[Qemu-devel] [Bug 1407808] [NEW] virtual console gives strange response to ANSI DSR

[Qemu-devel] [Bug 1407808] [NEW] virtual console gives strange response to ANSI DSR

[Nadav Har'El]

Public bug reported:

With "-serial vc" (which is the default), qemu make strange responses to
the ANSI DSR escape sequence (\033[6n) which can confuse guests.

Terminal emulators supporting the ANSI escape sequences usually support
the "Device Status Report" escape sequence, \033[6n, to which as a
response the terminal injects as input the response \033[n;mR,
containing the current cursor position. An application running in the
guest can use this escape sequence to, for example, figure out the size
of the terminal it is running under, which can be useful as the guest
has no other standard way to figure out a "size" for the serial port.

Unfortunately, it seems that qemu when run with "-serial vc" (which
appears to be the default), when qemu gets the \033[6n escape sequence
on the serial port, it just responds with a single \033, and that's it!
This can confuse an application, could concievably assume that a
terminal either supports this escape sequence and injects the correct
response (\033[n;mR), or doesn't support it and injects absolutely
nothing as input - but not something in between.

This caused a problem on one shell implementation on OSv that tried to
figure out the terminal's size, and had to work around this unexpected
behavior (see https://github.com/cloudius-
systems/osv/commit/b79223584be40459861d1c12e1cb67e3e49e2a12).

** Affects: qemu
     Importance: Undecided
         Status: New

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Title:
  virtual console gives strange response to ANSI DSR

Status in QEMU:
  New

Bug description:
  With "-serial vc" (which is the default), qemu make strange responses
  to the ANSI DSR escape sequence (\033[6n) which can confuse guests.

  Terminal emulators supporting the ANSI escape sequences usually
  support the "Device Status Report" escape sequence, \033[6n, to which
  as a response the terminal injects as input the response \033[n;mR,
  containing the current cursor position. An application running in the
  guest can use this escape sequence to, for example, figure out the
  size of the terminal it is running under, which can be useful as the
  guest has no other standard way to figure out a "size" for the serial
  port.

  Unfortunately, it seems that qemu when run with "-serial vc" (which
  appears to be the default), when qemu gets the \033[6n escape sequence
  on the serial port, it just responds with a single \033, and that's
  it! This can confuse an application, could concievably assume that a
  terminal either supports this escape sequence and injects the correct
  response (\033[n;mR), or doesn't support it and injects absolutely
  nothing as input - but not something in between.

  This caused a problem on one shell implementation on OSv that tried to
  figure out the terminal's size, and had to work around this unexpected
  behavior (see https://github.com/cloudius-
  systems/osv/commit/b79223584be40459861d1c12e1cb67e3e49e2a12).

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[Bug 1407808] Re: virtual console gives strange response to ANSI DSR

[Thomas Huth]

Looking through old bug tickets... is this still an issue with the
latest version of QEMU? Or could we close this ticket nowadays?


** Changed in: qemu
       Status: New => Incomplete

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https://bugs.launchpad.net/bugs/1407808

Title:
  virtual console gives strange response to ANSI DSR

Status in QEMU:
  Incomplete

Bug description:
  With "-serial vc" (which is the default), qemu make strange responses
  to the ANSI DSR escape sequence (\033[6n) which can confuse guests.

  Terminal emulators supporting the ANSI escape sequences usually
  support the "Device Status Report" escape sequence, \033[6n, to which
  as a response the terminal injects as input the response \033[n;mR,
  containing the current cursor position. An application running in the
  guest can use this escape sequence to, for example, figure out the
  size of the terminal it is running under, which can be useful as the
  guest has no other standard way to figure out a "size" for the serial
  port.

  Unfortunately, it seems that qemu when run with "-serial vc" (which
  appears to be the default), when qemu gets the \033[6n escape sequence
  on the serial port, it just responds with a single \033, and that's
  it! This can confuse an application, could concievably assume that a
  terminal either supports this escape sequence and injects the correct
  response (\033[n;mR), or doesn't support it and injects absolutely
  nothing as input - but not something in between.

  This caused a problem on one shell implementation on OSv that tried to
  figure out the terminal's size, and had to work around this unexpected
  behavior (see https://github.com/cloudius-
  systems/osv/commit/b79223584be40459861d1c12e1cb67e3e49e2a12).

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[Bug 1407808] Re: virtual console gives strange response to ANSI DSR

[Nadav Har'El]

The bug still very much exists (I tested qemu 4.2.1):
If you don't use "-serial stdio" (or its newer variants), by default Qemu opens a new black "console" to run the application. It is not clear to me exactly which terminal this console is supposed to emulate, but it does seem to support most ANSI escape sequences I tried. However, it supports the ANSI "DSR" (Device Status Report) escape sequence, ESC [ 6 n (see https://en.wikipedia.org/wiki/ANSI_escape_code), incorrectly, just as I reported in the original issue. This is still true today.

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Title:
  virtual console gives strange response to ANSI DSR

Status in QEMU:
  Incomplete

Bug description:
  With "-serial vc" (which is the default), qemu make strange responses
  to the ANSI DSR escape sequence (\033[6n) which can confuse guests.

  Terminal emulators supporting the ANSI escape sequences usually
  support the "Device Status Report" escape sequence, \033[6n, to which
  as a response the terminal injects as input the response \033[n;mR,
  containing the current cursor position. An application running in the
  guest can use this escape sequence to, for example, figure out the
  size of the terminal it is running under, which can be useful as the
  guest has no other standard way to figure out a "size" for the serial
  port.

  Unfortunately, it seems that qemu when run with "-serial vc" (which
  appears to be the default), when qemu gets the \033[6n escape sequence
  on the serial port, it just responds with a single \033, and that's
  it! This can confuse an application, could concievably assume that a
  terminal either supports this escape sequence and injects the correct
  response (\033[n;mR), or doesn't support it and injects absolutely
  nothing as input - but not something in between.

  This caused a problem on one shell implementation on OSv that tried to
  figure out the terminal's size, and had to work around this unexpected
  behavior (see https://github.com/cloudius-
  systems/osv/commit/b79223584be40459861d1c12e1cb67e3e49e2a12).

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[Bug 1407808] Re: virtual console gives strange response to ANSI DSR

[Thomas Huth]

** Changed in: qemu
       Status: Incomplete => Triaged

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https://bugs.launchpad.net/bugs/1407808

Title:
  virtual console gives strange response to ANSI DSR

Status in QEMU:
  Triaged

Bug description:
  With "-serial vc" (which is the default), qemu make strange responses
  to the ANSI DSR escape sequence (\033[6n) which can confuse guests.

  Terminal emulators supporting the ANSI escape sequences usually
  support the "Device Status Report" escape sequence, \033[6n, to which
  as a response the terminal injects as input the response \033[n;mR,
  containing the current cursor position. An application running in the
  guest can use this escape sequence to, for example, figure out the
  size of the terminal it is running under, which can be useful as the
  guest has no other standard way to figure out a "size" for the serial
  port.

  Unfortunately, it seems that qemu when run with "-serial vc" (which
  appears to be the default), when qemu gets the \033[6n escape sequence
  on the serial port, it just responds with a single \033, and that's
  it! This can confuse an application, could concievably assume that a
  terminal either supports this escape sequence and injects the correct
  response (\033[n;mR), or doesn't support it and injects absolutely
  nothing as input - but not something in between.

  This caused a problem on one shell implementation on OSv that tried to
  figure out the terminal's size, and had to work around this unexpected
  behavior (see https://github.com/cloudius-
  systems/osv/commit/b79223584be40459861d1c12e1cb67e3e49e2a12).

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[Bug 1407808] Re: virtual console gives strange response to ANSI DSR

[Peter Maydell]

This should be fixed in head-of-git by commit 8eb13bbbac08a, which will
be in QEMU 6.0. (The underlying bug is that when the GTK front-end tries
to send sequences of more than one byte to a UART, it didn't account for
UARTs which don't have a FIFO capable of holding the whole sequence at
once.)


** Changed in: qemu
       Status: Triaged => Fix Committed

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You received this bug notification because you are a member of qemu-
devel-ml, which is subscribed to QEMU.
https://bugs.launchpad.net/bugs/1407808

Title:
  virtual console gives strange response to ANSI DSR

Status in QEMU:
  Fix Committed

Bug description:
  With "-serial vc" (which is the default), qemu make strange responses
  to the ANSI DSR escape sequence (\033[6n) which can confuse guests.

  Terminal emulators supporting the ANSI escape sequences usually
  support the "Device Status Report" escape sequence, \033[6n, to which
  as a response the terminal injects as input the response \033[n;mR,
  containing the current cursor position. An application running in the
  guest can use this escape sequence to, for example, figure out the
  size of the terminal it is running under, which can be useful as the
  guest has no other standard way to figure out a "size" for the serial
  port.

  Unfortunately, it seems that qemu when run with "-serial vc" (which
  appears to be the default), when qemu gets the \033[6n escape sequence
  on the serial port, it just responds with a single \033, and that's
  it! This can confuse an application, could concievably assume that a
  terminal either supports this escape sequence and injects the correct
  response (\033[n;mR), or doesn't support it and injects absolutely
  nothing as input - but not something in between.

  This caused a problem on one shell implementation on OSv that tried to
  figure out the terminal's size, and had to work around this unexpected
  behavior (see https://github.com/cloudius-
  systems/osv/commit/b79223584be40459861d1c12e1cb67e3e49e2a12).

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[Bug 1407808] Re: virtual console gives strange response to ANSI DSR

[Thomas Huth]

** Changed in: qemu
       Status: Fix Committed => Fix Released

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You received this bug notification because you are a member of qemu-
devel-ml, which is subscribed to QEMU.
https://bugs.launchpad.net/bugs/1407808

Title:
  virtual console gives strange response to ANSI DSR

Status in QEMU:
  Fix Released

Bug description:
  With "-serial vc" (which is the default), qemu make strange responses
  to the ANSI DSR escape sequence (\033[6n) which can confuse guests.

  Terminal emulators supporting the ANSI escape sequences usually
  support the "Device Status Report" escape sequence, \033[6n, to which
  as a response the terminal injects as input the response \033[n;mR,
  containing the current cursor position. An application running in the
  guest can use this escape sequence to, for example, figure out the
  size of the terminal it is running under, which can be useful as the
  guest has no other standard way to figure out a "size" for the serial
  port.

  Unfortunately, it seems that qemu when run with "-serial vc" (which
  appears to be the default), when qemu gets the \033[6n escape sequence
  on the serial port, it just responds with a single \033, and that's
  it! This can confuse an application, could concievably assume that a
  terminal either supports this escape sequence and injects the correct
  response (\033[n;mR), or doesn't support it and injects absolutely
  nothing as input - but not something in between.

  This caused a problem on one shell implementation on OSv that tried to
  figure out the terminal's size, and had to work around this unexpected
  behavior (see https://github.com/cloudius-
  systems/osv/commit/b79223584be40459861d1c12e1cb67e3e49e2a12).

To manage notifications about this bug go to:
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