From 5202861b20d77b1d638da5f10af0f51ebcfc61bf Mon Sep 17 00:00:00 2001 From: Peter Maydell Date: Mon, 22 Aug 2022 15:12:24 +0100 Subject: semihosting: Allow optional use of semihosting from userspace MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 Acked-by: Alex Bennée Reviewed-by: Alistair Francis Reviewed-by: Philippe Mathieu-Daudé Reviewed-by: Richard Henderson Message-Id: <20220822141230.3658237-2-peter.maydell@linaro.org> Signed-off-by: Richard Henderson --- include/semihosting/semihost.h | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) (limited to 'include') diff --git a/include/semihosting/semihost.h b/include/semihosting/semihost.h index 93a3c21..efd2efa 100644 --- a/include/semihosting/semihost.h +++ b/include/semihosting/semihost.h @@ -27,7 +27,7 @@ typedef enum SemihostingTarget { } SemihostingTarget; #ifdef CONFIG_USER_ONLY -static inline bool semihosting_enabled(void) +static inline bool semihosting_enabled(bool is_user) { return true; } @@ -52,7 +52,13 @@ static inline const char *semihosting_get_cmdline(void) return NULL; } #else /* !CONFIG_USER_ONLY */ -bool semihosting_enabled(void); +/** + * semihosting_enabled: + * @is_user: true if guest code is in usermode (i.e. not privileged) + * + * Return true if guest code is allowed to make semihosting calls. + */ +bool semihosting_enabled(bool is_user); SemihostingTarget semihosting_get_target(void); const char *semihosting_get_arg(int i); int semihosting_get_argc(void); -- cgit v1.1