IOS: Difference between revisions

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The Starbuck MMU itself only has R/W permissions for data/instruction memory access, no XN. However, there is XN implemented via separate hardware registers at 0x0d8b0XXX. The register relative-offset is calculated with the physaddr of the memory being protected. Each u32 register corresponds to a different block of physical memory. Among other things, this controls whether the ARM is allowed to access the memory for instruction-access, and in what ARM-mode(userland/privileged) the instruction-access is permitted.

The Starbuck MMU itself only has R/W permissions for data/instruction memory access, no XN. However, there is XN implemented via separate hardware registers at [[Hardware/XN_Controller|0x0d8b0XXX]]. The register relative-offset is calculated with the physaddr of the memory being protected. Each u32 register corresponds to a different block of physical memory. Among other things, this controls whether the ARM is allowed to access the memory for instruction-access, and in what ARM-mode(userland/privileged) the instruction-access is permitted.

Hence, userland .text is ''only'' executable from userland. From userland, the ''only'' executable memory is the process .text. In privileged-mode, the ''only'' executable memory is the main kernel .text(0x08120000) and 0xffff0000(the latter is also RWX).

Revision as of 08:22, 6 April 2016 view source9 years ago Yellows8 (talk \| contribs) 340 edits →IOS-NET ← Older edit		Revision as of 11:20, 4 May 2016 view source9 years ago Neobrain (talk \| contribs) 47 edits →Virtual Memory Map Newer edit →
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	The Starbuck MMU itself only has R/W permissions for data/instruction memory access, no XN. However, there is XN implemented via separate hardware registers at 0x0d8b0XXX. The register relative-offset is calculated with the physaddr of the memory being protected. Each u32 register corresponds to a different block of physical memory. Among other things, this controls whether the ARM is allowed to access the memory for instruction-access, and in what ARM-mode(userland/privileged) the instruction-access is permitted.		The Starbuck MMU itself only has R/W permissions for data/instruction memory access, no XN. However, there is XN implemented via separate hardware registers at [[Hardware/XN_Controller\|0x0d8b0XXX]]. The register relative-offset is calculated with the physaddr of the memory being protected. Each u32 register corresponds to a different block of physical memory. Among other things, this controls whether the ARM is allowed to access the memory for instruction-access, and in what ARM-mode(userland/privileged) the instruction-access is permitted.

	Hence, userland .text is ''only'' executable from userland. From userland, the ''only'' executable memory is the process .text. In privileged-mode, the ''only'' executable memory is the main kernel .text(0x08120000) and 0xffff0000(the latter is also RWX).		Hence, userland .text is ''only'' executable from userland. From userland, the ''only'' executable memory is the process .text. In privileged-mode, the ''only'' executable memory is the main kernel .text(0x08120000) and 0xffff0000(the latter is also RWX).