From 4e6d0dc9476e5cf43ff0bc5e66a54d812ddb4225 Mon Sep 17 00:00:00 2001
From: Ron Yorston <rmy@pobox.com>
Date: Thu, 22 Feb 2018 11:40:53 +0000
Subject: win32: handle /dev/zero and /dev/urandom in open and read functions
Currently /dev/zero is handled as a special case in dd. Add hacks
to the open and read functions in mingw.c to handle the zero and
urandom devices.
- Opening /dev/zero or /dev/urandom actually opens the special
Windows file 'nul' which behaves like /dev/null. This allows
manipulation of the file descriptor with things like seek and
close
- When /dev/zero or /dev/urandom is opened the resulting file
descriptor is stored and used to override the behaviour of read.
- No attempt is made to track duplicated file descriptors, so using
these devices for redirections in the shell isn't going to work
and won't be permitted. (Could be, but won't.)
- Limited control of the special file descriptors is provided by
allowing the internal variables to be changed.
- The numbers from /dev/urandom aren't very random.
---
include/mingw.h | 5 +++++
win32/mingw.c | 61 +++++++++++++++++++++++++++++++++++++++++++++++++++++++--
win32/winansi.c | 2 +-
3 files changed, 65 insertions(+), 3 deletions(-)
diff --git a/include/mingw.h b/include/mingw.h
index a59ce6fc4..46be4dc23 100644
--- a/include/mingw.h
+++ b/include/mingw.h
@@ -395,6 +395,10 @@ int kill(pid_t pid, int sig);
int link(const char *oldpath, const char *newpath);
NOIMPL(mknod,const char *name UNUSED_PARAM, mode_t mode UNUSED_PARAM, dev_t device UNUSED_PARAM);
int mingw_open (const char *filename, int oflags, ...);
+void mingw_read_zero(int fd);
+void mingw_read_random(int fd);
+ssize_t mingw_read(int fd, void *buf, size_t count);
+int mingw_close(int fd);
int pipe(int filedes[2]);
NOIMPL(readlink,const char *path UNUSED_PARAM, char *buf UNUSED_PARAM, size_t bufsiz UNUSED_PARAM);
NOIMPL(setgid,gid_t gid UNUSED_PARAM);
@@ -418,6 +422,7 @@ int mingw_isatty(int fd);
#define getcwd mingw_getcwd
#define lchown chown
#define open mingw_open
+#define close mingw_close
#define unlink mingw_unlink
#define rmdir mingw_rmdir
#undef lseek
diff --git a/win32/mingw.c b/win32/mingw.c
index a55fb4f40..595042d85 100644
--- a/win32/mingw.c
+++ b/win32/mingw.c
@@ -138,12 +138,28 @@ int err_win_to_posix(DWORD winerr)
return error;
}
+static int zero_fd = -1;
+static int rand_fd = -1;
+
+void mingw_read_zero(int fd)
+{
+ zero_fd = fd;
+}
+
+void mingw_read_random(int fd)
+{
+ rand_fd = fd;
+}
+
#undef open
int mingw_open (const char *filename, int oflags, ...)
{
va_list args;
unsigned mode;
int fd;
+ int devnull = 0;
+ int devzero = 0;
+ int devrand = 0;
va_start(args, oflags);
mode = va_arg(args, int);
@@ -152,14 +168,29 @@ int mingw_open (const char *filename, int oflags, ...)
if (oflags & O_NONBLOCK) {
oflags &= ~O_NONBLOCK;
}
- if (filename && !strcmp(filename, "/dev/null"))
- filename = "nul";
+ if (filename && !strncmp(filename, "/dev/", 5)) {
+ if (!strcmp(filename+5, "null"))
+ devnull = 1;
+ else if (!strcmp(filename+5, "zero"))
+ devzero = 1;
+ else if (!strcmp(filename+5, "urandom"))
+ devrand = 1;
+
+ if (devnull || devzero || devrand )
+ filename = "nul";
+ }
fd = open(filename, oflags, mode);
if (fd < 0 && (oflags & O_ACCMODE) != O_RDONLY && errno == EACCES) {
DWORD attrs = GetFileAttributes(filename);
if (attrs != INVALID_FILE_ATTRIBUTES && (attrs & FILE_ATTRIBUTE_DIRECTORY))
errno = EISDIR;
}
+ if (fd >= 0 ) {
+ if (devzero)
+ zero_fd = fd;
+ else if (devrand)
+ rand_fd = fd;
+ }
return fd;
}
@@ -171,6 +202,32 @@ FILE *mingw_fopen (const char *filename, const char *otype)
return fopen(filename, otype);
}
+#undef read
+ssize_t mingw_read(int fd, void *buf, size_t count)
+{
+ if (fd == zero_fd) {
+ memset(buf, 0, count);
+ return count;
+ }
+ else if (fd == rand_fd) {
+ memset(buf, 0x5A, count);
+ return count;
+ }
+ return read(fd, buf, count);
+}
+
+#undef close
+int mingw_close(int fd)
+{
+ if (fd == zero_fd) {
+ zero_fd = -1;
+ }
+ if (fd == rand_fd) {
+ rand_fd = -1;
+ }
+ return close(fd);
+}
+
#undef dup2
int mingw_dup2 (int fd, int fdto)
{
diff --git a/win32/winansi.c b/win32/winansi.c
index 8fffc5a00..b357fc642 100644
--- a/win32/winansi.c
+++ b/win32/winansi.c
@@ -695,7 +695,7 @@ int winansi_read(int fd, void *buf, size_t count)
{
int rv;
- rv = read(fd, buf, count);
+ rv = mingw_read(fd, buf, count);
if (!isatty(fd))
return rv;
--
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