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author | Pablo Neira Ayuso <pablo@netfilter.org> | 2019-06-25 01:32:59 +0200 |
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committer | Pablo Neira Ayuso <pablo@netfilter.org> | 2019-06-25 01:32:59 +0200 |
commit | 1c5ba67d2277ac2faf37c61076e8b5fa312be492 (patch) | |
tree | a645a1a2f7aea7faafcd67c6ba1bfd424b95cd7d /Documentation/arm64/sve.txt | |
parent | dbb5281a1f84b2f93032d4864c211ce8a20811a7 (diff) | |
parent | 045df37e743c7448931131988e99e8fe0cc92a54 (diff) |
Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next
Resolve conflict between d2912cb15bdd ("treewide: Replace GPLv2
boilerplate/reference with SPDX - rule 500") removing the GPL disclaimer
and fe03d4745675 ("Update my email address") which updates Jozsef
Kadlecsik's email.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Diffstat (limited to 'Documentation/arm64/sve.txt')
-rw-r--r-- | Documentation/arm64/sve.txt | 16 |
1 files changed, 16 insertions, 0 deletions
diff --git a/Documentation/arm64/sve.txt b/Documentation/arm64/sve.txt index 9940e924a47e..5689fc9a976a 100644 --- a/Documentation/arm64/sve.txt +++ b/Documentation/arm64/sve.txt @@ -56,6 +56,18 @@ model features for SVE is included in Appendix A. is to connect to a target process first and then attempt a ptrace(PTRACE_GETREGSET, pid, NT_ARM_SVE, &iov). +* Whenever SVE scalable register values (Zn, Pn, FFR) are exchanged in memory + between userspace and the kernel, the register value is encoded in memory in + an endianness-invariant layout, with bits [(8 * i + 7) : (8 * i)] encoded at + byte offset i from the start of the memory representation. This affects for + example the signal frame (struct sve_context) and ptrace interface + (struct user_sve_header) and associated data. + + Beware that on big-endian systems this results in a different byte order than + for the FPSIMD V-registers, which are stored as single host-endian 128-bit + values, with bits [(127 - 8 * i) : (120 - 8 * i)] of the register encoded at + byte offset i. (struct fpsimd_context, struct user_fpsimd_state). + 2. Vector length terminology ----------------------------- @@ -124,6 +136,10 @@ the SVE instruction set architecture. size and layout. Macros SVE_SIG_* are defined [1] to facilitate access to the members. +* Each scalable register (Zn, Pn, FFR) is stored in an endianness-invariant + layout, with bits [(8 * i + 7) : (8 * i)] stored at byte offset i from the + start of the register's representation in memory. + * If the SVE context is too big to fit in sigcontext.__reserved[], then extra space is allocated on the stack, an extra_context record is written in __reserved[] referencing this space. sve_context is then written in the |