Use `uint_fast8_t` instead of `unsigned char` in various loop-type
situations. This avoids the need for a 16 or 32-bit system to insert
explicit narrow-to-8-bit instructions.
Not the result of an exhaustive source analysis, rather inspecting
the disassembly output for a cut-down Cortex-M0+ build looking for
UXTB etc instructions, so there could well be more in the complete
configuration.
Signed-off-by: Kevin Bracey <kevin.bracey@arm.com>
Place smallest items first, as this makes them most easily addressable
in Thumb architecture. 16-bit access instructions have a 5-bit offset
field, which is interpreted as bytes, halfwords, or words depending
on access size, so smaller fields have smaller range. Range is 0-31
times the access size.
The mbedtls_ssl_context structure is too large to be fully easily
accessed even for words, so reorder functional blocks to put more
frequently-referenced fields in the first 128 bytes, reducing
total code size.
Signed-off-by: Kevin Bracey <kevin.bracey@arm.com>
Bitfields in context structures do not have sufficient (if any) RAM
payoff for the ROM complexity to manipulate them. Replace with
plain uint8_t.
On the smallest targets, the configuration options mean that there
are 4 or fewer members anyway, so a bitfield saves no RAM compared
to uint8_t.
ROM saving will be further increased if the uint8_t members are at the
start of the structure (when compiling for Thumb).
Signed-off-by: Kevin Bracey <kevin.bracey@arm.com>
Follow the model of `MBEDTLS_SSL_CONF_ENDPOINT`. This saves a small
amount - most of the saving was already acheived via`
MBEDTLS_SSL_TRANSPORT_IS_TLS` but we can scrape out a little more by
totally eliminating `ssl->conf->transport` references.
Signed-off-by: Kevin Bracey <kevin.bracey@arm.com>
Old GCC (pre-5?) natively use divided syntax, so we must put it back
after changing it.
More recent GCCs natively use unified syntax, and themselves are
surrounding our blocks with divided/unified directives for backwards
compatibility, so we don't need to restore for those.
Signed-off-by: Kevin Bracey <kevin.bracey@arm.com>
Naked functions and basic assembler don't seem to work reliably - basic
assembler is assumed to not change registers or memory, and there does
not appear to be any special handling of naked functions in this regard.
Signed-off-by: Kevin Bracey <kevin.bracey@arm.com>
Optimize the key switching mechanism to set the key only if
a different operation is performed with the context.
Signed-off-by: Andrzej Kurek <andrzej.kurek@arm.com>
Store the raw encryption and decryption keys in transforms
to set them before each cipher operation. Add a config option
for this - MBEDTLS_SSL_TRANSFORM_OPTIMIZE_CIPHERS.
Signed-off-by: Andrzej Kurek <andrzej.kurek@arm.com>
