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charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Catalin Marinas writes: > On Thu, Dec 16, 2021 at 11:16:18AM -0800, D Scott Phillips wrote: >> diff --git a/arch/arm64/include/asm/elf.h b/arch/arm64/include/asm/elf.h >> index 97932fbf973d..24036b914226 100644 >> --- a/arch/arm64/include/asm/elf.h >> +++ b/arch/arm64/include/asm/elf.h >> @@ -160,8 +160,16 @@ typedef struct user_fpsimd_state elf_fpregset_t; >> >> #define SET_PERSONALITY(ex) \ >> ({ \ >> + if (IS_ENABLED(CONFIG_ARM64_ERRATUM_1418040)) \ >> + preempt_disable(); \ >> clear_thread_flag(TIF_32BIT); \ >> current->personality &= ~READ_IMPLIES_EXEC; \ >> + if (IS_ENABLED(CONFIG_ARM64_ERRATUM_1418040)) { \ >> + if (this_cpu_has_cap(ARM64_WORKAROUND_1418040)) \ >> + sysreg_clear_set(cntkctl_el1, 0, \ >> + ARCH_TIMER_USR_VCT_ACCESS_EN); \ >> + preempt_enable(); \ >> + } \ >> }) >> >> /* update AT_VECTOR_SIZE_ARCH if the number of NEW_AUX_ENT entries changes */ >> @@ -223,7 +231,16 @@ int compat_elf_check_arch(const struct elf32_hdr *); >> */ >> #define COMPAT_SET_PERSONALITY(ex) \ >> ({ \ >> + if (IS_ENABLED(CONFIG_ARM64_ERRATUM_1418040)) \ >> + preempt_disable(); \ >> set_thread_flag(TIF_32BIT); \ >> + if (IS_ENABLED(CONFIG_ARM64_ERRATUM_1418040)) { \ >> + if (this_cpu_has_cap(ARM64_WORKAROUND_1418040)) \ >> + sysreg_clear_set(cntkctl_el1, \ >> + ARCH_TIMER_USR_VCT_ACCESS_EN, \ >> + 0); \ >> + preempt_enable(); \ >> + } \ > > I don't particularly like adding more to these macros. There's > arch_setup_new_exec() that gets called after SET_PERSONALITY, so you can > check whether the task is compat or not. If the task is preemptible between the update to TIF_32BIT and the update to cntkctl then a window exists where preemption will confuse the workaround logic we have in switch_to, causing the desync between compat state and counter access trapping to propagate into other tasks. Agreed that this change gunks up a previously simple macro though. Maybe we could have SET_PERSONALITY only set a flag in arch_elf_state and arch_setup_new_exec() take over setting TIF_32BIT? Or move set_personality's implementation to a helper? Or something else? > Thanks. > > -- > Catalin _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel