diff options
Diffstat (limited to 'Documentation/arm64')
| -rw-r--r-- | Documentation/arm64/booting.txt | 26 | ||||
| -rw-r--r-- | Documentation/arm64/memory.txt | 44 | ||||
| -rw-r--r-- | Documentation/arm64/tagged-pointers.txt | 34 |
3 files changed, 95 insertions, 9 deletions
diff --git a/Documentation/arm64/booting.txt b/Documentation/arm64/booting.txt index 9c4d388daddc..1b0c968098aa 100644 --- a/Documentation/arm64/booting.txt +++ b/Documentation/arm64/booting.txt @@ -68,13 +68,23 @@ Image target is available instead. Requirement: MANDATORY -The decompressed kernel image contains a 32-byte header as follows: +The decompressed kernel image contains a 64-byte header as follows: - u32 magic = 0x14000008; /* branch to stext, little-endian */ - u32 res0 = 0; /* reserved */ + u32 code0; /* Executable code */ + u32 code1; /* Executable code */ u64 text_offset; /* Image load offset */ + u64 res0 = 0; /* reserved */ u64 res1 = 0; /* reserved */ u64 res2 = 0; /* reserved */ + u64 res3 = 0; /* reserved */ + u64 res4 = 0; /* reserved */ + u32 magic = 0x644d5241; /* Magic number, little endian, "ARM\x64" */ + u32 res5 = 0; /* reserved */ + + +Header notes: + +- code0/code1 are responsible for branching to stext. The image must be placed at the specified offset (currently 0x80000) from the start of the system RAM and called there. The start of the @@ -101,8 +111,14 @@ Before jumping into the kernel, the following conditions must be met: - Caches, MMUs The MMU must be off. Instruction cache may be on or off. - Data cache must be off and invalidated. - External caches (if present) must be configured and disabled. + The address range corresponding to the loaded kernel image must be + cleaned to the PoC. In the presence of a system cache or other + coherent masters with caches enabled, this will typically require + cache maintenance by VA rather than set/way operations. + System caches which respect the architected cache maintenance by VA + operations must be configured and may be enabled. + System caches which do not respect architected cache maintenance by VA + operations (not recommended) must be configured and disabled. - Architected timers CNTFRQ must be programmed with the timer frequency. diff --git a/Documentation/arm64/memory.txt b/Documentation/arm64/memory.txt index 5f583af0a6e1..d50fa618371b 100644 --- a/Documentation/arm64/memory.txt +++ b/Documentation/arm64/memory.txt @@ -21,7 +21,7 @@ The swapper_pgd_dir address is written to TTBR1 and never written to TTBR0. -AArch64 Linux memory layout: +AArch64 Linux memory layout with 4KB pages: Start End Size Use ----------------------------------------------------------------------- @@ -35,17 +35,46 @@ ffffffbc00000000 ffffffbdffffffff 8GB vmemmap ffffffbe00000000 ffffffbffbbfffff ~8GB [guard, future vmmemap] -ffffffbffbc00000 ffffffbffbdfffff 2MB earlyprintk device +ffffffbffa000000 ffffffbffaffffff 16MB PCI I/O space -ffffffbffbe00000 ffffffbffbe0ffff 64KB PCI I/O space +ffffffbffb000000 ffffffbffbbfffff 12MB [guard] -ffffffbbffff0000 ffffffbcffffffff ~2MB [guard] +ffffffbffbc00000 ffffffbffbdfffff 2MB fixed mappings + +ffffffbffbe00000 ffffffbffbffffff 2MB [guard] ffffffbffc000000 ffffffbfffffffff 64MB modules ffffffc000000000 ffffffffffffffff 256GB kernel logical memory map +AArch64 Linux memory layout with 64KB pages: + +Start End Size Use +----------------------------------------------------------------------- +0000000000000000 000003ffffffffff 4TB user + +fffffc0000000000 fffffdfbfffeffff ~2TB vmalloc + +fffffdfbffff0000 fffffdfbffffffff 64KB [guard page] + +fffffdfc00000000 fffffdfdffffffff 8GB vmemmap + +fffffdfe00000000 fffffdfffbbfffff ~8GB [guard, future vmmemap] + +fffffdfffa000000 fffffdfffaffffff 16MB PCI I/O space + +fffffdfffb000000 fffffdfffbbfffff 12MB [guard] + +fffffdfffbc00000 fffffdfffbdfffff 2MB fixed mappings + +fffffdfffbe00000 fffffdfffbffffff 2MB [guard] + +fffffdfffc000000 fffffdffffffffff 64MB modules + +fffffe0000000000 ffffffffffffffff 2TB kernel logical memory map + + Translation table lookup with 4KB pages: +--------+--------+--------+--------+--------+--------+--------+--------+ @@ -73,3 +102,10 @@ Translation table lookup with 64KB pages: | | +--------------------------> [41:29] L2 index (only 38:29 used) | +-------------------------------> [47:42] L1 index (not used) +-------------------------------------------------> [63] TTBR0/1 + +When using KVM, the hypervisor maps kernel pages in EL2, at a fixed +offset from the kernel VA (top 24bits of the kernel VA set to zero): + +Start End Size Use +----------------------------------------------------------------------- +0000004000000000 0000007fffffffff 256GB kernel objects mapped in HYP diff --git a/Documentation/arm64/tagged-pointers.txt b/Documentation/arm64/tagged-pointers.txt new file mode 100644 index 000000000000..d9995f1f51b3 --- /dev/null +++ b/Documentation/arm64/tagged-pointers.txt @@ -0,0 +1,34 @@ + Tagged virtual addresses in AArch64 Linux + ========================================= + +Author: Will Deacon <will.deacon@arm.com> +Date : 12 June 2013 + +This document briefly describes the provision of tagged virtual +addresses in the AArch64 translation system and their potential uses +in AArch64 Linux. + +The kernel configures the translation tables so that translations made +via TTBR0 (i.e. userspace mappings) have the top byte (bits 63:56) of +the virtual address ignored by the translation hardware. This frees up +this byte for application use, with the following caveats: + + (1) The kernel requires that all user addresses passed to EL1 + are tagged with tag 0x00. This means that any syscall + parameters containing user virtual addresses *must* have + their top byte cleared before trapping to the kernel. + + (2) Non-zero tags are not preserved when delivering signals. + This means that signal handlers in applications making use + of tags cannot rely on the tag information for user virtual + addresses being maintained for fields inside siginfo_t. + One exception to this rule is for signals raised in response + to watchpoint debug exceptions, where the tag information + will be preserved. + + (3) Special care should be taken when using tagged pointers, + since it is likely that C compilers will not hazard two + virtual addresses differing only in the upper byte. + +The architecture prevents the use of a tagged PC, so the upper byte will +be set to a sign-extension of bit 55 on exception return. |