Messages in this thread Patch in this message |  | | From | houdek.ryan@fex-emu ... | Subject | [PATCH 3/4] arm64: Enable userspace syscall dispatch | Date | Sat, 29 May 2021 01:16:19 -0700 |
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From: Ryan Houdek <Houdek.Ryan@fex-emu.org>
When `PR_SET_SYSCALL_USER_DISPATCH` is used this will set the thread's flags to enable `TIF_SYSCALL_USER_DISPATCH`.
This allows us to support userspace dispatch of syscalls through SIGSYS. This has feature parity with what is available on x86-64
Signed-off-by: Ryan Houdek <Houdek.Ryan@fex-emu.org> --- arch/arm64/Kconfig | 1 + arch/arm64/include/asm/syscall.h | 2 ++ arch/arm64/include/asm/thread_info.h | 4 +++- arch/arm64/kernel/ptrace.c | 24 ++++++++++++++++++++++++ arch/arm64/kernel/syscall.c | 9 +++++++++ 5 files changed, 39 insertions(+), 1 deletion(-)
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index 9f1d8566bbf9..8c5f2d1c7053 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -220,6 +220,7 @@ config ARM64 select SYSCTL_EXCEPTION_TRACE select THREAD_INFO_IN_TASK select HAVE_ARCH_USERFAULTFD_MINOR if USERFAULTFD + select SYSCALL_USER_DISPATCH help ARM 64-bit (AArch64) Linux support. diff --git a/arch/arm64/include/asm/syscall.h b/arch/arm64/include/asm/syscall.h index cfc0672013f6..8f6417822139 100644 --- a/arch/arm64/include/asm/syscall.h +++ b/arch/arm64/include/asm/syscall.h @@ -94,4 +94,6 @@ static inline int syscall_get_arch(struct task_struct *task) return AUDIT_ARCH_AARCH64; } +extern bool arch_syscall_is_vdso_sigreturn(struct pt_regs *regs); + #endif /* __ASM_SYSCALL_H */ diff --git a/arch/arm64/include/asm/thread_info.h b/arch/arm64/include/asm/thread_info.h index 6623c99f0984..7b9c6225c3c7 100644 --- a/arch/arm64/include/asm/thread_info.h +++ b/arch/arm64/include/asm/thread_info.h @@ -81,6 +81,7 @@ int arch_dup_task_struct(struct task_struct *dst, #define TIF_SVE_VL_INHERIT 24 /* Inherit sve_vl_onexec across exec */ #define TIF_SSBD 25 /* Wants SSB mitigation */ #define TIF_TAGGED_ADDR 26 /* Allow tagged user addresses */ +#define TIF_SYSCALL_USER_DISPATCH 27 /* Allow userspace syscall dispatch */ #define _TIF_SIGPENDING (1 << TIF_SIGPENDING) #define _TIF_NEED_RESCHED (1 << TIF_NEED_RESCHED) @@ -97,6 +98,7 @@ int arch_dup_task_struct(struct task_struct *dst, #define _TIF_SVE (1 << TIF_SVE) #define _TIF_MTE_ASYNC_FAULT (1 << TIF_MTE_ASYNC_FAULT) #define _TIF_NOTIFY_SIGNAL (1 << TIF_NOTIFY_SIGNAL) +#define _TIF_SYSCALL_USER_DISPATCH (1 << TIF_SYSCALL_USER_DISPATCH) #define _TIF_WORK_MASK (_TIF_NEED_RESCHED | _TIF_SIGPENDING | \ _TIF_NOTIFY_RESUME | _TIF_FOREIGN_FPSTATE | \ @@ -105,7 +107,7 @@ int arch_dup_task_struct(struct task_struct *dst, #define _TIF_SYSCALL_WORK (_TIF_SYSCALL_TRACE | _TIF_SYSCALL_AUDIT | \ _TIF_SYSCALL_TRACEPOINT | _TIF_SECCOMP | \ - _TIF_SYSCALL_EMU) + _TIF_SYSCALL_EMU | _TIF_SYSCALL_USER_DISPATCH) #ifdef CONFIG_SHADOW_CALL_STACK #define INIT_SCS \ diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c index eb2f73939b7b..ddff7d916592 100644 --- a/arch/arm64/kernel/ptrace.c +++ b/arch/arm64/kernel/ptrace.c @@ -13,6 +13,7 @@ #include <linux/kernel.h> #include <linux/sched/signal.h> #include <linux/sched/task_stack.h> +#include <linux/syscall_user_dispatch.h> #include <linux/mm.h> #include <linux/nospec.h> #include <linux/smp.h> @@ -1836,6 +1837,16 @@ int syscall_trace_enter(struct pt_regs *regs) { unsigned long flags = READ_ONCE(current_thread_info()->flags); + /* + * Handle Syscall User Dispatch. This must comes first, since + * the ABI here can be something that doesn't make sense for + * other syscall_work features. + */ + if (flags & _TIF_SYSCALL_USER_DISPATCH) { + if (syscall_user_dispatch(regs)) + return NO_SYSCALL; + } + if (flags & (_TIF_SYSCALL_EMU | _TIF_SYSCALL_TRACE)) { tracehook_report_syscall(regs, PTRACE_SYSCALL_ENTER); if (flags & _TIF_SYSCALL_EMU) @@ -1859,6 +1870,19 @@ void syscall_trace_exit(struct pt_regs *regs) { unsigned long flags = READ_ONCE(current_thread_info()->flags); + /* + * If the syscall was rolled back due to syscall user dispatching, + * then the tracers below are not invoked for the same reason as + * the entry side was not invoked in syscall_trace_enter(): The ABI + * of these syscalls is unknown. + */ + if (flags & _TIF_SYSCALL_USER_DISPATCH) { + if (unlikely(current->syscall_dispatch.on_dispatch)) { + current->syscall_dispatch.on_dispatch = false; + return; + } + } + audit_syscall_exit(regs); if (flags & _TIF_SYSCALL_TRACEPOINT) diff --git a/arch/arm64/kernel/syscall.c b/arch/arm64/kernel/syscall.c index 263d6c1a525f..2630cffe5725 100644 --- a/arch/arm64/kernel/syscall.c +++ b/arch/arm64/kernel/syscall.c @@ -15,6 +15,7 @@ #include <asm/syscall.h> #include <asm/thread_info.h> #include <asm/unistd.h> +#include <asm/vdso.h> long compat_arm_syscall(struct pt_regs *regs, int scno); long sys_ni_syscall(void); @@ -191,3 +192,11 @@ void do_el0_svc_compat(struct pt_regs *regs) compat_sys_call_table); } #endif + +bool arch_syscall_is_vdso_sigreturn(struct pt_regs *regs) +{ + if (regs->pc == (unsigned long)VDSO_SYMBOL(current->mm->context.vdso, + vdso_sigreturn_landing_pad)) + return true; + return false; +} -- 2.30.2
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