[Qemu-devel] [PATCH 0/9] target-arm: Implement A64 semihosting

[Peter Maydell]

This patch series implements support for semihosting for the
64-bit ARM instruction set.

It owes a significant debt to the patches sent earlier
by Christopher Covington (and with code written by Derek Hower).
However, it is a full from-scratch rewrite (since there were
several things which I felt those patches didn't take the
right approach on). I mostly just looked at the earlier
patches to check I hadn't missed anything.

The changes in the A64 API compared to the A32/T32 one are:
 * input syscall number is in register W0
 * return result is in register X0
 * all argument parameter blocks are 64 bits wide, not 32
 * there is a new SyncCacheRange syscall
 * the SYS_EXIT syscall takes a parameter block and is able
   to pass a guest exit status out
 * the insn used to trigger semihosting is a HLT, not an
   SVC or BKPT.

I've tested this for A32, T32 and A64 semihosting, for
both usermode and system emulation, with and without gdb
remote syscalls.

The test code I wrote to do the testing is here:
https://git.linaro.org/people/peter.maydell/semihosting-tests.git/
(not very exciting, but might be handy if anybody needs a
basic "how to run C code starting with bare metal system
emulation" template.)

The test series also includes a bugfix: we haven't correctly
forwarded SYS_WRITE0 (print string to terminal) to gdb since
the gdb hosted syscall support was added to QEMU back in 2007...

Christopher Covington (1):
  target-arm: Improve semihosting debug prints

Peter Maydell (8):
  target-arm/arm-semi.c: Fix broken SYS_WRITE0 via gdb
  gdbstub: Implement gdb_do_syscallv()
  target-arm/arm-semi.c: Factor out repeated 'return env->regs[0]'
  include/exec/softmmu-semi.h: Add support for 64-bit values
  target-arm/arm-semi.c: Support widening APIs to 64 bits
  target-arm/arm-semi.c: Implement A64 specific SyncCacheRange call
  target-arm/arm-semi.c: SYS_EXIT on A64 takes a parameter block
  target-arm: Wire up HLT 0xf000 as the A64 semihosting instruction

 gdbstub.c                   |  14 ++--
 include/exec/gdbstub.h      |  27 +++++++
 include/exec/softmmu-semi.h |  18 +++++
 linux-user/main.c           |   3 +
 target-arm/arm-semi.c       | 171 +++++++++++++++++++++++++++++++++-----------
 target-arm/cpu.h            |   3 +-
 target-arm/helper-a64.c     |   6 ++
 target-arm/helper.c         |  12 +++-
 target-arm/internals.h      |   2 +
 target-arm/translate-a64.c  |  14 +++-
 10 files changed, 217 insertions(+), 53 deletions(-)

-- 
1.9.1