[uml-devel] [RFC PATCH 4/9] SKAS4 - Guest siginfo_t support

[Jeff Dike <jdike@addtoit.com>]

Add guest support for getting page fault information using PTRACE_GETSIGINFO.

The nastiness at the top of arch/um/os-Linux/skas/process.c is
defining the new siginfo_t structure, which requires using CPP to
rename the old one out of the way.

Index: linux-2.6-skas4/arch/um/os-Linux/skas/process.c
===================================================================
--- linux-2.6-skas4.orig/arch/um/os-Linux/skas/process.c	2008-01-09 16:29:10.000000000 -0500
+++ linux-2.6-skas4/arch/um/os-Linux/skas/process.c	2008-01-09 16:44:25.000000000 -0500
@@ -3,6 +3,9 @@
  * Licensed under the GPL
  */
 
+#define siginfo old_siginfo
+#define siginfo_t old_siginfo_t
+
 #include <stdlib.h>
 #include <unistd.h>
 #include <sched.h>
@@ -26,6 +29,108 @@
 #include "user.h"
 #include "sysdep/stub.h"
 
+#undef siginfo
+#undef siginfo_t
+
+#define __ARCH_SI_TRAPNO
+#define __ARCH_SI_ERROR
+
+/*
+ * This is the size (including padding) of the part of the
+ * struct siginfo that is before the union.
+ */
+#ifndef __ARCH_SI_PREAMBLE_SIZE
+#define __ARCH_SI_PREAMBLE_SIZE	(3 * sizeof(int))
+#endif
+
+#define SI_MAX_SIZE	128
+#ifndef SI_PAD_SIZE
+#define SI_PAD_SIZE	((SI_MAX_SIZE - __ARCH_SI_PREAMBLE_SIZE) / sizeof(int))
+#endif
+
+#ifndef __ARCH_SI_UID_T
+#define __ARCH_SI_UID_T	uid_t
+#endif
+
+/*
+ * The default "si_band" type is "long", as specified by POSIX.
+ * However, some architectures want to override this to "int"
+ * for historical compatibility reasons, so we allow that.
+ */
+#ifndef __ARCH_SI_BAND_T
+#define __ARCH_SI_BAND_T long
+#endif
+
+#define __user
+
+typedef struct siginfo {
+	int si_signo;
+	int si_errno;
+	int si_code;
+
+	union {
+		int _pad[SI_PAD_SIZE];
+
+		/* kill() */
+		struct {
+			pid_t _pid;		/* sender's pid */
+			__ARCH_SI_UID_T _uid;	/* sender's uid */
+		} _kill;
+
+		/* POSIX.1b timers */
+		struct {
+			timer_t _tid;		/* timer id */
+			int _overrun;		/* overrun count */
+			char _pad[sizeof( __ARCH_SI_UID_T) - sizeof(int)];
+			sigval_t _sigval;	/* same as below */
+			int _sys_private;       /* not to be passed to user */
+		} _timer;
+
+		/* POSIX.1b signals */
+		struct {
+			pid_t _pid;		/* sender's pid */
+			__ARCH_SI_UID_T _uid;	/* sender's uid */
+			sigval_t _sigval;
+		} _rt;
+
+		/* SIGCHLD */
+		struct {
+			pid_t _pid;		/* which child */
+			__ARCH_SI_UID_T _uid;	/* sender's uid */
+			int _status;		/* exit code */
+			clock_t _utime;
+			clock_t _stime;
+		} _sigchld;
+
+		/* SIGILL, SIGFPE, SIGSEGV, SIGBUS */
+		struct {
+			void __user *_addr; /* faulting insn/memory ref. */
+#ifdef __ARCH_SI_TRAPNO
+			int _trapno;	/* TRAP # which caused the signal */
+#endif
+#ifdef __ARCH_SI_ERROR
+			int _error;	/* CPU error code */
+#endif
+		} _sigfault;
+
+		/* SIGPOLL */
+		struct {
+			__ARCH_SI_BAND_T _band;	/* POLL_IN, POLL_OUT, POLL_MSG */
+			int _fd;
+		} _sigpoll;
+	} _sifields;
+} siginfo_t;
+
+#ifdef __ARCH_SI_TRAPNO
+#define si_trapno	_sifields._sigfault._trapno
+#endif
+#ifdef __ARCH_SI_ERROR
+#define si_error	_sifields._sigfault._error
+#endif
+
+#undef si_addr
+#define si_addr	_sifields._sigfault._addr
+
 int is_skas_winch(int pid, int fd, void *data)
 {
 	if (pid != getpgrp())
@@ -91,11 +196,25 @@ bad_wait:
 
 extern unsigned long current_stub_stack(void);
 
+#ifndef PTRACE_GETSIGINFO
+#define PTRACE_GETSIGINFO	0x4202
+#endif
+
 void get_skas_faultinfo(int pid, struct faultinfo * fi)
 {
+	siginfo_t si;
 	int err;
 
-	if (ptrace_faultinfo) {
+	if(1){
+		err = ptrace(PTRACE_GETSIGINFO, pid, 0, &si);
+		if(err)
+			printk("PTRACE_GETSIGINFO failed, err = %d\n", errno);
+
+		fi->cr2 = (unsigned long) si.si_addr;
+		fi->error_code = si.si_error;
+		fi->trap_no = si.si_trapno;
+	}
+	else if (ptrace_faultinfo) {
 		err = ptrace(PTRACE_FAULTINFO, pid, 0, fi);
 		if (err)
 			panic("get_skas_faultinfo - PTRACE_FAULTINFO failed, "

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