The arm64 booting document requires that the bootloader has cleaned the kernel image to the PoC. However, when a CPU re-enters the kernel due to either a CPU hotplug "on" event or resuming from a low-power state (e.g. cpuidle), the kernel text may in-fact be dirty at the PoU due to things like alternative patching or even module loading. Thanks to I-cache speculation with the MMU off, stale instructions could be fetched prior to enabling the MMU, potentially leading to crashes when executing regions of code that have been modified at runtime. This patch addresses the issue by ensuring that the local I-cache is invalidated immediately after a CPU has enabled its MMU but before jumping out of the identity mapping. Any stale instructions fetched from the PoC will then be discarded and refetched correctly from the PoU. Patching kernel text executed prior to the MMU being enabled is prohibited, so the early entry code will always be clean. Reviewed-by: Mark Rutland <mark.rutland@xxxxxxx> Tested-by: Mark Rutland <mark.rutland@xxxxxxx> Signed-off-by: Will Deacon <will.deacon@xxxxxxx> Signed-off-by: Hanjun Guo <hanjun.guo@xxxxxxxxxx> --- arch/arm64/kernel/head.S | 8 ++++++++ arch/arm64/kernel/sleep.S | 8 ++++++++ arch/arm64/mm/proc.S | 1 - 3 files changed, 16 insertions(+), 1 deletion(-) diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S index 36aa31f..af6e4e8 100644 --- a/arch/arm64/kernel/head.S +++ b/arch/arm64/kernel/head.S @@ -682,5 +682,13 @@ __enable_mmu: isb msr sctlr_el1, x0 isb + /* + * Invalidate the local I-cache so that any instructions fetched + * speculatively from the PoC are discarded, since they may have + * been dynamically patched at the PoU. + */ + ic iallu + dsb nsh + isb br x27 ENDPROC(__enable_mmu) diff --git a/arch/arm64/kernel/sleep.S b/arch/arm64/kernel/sleep.S index ede186c..1c6969b 100644 --- a/arch/arm64/kernel/sleep.S +++ b/arch/arm64/kernel/sleep.S @@ -134,6 +134,14 @@ ENTRY(cpu_resume_mmu) ldr x3, =cpu_resume_after_mmu msr sctlr_el1, x0 // restore sctlr_el1 isb + /* + * Invalidate the local I-cache so that any instructions fetched + * speculatively from the PoC are discarded, since they may have + * been dynamically patched at the PoU. + */ + ic iallu + dsb nsh + isb br x3 // global jump to virtual address ENDPROC(cpu_resume_mmu) cpu_resume_after_mmu: diff --git a/arch/arm64/mm/proc.S b/arch/arm64/mm/proc.S index cdd754e..ee18bbc 100644 --- a/arch/arm64/mm/proc.S +++ b/arch/arm64/mm/proc.S @@ -196,7 +196,6 @@ ENDPROC(cpu_do_switch_mm) * value of the SCTLR_EL1 register. */ ENTRY(__cpu_setup) - ic iallu // I+BTB cache invalidate tlbi vmalle1is // invalidate I + D TLBs dsb ish -- 1.9.1 -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html