diff options
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/arm64/kasan-offsets.sh | 3 | ||||
| -rw-r--r-- | Documentation/arm64/memory.rst | 45 | ||||
| -rw-r--r-- | Documentation/arm64/tagged-pointers.rst | 25 |
3 files changed, 41 insertions, 32 deletions
diff --git a/Documentation/arm64/kasan-offsets.sh b/Documentation/arm64/kasan-offsets.sh index 2b7a021db363..2dc5f9e18039 100644 --- a/Documentation/arm64/kasan-offsets.sh +++ b/Documentation/arm64/kasan-offsets.sh @@ -1,12 +1,11 @@ #!/bin/sh # Print out the KASAN_SHADOW_OFFSETS required to place the KASAN SHADOW -# start address at the mid-point of the kernel VA space +# start address at the top of the linear region print_kasan_offset () { printf "%02d\t" $1 printf "0x%08x00000000\n" $(( (0xffffffff & (-1 << ($1 - 1 - 32))) \ - + (1 << ($1 - 32 - $2)) \ - (1 << (64 - 32 - $2)) )) } diff --git a/Documentation/arm64/memory.rst b/Documentation/arm64/memory.rst index cf03b3290800..e7522e5c8322 100644 --- a/Documentation/arm64/memory.rst +++ b/Documentation/arm64/memory.rst @@ -32,17 +32,16 @@ AArch64 Linux memory layout with 4KB pages + 4 levels (48-bit):: ----------------------------------------------------------------------- 0000000000000000 0000ffffffffffff 256TB user ffff000000000000 ffff7fffffffffff 128TB kernel logical memory map - ffff800000000000 ffff9fffffffffff 32TB kasan shadow region - ffffa00000000000 ffffa00007ffffff 128MB bpf jit region - ffffa00008000000 ffffa0000fffffff 128MB modules - ffffa00010000000 fffffdffbffeffff ~93TB vmalloc - fffffdffbfff0000 fffffdfffe5f8fff ~998MB [guard region] - fffffdfffe5f9000 fffffdfffe9fffff 4124KB fixed mappings - fffffdfffea00000 fffffdfffebfffff 2MB [guard region] - fffffdfffec00000 fffffdffffbfffff 16MB PCI I/O space - fffffdffffc00000 fffffdffffdfffff 2MB [guard region] - fffffdffffe00000 ffffffffffdfffff 2TB vmemmap - ffffffffffe00000 ffffffffffffffff 2MB [guard region] + [ffff600000000000 ffff7fffffffffff] 32TB [kasan shadow region] + ffff800000000000 ffff800007ffffff 128MB bpf jit region + ffff800008000000 ffff80000fffffff 128MB modules + ffff800010000000 fffffbffefffffff 124TB vmalloc + fffffbfff0000000 fffffbfffdffffff 224MB fixed mappings (top down) + fffffbfffe000000 fffffbfffe7fffff 8MB [guard region] + fffffbfffe800000 fffffbffff7fffff 16MB PCI I/O space + fffffbffff800000 fffffbffffffffff 8MB [guard region] + fffffc0000000000 fffffdffffffffff 2TB vmemmap + fffffe0000000000 ffffffffffffffff 2TB [guard region] AArch64 Linux memory layout with 64KB pages + 3 levels (52-bit with HW support):: @@ -50,19 +49,17 @@ AArch64 Linux memory layout with 64KB pages + 3 levels (52-bit with HW support): Start End Size Use ----------------------------------------------------------------------- 0000000000000000 000fffffffffffff 4PB user - fff0000000000000 fff7ffffffffffff 2PB kernel logical memory map - fff8000000000000 fffd9fffffffffff 1440TB [gap] - fffda00000000000 ffff9fffffffffff 512TB kasan shadow region - ffffa00000000000 ffffa00007ffffff 128MB bpf jit region - ffffa00008000000 ffffa0000fffffff 128MB modules - ffffa00010000000 fffff81ffffeffff ~88TB vmalloc - fffff81fffff0000 fffffc1ffe58ffff ~3TB [guard region] - fffffc1ffe590000 fffffc1ffe9fffff 4544KB fixed mappings - fffffc1ffea00000 fffffc1ffebfffff 2MB [guard region] - fffffc1ffec00000 fffffc1fffbfffff 16MB PCI I/O space - fffffc1fffc00000 fffffc1fffdfffff 2MB [guard region] - fffffc1fffe00000 ffffffffffdfffff 3968GB vmemmap - ffffffffffe00000 ffffffffffffffff 2MB [guard region] + fff0000000000000 ffff7fffffffffff ~4PB kernel logical memory map + [fffd800000000000 ffff7fffffffffff] 512TB [kasan shadow region] + ffff800000000000 ffff800007ffffff 128MB bpf jit region + ffff800008000000 ffff80000fffffff 128MB modules + ffff800010000000 fffffbffefffffff 124TB vmalloc + fffffbfff0000000 fffffbfffdffffff 224MB fixed mappings (top down) + fffffbfffe000000 fffffbfffe7fffff 8MB [guard region] + fffffbfffe800000 fffffbffff7fffff 16MB PCI I/O space + fffffbffff800000 fffffbffffffffff 8MB [guard region] + fffffc0000000000 ffffffdfffffffff ~4TB vmemmap + ffffffe000000000 ffffffffffffffff 128GB [guard region] Translation table lookup with 4KB pages:: diff --git a/Documentation/arm64/tagged-pointers.rst b/Documentation/arm64/tagged-pointers.rst index eab4323609b9..19d284b70384 100644 --- a/Documentation/arm64/tagged-pointers.rst +++ b/Documentation/arm64/tagged-pointers.rst @@ -53,12 +53,25 @@ visibility. Preserving tags --------------- -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. +When delivering signals, non-zero tags are not preserved in +siginfo.si_addr unless the flag SA_EXPOSE_TAGBITS was set in +sigaction.sa_flags when the signal handler was installed. This means +that signal handlers in applications making use of tags cannot rely +on the tag information for user virtual addresses being maintained +in these fields unless the flag was set. + +Due to architecture limitations, bits 63:60 of the fault address +are not preserved in response to synchronous tag check faults +(SEGV_MTESERR) even if SA_EXPOSE_TAGBITS was set. Applications should +treat the values of these bits as undefined in order to accommodate +future architecture revisions which may preserve the bits. + +For signals raised in response to watchpoint debug exceptions, the +tag information will be preserved regardless of the SA_EXPOSE_TAGBITS +flag setting. + +Non-zero tags are never preserved in sigcontext.fault_address +regardless of the SA_EXPOSE_TAGBITS flag setting. 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. |