diff options
Diffstat (limited to 'Documentation/arm64')
| -rw-r--r-- | Documentation/arm64/booting.txt | 51 | ||||
| -rw-r--r-- | Documentation/arm64/memory.txt | 69 |
2 files changed, 69 insertions, 51 deletions
diff --git a/Documentation/arm64/booting.txt b/Documentation/arm64/booting.txt index 37fc4f632176..f3c05b5f9f08 100644 --- a/Documentation/arm64/booting.txt +++ b/Documentation/arm64/booting.txt @@ -72,27 +72,54 @@ The decompressed kernel image contains a 64-byte header as follows: u32 code0; /* Executable code */ u32 code1; /* Executable code */ - u64 text_offset; /* Image load offset */ - u64 res0 = 0; /* reserved */ - u64 res1 = 0; /* reserved */ + u64 text_offset; /* Image load offset, little endian */ + u64 image_size; /* Effective Image size, little endian */ + u64 flags; /* kernel flags, little endian */ 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 */ + u32 res5; /* reserved (used for PE COFF offset) */ Header notes: +- As of v3.17, all fields are little endian unless stated otherwise. + - code0/code1 are responsible for branching to stext. + - when booting through EFI, code0/code1 are initially skipped. res5 is an offset to the PE header and the PE header has the EFI - entry point (efi_stub_entry). When the stub has done its work, it + entry point (efi_stub_entry). When the stub has done its work, it jumps to code0 to resume the normal boot process. -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 -system RAM must be aligned to 2MB. +- Prior to v3.17, the endianness of text_offset was not specified. In + these cases image_size is zero and text_offset is 0x80000 in the + endianness of the kernel. Where image_size is non-zero image_size is + little-endian and must be respected. Where image_size is zero, + text_offset can be assumed to be 0x80000. + +- The flags field (introduced in v3.17) is a little-endian 64-bit field + composed as follows: + Bit 0: Kernel endianness. 1 if BE, 0 if LE. + Bits 1-63: Reserved. + +- When image_size is zero, a bootloader should attempt to keep as much + memory as possible free for use by the kernel immediately after the + end of the kernel image. The amount of space required will vary + depending on selected features, and is effectively unbound. + +The Image must be placed text_offset bytes from a 2MB aligned base +address near the start of usable system RAM and called there. Memory +below that base address is currently unusable by Linux, and therefore it +is strongly recommended that this location is the start of system RAM. +At least image_size bytes from the start of the image must be free for +use by the kernel. + +Any memory described to the kernel (even that below the 2MB aligned base +address) which is not marked as reserved from the kernel e.g. with a +memreserve region in the device tree) will be considered as available to +the kernel. Before jumping into the kernel, the following conditions must be met: @@ -141,6 +168,14 @@ Before jumping into the kernel, the following conditions must be met: the kernel image will be entered must be initialised by software at a higher exception level to prevent execution in an UNKNOWN state. + For systems with a GICv3 interrupt controller: + - If EL3 is present: + ICC_SRE_EL3.Enable (bit 3) must be initialiased to 0b1. + ICC_SRE_EL3.SRE (bit 0) must be initialised to 0b1. + - If the kernel is entered at EL1: + ICC.SRE_EL2.Enable (bit 3) must be initialised to 0b1 + ICC_SRE_EL2.SRE (bit 0) must be initialised to 0b1. + The requirements described above for CPU mode, caches, MMUs, architected timers, coherency and system registers apply to all CPUs. All CPUs must enter the kernel in the same exception level. diff --git a/Documentation/arm64/memory.txt b/Documentation/arm64/memory.txt index d50fa618371b..344e85cc7323 100644 --- a/Documentation/arm64/memory.txt +++ b/Documentation/arm64/memory.txt @@ -2,18 +2,18 @@ ============================== Author: Catalin Marinas <catalin.marinas@arm.com> -Date : 20 February 2012 This document describes the virtual memory layout used by the AArch64 Linux kernel. The architecture allows up to 4 levels of translation tables with a 4KB page size and up to 3 levels with a 64KB page size. -AArch64 Linux uses 3 levels of translation tables with the 4KB page -configuration, allowing 39-bit (512GB) virtual addresses for both user -and kernel. With 64KB pages, only 2 levels of translation tables are -used but the memory layout is the same. +AArch64 Linux uses either 3 levels or 4 levels of translation tables +with the 4KB page configuration, allowing 39-bit (512GB) or 48-bit +(256TB) virtual addresses, respectively, for both user and kernel. With +64KB pages, only 2 levels of translation tables, allowing 42-bit (4TB) +virtual address, are used but the memory layout is the same. -User addresses have bits 63:39 set to 0 while the kernel addresses have +User addresses have bits 63:48 set to 0 while the kernel addresses have the same bits set to 1. TTBRx selection is given by bit 63 of the virtual address. The swapper_pg_dir contains only kernel (global) mappings while the user pgd contains only user (non-global) mappings. @@ -21,58 +21,40 @@ The swapper_pgd_dir address is written to TTBR1 and never written to TTBR0. -AArch64 Linux memory layout with 4KB pages: +AArch64 Linux memory layout with 4KB pages + 3 levels: Start End Size Use ----------------------------------------------------------------------- 0000000000000000 0000007fffffffff 512GB user +ffffff8000000000 ffffffffffffffff 512GB kernel -ffffff8000000000 ffffffbbfffeffff ~240GB vmalloc -ffffffbbffff0000 ffffffbbffffffff 64KB [guard page] +AArch64 Linux memory layout with 4KB pages + 4 levels: -ffffffbc00000000 ffffffbdffffffff 8GB vmemmap - -ffffffbe00000000 ffffffbffbbfffff ~8GB [guard, future vmmemap] - -ffffffbffa000000 ffffffbffaffffff 16MB PCI I/O space - -ffffffbffb000000 ffffffbffbbfffff 12MB [guard] - -ffffffbffbc00000 ffffffbffbdfffff 2MB fixed mappings - -ffffffbffbe00000 ffffffbffbffffff 2MB [guard] - -ffffffbffc000000 ffffffbfffffffff 64MB modules - -ffffffc000000000 ffffffffffffffff 256GB kernel logical memory map +Start End Size Use +----------------------------------------------------------------------- +0000000000000000 0000ffffffffffff 256TB user +ffff000000000000 ffffffffffffffff 256TB kernel -AArch64 Linux memory layout with 64KB pages: +AArch64 Linux memory layout with 64KB pages + 2 levels: Start End Size Use ----------------------------------------------------------------------- 0000000000000000 000003ffffffffff 4TB user +fffffc0000000000 ffffffffffffffff 4TB kernel -fffffc0000000000 fffffdfbfffeffff ~2TB vmalloc -fffffdfbffff0000 fffffdfbffffffff 64KB [guard page] +AArch64 Linux memory layout with 64KB pages + 3 levels: -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] +Start End Size Use +----------------------------------------------------------------------- +0000000000000000 0000ffffffffffff 256TB user +ffff000000000000 ffffffffffffffff 256TB kernel -fffffdfffc000000 fffffdffffffffff 64MB modules -fffffe0000000000 ffffffffffffffff 2TB kernel logical memory map +For details of the virtual kernel memory layout please see the kernel +booting log. Translation table lookup with 4KB pages: @@ -86,7 +68,7 @@ Translation table lookup with 4KB pages: | | | | +-> [20:12] L3 index | | | +-----------> [29:21] L2 index | | +---------------------> [38:30] L1 index - | +-------------------------------> [47:39] L0 index (not used) + | +-------------------------------> [47:39] L0 index +-------------------------------------------------> [63] TTBR0/1 @@ -99,10 +81,11 @@ Translation table lookup with 64KB pages: | | | | v | | | | [15:0] in-page offset | | | +----------> [28:16] L3 index - | | +--------------------------> [41:29] L2 index (only 38:29 used) - | +-------------------------------> [47:42] L1 index (not used) + | | +--------------------------> [41:29] L2 index + | +-------------------------------> [47:42] L1 index +-------------------------------------------------> [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): |