Re: [PATCH v2 5/7] linux-user/nios2: Fix EA vs PC confusion

[Laurent Vivier]

Le 21/12/2021 à 03:50, Richard Henderson a écrit :
> The real kernel will talk about the user PC as EA,
> because that's where the hardware will have copied it,
> and where it expects to put it to then use ERET.
> But qemu does not emulate all of the exception stuff
> while emulating user-only.  Manipulate PC directly.
>
> This fixes signal entry and return, and eliminates
> some slight confusion from target_cpu_copy_regs.
>
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> ---
>   linux-user/nios2/cpu_loop.c | 5 +----
>   linux-user/nios2/signal.c   | 6 +++---
>   2 files changed, 4 insertions(+), 7 deletions(-)
>
> diff --git a/linux-user/nios2/cpu_loop.c b/linux-user/nios2/cpu_loop.c
> index de0fc63e21..1e93ef34e6 100644
> --- a/linux-user/nios2/cpu_loop.c
> +++ b/linux-user/nios2/cpu_loop.c
> @@ -155,9 +155,6 @@ void target_cpu_copy_regs(CPUArchState *env, struct 
> target_pt_regs *regs)
>       env->regs[R_SP] = regs->sp;
>       env->regs[R_GP] = regs->gp;
>       env->regs[CR_ESTATUS] = regs->estatus;
> -    env->regs[R_EA] = regs->ea;
> -    /* TODO: unsigned long  orig_r7; */
> -
> -    /* Emulate eret when starting thread. */
>       env->regs[R_PC] = regs->ea;
> +    /* TODO: unsigned long  orig_r7; */
>   }
> diff --git a/linux-user/nios2/signal.c b/linux-user/nios2/signal.c
> index adbffe32e3..20b65aa06e 100644
> --- a/linux-user/nios2/signal.c
> +++ b/linux-user/nios2/signal.c
> @@ -73,7 +73,7 @@ static void rt_setup_ucontext(struct target_ucontext *uc, 
> CPUNios2State *env)
>       __put_user(env->regs[R_RA], &gregs[23]);
>       __put_user(env->regs[R_FP], &gregs[24]);
>       __put_user(env->regs[R_GP], &gregs[25]);
> -    __put_user(env->regs[R_EA], &gregs[27]);
> +    __put_user(env->regs[R_PC], &gregs[27]);
>       __put_user(env->regs[R_SP], &gregs[28]);
>   }
>   
> @@ -122,7 +122,7 @@ static int rt_restore_ucontext(CPUNios2State *env, struct target_ucontext *uc,
>       __get_user(env->regs[R_GP], &gregs[25]);
>       /* Not really necessary no user settable bits */
>       __get_user(temp, &gregs[26]);
> -    __get_user(env->regs[R_EA], &gregs[27]);
> +    __get_user(env->regs[R_PC], &gregs[27]);
>   
>       __get_user(env->regs[R_RA], &gregs[23]);
>       __get_user(env->regs[R_SP], &gregs[28]);
> @@ -181,7 +181,7 @@ void setup_rt_frame(int sig, struct target_sigaction *ka,
>       env->regs[4] = sig;
>       env->regs[5] = frame_addr + offsetof(struct target_rt_sigframe, info);
>       env->regs[6] = frame_addr + offsetof(struct target_rt_sigframe, uc);
> -    env->regs[R_EA] = ka->_sa_handler;
> +    env->regs[R_PC] = ka->_sa_handler;
>   
>       unlock_user_struct(frame, frame_addr, 1);
>   }

Applied to my linux-user-for-7.0 branch.

Thanks,
Laurent