| Message ID | 10606d7429239b5a2b7dffcb22eeb1ce5e73e991.1690449587.git.nicola.vetrini@bugseng.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | address violations of MISRA C:2012 Rule 5.3 on x86 | expand |
On 27.07.2023 12:48, Nicola Vetrini wrote: > --- a/xen/arch/x86/x86_emulate/x86_emulate.c > +++ b/xen/arch/x86/x86_emulate/x86_emulate.c > @@ -1483,7 +1483,7 @@ x86_emulate( > { > enum x86_segment seg; > struct segment_register cs, sreg; > - struct cpuid_leaf cpuid_leaf; > + struct cpuid_leaf res; This is too generic a name for a variable with a scope of several thousand lines. Perhaps just "leaf"? > @@ -8408,8 +8408,6 @@ x86_emulate( > generate_exception(X86_EXC_MF); > if ( stub_exn.info.fields.trapnr == X86_EXC_XM ) > { > - unsigned long cr4; > - > if ( !ops->read_cr || ops->read_cr(4, &cr4, ctxt) != X86EMUL_OKAY ) > cr4 = X86_CR4_OSXMMEXCPT; > generate_exception(cr4 & X86_CR4_OSXMMEXCPT ? X86_EXC_XM : X86_EXC_UD); This change looks okay to me, but I'd like to strongly encourage you to split both changes. They're of different nature, and for the latter it may even be worthwhile pointing out when exactly this duplication of variables was introduced (it clearly would better have been avoided). Jan
On 27/07/23 17:41, Jan Beulich wrote: > On 27.07.2023 12:48, Nicola Vetrini wrote: >> --- a/xen/arch/x86/x86_emulate/x86_emulate.c >> +++ b/xen/arch/x86/x86_emulate/x86_emulate.c >> @@ -1483,7 +1483,7 @@ x86_emulate( >> { >> enum x86_segment seg; >> struct segment_register cs, sreg; >> - struct cpuid_leaf cpuid_leaf; >> + struct cpuid_leaf res; > > This is too generic a name for a variable with a scope of several > thousand lines. Perhaps just "leaf"? It can also be defined inside the switch clause, since it has no other purpose than store a result. > >> @@ -8408,8 +8408,6 @@ x86_emulate( >> generate_exception(X86_EXC_MF); >> if ( stub_exn.info.fields.trapnr == X86_EXC_XM ) >> { >> - unsigned long cr4; >> - >> if ( !ops->read_cr || ops->read_cr(4, &cr4, ctxt) != X86EMUL_OKAY ) >> cr4 = X86_CR4_OSXMMEXCPT; >> generate_exception(cr4 & X86_CR4_OSXMMEXCPT ? X86_EXC_XM : X86_EXC_UD); > > This change looks okay to me, but I'd like to strongly encourage > you to split both changes. They're of different nature, and for > the latter it may even be worthwhile pointing out when exactly > this duplication of variables was introduced (it clearly would > better have been avoided). > I did it this way because they are the only violations of R5.3 left in this file (among those not subject to deviation). By splitting you mean two patches in this series or a separate patch just for this change?
On 27.07.2023 17:58, Nicola Vetrini wrote: > > > On 27/07/23 17:41, Jan Beulich wrote: >> On 27.07.2023 12:48, Nicola Vetrini wrote: >>> --- a/xen/arch/x86/x86_emulate/x86_emulate.c >>> +++ b/xen/arch/x86/x86_emulate/x86_emulate.c >>> @@ -1483,7 +1483,7 @@ x86_emulate( >>> { >>> enum x86_segment seg; >>> struct segment_register cs, sreg; >>> - struct cpuid_leaf cpuid_leaf; >>> + struct cpuid_leaf res; >> >> This is too generic a name for a variable with a scope of several >> thousand lines. Perhaps just "leaf"? > > It can also be defined inside the switch clause, since it has no other > purpose than store a result. That would be more code churn, though. >>> @@ -8408,8 +8408,6 @@ x86_emulate( >>> generate_exception(X86_EXC_MF); >>> if ( stub_exn.info.fields.trapnr == X86_EXC_XM ) >>> { >>> - unsigned long cr4; >>> - >>> if ( !ops->read_cr || ops->read_cr(4, &cr4, ctxt) != X86EMUL_OKAY ) >>> cr4 = X86_CR4_OSXMMEXCPT; >>> generate_exception(cr4 & X86_CR4_OSXMMEXCPT ? X86_EXC_XM : X86_EXC_UD); >> >> This change looks okay to me, but I'd like to strongly encourage >> you to split both changes. They're of different nature, and for >> the latter it may even be worthwhile pointing out when exactly >> this duplication of variables was introduced (it clearly would >> better have been avoided). >> > > I did it this way because they are the only violations of R5.3 left in > this file (among those not subject to deviation). By splitting you mean > two patches in this series or a separate patch just for this change? Separate or within a series doesn't matter. Just preferably not in the same patch. (And btw, if you split larger patches more, some of your changes may also go in more quickly. Yet of course this shouldn't get too fine grained.) Jan
diff --git a/xen/arch/x86/x86_emulate/x86_emulate.c b/xen/arch/x86/x86_emulate/x86_emulate.c index 2de1be7996..9403beb20f 100644 --- a/xen/arch/x86/x86_emulate/x86_emulate.c +++ b/xen/arch/x86/x86_emulate/x86_emulate.c @@ -1483,7 +1483,7 @@ x86_emulate( { enum x86_segment seg; struct segment_register cs, sreg; - struct cpuid_leaf cpuid_leaf; + struct cpuid_leaf res; uint64_t msr_val; unsigned int i, n; unsigned long dummy; @@ -5024,13 +5024,13 @@ x86_emulate( generate_exception_if((msr_val & MSR_MISC_FEATURES_CPUID_FAULTING), X86_EXC_GP, 0); /* Faulting active? (Inc. CPL test) */ - rc = ops->cpuid(_regs.eax, _regs.ecx, &cpuid_leaf, ctxt); + rc = ops->cpuid(_regs.eax, _regs.ecx, &res, ctxt); if ( rc != X86EMUL_OKAY ) goto done; - _regs.r(ax) = cpuid_leaf.a; - _regs.r(bx) = cpuid_leaf.b; - _regs.r(cx) = cpuid_leaf.c; - _regs.r(dx) = cpuid_leaf.d; + _regs.r(ax) = res.a; + _regs.r(bx) = res.b; + _regs.r(cx) = res.c; + _regs.r(dx) = res.d; break; case X86EMUL_OPC(0x0f, 0xa3): bt: /* bt */ @@ -8408,8 +8408,6 @@ x86_emulate( generate_exception(X86_EXC_MF); if ( stub_exn.info.fields.trapnr == X86_EXC_XM ) { - unsigned long cr4; - if ( !ops->read_cr || ops->read_cr(4, &cr4, ctxt) != X86EMUL_OKAY ) cr4 = X86_CR4_OSXMMEXCPT; generate_exception(cr4 & X86_CR4_OSXMMEXCPT ? X86_EXC_XM : X86_EXC_UD);
Rule 5.3 has the following headline: "An identifier declared in an inner scope shall not hide an identifier declared in an outer scope" The declaration of local variable 'cpuid_leaf' causes shadowing with the homonymous function to happen, therefore the variable is renamed to avoid this. Local variable 'cr4' that shadows a previous declaration is removed, as it is unnecessary and doing so does not alter the semantics. Signed-off-by: Nicola Vetrini <nicola.vetrini@bugseng.com> --- xen/arch/x86/x86_emulate/x86_emulate.c | 14 ++++++-------- 1 file changed, 6 insertions(+), 8 deletions(-)