This patch allows UML to get page fault information for its processes
using PTRACE_GETSIGINFO by reading the fault address, trap number, and
error code from the siginfo_t.
The nastiness in arch/um/include/siginfo_segv.h is defining the new
siginfo_t structure in place of the old one, which requires using CPP
to rename the old one out of the way.
diff --git a/arch/um/include/siginfo_segv.h b/arch/um/include/siginfo_segv.h
new file mode 100644
index 0000000..c000267
--- /dev/null
+++ b/arch/um/include/siginfo_segv.h
@@ -0,0 +1,133 @@
+/*
+ * Copyright (C) 2002- 2007 Jeff Dike ([EMAIL PROTECTED],linux.intel}.com)
+ * Licensed under the GPL
+ */
+
+#ifndef __SIGINFO_SIGSEGV_H_
+#define __SIGINFO_SIGSEGV_H_
+
+/*
+ * Provide signal.h, except for replacing siginfo_t with one that has
+ * the CPU trap number and error code in the SIGSEGV case.
+ */
+
+#include <time.h>
+
+/* Rename the signal.h siginfo and siginfo_t out of the way */
+#define siginfo old_siginfo
+#define siginfo_t old_siginfo_t
+
+#include <signal.h>
+
+#undef siginfo
+#undef siginfo_t
+
+#define __ARCH_SI_TRAPNO
+#define __ARCH_SI_ERROR
+
+/* The new siginfo_t, plus associated definitions */
+
+/*
+ * 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
+
+#define GET_FAULTINFO_FROM_SI(fi, si) \
+ { \
+ (fi).cr2 = (unsigned long) (si).si_addr; \
+ (fi).error_code = (si).si_error; \
+ (fi).trap_no = (si).si_trapno; \
+ }
+
+#endif
diff --git a/arch/um/include/skas/skas.h b/arch/um/include/skas/skas.h
index b073f8a..d6cbb4f 100644
--- a/arch/um/include/skas/skas.h
+++ b/arch/um/include/skas/skas.h
@@ -8,6 +8,8 @@
#include "sysdep/ptrace.h"
+extern int have_siginfo_segv;
+
extern int userspace_pid[];
extern int proc_mm, ptrace_faultinfo, ptrace_ldt;
extern int skas_needs_stub;
diff --git a/arch/um/os-Linux/skas/process.c b/arch/um/os-Linux/skas/process.c
index 21e24ba..7cb760b 100644
--- a/arch/um/os-Linux/skas/process.c
+++ b/arch/um/os-Linux/skas/process.c
@@ -3,6 +3,9 @@
* Licensed under the GPL
*/
+/* Include this first, before anything else includes <signal.h> */
+#include "siginfo_segv.h"
+
#include <stdlib.h>
#include <unistd.h>
#include <sched.h>
@@ -96,11 +99,23 @@ 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 (have_siginfo_segv) {
+ err = ptrace(PTRACE_GETSIGINFO, pid, 0, &si);
+ if (err)
+ printk(UM_KERN_ERR "PTRACE_GETSIGINFO failed, "
+ "err = %d\n", errno);
+
+ GET_FAULTINFO_FROM_SI(*fi, si);
+ } else if (ptrace_faultinfo) {
err = ptrace(PTRACE_FAULTINFO, pid, 0, fi);
if (err) {
printk(UM_KERN_ERR "get_skas_faultinfo - "
@@ -113,8 +128,7 @@ void get_skas_faultinfo(int pid, struct faultinfo * fi)
memset((char *)fi + sizeof(struct ptrace_faultinfo), 0,
sizeof(struct faultinfo) -
sizeof(struct ptrace_faultinfo));
- }
- else {
+ } else {
unsigned long fpregs[FP_SIZE];
err = get_fp_registers(pid, fpregs);
diff --git a/arch/um/os-Linux/start_up.c b/arch/um/os-Linux/start_up.c
index e32cede..81e1333 100644
--- a/arch/um/os-Linux/start_up.c
+++ b/arch/um/os-Linux/start_up.c
@@ -3,6 +3,9 @@
* Licensed under the GPL
*/
+/* Include this first, before anything else includes <signal.h> */
+#include "siginfo_segv.h"
+
#include <stdio.h>
#include <stdlib.h>
#include <stdarg.h>
@@ -25,6 +28,7 @@
#include "registers.h"
#include "skas.h"
#include "skas_ptrace.h"
+#include "sysdep/sigcontext.h"
static int ptrace_child(void)
{
@@ -155,6 +159,9 @@ static int disable_proc_mm;
int have_switch_mm;
static int disable_switch_mm;
+int have_siginfo_segv;
+static int disable_siginfo_segv;
+
int skas_needs_stub;
static int __init skas0_cmd_param(char *str, int* add)
@@ -163,6 +170,7 @@ static int __init skas0_cmd_param(char *str, int* add)
disable_ptrace_ldt = 1;
disable_proc_mm = 1;
disable_switch_mm = 1;
+ disable_siginfo_segv = 1;
return 0;
}
@@ -475,6 +483,137 @@ static inline void check_skas3_proc_mm(void)
}
}
+static void *fault_address;
+
+static int check_fault_info(struct faultinfo *fi)
+{
+ return (FAULT_ADDRESS(*fi) == (unsigned long) fault_address) &&
+ FAULT_WRITE(*fi) && SEGV_IS_FIXABLE(fi);
+}
+
+static jmp_buf siginfo_buf;
+
+static void segv_handler(int sig, siginfo_t *si, void *foo)
+{
+ struct faultinfo fi;
+ int n;
+
+ GET_FAULTINFO_FROM_SI(fi, *si);
+ n = check_fault_info(&fi) ? 1 : 2;
+ longjmp(siginfo_buf, n);
+}
+
+static int fault(void)
+{
+ struct sigaction sa, old;
+ int err, n;
+
+ /*
+ * The cast is needed because the CPP manipulations of
+ * siginfo_t resulted in sa_sigaction having an old_siginfo_t
+ * parameter.
+ */
+ sa.sa_sigaction = (void (*)(int, old_siginfo_t *, void *)) segv_handler;
+ sigemptyset(&sa.sa_mask);
+ sa.sa_flags = SA_SIGINFO | SA_NODEFER;
+
+ err = sigaction(SIGSEGV, &sa, &old);
+ if (err)
+ fatal_perror("sigaction");
+
+ /*
+ * Provide a guaranteed invalid address by mapping a page into
+ * a hole in the address space and then unmapping it.
+ */
+ fault_address = mmap(NULL, UM_KERN_PAGE_SIZE, PROT_READ | PROT_WRITE,
+ MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
+ if (fault_address == MAP_FAILED)
+ fatal_perror("mmap failed");
+
+ if (munmap(fault_address, UM_KERN_PAGE_SIZE) < 0)
+ fatal_perror("munmap failed");
+
+ n = setjmp(siginfo_buf);
+ if (n == 0)
+ *((unsigned long *) fault_address) = 0;
+
+ err = sigaction(SIGSEGV, &old, NULL);
+
+ return n;
+}
+
+static int __init nogetsiginfo_cmd_param(char *str, int *add)
+{
+ disable_siginfo_segv = 1;
+ return 0;
+}
+
+__uml_setup("nogetsiginfo", nogetsiginfo_cmd_param,
+"nogetsiginfo\n"
+" Turns off usage of PTRACE_GETSIGINFO to read page fault information\n"
+" from a child process, even if the host supports it.\n\n");
+
+#ifndef PTRACE_GETSIGINFO
+#define PTRACE_GETSIGINFO 0x4202
+#endif
+
+static int check_siginfo(void)
+{
+ siginfo_t si;
+ struct faultinfo fi;
+ int ok, pid, err, status;
+
+ non_fatal("\tFull CPU fault information in siginfo_t ... ");
+ ok = fault();
+ if (ok)
+ non_fatal("OK\n");
+ else {
+ non_fatal("Failed\n");
+ return 0;
+ }
+
+ non_fatal("\tFull CPU fault information in PTRACE_GETSIGINFO ... ");
+
+ pid = fork();
+ if (pid < 0)
+ fatal_perror("fork failed");
+ else if (pid == 0) {
+ ptrace(PTRACE_TRACEME, 0, 0, 0);
+ fault();
+ exit(1);
+ }
+
+ while (1) {
+ err = waitpid(pid, &status, WUNTRACED);
+ if (err < 0)
+ fatal_perror("wait failed");
+
+ if (WIFSTOPPED(status) && (WSTOPSIG(status) == SIGSEGV))
+ break;
+ }
+
+ err = ptrace(PTRACE_GETSIGINFO, pid, 0, &si);
+ if (err < 0)
+ fatal_perror("PTRACE_GETSIGINFO failed");
+
+ ptrace(PTRACE_KILL, pid, 0, 0);
+
+ GET_FAULTINFO_FROM_SI(fi, si);
+ ok = check_fault_info(&fi);
+ if (ok)
+ non_fatal("OK\n");
+ else
+ non_fatal("Failed\n");
+
+ if (disable_siginfo_segv)
+ non_fatal("Extended PTRACE_GETSIGINFO disabled on command "
+ "line");
+ else
+ have_siginfo_segv = 1;
+
+ return ok;
+}
+
void can_do_skas(void)
{
non_fatal("Checking for the skas3 patch in the host:\n");
@@ -482,8 +621,10 @@ void can_do_skas(void)
check_skas3_proc_mm();
check_skas3_ptrace_faultinfo();
check_skas3_ptrace_ldt();
+ check_siginfo();
- if (!proc_mm || !ptrace_faultinfo || !ptrace_ldt)
+ if (!proc_mm || (!ptrace_faultinfo && !have_siginfo_segv) ||
+ !ptrace_ldt)
skas_needs_stub = 1;
}
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