| Message ID | 20190110121736.23448-11-richard.henderson@linaro.org |
|---|---|
| State | New |
| Headers | show |
| Series | target/arm: Implement ARMv8.5-BTI | expand |
On Thu, 10 Jan 2019 at 12:18, Richard Henderson <richard.henderson@linaro.org> wrote: > > It does not make sense for a SIGILL handler to enter with the > btype set as for the indirect branch that caused the SIGILL. > > Nor does it make sense to return from a handler with BTYPE set. > This could be argued to be the handler's job, setting BTYPE > within ucontext->uc_mcontext.pstate, but handling this here > while the ABI is undiscussed. > > Signed-off-by: Richard Henderson <richard.henderson@linaro.org> > --- > linux-user/aarch64/signal.c | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/linux-user/aarch64/signal.c b/linux-user/aarch64/signal.c > index f84a9cf28a..1fb229e696 100644 > --- a/linux-user/aarch64/signal.c > +++ b/linux-user/aarch64/signal.c > @@ -218,6 +218,8 @@ static void target_restore_general_frame(CPUARMState *env, > __get_user(env->pc, &sf->uc.tuc_mcontext.pc); > __get_user(pstate, &sf->uc.tuc_mcontext.pstate); > pstate_write(env, pstate); > + /* Reset btype that might have been there going into the frame. */ > + env->btype = 0; Conceptually we should do this the way the kernel would, by sanitizing the value of "pstate" before passing it to pstate_write(). This is done in valid_native_regs() in arch/arm64/kernel/ptrace.c and forbids other things like messing with the DAIF bits or the mode bits. > } > > static void target_restore_fpsimd_record(CPUARMState *env, > @@ -510,6 +512,8 @@ static void target_setup_frame(int usig, struct target_sigaction *ka, > env->xregs[29] = frame_addr + fr_ofs; > env->pc = ka->_sa_handler; > env->xregs[30] = return_addr; > + /* Reset btype going into the signal handler. */ > + env->btype = 0; > if (info) { > tswap_siginfo(&frame->info, info); > env->xregs[1] = frame_addr + offsetof(struct target_rt_sigframe, info); > -- > 2.17.2 thanks -- PMM
diff --git a/linux-user/aarch64/signal.c b/linux-user/aarch64/signal.c index f84a9cf28a..1fb229e696 100644 --- a/linux-user/aarch64/signal.c +++ b/linux-user/aarch64/signal.c @@ -218,6 +218,8 @@ static void target_restore_general_frame(CPUARMState *env, __get_user(env->pc, &sf->uc.tuc_mcontext.pc); __get_user(pstate, &sf->uc.tuc_mcontext.pstate); pstate_write(env, pstate); + /* Reset btype that might have been there going into the frame. */ + env->btype = 0; } static void target_restore_fpsimd_record(CPUARMState *env, @@ -510,6 +512,8 @@ static void target_setup_frame(int usig, struct target_sigaction *ka, env->xregs[29] = frame_addr + fr_ofs; env->pc = ka->_sa_handler; env->xregs[30] = return_addr; + /* Reset btype going into the signal handler. */ + env->btype = 0; if (info) { tswap_siginfo(&frame->info, info); env->xregs[1] = frame_addr + offsetof(struct target_rt_sigframe, info);
It does not make sense for a SIGILL handler to enter with the btype set as for the indirect branch that caused the SIGILL. Nor does it make sense to return from a handler with BTYPE set. This could be argued to be the handler's job, setting BTYPE within ucontext->uc_mcontext.pstate, but handling this here while the ABI is undiscussed. Signed-off-by: Richard Henderson <richard.henderson@linaro.org> --- linux-user/aarch64/signal.c | 4 ++++ 1 file changed, 4 insertions(+) -- 2.17.2