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Re: [Qemu-devel] [PATCH 10/11] linux-user/aarch64: Reset btype for signa
From: |
Peter Maydell |
Subject: |
Re: [Qemu-devel] [PATCH 10/11] linux-user/aarch64: Reset btype for signal handlers |
Date: |
Tue, 22 Jan 2019 15:46:40 +0000 |
On Thu, 10 Jan 2019 at 12:18, Richard Henderson
<address@hidden> 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 <address@hidden>
> ---
> 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
- [Qemu-devel] [PATCH 07/11] target/arm: Set btype for indirect branches, (continued)
[Qemu-devel] [PATCH 09/11] target/arm: Enable BTI for -cpu max, Richard Henderson, 2019/01/10
[Qemu-devel] [PATCH 10/11] linux-user/aarch64: Reset btype for signal handlers, Richard Henderson, 2019/01/10
- Re: [Qemu-devel] [PATCH 10/11] linux-user/aarch64: Reset btype for signal handlers,
Peter Maydell <=
[Qemu-devel] [PATCH 11/11] tests/tcg/aarch64: Add bti smoke test, Richard Henderson, 2019/01/10
Re: [Qemu-devel] [PATCH 00/11] target/arm: Implement ARMv8.5-BTI, no-reply, 2019/01/31