Fall back to TCGETS if TCGETS2 fails (#1147)

Android and some other seccomp environments don't recognize `TCGETS2`/`TCSETS2` and fail them with `Errno::ACCESS`, and WSL doesn't recognize them either and fails them with `Errno::NOTTY`, so add code to fall back to `TCGETS`/`TCSETS` in those cases, and manually initialize the missing speed fields.

Doing the `TCGETS2`/`TCSETS2` first means we can do more of the fallback code in `#[cold]` functions, and makes the code easier to follow.

Also, fix some bugs in QEMU related to the handling of termios syscalls. This eliminates the need for having rustix do extra fixups on PowerPC. And this fixes the tests on MIPS.

Add more tests for `tcgetattr`/`tcsetattr` covering more speed cases, input/output/local/control modes, and special codes.

Define more `SpecialCodeIndex` constants for bsd and solarish platforms.

And fix capitalization of MIPS and SPARC in various comments.

This fixes crossterm-rs/crossterm#912.

ci/tcgets2-tcsets2.patch

@@ -6,15 +6,22 @@ This implements the `TCGETS2` and `TCSETS2` ioctls.
 diff -ur a/linux-user/ioctls.h b/linux-user/ioctls.h
 --- a/linux-user/ioctls.h
 +++ b/linux-user/ioctls.h
-@@ -2,6 +2,8 @@
+@@ -1,5 +1,15 @@
+      /* emulated ioctl list */
 
-      IOCTL(TCGETS, IOC_R, MK_PTR(MK_STRUCT(STRUCT_termios)))
-      IOCTL(TCSETS, IOC_W, MK_PTR(MK_STRUCT(STRUCT_termios)))
++     /*
++      * Put `TCGETS2`/`TCGETS2` before `TCGETS`/`TCSETS` so that on targets
++      * where these have the same value, we find the `TCGETS2`/`TCSETS2`
++      * entries first, which ensures that we set the `c_ispeed` and `c_ospeed`
++      * fields if the target needed them.
++      */
 +     IOCTL(TCGETS2, IOC_R, MK_PTR(MK_STRUCT(STRUCT_termios2)))
 +     IOCTL(TCSETS2, IOC_W, MK_PTR(MK_STRUCT(STRUCT_termios2)))
++     IOCTL(TCSETSF2, IOC_W, MK_PTR(MK_STRUCT(STRUCT_termios2)))
++     IOCTL(TCSETSW2, IOC_W, MK_PTR(MK_STRUCT(STRUCT_termios2)))
+      IOCTL(TCGETS, IOC_R, MK_PTR(MK_STRUCT(STRUCT_termios)))
+      IOCTL(TCSETS, IOC_W, MK_PTR(MK_STRUCT(STRUCT_termios)))
       IOCTL(TCSETSF, IOC_W, MK_PTR(MK_STRUCT(STRUCT_termios)))
-      IOCTL(TCSETSW, IOC_W, MK_PTR(MK_STRUCT(STRUCT_termios)))
-      IOCTL(TIOCGWINSZ, IOC_R, MK_PTR(MK_STRUCT(STRUCT_winsize)))
 diff -ur a/linux-user/ppc/termbits.h b/linux-user/ppc/termbits.h
 --- a/linux-user/ppc/termbits.h
 +++ b/linux-user/ppc/termbits.h
@@ -53,12 +60,14 @@ diff -ur a/linux-user/ppc/termbits.h b/linux-user/ppc/termbits.h
 
  #define TARGET_CSIZE	00001400
  #define   TARGET_CS5	00000000
-@@ -178,6 +192,8 @@
+@@ -178,6 +192,10 @@
  #define TARGET_TCSETS		TARGET_IOW('t', 20, struct target_termios)
  #define TARGET_TCSETSW		TARGET_IOW('t', 21, struct target_termios)
  #define TARGET_TCSETSF		TARGET_IOW('t', 22, struct target_termios)
 +#define TARGET_TCGETS2		TARGET_TCGETS
 +#define TARGET_TCSETS2		TARGET_TCSETS
++#define TARGET_TCSETSW2		TARGET_TCSETSW
++#define TARGET_TCSETSF2		TARGET_TCSETSF
 
  #define TARGET_TCGETA		TARGET_IOR('t', 23, struct target_termio)
  #define TARGET_TCSETA		TARGET_IOW('t', 24, struct target_termio)
@@ -157,6 +166,15 @@ diff -ur a/linux-user/strace.c b/linux-user/strace.c
 
  #undef UNUSED
 
+@@ -4161,7 +4161,7 @@
+     int target_size;
+
+     for (ie = ioctl_entries; ie->target_cmd != 0; ie++) {
+-        if (ie->target_cmd == arg1) {
++        if (ie->target_cmd == (int)arg1) {
+             break;
+         }
+     }
 diff -ur a/linux-user/syscall.c b/linux-user/syscall.c
 --- a/linux-user/syscall.c
 +++ b/linux-user/syscall.c
@@ -326,3 +344,60 @@ diff -ur a/linux-user/user-internals.h b/linux-user/user-internals.h
 
  /* ARM EABI and MIPS expect 64bit types aligned even on pairs or registers */
  #ifdef TARGET_ARM
+diff -ur -x build -x roms a/linux-user/mips/termbits.h b/linux-user/mips/termbits.h
+--- a/linux-user/mips/termbits.h
++++ b/linux-user/mips/termbits.h
+@@ -18,6 +18,17 @@
+     target_cc_t c_cc[TARGET_NCCS];         /* control characters */
+ };
+
++struct target_termios2 {
++    target_tcflag_t c_iflag;               /* input mode flags */
++    target_tcflag_t c_oflag;               /* output mode flags */
++    target_tcflag_t c_cflag;               /* control mode flags */
++    target_tcflag_t c_lflag;               /* local mode flags */
++    target_cc_t c_line;                    /* line discipline */
++    target_cc_t c_cc[TARGET_NCCS];         /* control characters */
++    target_speed_t c_ispeed;               /* input speed */
++    target_speed_t c_ospeed;               /* output speed */
++};
++
+ /* c_iflag bits */
+ #define TARGET_IGNBRK  0000001
+ #define TARGET_BRKINT  0000002
+@@ -117,6 +128,7 @@
+ #define  TARGET_B3500000 0010016
+ #define  TARGET_B4000000 0010017
+ #define TARGET_CIBAUD    002003600000  /* input baud rate (not used) */
++#define TARGET_IBSHIFT 16
+ #define TARGET_CMSPAR    010000000000  /* mark or space (stick) parity */
+ #define TARGET_CRTSCTS   020000000000  /* flow control */
+
+@@ -217,9 +229,9 @@
+ #define TARGET_TIOCSETP        0x7409
+ #define TARGET_TIOCSETN        0x740a			/* TIOCSETP wo flush */
+
+-/* #define TARGET_TIOCSETA	TARGET_IOW('t', 20, struct termios) set termios struct */
+-/* #define TARGET_TIOCSETAW	TARGET_IOW('t', 21, struct termios) drain output, set */
+-/* #define TARGET_TIOCSETAF	TARGET_IOW('t', 22, struct termios) drn out, fls in, set */
++/* #define TARGET_TIOCSETA	TARGET_IOW('t', 20, struct target_termios) set termios struct */
++/* #define TARGET_TIOCSETAW	TARGET_IOW('t', 21, struct target_termios) drain output, set */
++/* #define TARGET_TIOCSETAF	TARGET_IOW('t', 22, struct target_termios) drn out, fls in, set */
+ /* #define TARGET_TIOCGETD	TARGET_IOR('t', 26, int)	get line discipline */
+ /* #define TARGET_TIOCSETD	TARGET_IOW('t', 27, int)	set line discipline */
+ 						/* 127-124 compat */
+@@ -227,10 +239,10 @@
+ #define TARGET_TIOCSBRK	0x5427  /* BSD compatibility */
+ #define TARGET_TIOCCBRK	0x5428  /* BSD compatibility */
+ #define TARGET_TIOCGSID	0x7416  /* Return the session ID of FD */
+-#define TARGET_TCGETS2          TARGET_IOR('T', 0x2A, struct termios2)
+-#define TARGET_TCSETS2          TARGET_IOW('T', 0x2B, struct termios2)
+-#define TARGET_TCSETSW2         TARGET_IOW('T', 0x2C, struct termios2)
+-#define TARGET_TCSETSF2         TARGET_IOW('T', 0x2D, struct termios2)
++#define TARGET_TCGETS2          TARGET_IOR('T', 0x2A, struct target_termios2)
++#define TARGET_TCSETS2          TARGET_IOW('T', 0x2B, struct target_termios2)
++#define TARGET_TCSETSW2         TARGET_IOW('T', 0x2C, struct target_termios2)
++#define TARGET_TCSETSF2         TARGET_IOW('T', 0x2D, struct target_termios2)
+ #define TARGET_TIOCGRS485       TARGET_IOR('T', 0x2E, struct serial_rs485)
+ #define TARGET_TIOCSRS485       TARGET_IOWR('T', 0x2F, struct serial_rs485)
+ #define TARGET_TIOCGPTN	TARGET_IOR('T',0x30, unsigned int) /* Get Pty Number (of pty-mux device) */

src/backend/libc/c.rs

@@ -102,19 +102,26 @@ pub(crate) const O_LARGEFILE: c_int = 0x2000;
 pub(crate) const MAP_DROPPABLE: u32 = 0x8;
 
 // On PowerPC, the regular `termios` has the `termios2` fields and there is no
-// `termios2`. linux-raw-sys has aliases `termios2` to `termios` to cover this
-// difference, but we still need to manually import it since `libc` doesn't
-// have this.
+// `termios2`, so we define aliases.
 #[cfg(all(
     linux_kernel,
     feature = "termios",
     any(target_arch = "powerpc", target_arch = "powerpc64")
 ))]
-pub(crate) use {
-    linux_raw_sys::general::{termios2, CIBAUD},
-    linux_raw_sys::ioctl::{TCGETS2, TCSETS2, TCSETSF2, TCSETSW2},
+pub(crate) use libc::{
+    termios as termios2, TCGETS as TCGETS2, TCSETS as TCSETS2, TCSETSF as TCSETSF2,
+    TCSETSW as TCSETSW2,
 };
 
+// And PowerPC doesn't define `CIBAUD`, but it does define `IBSHIFT`, so we can
+// compute `CIBAUD` ourselves.
+#[cfg(all(
+    linux_kernel,
+    feature = "termios",
+    any(target_arch = "powerpc", target_arch = "powerpc64")
+))]
+pub(crate) const CIBAUD: u32 = libc::CBAUD << libc::IBSHIFT;
+
 // Automatically enable “large file” support (LFS) features.
 
 #[cfg(target_os = "vxworks")]