qemu/semihosting
Peter Maydell 5202861b20 semihosting: Allow optional use of semihosting from userspace
Currently our semihosting implementations generally prohibit use of
semihosting calls in system emulation from the guest userspace.  This
is a very long standing behaviour justified originally "to provide
some semblance of security" (since code with access to the
semihosting ABI can do things like read and write arbitrary files on
the host system).  However, it is sometimes useful to be able to run
trusted guest code which performs semihosting calls from guest
userspace, notably for test code.  Add a command line suboption to
the existing semihosting-config option group so that you can
explicitly opt in to semihosting from guest userspace with
 -semihosting-config userspace=on

(There is no equivalent option for the user-mode emulator, because
there by definition all code runs in userspace and has access to
semihosting already.)

This commit adds the infrastructure for the command line option and
adds a bool 'is_user' parameter to the function
semihosting_userspace_enabled() that target code can use to check
whether it should be permitting the semihosting call for userspace.
It mechanically makes all the callsites pass 'false', so they
continue checking "is semihosting enabled in general".  Subsequent
commits will make each target that implements semihosting honour the
userspace=on option by passing the correct value and removing
whatever "don't do this for userspace" checking they were doing by
hand.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Acked-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20220822141230.3658237-2-peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
2022-09-13 17:18:21 +01:00
..
arm-compat-semi.c semihosting: Fix handling of buffer in TARGET_SYS_TMPNAM 2022-07-29 09:48:01 +01:00
config.c semihosting: Allow optional use of semihosting from userspace 2022-09-13 17:18:21 +01:00
console.c semihosting: Don't return negative values on qemu_semihosting_console_write() failure 2022-07-29 09:48:01 +01:00
guestfd.c semihosting: Create qemu_semihosting_guestfd_init 2022-06-28 04:36:50 +05:30
Kconfig semihosting: Move hw/semihosting/ -> semihosting/ 2021-03-10 15:34:12 +00:00
meson.build semihosting: Split out semihost_sys_open 2022-06-28 04:35:39 +05:30
syscalls.c semihosting: Don't copy buffer after console_write() 2022-07-29 09:48:01 +01:00
uaccess.c semihosting: Simplify softmmu_lock_user_string 2022-06-28 04:35:06 +05:30