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@xxxxxxxxxx>
---
arch/riscv/Kconfig | 1 +
arch/riscv/kernel/entry.S | 4 ++++
arch/riscv/kernel/signal.c | 2 ++
3 files changed, 7 insertions(+)
diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index fa98b279257e..ded32979d33d 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -67,6 +67,7 @@ config RISCV
select HAVE_COPY_THREAD_TLS
select HAVE_ARCH_KASAN if MMU && 64BIT
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 bad4d85b5e91..89d3713b0aef 100644
--- a/arch/riscv/kernel/entry.S
+++ b/arch/riscv/kernel/entry.S
@@ -214,6 +214,10 @@ 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 17ba190e84a5..d939c5de41c4 100644
--- a/arch/riscv/kernel/signal.c
+++ b/arch/riscv/kernel/signal.c
@@ -234,6 +234,7 @@ 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->cause == EXC_SYSCALL) {
/* Avoid additional syscall restarting via ret_from_exception */
@@ -316,5 +317,6 @@ 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);
}
}
--
2.7.4
