file.c: move lseek and llseek parsers to a separate file

[strace] / lseek.c

diff --git a/lseek.c b/lseek.c
new file mode 100644 (file)
index 0000000..7a0a501
--- /dev/null
+++ b/lseek.c
@@ -0,0 +1,88 @@
+#include "defs.h"
+
+#include "xlat/whence_codes.h"
+
+/* Linux kernel has exactly one version of lseek:
+ * fs/read_write.c::SYSCALL_DEFINE3(lseek, unsigned, fd, off_t, offset, unsigned, origin)
+ * In kernel, off_t is always the same as (kernel's) long
+ * (see include/uapi/asm-generic/posix_types.h),
+ * which means that on x32 we need to use tcp->ext_arg[N] to get offset argument.
+ * Use test/x32_lseek.c to test lseek decoding.
+ */
+#if defined(LINUX_MIPSN32) || defined(X32)
+int
+sys_lseek(struct tcb *tcp)
+{
+       long long offset;
+       int whence;
+
+       if (entering(tcp)) {
+               printfd(tcp, tcp->u_arg[0]);
+               offset = tcp->ext_arg[1];
+               whence = tcp->u_arg[2];
+               if (whence == SEEK_SET)
+                       tprintf(", %llu, ", offset);
+               else
+                       tprintf(", %lld, ", offset);
+               printxval(whence_codes, whence, "SEEK_???");
+       }
+       return RVAL_LUDECIMAL;
+}
+#else
+int
+sys_lseek(struct tcb *tcp)
+{
+       long offset;
+       int whence;
+
+       if (entering(tcp)) {
+               printfd(tcp, tcp->u_arg[0]);
+               offset = tcp->u_arg[1];
+               whence = tcp->u_arg[2];
+               if (whence == SEEK_SET)
+                       tprintf(", %lu, ", offset);
+               else
+                       tprintf(", %ld, ", offset);
+               printxval(whence_codes, whence, "SEEK_???");
+       }
+       return RVAL_UDECIMAL;
+}
+#endif
+
+/* llseek syscall takes explicitly two ulong arguments hi, lo,
+ * rather than one 64-bit argument for which LONG_LONG works
+ * appropriate for the native byte order.
+ *
+ * See kernel's fs/read_write.c::SYSCALL_DEFINE5(llseek, ...)
+ *
+ * hi,lo are "unsigned longs" and combined exactly this way in kernel:
+ * ((loff_t) hi << 32) | lo
+ * Note that for architectures with kernel's long wider than userspace long
+ * (such as x32), combining code will use *kernel's*, i.e. *wide* longs
+ * for hi and lo. We would need to use tcp->ext_arg[N] on x32...
+ * ...however, x32 (and x86_64) does not _have_ llseek syscall as such.
+ */
+int
+sys_llseek(struct tcb *tcp)
+{
+       if (entering(tcp)) {
+               printfd(tcp, tcp->u_arg[0]);
+               if (tcp->u_arg[4] == SEEK_SET)
+                       tprintf(", %llu, ",
+                               ((long long) tcp->u_arg[1]) << 32 |
+                               (unsigned long long) (unsigned) tcp->u_arg[2]);
+               else
+                       tprintf(", %lld, ",
+                               ((long long) tcp->u_arg[1]) << 32 |
+                               (unsigned long long) (unsigned) tcp->u_arg[2]);
+       }
+       else {
+               long long off;
+               if (syserror(tcp) || umove(tcp, tcp->u_arg[3], &off) < 0)
+                       tprintf("%#lx, ", tcp->u_arg[3]);
+               else
+                       tprintf("[%llu], ", off);
+               printxval(whence_codes, tcp->u_arg[4], "SEEK_???");
+       }
+       return 0;
+}