cris/syscall.h b/linux-user/cris/syscall.h
index 50e50b4..832ee64 100644
--- a/linux-user/cris/syscall.h
+++ b/linux-user/cris/syscall.h
@@ -38,4 +38,6 @@ struct target_pt_regs {
         unsigned long eda;
 };
 
+#define TARGET_CLONE_BACKWARDS2
+
 #endif
diff --git a/linux-user/i386/syscall.h b/linux-user/i386/syscall.h
index 266e2c4..12b8c3b 100644
--- a/linux-user/i386/syscall.h
+++ b/linux-user/i386/syscall.h
@@ -144,3 +144,5 @@ struct target_vm86plus_struct {
 };
 
 #define UNAME_MACHINE "i686"
+
+#define TARGET_CLONE_BACKWARDS
diff --git a/linux-user/microblaze/syscall.h b/linux-user/microblaze/syscall.h
index c3e5c55..d550989 100644
--- a/linux-user/microblaze/syscall.h
+++ b/linux-user/microblaze/syscall.h
@@ -48,4 +48,6 @@ struct target_pt_regs {
         uint32_t kernel_mode;
 };
 
+#define TARGET_CLONE_BACKWARDS
+
 #endif
diff --git a/linux-user/mips/syscall.h b/linux-user/mips/syscall.h
index 3deb862..9d437d9 100644
--- a/linux-user/mips/syscall.h
+++ b/linux-user/mips/syscall.h
@@ -225,3 +225,5 @@ struct target_pt_regs {
 #define TARGET_QEMU_ESIGRETURN 255
 
 #define UNAME_MACHINE "mips"
+
+#define TARGET_CLONE_BACKWARDS
diff --git a/linux-user/mips64/syscall.h b/linux-user/mips64/syscall.h
index cd707df..1710f76 100644
--- a/linux-user/mips64/syscall.h
+++ b/linux-user/mips64/syscall.h
@@ -222,3 +222,5 @@ struct target_pt_regs {
 #define TARGET_QEMU_ESIGRETURN 255
 
 #define UNAME_MACHINE "mips64"
+
+#define TARGET_CLONE_BACKWARDS
diff --git a/linux-user/ppc/syscall.h b/linux-user/ppc/syscall.h
index 481047b..ba36acb 100644
--- a/linux-user/ppc/syscall.h
+++ b/linux-user/ppc/syscall.h
@@ -62,3 +62,5 @@ struct target_revectored_struct {
 #else
 #define UNAME_MACHINE "ppc"
 #endif
+
+#define TARGET_CLONE_BACKWARDS
diff --git a/linux-user/s390x/syscall.h b/linux-user/s390x/syscall.h
index e4603b7..ea8c304 100644
--- a/linux-user/s390x/syscall.h
+++ b/linux-user/s390x/syscall.h
@@ -21,3 +21,5 @@ struct target_pt_regs {
 };
 
 #define UNAME_MACHINE "s390x"
+
+#define TARGET_CLONE_BACKWARDS
diff --git a/linux-user/sparc/syscall.h b/linux-user/sparc/syscall.h
index 5a9bb7e..4cd64bf 100644
--- a/linux-user/sparc/syscall.h
+++ b/linux-user/sparc/syscall.h
@@ -7,3 +7,10 @@ struct target_pt_regs {
 };
 
 #define UNAME_MACHINE "sun4"
+
+/* SPARC kernels don't define this in their Kconfig, but they have the
+ * same ABI as if they did, implemented by sparc-specific code which fishes
+ * directly in the u_regs() struct for half the parameters in sparc_do_fork()
+ * and copy_thread().
+ */
+#define TARGET_CLONE_BACKWARDS
diff --git a/linux-user/sparc64/syscall.h b/linux-user/sparc64/syscall.h
index 81a816d..e60bf31 100644
--- a/linux-user/sparc64/syscall.h
+++ b/linux-user/sparc64/syscall.h
@@ -8,3 +8,10 @@ struct target_pt_regs {
 };
 
 #define UNAME_MACHINE "sun4u"
+
+/* SPARC kernels don't define this in their Kconfig, but they have the
+ * same ABI as if they did, implemented by sparc-specific code which fishes
+ * directly in the u_regs() struct for half the parameters in sparc_do_fork()
+ * and copy_thread().
+ */
+#define TARGET_CLONE_BACKWARDS
diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index 642d0a3..b167d7f 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -6956,16 +6956,20 @@ abi_long do_syscall(void *cpu_env, int num, abi_long 
arg1,
         ret = get_errno(fsync(arg1));
         break;
     case TARGET_NR_clone:
-#if defined(TARGET_SH4) || defined(TARGET_ALPHA)
-        ret = get_errno(do_fork(cpu_env, arg1, arg2, arg3, arg5, arg4));
-#elif defined(TARGET_CRIS)
-        ret = get_errno(do_fork(cpu_env, arg2, arg1, arg3, arg4, arg5));
-#elif defined(TARGET_MICROBLAZE)
+        /* Linux manages to have three different orderings for its
+         * arguments to clone(); the BACKWARDS and BACKWARDS2 defines
+         * match the kernel's CONFIG_CLONE_* settings.
+         * Microblaze is further special in that it uses a sixth
+         * implicit argument to clone for the TLS pointer.
+         */
+#if defined(TARGET_MICROBLAZE)
         ret = get_errno(do_fork(cpu_env, arg1, arg2, arg4, arg6, arg5));
-#elif defined(TARGET_S390X)
+#elif defined(TARGET_CLONE_BACKWARDS)
+        ret = get_errno(do_fork(cpu_env, arg1, arg2, arg3, arg4, arg5));
+#elif defined(TARGET_CLONE_BACKWARDS2)
         ret = get_errno(do_fork(cpu_env, arg2, arg1, arg3, arg5, arg4));
 #else
-        ret = get_errno(do_fork(cpu_env, arg1, arg2, arg3, arg4, arg5));
+        ret = get_errno(do_fork(cpu_env, arg1, arg2, arg3, arg5, arg4));
 #endif
         break;
 #ifdef __NR_exit_group
-- 
1.7.9.5