riscv: Add basic vector extension support

The RISC-V vector extension comes with an implementation-defined
number of bits per vector register (VLEN), which can be read out at
run-tim

riscv: Add basic vector extension support

The RISC-V vector extension comes with an implementation-defined
number of bits per vector register (VLEN), which can be read out at
run-time using the CSR 'vlenb' (which returns VLEN/8) followed by a
multiplication by 8 (to convert bytes to bits).

This patch introduces a RISC-V capability 'V' to specify the
availability of the vector extension. If this extension is found at
run-time, then we read out VLEN as described above and cache it.
Caching ensures that we only read the CSR once at startup.
This is necessary because reading out CSR can be expensive
(e.g. if CSR readout is implemented using trap-and-emulate).

Follow-up patches can make use of VLEN and chose the best strategy
based on the available length of the vector registers.

Signed-off-by: Christoph Müllner <christoph.muellner@vrull.eu>

Reviewed-by: Tomas Mraz <tomas@openssl.org>
Reviewed-by: Paul Dale <pauli@openssl.org>
Reviewed-by: Hugo Landau <hlandau@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/21923)

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Add basic RISC-V cpuid and OPENSSL_riscvcap

RISC-V cpuid implementation allows bitmanip extensions Zb[abcs] to
be enabled at runtime using OPENSSL_riscvcap environment variable.

Add basic RISC-V cpuid and OPENSSL_riscvcap

RISC-V cpuid implementation allows bitmanip extensions Zb[abcs] to
be enabled at runtime using OPENSSL_riscvcap environment variable.

For example, to specify 64-bit RISC-V with the G,C,Zba,Zbb,Zbc
extensions, one could write: OPENSSL_riscvcap="rv64gc_zba_zbb_zbc"

Architecture string parsing is still very primitive, but can be
expanded in the future. Currently, only bitmanip extensions Zba, Zbb,
Zbc and Zbs are supported.

Includes implementation of constant-time CRYPTO_memcmp in riscv64 asm,
as well as OPENSSL_cleanse. Assembly implementations are written using
perlasm.

Reviewed-by: Philipp Tomsich <philipp.tomsich@vrull.eu>
Signed-off-by: Henry Brausen <henry.brausen@vrull.eu>

Reviewed-by: Tomas Mraz <tomas@openssl.org>
Reviewed-by: Paul Dale <pauli@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/17640)

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