[Qemu-devel] [PATCH 00/13] target/arm: Implement semihosting v2.0

[Peter Maydell <peter.maydell@linaro.org>]

This patchset implements support in QEMU for v2.0 of the
Arm semihosting specification:
 https://developer.arm.com/docs/100863/latest/preface

Specifically, v2.0 has:
 * a mechanism for detection of optional extra features,
   which works by allowing the guest to open a magic file
   named ":semihosting-features" and read some feature
   flags from it
 * two defined extensions:
  - STDOUT_STDERR lets the guest separately open stdout and
    stderr via the ":tt" magic filename (v1.0 only allowed
    access to stdout)
  - EXIT_EXTENDED lets A32/T32 guests exit with a specified
    exit status (otherwise only available to A64 guests).
    This is something that people have been complaining
    about for a long time.

(Technically some of the things we already support, like
having an A64 semihosting interface at all, are also part of
the v2.0 spec.)

This patchset:
 * fixes some bugs relating to errnos in some cases
 * makes semihosting hand out its own filedescriptors rather
   than just passing out host fd numbers
 * abstracts out the fd-related semihosting calls so they
   indirect via a function table based on the type of the fd
 * adds a new type of fd representing the magic file
   ":semihosting-features" which is used for feature-detection
 * implements both of the extensions defined by the v2.0 spec

I've tested this by improving my semihosting test suite:
 https://git.linaro.org/people/peter.maydell/semihosting-tests.git/
(if people have other guest binaries that make much use of
semihosting then testing would certainly be welcome.)

thanks
-- PMM

Peter Maydell (13):
  target/arm/arm-semi: Capture errno in softmmu version of
    set_swi_errno()
  target/arm/arm-semi: Always set some kind of errno for failed calls
  target/arm/arm-semi: Make semihosting code hand out its own file
    descriptors
  target/arm/arm-semi: clean up TaskState* usage in non-user-only code
  target/arm/arm-semi: Factor out implementation of SYS_CLOSE
  target/arm/arm-semi: Factor out implementation of SYS_WRITE
  target/arm/arm-semi: Factor out implementation of SYS_READ
  target/arm/arm-semi: Factor out implementation of SYS_ISTTY
  target/arm/arm-semi: Factor out implementation of SYS_SEEK
  target/arm/arm-semi: Factor out implementation of SYS_FLEN
  target/arm/arm-semi: Implement support for semihosting feature
    detection
  target/arm/arm-semi: Implement SH_EXT_STDOUT_STDERR extension
  target/arm/arm-semi: Implement SH_EXT_EXIT_EXTENDED extension

 target/arm/arm-semi.c | 613 +++++++++++++++++++++++++++++++++++-------
 1 file changed, 513 insertions(+), 100 deletions(-)

-- 
2.20.1