Re: [PATCH for-5.2 1/3] linux-user/sparc: Fix errors in target_ucontext structures

[Laurent Vivier <laurent@vivier.eu>]

Le 05/11/2020 à 22:23, Peter Maydell a écrit :
> The various structs that make up the SPARC target_ucontext had some
> errors:
>  * target structures must not include fields which are host pointers,
>    which might be the wrong size.  These should be abi_ulong instead
>  * because we don't have the 'long double' part of the mcfpu_fregs
>    union in our version of the target_mc_fpu struct, we need to
>    manually force it to be 16-aligned
> 
> In particular, the lack of 16-alignment caused sparc64_get_context()
> and sparc64_set_context() to read and write all the registers at the
> wrong offset, which triggered a guest glibc stack check in
> siglongjmp:
>   *** longjmp causes uninitialized stack frame ***: terminated
> when trying to run bash.
> 
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> ---
>  linux-user/sparc/signal.c | 13 +++++++++----
>  1 file changed, 9 insertions(+), 4 deletions(-)
> 
> diff --git a/linux-user/sparc/signal.c b/linux-user/sparc/signal.c
> index d796f50f665..57ea1593bfc 100644
> --- a/linux-user/sparc/signal.c
> +++ b/linux-user/sparc/signal.c
> @@ -349,10 +349,15 @@ typedef abi_ulong target_mc_greg_t;
>  typedef target_mc_greg_t target_mc_gregset_t[SPARC_MC_NGREG];
>  
>  struct target_mc_fq {
> -    abi_ulong *mcfq_addr;
> +    abi_ulong mcfq_addr;
>      uint32_t mcfq_insn;
>  };
>  
> +/*
> + * Note the manual 16-alignment; the kernel gets this because it
> + * includes a "long double qregs[16]" in the mcpu_fregs union,
> + * which we can't do.
> + */
>  struct target_mc_fpu {
>      union {
>          uint32_t sregs[32];
> @@ -362,11 +367,11 @@ struct target_mc_fpu {
>      abi_ulong mcfpu_fsr;
>      abi_ulong mcfpu_fprs;
>      abi_ulong mcfpu_gsr;
> -    struct target_mc_fq *mcfpu_fq;
> +    abi_ulong mcfpu_fq;
>      unsigned char mcfpu_qcnt;
>      unsigned char mcfpu_qentsz;
>      unsigned char mcfpu_enab;
> -};
> +} __attribute__((aligned(16)));
>  typedef struct target_mc_fpu target_mc_fpu_t;
>  
>  typedef struct {
> @@ -377,7 +382,7 @@ typedef struct {
>  } target_mcontext_t;
>  
>  struct target_ucontext {
> -    struct target_ucontext *tuc_link;
> +    abi_ulong tuc_link;
>      abi_ulong tuc_flags;
>      target_sigset_t tuc_sigmask;
>      target_mcontext_t tuc_mcontext;
> 

Applied to my linux-user-for-5.2 branch.

Thanks,
Laurent