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[Qemu-devel] [PATCH 2/6] linux-user: Add host_fds and manipulators
From: |
Richard Henderson |
Subject: |
[Qemu-devel] [PATCH 2/6] linux-user: Add host_fds and manipulators |
Date: |
Thu, 31 May 2018 15:49:07 -0700 |
This allows emulation of guest syscalls to reject
manipulations to fds used by the host.
Signed-off-by: Richard Henderson <address@hidden>
---
linux-user/qemu.h | 30 ++++++++++++++++++++++++++++++
linux-user/main.c | 27 ++++++++++++++++++++++++++-
2 files changed, 56 insertions(+), 1 deletion(-)
diff --git a/linux-user/qemu.h b/linux-user/qemu.h
index c55c8e294b..33dafbe0e4 100644
--- a/linux-user/qemu.h
+++ b/linux-user/qemu.h
@@ -155,6 +155,36 @@ void task_settid(TaskState *);
void stop_all_tasks(void);
extern const char *qemu_uname_release;
extern unsigned long mmap_min_addr;
+extern fd_set host_fds;
+
+/**
+ * is_hostfd:
+ * @fd: file descriptor to check
+ *
+ * Return true if @fd is being used by the host and therefore any
+ * guest system call referencing @fd should return EBADF.
+ */
+static inline bool is_hostfd(int fd)
+{
+ return fd >= 0 && fd < FD_SETSIZE && FD_ISSET(fd, &host_fds);
+}
+
+/**
+ * contains_hostfd:
+ * @fds: fd_set of descriptors to check
+ *
+ * Return true if any descriptor in @fds are being used by the host
+ * and therefore the guest system call should return EBADF.
+ */
+bool contains_hostfd(const fd_set *fds);
+
+/**
+ * add_hostfd:
+ * @fd: file descriptor to reserve
+ *
+ * Add @fd to the set of file descriptors to reserve for the host.
+ */
+void add_hostfd(int fd);
/* ??? See if we can avoid exposing so much of the loader internals. */
diff --git a/linux-user/main.c b/linux-user/main.c
index 78d6d3e7eb..ee3f323c08 100644
--- a/linux-user/main.c
+++ b/linux-user/main.c
@@ -49,6 +49,7 @@ static const char *cpu_type;
unsigned long mmap_min_addr;
unsigned long guest_base;
int have_guest_base;
+fd_set host_fds;
/*
* When running 32-on-64 we should make sure we can fit all of the possible
@@ -112,6 +113,23 @@ int cpu_get_pic_interrupt(CPUX86State *env)
}
#endif
+bool contains_hostfd(const fd_set *fds)
+{
+ int i;
+ for (i = 0; i < ARRAY_SIZE(__FDS_BITS(fds)); ++i) {
+ if (__FDS_BITS(fds)[i] & __FDS_BITS(&host_fds)[i]) {
+ return true;
+ }
+ }
+ return true;
+}
+
+void add_hostfd(int fd)
+{
+ g_assert(fd >= 0 && fd < FD_SETSIZE);
+ FD_SET(fd, &host_fds);
+}
+
/***********************************************************/
/* Helper routines for implementing atomic operations. */
@@ -805,12 +823,19 @@ int main(int argc, char **argv, char **envp)
target_cpu_copy_regs(env, regs);
+ /* Prevent the guest from closing the log file. */
+ if (qemu_logfile && qemu_logfile != stderr) {
+ add_hostfd(fileno(qemu_logfile));
+ }
+
if (gdbstub_port) {
- if (gdbserver_start(gdbstub_port) < 0) {
+ int fd = gdbserver_start(gdbstub_port);
+ if (fd < 0) {
fprintf(stderr, "qemu: could not open gdbserver on port %d\n",
gdbstub_port);
exit(EXIT_FAILURE);
}
+ add_hostfd(fd);
gdb_handlesig(cpu, 0);
}
cpu_loop(env);
--
2.17.0
- [Qemu-devel] [PATCH v5 0/6] linux-user: Reorg interp_prefix handling, Richard Henderson, 2018/05/31
- [Qemu-devel] [PATCH 1/6] gdbstub: Return the fd from gdbserver_start, Richard Henderson, 2018/05/31
- [Qemu-devel] [PATCH 2/6] linux-user: Add host_fds and manipulators,
Richard Henderson <=
- [Qemu-devel] [PATCH 4/6] linux-user: Check contains_hostfd in select syscalls, Richard Henderson, 2018/05/31
- [Qemu-devel] [PATCH 5/6] linux-user: Check is_hostfd in mmap syscalls, Richard Henderson, 2018/05/31
- [Qemu-devel] [PATCH 3/6] linux-user: Check is_hostfd in do_syscall, Richard Henderson, 2018/05/31
- [Qemu-devel] [PATCH 6/6] linux-user: Use *at functions to implement interp_prefix, Richard Henderson, 2018/05/31
- Re: [Qemu-devel] [PATCH v5 0/6] linux-user: Reorg interp_prefix handling, no-reply, 2018/05/31