From: Nicola Vetrini <[email protected]> Rule 19.1 states: "An object shall not be assigned or copied to an overlapping object". Since the "call" and "compat_call" are fields of the same union, reading from one member and writing to the other violates the rule, while not causing Undefined Behavior due to their relative sizes. However, a dummy variables are used to address the violations and prevent the future possibility of incurring in UB.
No functional change. Signed-off-by: Nicola Vetrini <[email protected]> Signed-off-by: Federico Serafini <[email protected]> Signed-off-by: Victor Lira <[email protected]> --- Cc: Andrew Cooper <[email protected]> Cc: Anthony PERARD <[email protected]> Cc: Michal Orzel <[email protected]> Cc: Jan Beulich <[email protected]> Cc: Julien Grall <[email protected]> Cc: Roger Pau Monné <[email protected]> Cc: Stefano Stabellini <[email protected]> Cc: Nicola Vetrini <[email protected]> Cc: Federico Serafini <[email protected]> Cc: Bertrand Marquis <[email protected]> --- xen/arch/x86/x86_emulate/x86_emulate.c | 21 ++++++++++++++++++--- 1 file changed, 18 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..44dc3039f3 100644 --- a/xen/arch/x86/x86_emulate/x86_emulate.c +++ b/xen/arch/x86/x86_emulate/x86_emulate.c @@ -526,9 +526,19 @@ static inline void put_loop_count( */ \ if ( !amd_like(ctxt) && mode_64bit() && ad_bytes == 4 ) \ { \ + uint64_t tmp; \ + \ _regs.r(cx) = 0; \ - if ( extend_si ) _regs.r(si) = _regs.esi; \ - if ( extend_di ) _regs.r(di) = _regs.edi; \ + if ( extend_si ) \ + { \ + tmp = _regs.esi; \ + _regs.r(si) = tmp; \ + } \ + if ( extend_di ) \ + { \ + tmp = _regs.edi; \ + _regs.r(di) = tmp; \ + } \ } \ goto complete_insn; \ } \ @@ -2029,7 +2039,12 @@ 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: + { + uint32_t tmp = (uint32_t)(int16_t)_regs.ax; + _regs.r(ax) = tmp; + break; /* cwde */ + } case 8: _regs.r(ax) = (int32_t)_regs.r(ax); break; /* cdqe */ } break; -- 2.47.0
