Hi Richard
On 2022/6/21 上午12:23, Richard Henderson wrote:
On 6/20/22 02:33, Song Gao wrote:
+static int restore_sigcontext(CPULoongArchState *env,
+ struct target_sigcontext *sc)
+{
+ int i;
+ int ret = 0;
+ struct extctx_layout extctx;
+
+ memset(&extctx, 0, sizeof(struct extctx_layout));
+
+ __get_user(extctx.flags, &sc->sc_flags);
+
+ ret = parse_extcontext(sc, &extctx);
+ if (ret < 0) {
+ goto bad;
+ }
+
+ __get_user(env->pc, &sc->sc_pc);
+ for (i = 1; i < 32; ++i) {
+ __get_user(env->gpr[i], &sc->sc_regs[i]);
+ }
+
+ if (extctx.fpu.addr) {
+ copy_fpu_from_sigcontext(env, &extctx);
+ restore_fp_status(env);
+ }
+bad:
+ return ret;
+}
This is missing lock_user/unlock_user somewhere.
You can't use the double-underscore __get/__put_user without having
done that.
My understanding is that the struct exctx need
lock_user_struct/unlock_user_struct, then we can use __get/__put the
struct extctx.
You can use the non-underscore get_user in parse_extcontext, and
separately lock the target_fpu_context. Failures must goto invalid.
+void setup_rt_frame(int sig, struct target_sigaction *ka,
+ target_siginfo_t *info,
+ target_sigset_t *set, CPULoongArchState *env)
+{
+ struct target_rt_sigframe *frame;
+ struct extctx_layout extctx;
+ abi_ulong frame_addr;
+ int i;
+
+ frame_addr = get_sigframe(ka, env, sizeof(*frame), &extctx);
+ trace_user_setup_rt_frame(env, frame_addr);
+ if (!lock_user_struct(VERIFY_WRITE, frame, frame_addr, 0)) {
+ goto give_sigsegv;
+ }
Similarly, this lock...
+
+ tswap_siginfo(&frame->rs_info, info);
+
+ __put_user(0, &frame->rs_uc.tuc_flags);
+ __put_user(0, &frame->rs_uc.tuc_link);
+ target_save_altstack(&frame->rs_uc.tuc_stack, env);
+
+ setup_sigcontext(env, &frame->rs_uc.tuc_mcontext, &extctx);
... fails to cover the extra memory allocated for extctx.
This is why I suggested statically allocating the extra
pieces of the signal frame *on write*. You obviously
cannot rely on the signal frame being identical on
signal return -- the guest is allowed to create any valid
context to give to rt_sigreturn.
I don’t know if my understanding is correct,
we can put the exctx or target_fpu_context into target_rt_sigframe, like
this:
struct target_rt_sigframe {
struct target_siginfo rs_info;
struct target_ucontext rs_uc;
struct extctx_layout rs_ext;
};
This way that we just need lo lock/unlock target_rt_sigframe on
setup_sigcontext/restore_sigcontext,
Thanks.
Song Gao
