On Wed, 7 May 2025, victorm.l...@amd.com wrote:
> From: Nicola Vetrini <nicola.vetr...@bugseng.com>
>
> Rule 13.2 states: "The value of an expression and its persistent
> side effects shall be the same under all permitted evaluation orders".
>
> The full expansion of macro "commit_far_branch" contains an assignment to
> variable "rc", which is also assigned to the result of the GNU statement
> expression which "commit_far_branch" expands to.
>
> To avoid any dependence on the order of evaluation, the latter assignment
> is moved inside the macro.
>
> Signed-off-by: Nicola Vetrini <nicola.vetr...@bugseng.com>
> Signed-off-by: Victor Lira <victorm.l...@amd.com>
Reviewed-by: Stefano Stabellini <sstabell...@kernel.org>
> ---
> 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 Monné <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 | 8 ++++----
> 1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/xen/arch/x86/x86_emulate/x86_emulate.c
> b/xen/arch/x86/x86_emulate/x86_emulate.c
> index 8e14ebb35b..7108fe7b30 100644
> --- a/xen/arch/x86/x86_emulate/x86_emulate.c
> +++ b/xen/arch/x86/x86_emulate/x86_emulate.c
> @@ -337,7 +337,7 @@ do {
> \
> validate_far_branch(cs, newip); \
> _regs.r(ip) = (newip); \
> singlestep = _regs.eflags & X86_EFLAGS_TF; \
> - ops->write_segment(x86_seg_cs, cs, ctxt); \
> + rc = ops->write_segment(x86_seg_cs, cs, ctxt); \
> })
>
> int x86emul_get_fpu(
> @@ -2382,7 +2382,7 @@ x86_emulate(
> (rc = read_ulong(x86_seg_ss, sp_post_inc(op_bytes + src.val),
> &src.val, op_bytes, ctxt, ops)) ||
> (rc = load_seg(x86_seg_cs, src.val, 1, &cs, ctxt, ops)) ||
> - (rc = commit_far_branch(&cs, dst.val)) )
> + commit_far_branch(&cs, dst.val) )
> goto done;
> break;
>
> @@ -2438,7 +2438,7 @@ x86_emulate(
> _regs.eflags &= mask;
> _regs.eflags |= (eflags & ~mask) | X86_EFLAGS_MBS;
> if ( (rc = load_seg(x86_seg_cs, sel, 1, &cs, ctxt, ops)) ||
> - (rc = commit_far_branch(&cs, (uint32_t)eip)) )
> + commit_far_branch(&cs, (uint32_t)eip) )
> goto done;
> break;
> }
> @@ -2557,7 +2557,7 @@ x86_emulate(
> ASSERT(!mode_64bit());
> far_jmp:
> if ( (rc = load_seg(x86_seg_cs, imm2, 0, &cs, ctxt, ops)) ||
> - (rc = commit_far_branch(&cs, imm1)) )
> + commit_far_branch(&cs, imm1) )
> goto done;
> break;
>
> --
> 2.47.0
>
