Add calls to rseq_signal_deliver(), rseq_handle_notify_resume() and rseq_syscall() to introduce RSEQ support.
1. Call the rseq_handle_notify_resume() function on return to userspace if TIF_NOTIFY_RESUME thread flag is set.
2. Call the rseq_signal_deliver() function to fixup on the pre-signal frame when a signal is delivered on top of a restartable sequence critical section.
3. Check that system calls are not invoked from within rseq critical sections by invoking rseq_signal() from ret_from_syscall(). With CONFIG_DEBUG_RSEQ, such behavior results in termination of the process with SIGSEGV.
Signed-off-by: Vincent Chen vincent.chen@sifive.com --- arch/riscv/Kconfig | 1 + arch/riscv/kernel/entry.S | 4 ++++ arch/riscv/kernel/signal.c | 3 +++ 3 files changed, 8 insertions(+)
diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig index d5bbf4223fd2..58759a4f8dff 100644 --- a/arch/riscv/Kconfig +++ b/arch/riscv/Kconfig @@ -62,6 +62,7 @@ config RISCV select ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT if MMU select HAVE_ARCH_MMAP_RND_BITS select HAVE_REGS_AND_STACK_ACCESS_API + select HAVE_RSEQ
config ARCH_MMAP_RND_BITS_MIN default 18 if 64BIT diff --git a/arch/riscv/kernel/entry.S b/arch/riscv/kernel/entry.S index 8ca479831142..00e9eaa02969 100644 --- a/arch/riscv/kernel/entry.S +++ b/arch/riscv/kernel/entry.S @@ -212,6 +212,10 @@ ENTRY(handle_exception) handle_syscall: /* save the initial A0 value (needed in signal handlers) */ REG_S a0, PT_ORIG_A0(sp) +#ifdef CONFIG_RSEQ_DEBUG + move a0, sp + call rseq_syscall +#endif /* * Advance SEPC to avoid executing the original * scall instruction on sret diff --git a/arch/riscv/kernel/signal.c b/arch/riscv/kernel/signal.c index d0f6f212f5df..f2f6017f92d0 100644 --- a/arch/riscv/kernel/signal.c +++ b/arch/riscv/kernel/signal.c @@ -219,6 +219,8 @@ static void handle_signal(struct ksignal *ksig, struct pt_regs *regs) sigset_t *oldset = sigmask_to_save(); int ret;
+ rseq_signal_deliver(ksig, regs); + /* Are we from a system call? */ if (regs->scause == EXC_SYSCALL) { /* Avoid additional syscall restarting via ret_from_exception */ @@ -302,5 +304,6 @@ asmlinkage __visible void do_notify_resume(struct pt_regs *regs, if (thread_info_flags & _TIF_NOTIFY_RESUME) { clear_thread_flag(TIF_NOTIFY_RESUME); tracehook_notify_resume(regs); + rseq_handle_notify_resume(NULL, regs); } }