[LibOS,Pal] Support Glibc logic of line-buffered/fully-buffered STDOUT

Glibc has special handling of STDOUT: it checks whether STDOUT is
TTY (app writes to a terminal) or non-TTY (app writes to a pipe/file)
and makes STDOUT line-buffered or fully-buffered respectively. Glibc
uses a trick with IOCTL(TCGETS) to find out whether it is TTY or
non-TTY. Previously, Graphene always returned -EINVAL on this IOCTL,
so STDOUT in Graphene was always fully-buffered. This inconsistency
led to e.g. close(STDOUT) without printing out buffered strings.
This commit fixes this by propagating info on TTY/non-TTY from the
host.

LibOS/shim/src/sys/shim_ioctl.c

@@ -41,7 +41,7 @@
 #define TERM_DEFAULT_CFLAG (B38400 | CS8 | CREAD)
 #define TERM_DEFAULT_LFLAG (ICANON | ECHO | ECHOE | ECHOK | ECHOCTL | ECHOKE | IEXTEN)
 
-static int ioctl_termios(struct shim_handle* hdl, unsigned int cmd, unsigned long arg) {
+static int ioctl_termios(int fd, struct shim_handle* hdl, unsigned int cmd, unsigned long arg) {
     if (hdl->type != TYPE_FILE || hdl->info.file.type != FILE_TTY)
         return -ENOTTY;
 
@@ -58,14 +58,21 @@ static int ioctl_termios(struct shim_handle* hdl, unsigned int cmd, unsigned lon
             return -EINVAL;
 
         case TCGETS: {
-#if 0
-            struct termios * termios = (struct termios *) arg;
+            /* proactively set termios, it doesn't hurt */
+            struct termios* termios = (struct termios*)arg;
             termios->c_iflag = TERM_DEFAULT_IFLAG;
             termios->c_oflag = TERM_DEFAULT_OFLAG;
             termios->c_cflag = TERM_DEFAULT_CFLAG;
             termios->c_lflag = TERM_DEFAULT_LFLAG;
-            return 0;
-#endif
+
+            if (fd == STDOUT_FILENO) {
+                /* special case: Glibc wants to know whether STDOUT is TTY (app writes to terminal)
+                 * or non-TTY (app writes to pipe/file); Graphene buffers this info in PAL's
+                 * is_stdout_tty field */
+                if (PAL_CB(is_stdout_tty))
+                    return 0;
+            }
+
             return -EINVAL;
         }
 
@@ -346,7 +353,7 @@ int shim_do_ioctl(int fd, unsigned long cmd, unsigned long arg) {
         case TIOCSETD:
         case TIOCGETD:
         case TCSBRKP:
-            ret = ioctl_termios(hdl, cmd, arg);
+            ret = ioctl_termios(fd, hdl, cmd, arg);
             break;
         case FIONBIO:
             if (hdl->fs && hdl->fs->fs_ops && hdl->fs->fs_ops->setflags)
@@ -374,7 +381,7 @@ int shim_do_ioctl(int fd, unsigned long cmd, unsigned long arg) {
         case TIOCSERGETLSR:
         case TIOCSERGETMULTI:
         case TIOCSERSETMULTI:
-            ret = ioctl_termios(hdl, cmd, arg);
+            ret = ioctl_termios(fd, hdl, cmd, arg);
             break;
 
         case FDCLRPRM:

Pal/include/pal/pal.h

@@ -341,6 +341,11 @@ typedef struct PAL_CONTROL_ {
 
     PAL_CPU_INFO cpu_info; /*!< CPU information (only required ones) */
     PAL_MEM_INFO mem_info; /*!< memory information (only required ones) */
+
+    /*
+     * Misc
+     */
+    PAL_BOL is_stdout_tty; /*!< STDOUT is TTY (app prints to term) or non-TTY (to pipe/file) */
 } PAL_CONTROL;
 
 #define pal_control (*pal_control_addr())

Pal/src/db_main.c

@@ -395,6 +395,7 @@ noreturn void pal_main (
     __pal_control.host_type          = XSTRINGIFY(HOST_TYPE);
     __pal_control.process_id         = _DkGetProcessId();
     __pal_control.host_id            = _DkGetHostId();
+    __pal_control.is_stdout_tty      = _DkIsStdoutTty();
     __pal_control.manifest_handle    = manifest_handle;
     __pal_control.executable         = exec_uri;
     __pal_control.parent_process     = parent_process;

Pal/src/host/Linux-SGX/db_main.c

@@ -82,6 +82,11 @@ PAL_NUM _DkGetHostId (void)
     return 0;
 }
 
+PAL_BOL _DkIsStdoutTty(void) {
+    /* is_stdout_tty is initialized in untrusted runtime during enclave creation and buffered */
+    return pal_sec.is_stdout_tty;
+}
+
 #include "elf-x86_64.h"
 #include "dynamic_link.h"
 #include <asm/errno.h>
@@ -272,6 +277,7 @@ void pal_linux_main(char * uptr_args, uint64_t args_size,
 
     COPY_ARRAY(pal_sec.pipe_prefix, sec_info.pipe_prefix);
     pal_sec.qe_targetinfo = sec_info.qe_targetinfo;
+    pal_sec.is_stdout_tty = sec_info.is_stdout_tty;
 #ifdef DEBUG
     pal_sec.in_gdb = sec_info.in_gdb;
 #endif

Pal/src/host/Linux-SGX/pal_security.h

@@ -52,6 +52,9 @@ struct pal_sec {
     /* Need to pass in the number of cores */
     PAL_NUM         num_cpus;
 
+    /* STDOUT is TTY (app prints to term) or non-TTY (app prints to pipe/file) */
+    PAL_BOL         is_stdout_tty;
+
 #ifdef DEBUG
     PAL_BOL         in_gdb;
 #endif

Pal/src/host/Linux-SGX/sgx_main.c

@@ -10,16 +10,17 @@
 #include "sgx_internal.h"
 #include "sgx_tls.h"
 
+#include <asm/errno.h>
 #include <asm/fcntl.h>
+#include <asm/ioctls.h>
 #include <asm/socket.h>
+#include <ctype.h>
 #include <linux/fs.h>
 #include <linux/in.h>
 #include <linux/in6.h>
-#include <asm/errno.h>
-#include <ctype.h>
-
 #include <sysdep.h>
 #include <sysdeps/generic/ldsodefs.h>
+#include <termios.h>
 
 size_t g_page_size = PRESET_PAGESIZE;
 
@@ -789,6 +790,15 @@ static int load_enclave (struct pal_enclave * enclave,
     }
 #endif
 
+    struct termios term;
+    ret = INLINE_SYSCALL(ioctl, 3, STDOUT_FILENO, TCGETS, &term);
+    if (IS_ERR(ret)) {
+        /* mark STDOUT as not TTY (app writes to pipe/file); Glibc considers it fully-buffered */
+        pal_sec->is_stdout_tty = false;
+    }
+    /* mark STDOUT as TTY (app writes to terminal); Glibc considers it line-buffered */
+    pal_sec->is_stdout_tty = true;
+
     enclave->manifest = manifest_fd;
 
     ret = load_manifest(enclave->manifest, &enclave->config);

Pal/src/host/Linux/db_main.c

@@ -37,6 +37,7 @@
 #include <asm/mman.h>
 #include <elf/elf.h>
 #include <sysdeps/generic/ldsodefs.h>
+#include <termios.h>
 
 /* At the begining of entry point, rsp starts at argc, then argvs,
    envps and auxvs. Here we store rsp to rdi, so it will not be
@@ -188,6 +189,18 @@ PAL_NUM _DkGetHostId (void)
     return 0;
 }
 
+PAL_BOL _DkIsStdoutTty(void) {
+    struct termios term;
+    int ret = INLINE_SYSCALL(ioctl, 3, STDOUT_FILENO, TCGETS, &term);
+    if (IS_ERR(ret)) {
+        /* mark STDOUT as not TTY (app writes to pipe/file); Glibc considers it fully-buffered */
+        return false;
+    }
+
+    /* mark STDOUT as TTY (app writes to terminal); Glibc considers it line-buffered */
+    return true;
+}
+
 #include "dynamic_link.h"
 
 void setup_pal_map (struct link_map * map);

Pal/src/host/Skeleton/db_main.c

@@ -56,6 +56,12 @@ PAL_NUM _DkGetHostId (void)
     return 0;
 }
 
+PAL_BOL _DkIsStdoutTty(void) {
+    /* mark STDOUT as not TTY (app writes to pipe/file); Glibc considers it fully-buffered */
+    return false;
+}
+
+int _DkGetCPUInfo (PAL_CPU_INFO * ci)
 int _DkGetCPUInfo (PAL_CPU_INFO * ci)
 {
     /* needs to be implemented */

Pal/src/pal_internal.h

@@ -219,6 +219,7 @@ void _DkGetAvailableUserAddressRange (PAL_PTR * start, PAL_PTR * end, PAL_PTR *
 bool _DkCheckMemoryMappable (const void * addr, size_t size);
 PAL_NUM _DkGetProcessId (void);
 PAL_NUM _DkGetHostId (void);
+PAL_BOL _DkIsStdoutTty(void);
 unsigned long _DkMemoryQuota (void);
 unsigned long _DkMemoryAvailableQuota (void);
 // Returns 0 on success, negative PAL code on failure