When setting up page tables, barebox marks all the address space as eXecute Never and uncached, except for the memory banks. If we happen to have secure memory, this is andequate as speculative execution may read from secure memory or even attempt to execute it leading to spurious data aborts. The way around this so far was either having OP-TEE in SRAM (which normally isn't a barebox memory bank) or having it at the end of DRAM, but adjusting size, so it's not covered by a memory bank. This adds a generic solution to the issue. We already request the SDRAM regions described by the reserved memory entries in the DT. We go a step further and mark them as IORESOURCE_BUSY, which we can then evaluat in the MMU setup code to map these regions uncached and eXecute Never. There has been previous attempts by Rouven to achieve this, the latest being: https://lore.barebox.org/barebox/20210803094418.475609-1-r.czerwinski@xxxxxxxxxxxxxx/ While this series tries to achieve the same end goal, it goes about it in a different manner: We don't use FDT fixup table to tell us what to nstead have both the FDT fixup table and the /reserved-memory child nodes feed into the barebox request_sdram_region allocator and then use to apply caching attributes. Note that this doesn't yet solve all problems. For example, PPA secure monitor installation on Layerscape may happen with CONFIG_MMU_EARLY=y, in which case barebox in EL2 may speculate into the secure memory before any device tree reserved-memory settings are considered. For this reason, both early MMU and normal MMU setup must be aware of the reserved memory regions. The original patch set by Rouven used FDT parsing in PBL to achieve this, but this is omitted here to limit scope of the patch series. Instead we only handle the CONFIG_OPTEE_SIZE case out-of-the-box. Ahmad Fatoum (9): resource: add flags parameter to __request_region common: allow requesting SDRAM regions with custom flags memory: define reserve_sdram_region helper init: define new postmem_initcall() of: reserved-mem: reserve regions prior to mmu_initcall() ARM: mmu64: map reserved regions uncached ARM: mmu: define attrs_uncached_mem() helper ARM: early-mmu: don't cache/prefetch OPTEE_SIZE bytes from end of memory commands: iomem: point out [R]eserved regions Rouven Czerwinski (1): ARM: mmu: use reserve mem entries to modify maps arch/arm/cpu/mmu-common.h | 15 ++++++++++++ arch/arm/cpu/mmu.c | 40 ++++++++++++++++++++++--------- arch/arm/cpu/mmu.h | 9 +++++-- arch/arm/cpu/mmu_64.c | 10 +++++++- arch/arm/cpu/start.c | 2 +- arch/arm/cpu/uncompress.c | 2 +- commands/iomemport.c | 9 ++++--- common/memory.c | 27 ++++++++------------- common/resource.c | 13 +++++----- drivers/of/reserved-mem.c | 34 +++++++++++++++++--------- include/asm-generic/barebox.lds.h | 1 + include/init.h | 21 ++++++++-------- include/linux/ioport.h | 4 ++-- include/memory.h | 25 +++++++++++++++++-- include/of.h | 7 ------ 15 files changed, 145 insertions(+), 74 deletions(-) -- 2.30.2
