On Fri, 2 May 2025, victorm.l...@amd.com wrote:
> From: Nicola Vetrini <nicola.vetr...@bugseng.com>
>
> Rule 19.1 states: "An object shall not be assigned or copied
> to an overlapping object". In the function like macro "get_rep_prefix",
> one member of a union is assigned the value of another member. Reading from
> one
> member and writing to the other violates the rule, while not causing Undefined
> Behavior due to their relative sizes. Instead, use casts combined with exactly
> overlapping accesses to address violations.
>
> No functional change.
>
> Signed-off-by: Nicola Vetrini <nicola.vetr...@bugseng.com>
> Signed-off-by: Federico Serafini <federico.seraf...@bugseng.com>
> Signed-off-by: Victor Lira <victorm.l...@amd.com>
> ---
> Changes in v2:
> - Use casts combined with exactly overlapping accesses to address
> violations
> - fix commit message
> ---
> Cc: Andrew Cooper <andrew.coop...@citrix.com>
> Cc: Anthony PERARD <anthony.per...@vates.tech>
> Cc: Michal Orzel <michal.or...@amd.com>
> Cc: Jan Beulich <jbeul...@suse.com>
> Cc: Julien Grall <jul...@xen.org>
> Cc: Roger Pau Monn?? <roger....@citrix.com>
> Cc: Stefano Stabellini <sstabell...@kernel.org>
> Cc: Nicola Vetrini <nicola.vetr...@bugseng.com>
> Cc: Federico Serafini <federico.seraf...@bugseng.com>
> Cc: Bertrand Marquis <bertrand.marq...@arm.com>
> ---
> xen/arch/x86/x86_emulate/x86_emulate.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/xen/arch/x86/x86_emulate/x86_emulate.c
> b/xen/arch/x86/x86_emulate/x86_emulate.c
> index 8e14ebb35b..d678855238 100644
> --- a/xen/arch/x86/x86_emulate/x86_emulate.c
> +++ b/xen/arch/x86/x86_emulate/x86_emulate.c
> @@ -527,8 +527,8 @@ static inline void put_loop_count(
> if ( !amd_like(ctxt) && mode_64bit() && ad_bytes == 4 ) \
> { \
> _regs.r(cx) = 0; \
> - if ( extend_si ) _regs.r(si) = _regs.esi; \
> - if ( extend_di ) _regs.r(di) = _regs.edi; \
> + if ( extend_si ) _regs.r(si) = (uint32_t)_regs.r(si); \
> + if ( extend_di ) _regs.r(di) = (uint32_t)_regs.r(di); \
NIT: code style, alignment of the \
Can be fixed on commit.
Reviewed-by: Stefano Stabellini <sstabell...@kernel.org>
> } \
> goto complete_insn; \
> } \
> @@ -2029,7 +2029,7 @@ x86_emulate(
> switch ( op_bytes )
> {
> case 2: _regs.ax = (int8_t)_regs.ax; break; /* cbw */
> - case 4: _regs.r(ax) = (uint32_t)(int16_t)_regs.ax; break; /* cwde */
> + case 4: _regs.r(ax) = (uint32_t)(int16_t)_regs.r(ax); break; /* cwde
> */
> case 8: _regs.r(ax) = (int32_t)_regs.r(ax); break; /* cdqe */
> }
> break;
> --
> 2.25.1
>
