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5202861b20
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>
71 lines
1.2 KiB
C
71 lines
1.2 KiB
C
/*
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* Semihosting Stubs for SoftMMU
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*
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* Copyright (c) 2019 Linaro Ltd
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*
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* Stubs for SoftMMU targets that don't actually do semihosting.
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*
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* SPDX-License-Identifier: GPL-2.0-or-later
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*/
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#include "qemu/osdep.h"
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#include "qemu/option.h"
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#include "qemu/error-report.h"
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#include "semihosting/semihost.h"
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/* Empty config */
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QemuOptsList qemu_semihosting_config_opts = {
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.name = "",
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.head = QTAILQ_HEAD_INITIALIZER(qemu_semihosting_config_opts.head),
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.desc = {
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{ /* end of list */ }
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},
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};
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/* Queries to config status default to off */
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bool semihosting_enabled(bool is_user)
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{
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return false;
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}
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SemihostingTarget semihosting_get_target(void)
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{
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return SEMIHOSTING_TARGET_AUTO;
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}
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/*
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* All the rest are empty subs. We could g_assert_not_reached() but
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* that adds extra weight to the final binary. Waste not want not.
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*/
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void qemu_semihosting_enable(void)
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{
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}
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int qemu_semihosting_config_options(const char *optarg)
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{
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return 1;
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}
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const char *semihosting_get_arg(int i)
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{
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return NULL;
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}
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int semihosting_get_argc(void)
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{
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return 0;
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}
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const char *semihosting_get_cmdline(void)
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{
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return NULL;
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}
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void semihosting_arg_fallback(const char *file, const char *cmd)
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{
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}
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void qemu_semihosting_chardev_init(void)
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{
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}
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