Enable write-implies-execute-never when applicable #1550
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| @@ -189,6 +189,9 @@ UNWIND( .cantunwind) | |||
| orr r0, r0, #SCTLR_A | |||
| bic r0, r0, #SCTLR_C | |||
| bic r0, r0, #SCTLR_I | |||
| #if defined(CFG_HWSUPP_MEM_PERM_WXN) && defined(CFG_CORE_RWDATA_NOEXEC) | |||
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Better to test only CFG_CORE_RWDATA_NOEXEC here.
Optionally, add a dependency check in a core/arc/arm/arm.mk (but see my other comment, I feel the HWSUPP config is useless):
ifeq ($(CFG_CORE_RWDATA_NOEXEC))
ifneq ($(CFG_HWSUPP_MEM_PERM_WXN),y)
$(error ...)
endif
endif
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Some HW (C-A5, C-A9) do not support WXN and UWXN in SCTLR.
So we need this CFG_HWSUPP_MEM_PERM_WXN.
This is why the directive is not used in AARCH64, as all ARMv8-A do support SCTLR[WXN].
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I understand that. But we can simply assume that platforms that don't support CFG_CORE_RWDATA_NOEXEC simply don't enable it, no?
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No. At least for the few platforms lacking this hw hardening, op-tee core can still build a mmu that does rw-data-noexec. Weaker protection but at least optee legitimate mapping is clean.
The arm-tf does both: its mmu api never maps rwx memory and it sets STCRL[WXs], of course.
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Ah, now I get it. We really have two things to configure here. Sorry for the confusion.
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rebased |
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So, for both patches: |
HW may or may not support STCLR "WXN" configuration field. CFG_HWSUPP_MEM_PERM_WXN reflects this state. AArch64 is assumed to always support this field. Enable the "WXN" (and UWXN) bits in STCLR upon configuration directive CFG_CORE_RWDATA_NOEXEC. Signed-off-by: Etienne Carriere <etienne.carriere@linaro.org> Acked-by: Jerome Forissier <jerome.forissier@linaro.org>
Create core/arch/arm/cpu/<cpu-name>.mk to store CPU generic configurations settings. Update supported platforms to rely on the generic CPU support. Platform shall still specify whether they support or not the NEON extension. Cortex-A53 and Cortex-A57 are all ARMv8.0 compliant. For ARMv8 core, we will use ARMv8-A architecture minor version configuration files. Signed-off-by: Etienne Carriere <etienne.carriere@linaro.org> Acked-by: Jerome Forissier <jerome.forissier@linaro.org>
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Rebased, tag applied. |
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