tree ce379ea1cfb29fb9b03061b874eec6e8719db449
parent 8834d87ef65443871cbe3b0cd1b167e43eb6f42f
author Gilles Peskine <Gilles.Peskine@arm.com> 1637083906 +0100
committer Gilles Peskine <Gilles.Peskine@arm.com> 1638186289 +0100

mbedtls_ssl_config: Replace bit-fields by separate bytes

This slightly increases the RAM consumption per context, but saves code
size on architectures with an instruction for direct byte access (which is
most of them).

Although this is technically an API break, in practice, a realistic
application won't break: it would have had to bypass API functions and rely
on the field size (e.g. relying on -1 == 1 in a 1-bit field).

Results (arm-none-eabi-gcc 7.3.1, build_arm_none_eabi_gcc_m0plus build):
library/ssl_cli.o: 19543 -> 19559 (diff: -16)
library/ssl_msg.o: 24726 -> 24690 (diff: 36)
library/ssl_srv.o: 20462 -> 20418 (diff: 44)
library/ssl_tls.o: 20707 -> 20555 (diff: 152)
library/ssl_tls13_client.o: 7252 -> 7244 (diff: 8)
library/ssl_tls13_generic.o: 4705 -> 4693 (diff: 12)

Results (same architecture, config-suite-b.h + MBEDTLS_ECDH_LEGACY_CONTEXT +
MBEDTLS_ECP_RESTARTABLE):
library/ssl_cli.o: 2876 -> 2864 (diff: 12)
library/ssl_msg.o: 3068 -> 3080 (diff: -12)
library/ssl_srv.o: 3372 -> 3340 (diff: 32)
library/ssl_tls.o: 6658 -> 6566 (diff: 92)

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>