linux-user: Extend strace support to enable argument printing after syscall execution
Structure "struct syscallname" in file "strace.c" is used for "-strace"
to print arguments and return values of syscalls. The last field of
this structure "result" represents the calling function that prints the
return values. This field was extended in this patch so that this function
takes all syscalls arguments beside the return value. In this way, it enables
"-strace" to print arguments of syscalls that have changed after the syscall
execution. This extension will be useful as there are many syscalls that
return values inside their arguments (i.e. listxattr() that returns the list
of extended attributes inside the "list" argument).
Implementation notes:
Since there are already three existing "print_syscall_ret*" functions inside
"strace.c" ("print_syscall_ret_addr()", "print_syscall_ret_adjtimex()",
"print_syscall_ret_newselect()"), they were changed to have all syscall arguments
beside the return value. This was done so that these functions don't cause build
errors (even though syscall arguments are not used in these functions).
There is code repetition in these functions for checking the return value
and printing the approppriate error message (this code is also located in
print_syscall_ret() at the end of "strace.c"). That is the reason why a
function "syscall_print_err()" was added for this code and put inside these
functions. Functions "print_newselect()" and "print_syscall_ret_newselect()"
were changed to use this new implemented functionality and not store the syscall
argument values in separate static variables.
Signed-off-by: Filip Bozuta <Filip.Bozuta@syrmia.com>
Reviewed-by: Laurent Vivier <laurent@vivier.eu>
Message-Id: <20200619123331.17387-2-filip.bozuta@syrmia.com>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>
diff --git a/linux-user/qemu.h b/linux-user/qemu.h
index ce902f5..8f938b8 100644
--- a/linux-user/qemu.h
+++ b/linux-user/qemu.h
@@ -383,7 +383,9 @@
void print_syscall(int num,
abi_long arg1, abi_long arg2, abi_long arg3,
abi_long arg4, abi_long arg5, abi_long arg6);
-void print_syscall_ret(int num, abi_long arg1);
+void print_syscall_ret(int num, abi_long ret,
+ abi_long arg1, abi_long arg2, abi_long arg3,
+ abi_long arg4, abi_long arg5, abi_long arg6);
/**
* print_taken_signal:
* @target_signum: target signal being taken
diff --git a/linux-user/strace.c b/linux-user/strace.c
index 0d9095c..62117e8 100644
--- a/linux-user/strace.c
+++ b/linux-user/strace.c
@@ -19,7 +19,9 @@
void (*call)(const struct syscallname *,
abi_long, abi_long, abi_long,
abi_long, abi_long, abi_long);
- void (*result)(const struct syscallname *, abi_long);
+ void (*result)(const struct syscallname *, abi_long,
+ abi_long, abi_long, abi_long,
+ abi_long, abi_long, abi_long);
};
#ifdef __GNUC__
@@ -631,18 +633,12 @@
/* select */
#ifdef TARGET_NR__newselect
-static long newselect_arg1 = 0;
-static long newselect_arg2 = 0;
-static long newselect_arg3 = 0;
-static long newselect_arg4 = 0;
-static long newselect_arg5 = 0;
-
static void
print_newselect(const struct syscallname *name,
abi_long arg1, abi_long arg2, abi_long arg3,
abi_long arg4, abi_long arg5, abi_long arg6)
{
- qemu_log("%s(" TARGET_ABI_FMT_ld ",", name->name, arg1);
+ print_syscall_prologue(name);
print_fdset(arg1, arg2);
qemu_log(",");
print_fdset(arg1, arg3);
@@ -650,14 +646,7 @@
print_fdset(arg1, arg4);
qemu_log(",");
print_timeval(arg5, 1);
- qemu_log(")");
-
- /* save for use in the return output function below */
- newselect_arg1=arg1;
- newselect_arg2=arg2;
- newselect_arg3=arg3;
- newselect_arg4=arg4;
- newselect_arg5=arg5;
+ print_syscall_epilogue(name);
}
#endif
@@ -736,17 +725,29 @@
*/
static void
-print_syscall_ret_addr(const struct syscallname *name, abi_long ret)
+print_syscall_err(abi_long ret)
{
const char *errstr = NULL;
+ qemu_log(" = ");
if (ret < 0) {
+ qemu_log("-1 errno=%d", errno);
errstr = target_strerror(-ret);
+ if (errstr) {
+ qemu_log(" (%s)", errstr);
+ }
}
- if (errstr) {
- qemu_log(" = -1 errno=%d (%s)\n", (int)-ret, errstr);
- } else {
- qemu_log(" = 0x" TARGET_ABI_FMT_lx "\n", ret);
+}
+
+static void
+print_syscall_ret_addr(const struct syscallname *name, abi_long ret,
+ abi_long arg0, abi_long arg1, abi_long arg2,
+ abi_long arg3, abi_long arg4, abi_long arg5)
+{
+ print_syscall_err(ret);
+
+ if (ret >= 0) {
+ qemu_log("0x" TARGET_ABI_FMT_lx "\n", ret);
}
}
@@ -760,17 +761,25 @@
#ifdef TARGET_NR__newselect
static void
-print_syscall_ret_newselect(const struct syscallname *name, abi_long ret)
+print_syscall_ret_newselect(const struct syscallname *name, abi_long ret,
+ abi_long arg0, abi_long arg1, abi_long arg2,
+ abi_long arg3, abi_long arg4, abi_long arg5)
{
- qemu_log(" = 0x" TARGET_ABI_FMT_lx " (", ret);
- print_fdset(newselect_arg1,newselect_arg2);
- qemu_log(",");
- print_fdset(newselect_arg1,newselect_arg3);
- qemu_log(",");
- print_fdset(newselect_arg1,newselect_arg4);
- qemu_log(",");
- print_timeval(newselect_arg5, 1);
- qemu_log(")\n");
+ print_syscall_err(ret);
+
+ if (ret >= 0) {
+ qemu_log(" = 0x" TARGET_ABI_FMT_lx " (", ret);
+ print_fdset(arg0, arg1);
+ qemu_log(",");
+ print_fdset(arg0, arg2);
+ qemu_log(",");
+ print_fdset(arg0, arg3);
+ qemu_log(",");
+ print_timeval(arg4, 1);
+ qemu_log(")");
+ }
+
+ qemu_log("\n");
}
#endif
@@ -783,18 +792,13 @@
#define TARGET_TIME_ERROR 5 /* clock not synchronized */
#ifdef TARGET_NR_adjtimex
static void
-print_syscall_ret_adjtimex(const struct syscallname *name, abi_long ret)
+print_syscall_ret_adjtimex(const struct syscallname *name, abi_long ret,
+ abi_long arg0, abi_long arg1, abi_long arg2,
+ abi_long arg3, abi_long arg4, abi_long arg5)
{
- const char *errstr = NULL;
+ print_syscall_err(ret);
- qemu_log(" = ");
- if (ret < 0) {
- qemu_log("-1 errno=%d", errno);
- errstr = target_strerror(-ret);
- if (errstr) {
- qemu_log(" (%s)", errstr);
- }
- } else {
+ if (ret >= 0) {
qemu_log(TARGET_ABI_FMT_ld, ret);
switch (ret) {
case TARGET_TIME_OK:
@@ -2847,25 +2851,25 @@
void
-print_syscall_ret(int num, abi_long ret)
+print_syscall_ret(int num, abi_long ret,
+ abi_long arg1, abi_long arg2, abi_long arg3,
+ abi_long arg4, abi_long arg5, abi_long arg6)
{
int i;
- const char *errstr = NULL;
for(i=0;i<nsyscalls;i++)
if( scnames[i].nr == num ) {
if( scnames[i].result != NULL ) {
- scnames[i].result(&scnames[i], ret);
+ scnames[i].result(&scnames[i], ret,
+ arg1, arg2, arg3,
+ arg4, arg5, arg6);
} else {
- if (ret < 0) {
- errstr = target_strerror(-ret);
+ print_syscall_err(ret);
+
+ if (ret >= 0) {
+ qemu_log(TARGET_ABI_FMT_ld, ret);
}
- if (errstr) {
- qemu_log(" = -1 errno=" TARGET_ABI_FMT_ld " (%s)\n",
- -ret, errstr);
- } else {
- qemu_log(" = " TARGET_ABI_FMT_ld "\n", ret);
- }
+ qemu_log("\n");
}
break;
}
diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index 17ed7f8..1b971c0 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -12565,7 +12565,7 @@
arg5, arg6, arg7, arg8);
if (unlikely(qemu_loglevel_mask(LOG_STRACE))) {
- print_syscall_ret(num, ret);
+ print_syscall_ret(num, ret, arg1, arg2, arg3, arg4, arg5, arg6);
}
record_syscall_return(cpu, num, ret);
