[PATCH 5/5] linux-user: Add strace support for printing arguments of fallocate()

[Filip Bozuta]

From: Filip Bozuta <Filip.Bozuta@syrmia.com>

This patch implements strace argument printing functionality for following 
syscall:

    *fallocate - manipulate file space

        int fallocate(int fd, int mode, off_t offset, off_t len)
        man page: https://www.man7.org/linux/man-pages/man2/fallocate.2.html

Implementation notes:

    This syscall's second argument "mode" is composed of predefined values
    which represent flags that determine the type of operation that is
    to be performed on the file space. For that reason, a printing
    function "print_fallocate" was stated in file "strace.list". This printing
    function uses an already existing function "print_flags()" to print flags of
    the "mode" argument. These flags are stated inside an array "falloc_flags"
    that contains values of type "struct flags". These values are instantiated
    using an existing macro "FLAG_GENERIC()". Most of these flags are defined
    after kernel version 3.0 which is why they are enwrapped in an #ifdef
    directive.
    The syscall's third ant fourth argument are of type "off_t" which can
    cause variations between 32/64-bit architectures. To handle this variation,
    function "target_offset64()" was copied from file "strace.c" and used in
    "print_fallocate" to print "off_t" arguments for 32-bit architectures.

Signed-off-by: Filip Bozuta <Filip.Bozuta@syrmia.com>
---
 linux-user/strace.c    | 56 ++++++++++++++++++++++++++++++++++++++++++
 linux-user/strace.list |  2 +-
 2 files changed, 57 insertions(+), 1 deletion(-)

diff --git a/linux-user/strace.c b/linux-user/strace.c
index 542bfdeb91..3998a00bb4 100644
--- a/linux-user/strace.c
+++ b/linux-user/strace.c
@@ -34,6 +34,22 @@ struct syscallname {
 #define UNUSED
 #endif
 
+#if TARGET_ABI_BITS == 32
+static inline uint64_t target_offset64(uint32_t word0, uint32_t word1)
+{
+#ifdef TARGET_WORDS_BIGENDIAN
+    return ((uint64_t)word0 << 32) | word1;
+#else
+    return ((uint64_t)word1 << 32) | word0;
+#endif
+}
+#else /* TARGET_ABI_BITS == 32 */
+static inline uint64_t target_offset64(uint64_t word0, uint64_t word1)
+{
+    return word0;
+}
+#endif /* TARGET_ABI_BITS != 32 */
+
 /*
  * Structure used to translate flag values into strings.  This is
  * similar that is in the actual strace tool.
@@ -1097,6 +1113,26 @@ UNUSED static struct flags statx_mask[] = {
     FLAG_END,
 };
 
+UNUSED static struct flags falloc_flags[] = {
+    FLAG_GENERIC(FALLOC_FL_KEEP_SIZE),
+    FLAG_GENERIC(FALLOC_FL_PUNCH_HOLE),
+#ifdef FALLOC_FL_NO_HIDE_STALE
+    FLAG_GENERIC(FALLOC_FL_NO_HIDE_STALE),
+#endif
+#ifdef FALLOC_FL_COLLAPSE_RANGE
+    FLAG_GENERIC(FALLOC_FL_COLLAPSE_RANGE),
+#endif
+#ifdef FALLOC_FL_ZERO_RANGE
+    FLAG_GENERIC(FALLOC_FL_ZERO_RANGE),
+#endif
+#ifdef FALLOC_FL_INSERT_RANGE
+    FLAG_GENERIC(FALLOC_FL_INSERT_RANGE),
+#endif
+#ifdef FALLOC_FL_UNSHARE_RANGE
+    FLAG_GENERIC(FALLOC_FL_UNSHARE_RANGE),
+#endif
+};
+
 /*
  * print_xxx utility functions.  These are used to print syscall
  * parameters in certain format.  All of these have parameter
@@ -1514,6 +1550,26 @@ print_faccessat(const struct syscallname *name,
 }
 #endif
 
+#ifdef TARGET_NR_fallocate
+static void
+print_fallocate(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);
+    print_flags(falloc_flags, arg1, 0);
+#if TARGET_ABI_BITS == 32
+    print_raw_param("%ld", target_offset64(arg2, arg3), 0);
+    print_raw_param("%ld", target_offset64(arg4, arg5), 1);
+#else
+    print_raw_param("%ld", arg2, 0);
+    print_raw_param("%ld", arg3, 1);
+#endif
+    print_syscall_epilogue(name);
+}
+#endif
+
 #ifdef TARGET_NR_fchmodat
 static void
 print_fchmodat(const struct syscallname *name,
diff --git a/linux-user/strace.list b/linux-user/strace.list
index b72f757d3f..d7458ce884 100644
--- a/linux-user/strace.list
+++ b/linux-user/strace.list
@@ -182,7 +182,7 @@
 { TARGET_NR_fadvise64_64, "fadvise64_64" , NULL, NULL, NULL },
 #endif
 #ifdef TARGET_NR_fallocate
-{ TARGET_NR_fallocate, "fallocate" , NULL, NULL, NULL },
+{ TARGET_NR_fallocate, "fallocate" , NULL, print_fallocate, NULL },
 #endif
 #ifdef TARGET_NR_fanotify_init
 { TARGET_NR_fanotify_init, "fanotify_init" , NULL, NULL, NULL },
-- 
2.17.1