[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>

1 files changed, 18 insertions, 8 deletions

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 "