[PATCH] uml: S390 preparation, abstract host page fault data

This patch removes the arch-specific fault/trap-infos from thread and
skas-regs.

It adds a new struct faultinfo, that is arch-specific defined in
sysdep/faultinfo.h.

The structure is inserted in thread.arch and thread.regs.skas and
thread.regs.tt

Now, segv and other trap-handlers can copy the contents from regs.X.faultinfo
to thread.arch.faultinfo with one simple assignment.

Also, the number of macros necessary is reduced to

FAULT_ADDRESS(struct faultinfo)
    extracts the faulting address from faultinfo

FAULT_WRITE(struct faultinfo)
    extracts the "is_write" flag

SEGV_IS_FIXABLE(struct faultinfo)
    is true for the fixable segvs, i.e. (TRAP == 14)
    on i386

UPT_FAULTINFO(regs)
    result is (struct faultinfo *) to the faultinfo
    in regs->skas.faultinfo

GET_FAULTINFO_FROM_SC(struct faultinfo, struct sigcontext *)
    copies the relevant parts of the sigcontext to
    struct faultinfo.

On SIGSEGV, call user_signal() instead of handle_segv(), if the architecture
provides the information needed in PTRACE_FAULTINFO, or if PTRACE_FAULTINFO is
missing, because segv-stub will provide the info.

The benefit of the change is, that in case of a non-fixable SIGSEGV, we can
give user processes a SIGSEGV, instead of possibly looping on pagefault
handling.

Since handle_segv() sikked arch_fixup() implicitly by passing ip==0 to segv(),
I changed segv() to call arch_fixup() only, if !is_user.

Signed-off-by: Bodo Stroesser <bstroesser@fujitsu-siemens.com>
Signed-off-by: Jeff Dike <jdike@addtoit.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

3 files changed, 36 insertions, 17 deletions

diff --git a/arch/um/kernel/skas/include/skas.h b/arch/um/kernel/skas/include/skas.h
index f0702c2c7204..96b51dba3471 100644
--- a/arch/um/kernel/skas/include/skas.h
+++ b/arch/um/kernel/skas/include/skas.h
@@ -27,9 +27,10 @@ extern void map(int fd, unsigned long virt, unsigned long len, int r, int w,
 extern int unmap(int fd, void *addr, unsigned long len);
 extern int protect(int fd, unsigned long addr, unsigned long len, 
                    int r, int w, int x);
-extern void user_signal(int sig, union uml_pt_regs *regs);
+extern void user_signal(int sig, union uml_pt_regs *regs, int pid);
 extern int new_mm(int from);
 extern void start_userspace(int cpu);
+extern void get_skas_faultinfo(int pid, struct faultinfo * fi);
 extern long execute_syscall_skas(void *r);
 
 #endif
diff --git a/arch/um/kernel/skas/process.c b/arch/um/kernel/skas/process.c
index b4ffaaa81241..c0b30515dfb6 100644
--- a/arch/um/kernel/skas/process.c
+++ b/arch/um/kernel/skas/process.c
@@ -4,6 +4,7 @@
  */
 
 #include <stdlib.h>
+#include <string.h>
 #include <unistd.h>
 #include <errno.h>
 #include <signal.h>
@@ -37,17 +38,26 @@ int is_skas_winch(int pid, int fd, void *data)
         return(1);
 }
 
-static void handle_segv(int pid)
+void get_skas_faultinfo(int pid, struct faultinfo * fi)
 {
-        struct ptrace_faultinfo fault;
         int err;
 
-        err = ptrace(PTRACE_FAULTINFO, pid, 0, &fault);
+        err = ptrace(PTRACE_FAULTINFO, pid, 0, fi);
         if(err)
-                panic("handle_segv - PTRACE_FAULTINFO failed, errno = %d\n",
-                      errno);
+                panic("get_skas_faultinfo - PTRACE_FAULTINFO failed, "
+                      "errno = %d\n", errno);
+
+        /* Special handling for i386, which has different structs */
+        if (sizeof(struct ptrace_faultinfo) < sizeof(struct faultinfo))
+                memset((char *)fi + sizeof(struct ptrace_faultinfo), 0,
+                       sizeof(struct faultinfo) -
+                       sizeof(struct ptrace_faultinfo));
+}
 
-        segv(fault.addr, 0, FAULT_WRITE(fault.is_write), 1, NULL);
+static void handle_segv(int pid, union uml_pt_regs * regs)
+{
+        get_skas_faultinfo(pid, &regs->skas.faultinfo);
+        segv(regs->skas.faultinfo, 0, 1, NULL);
 }
 
 /*To use the same value of using_sysemu as the caller, ask it that value (in local_using_sysemu)*/
@@ -163,7 +173,7 @@ void userspace(union uml_pt_regs *regs)
                 if(WIFSTOPPED(status)){
                         switch(WSTOPSIG(status)){
                         case SIGSEGV:
-                                handle_segv(pid);
+                                handle_segv(pid, regs);
                                 break;
                         case SIGTRAP + 0x80:
                                 handle_trap(pid, regs, local_using_sysemu);
@@ -177,7 +187,7 @@ void userspace(union uml_pt_regs *regs)
                         case SIGBUS:
                         case SIGFPE:
                         case SIGWINCH:
-                                user_signal(WSTOPSIG(status), regs);
+                                user_signal(WSTOPSIG(status), regs, pid);
                                 break;
                         default:
                                 printk("userspace - child stopped with signal "
diff --git a/arch/um/kernel/skas/trap_user.c b/arch/um/kernel/skas/trap_user.c
index 8e9b46d4702e..0dee1d95c806 100644
--- a/arch/um/kernel/skas/trap_user.c
+++ b/arch/um/kernel/skas/trap_user.c
@@ -5,12 +5,15 @@
 
 #include <signal.h>
 #include <errno.h>
-#include "sysdep/ptrace.h"
 #include "signal_user.h"
 #include "user_util.h"
 #include "kern_util.h"
 #include "task.h"
 #include "sigcontext.h"
+#include "skas.h"
+#include "ptrace_user.h"
+#include "sysdep/ptrace.h"
+#include "sysdep/ptrace_user.h"
 
 void sig_handler_common_skas(int sig, void *sc_ptr)
 {
@@ -31,9 +34,11 @@ void sig_handler_common_skas(int sig, void *sc_ptr)
         r = &TASK_REGS(get_current())->skas;
         save_user = r->is_user;
         r->is_user = 0;
-        r->fault_addr = SC_FAULT_ADDR(sc);
-        r->fault_type = SC_FAULT_TYPE(sc);
-        r->trap_type = SC_TRAP_TYPE(sc);
+        if ( sig == SIGFPE || sig == SIGSEGV ||
+             sig == SIGBUS || sig == SIGILL ||
+             sig == SIGTRAP ) {
+                GET_FAULTINFO_FROM_SC(r->faultinfo, sc);
+        }
 
         change_sig(SIGUSR1, 1);
         info = &sig_info[sig];
@@ -45,14 +50,17 @@ void sig_handler_common_skas(int sig, void *sc_ptr)
         r->is_user = save_user;
 }
 
-void user_signal(int sig, union uml_pt_regs *regs)
+extern int ptrace_faultinfo;
+
+void user_signal(int sig, union uml_pt_regs *regs, int pid)
 {
         struct signal_info *info;
+        int segv = ((sig == SIGFPE) || (sig == SIGSEGV) || (sig == SIGBUS) ||
+                    (sig == SIGILL) || (sig == SIGTRAP));
 
         regs->skas.is_user = 1;
-        regs->skas.fault_addr = 0;
-        regs->skas.fault_type = 0;
-        regs->skas.trap_type = 0;
+        if (segv)
+                get_skas_faultinfo(pid, &regs->skas.faultinfo);
         info = &sig_info[sig];
         (*info->handler)(sig, regs);