| Message ID | 1dec05cc8f54d0b85acffce69d929f13e6d81313.1698069331.git.andrea.porta@suse.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | arm64: Make Aarch32 compatibility enablement optional at boot | expand |
On 23/10/2023 3:42 pm, Andrea della Porta wrote: > Aarch32 bit support on 64bit kernels depends on whether CONFIG_COMPAT > is selected or not. As it is a compile time option it doesn't > provide the flexibility to have distributions set their own policy for > Aarch32 support and give the user the flexibility to override it. > > As a first step introduce aarch32_enabled() which abstracts whether 32 > bit compat is turned on or off. Upcoming patches will implement > the ability to set Aarch32 compat state at boot time. Other than patch #3, which as previously mentioned should be unnecessary if the kernel correctly never starts an "unsupported" AArch32 process to begin with, what does this do that simply overriding ID_AA64PFR0_EL1.EL0 via the existing idreg-override mechanism wouldn't? Thanks, Robin. > Signed-off-by: Andrea della Porta <andrea.porta@suse.com> > --- > arch/arm64/include/asm/cpufeature.h | 15 +++++++++++++++ > arch/arm64/kernel/entry-common.c | 2 ++ > 2 files changed, 17 insertions(+) > > diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h > index 396af9b9c857..1180d68daaff 100644 > --- a/arch/arm64/include/asm/cpufeature.h > +++ b/arch/arm64/include/asm/cpufeature.h > @@ -657,6 +657,21 @@ static inline bool supports_clearbhb(int scope) > ID_AA64ISAR2_EL1_CLRBHB_SHIFT); > } > > +#ifdef CONFIG_COMPAT > +extern bool __aarch32_enabled; > + > +static inline bool aarch32_enabled(void) > +{ > + return __aarch32_enabled; > +} > +#else /* !CONFIG_COMPAT */ > + > +static inline bool aarch32_enabled(void) > +{ > + return false; > +} > +#endif > + > const struct cpumask *system_32bit_el0_cpumask(void); > DECLARE_STATIC_KEY_FALSE(arm64_mismatched_32bit_el0); > > diff --git a/arch/arm64/kernel/entry-common.c b/arch/arm64/kernel/entry-common.c > index 0fc94207e69a..69ff9b8c0bde 100644 > --- a/arch/arm64/kernel/entry-common.c > +++ b/arch/arm64/kernel/entry-common.c > @@ -877,6 +877,8 @@ asmlinkage void noinstr el0t_32_error_handler(struct pt_regs *regs) > { > __el0_error_handler_common(regs); > } > + > +bool __aarch32_enabled __ro_after_init = true; > #else /* CONFIG_COMPAT */ > UNHANDLED(el0t, 32, sync) > UNHANDLED(el0t, 32, irq)
On 12:56 Tue 24 Oct , Robin Murphy wrote: > On 23/10/2023 3:42 pm, Andrea della Porta wrote: > > Aarch32 bit support on 64bit kernels depends on whether CONFIG_COMPAT > > is selected or not. As it is a compile time option it doesn't > > provide the flexibility to have distributions set their own policy for > > Aarch32 support and give the user the flexibility to override it. > > > > As a first step introduce aarch32_enabled() which abstracts whether 32 > > bit compat is turned on or off. Upcoming patches will implement > > the ability to set Aarch32 compat state at boot time. > > Other than patch #3, which as previously mentioned should be unnecessary if > the kernel correctly never starts an "unsupported" AArch32 process to begin > with, what does this do that simply overriding ID_AA64PFR0_EL1.EL0 via the > existing idreg-override mechanism wouldn't? > > Thanks, > Robin You're right, I guess we can simpluy leverage system_supports_32bit_el0() calling id_aa64pfr0_32bit_el0() and override the el0 nibble from command line, instead of inventing a new kernel parameter. For the sake of simplicity, maybe we can add a new alias in idreg-override, something like 'arm64.no32bit-el0'. Thanks, Andrea
diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h index 396af9b9c857..1180d68daaff 100644 --- a/arch/arm64/include/asm/cpufeature.h +++ b/arch/arm64/include/asm/cpufeature.h @@ -657,6 +657,21 @@ static inline bool supports_clearbhb(int scope) ID_AA64ISAR2_EL1_CLRBHB_SHIFT); } +#ifdef CONFIG_COMPAT +extern bool __aarch32_enabled; + +static inline bool aarch32_enabled(void) +{ + return __aarch32_enabled; +} +#else /* !CONFIG_COMPAT */ + +static inline bool aarch32_enabled(void) +{ + return false; +} +#endif + const struct cpumask *system_32bit_el0_cpumask(void); DECLARE_STATIC_KEY_FALSE(arm64_mismatched_32bit_el0); diff --git a/arch/arm64/kernel/entry-common.c b/arch/arm64/kernel/entry-common.c index 0fc94207e69a..69ff9b8c0bde 100644 --- a/arch/arm64/kernel/entry-common.c +++ b/arch/arm64/kernel/entry-common.c @@ -877,6 +877,8 @@ asmlinkage void noinstr el0t_32_error_handler(struct pt_regs *regs) { __el0_error_handler_common(regs); } + +bool __aarch32_enabled __ro_after_init = true; #else /* CONFIG_COMPAT */ UNHANDLED(el0t, 32, sync) UNHANDLED(el0t, 32, irq)
Aarch32 bit support on 64bit kernels depends on whether CONFIG_COMPAT is selected or not. As it is a compile time option it doesn't provide the flexibility to have distributions set their own policy for Aarch32 support and give the user the flexibility to override it. As a first step introduce aarch32_enabled() which abstracts whether 32 bit compat is turned on or off. Upcoming patches will implement the ability to set Aarch32 compat state at boot time. Signed-off-by: Andrea della Porta <andrea.porta@suse.com> --- arch/arm64/include/asm/cpufeature.h | 15 +++++++++++++++ arch/arm64/kernel/entry-common.c | 2 ++ 2 files changed, 17 insertions(+)