linux-user: Add strace support for printing arguments of ioctl()

This patch implements functionality for strace argument printing for ioctls.
When running ioctls through qemu with "-strace", they get printed in format:

    "ioctl(fd_num,0x*,0x*) = ret_value"

where the request code an the ioctl's third argument get printed in a hexadicemal
format. This patch changes that by enabling strace to print both the request code
name and the contents of the third argument. For example, when running ioctl
RTC_SET_TIME with "-strace", with changes from this patch, it gets printed in
this way:

    "ioctl(3,RTC_SET_TIME,{12,13,15,20,10,119,0,0,0}) = 0"

In case of IOC_R type ioctls, the contents of the third argument get printed
after the return value, and the argument inside the ioctl call gets printed
as pointer in hexadecimal format. For example, when running RTC_RD_TIME with
"-strace", with changes from this patch, it gets printed in this way:

    "ioctl(3,RTC_RD_TIME,0x40800374) = 0 ({22,9,13,11,5,120,0,0,0})"

In case of IOC_RW type ioctls, the contents of the third argument get printed
both inside the ioctl call and after the return value.

Implementation notes:

    Functions "print_ioctl()" and "print_syscall_ret_ioctl()", that are defined
    in "strace.c", are listed in file "strace.list" as "call" and "result"
    value for ioctl. Structure definition "IOCTLEntry" as well as predefined
    values for IOC_R, IOC_W and IOC_RW were cut and pasted from file "syscall.c"
    to file "qemu.h" so that they can be used by these functions to print the
    contents of the third ioctl argument. Also, the "static" identifier for array
    "ioctl_entries[]" was removed and this array was declared as "extern" in "qemu.h"
    so that it can also be used by these functions. To decode the structure type
    of the ioctl third argument, function "thunk_print()" was defined in file
    "thunk.c" and its definition is somewhat simillar to that of function
    "thunk_convert()".

Signed-off-by: Filip Bozuta <Filip.Bozuta@syrmia.com>
Reviewed-by: Laurent Vivier <laurent@vivier.eu>
Message-Id: <20200619124727.18080-3-filip.bozuta@syrmia.com>
[lv: fix close-bracket]
Signed-off-by: Laurent Vivier <laurent@vivier.eu>

4 files changed, 130 insertions, 20 deletions

diff --git a/linux-user/qemu.h b/linux-user/qemu.h
index be67391ba4..5c964389c1 100644
--- a/linux-user/qemu.h
+++ b/linux-user/qemu.h
@@ -184,6 +184,26 @@ struct linux_binprm {
         int (*core_dump)(int, const CPUArchState *); /* coredump routine */
 };
 
+typedef struct IOCTLEntry IOCTLEntry;
+
+typedef abi_long do_ioctl_fn(const IOCTLEntry *ie, uint8_t *buf_temp,
+                             int fd, int cmd, abi_long arg);
+
+struct IOCTLEntry {
+    int target_cmd;
+    unsigned int host_cmd;
+    const char *name;
+    int access;
+    do_ioctl_fn *do_ioctl;
+    const argtype arg_type[5];
+};
+
+extern IOCTLEntry ioctl_entries[];
+
+#define IOC_R 0x0001
+#define IOC_W 0x0002
+#define IOC_RW (IOC_R | IOC_W)
+
 void do_init_thread(struct target_pt_regs *regs, struct image_info *infop);
 abi_ulong loader_build_argptr(int envc, int argc, abi_ulong sp,
                               abi_ulong stringp, int push_ptr);
diff --git a/linux-user/strace.c b/linux-user/strace.c
index 32e5e987ac..5235b2260c 100644
--- a/linux-user/strace.c
+++ b/linux-user/strace.c
@@ -860,6 +860,44 @@ print_syscall_ret_listxattr(const struct syscallname *name, abi_long ret,
 #define print_syscall_ret_flistxattr     print_syscall_ret_listxattr
 #endif
 
+#ifdef TARGET_NR_ioctl
+static void
+print_syscall_ret_ioctl(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(TARGET_ABI_FMT_ld, ret);
+
+        const IOCTLEntry *ie;
+        const argtype *arg_type;
+        void *argptr;
+        int target_size;
+
+        for (ie = ioctl_entries; ie->target_cmd != 0; ie++) {
+            if (ie->target_cmd == arg1) {
+                break;
+            }
+        }
+
+        if (ie->target_cmd == arg1 &&
+           (ie->access == IOC_R || ie->access == IOC_RW)) {
+            arg_type = ie->arg_type;
+            qemu_log(" (");
+            arg_type++;
+            target_size = thunk_type_size(arg_type, 0);
+            argptr = lock_user(VERIFY_READ, arg2, target_size, 1);
+            thunk_print(argptr, arg_type);
+            unlock_user(argptr, arg2, target_size);
+            qemu_log(")");
+        }
+    }
+    qemu_log("\n");
+}
+#endif
+
 UNUSED static struct flags access_flags[] = {
     FLAG_GENERIC(F_OK),
     FLAG_GENERIC(R_OK),
@@ -3026,6 +3064,75 @@ print_statx(const struct syscallname *name,
 }
 #endif
 
+#ifdef TARGET_NR_ioctl
+static void
+print_ioctl(const struct syscallname *name,
+            abi_long arg0, abi_long arg1, abi_long arg2,
+            abi_long arg3, abi_long arg4, abi_long arg5)
+{
+    print_syscall_prologue(name);
+    print_raw_param("%d", arg0, 0);
+
+    const IOCTLEntry *ie;
+    const argtype *arg_type;
+    void *argptr;
+    int target_size;
+
+    for (ie = ioctl_entries; ie->target_cmd != 0; ie++) {
+        if (ie->target_cmd == arg1) {
+            break;
+        }
+    }
+
+    if (ie->target_cmd == 0) {
+        print_raw_param("%#x", arg1, 0);
+        print_raw_param("%#x", arg2, 1);
+    } else {
+        qemu_log("%s", ie->name);
+        arg_type = ie->arg_type;
+
+        if (arg_type[0] != TYPE_NULL) {
+            qemu_log(",");
+
+            switch (arg_type[0]) {
+            case TYPE_PTRVOID:
+                print_pointer(arg2, 1);
+                break;
+            case TYPE_CHAR:
+            case TYPE_SHORT:
+            case TYPE_INT:
+                print_raw_param("%d", arg2, 1);
+                break;
+            case TYPE_LONG:
+                print_raw_param(TARGET_ABI_FMT_ld, arg2, 1);
+                break;
+            case TYPE_ULONG:
+                print_raw_param(TARGET_ABI_FMT_lu, arg2, 1);
+                break;
+            case TYPE_PTR:
+                switch (ie->access) {
+                case IOC_R:
+                    print_pointer(arg2, 1);
+                    break;
+                case IOC_W:
+                case IOC_RW:
+                    arg_type++;
+                    target_size = thunk_type_size(arg_type, 0);
+                    argptr = lock_user(VERIFY_READ, arg2, target_size, 1);
+                    thunk_print(argptr, arg_type);
+                    unlock_user(argptr, arg2, target_size);
+                    break;
+                }
+                break;
+            default:
+                g_assert_not_reached();
+            }
+        }
+    }
+    print_syscall_epilogue(name);
+}
+#endif
+
 /*
  * An array of all of the syscalls we know about
  */
diff --git a/linux-user/strace.list b/linux-user/strace.list
index ebb713252c..a04706a524 100644
--- a/linux-user/strace.list
+++ b/linux-user/strace.list
@@ -433,7 +433,8 @@
 { TARGET_NR_io_cancel, "io_cancel" , NULL, NULL, NULL },
 #endif
 #ifdef TARGET_NR_ioctl
-{ TARGET_NR_ioctl, "ioctl" , "%s(%d,%#x,%#x)", NULL, NULL },
+{ TARGET_NR_ioctl, "ioctl" , NULL, print_ioctl,
+                   print_syscall_ret_ioctl},
 #endif
 #ifdef TARGET_NR_io_destroy
 { TARGET_NR_io_destroy, "io_destroy" , NULL, NULL, NULL },
diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index 506b94a12c..82afadcea0 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -4481,24 +4481,6 @@ STRUCT_MAX
 #undef STRUCT
 #undef STRUCT_SPECIAL
 
-typedef struct IOCTLEntry IOCTLEntry;
-
-typedef abi_long do_ioctl_fn(const IOCTLEntry *ie, uint8_t *buf_temp,
-                             int fd, int cmd, abi_long arg);
-
-struct IOCTLEntry {
-    int target_cmd;
-    unsigned int host_cmd;
-    const char *name;
-    int access;
-    do_ioctl_fn *do_ioctl;
-    const argtype arg_type[5];
-};
-
-#define IOC_R 0x0001
-#define IOC_W 0x0002
-#define IOC_RW (IOC_R | IOC_W)
-
 #define MAX_STRUCT_SIZE 4096
 
 #ifdef CONFIG_FIEMAP
@@ -5374,7 +5356,7 @@ static abi_long do_ioctl_drm(const IOCTLEntry *ie, uint8_t *buf_temp,
 
 #endif
 
-static IOCTLEntry ioctl_entries[] = {
+IOCTLEntry ioctl_entries[] = {
 #define IOCTL(cmd, access, ...) \
     { TARGET_ ## cmd, cmd, #cmd, access, 0, {  __VA_ARGS__ } },
 #define IOCTL_SPECIAL(cmd, access, dofn, ...)                      \