linux/lib/mpi
Nicolai Stange 85d541a3d1 lib/mpi: mpi_read_raw_from_sgl(): sanitize meaning of indices
Within the byte reading loop in mpi_read_raw_sgl(), there are two
housekeeping indices used, z and x.

At all times, the index z represents the number of output bytes covered
by the input SGEs for which processing has completed so far. This includes
any leading zero bytes within the most significant limb.

The index x changes its meaning after the first outer loop's iteration
though: while processing the first input SGE, it represents

  "number of leading zero bytes in most significant output limb" +
   "current position within current SGE"

For the remaining SGEs OTOH, x corresponds just to

  "current position within current SGE"

After all, it is only the sum of z and x that has any meaning for the
output buffer and thus, the

  "number of leading zero bytes in most significant output limb"

part can be moved away from x into z from the beginning, opening up the
opportunity for cleaner code.

Before the outer loop iterating over the SGEs, don't initialize z with
zero, but with the number of leading zero bytes in the most significant
output limb. For the inner loop iterating over a single SGE's bytes,
get rid of the buf_shift offset to x' bounds and let x run from zero to
sg->length - 1.

Signed-off-by: Nicolai Stange <nicstange@gmail.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
2016-04-05 20:35:51 +08:00
..
generic_mpih-add1.c
generic_mpih-lshift.c
generic_mpih-mul1.c
generic_mpih-mul2.c
generic_mpih-mul3.c
generic_mpih-rshift.c
generic_mpih-sub1.c
longlong.h lib/mpi: avoid assembler warning 2016-02-28 03:26:34 +08:00
Makefile MPILIB: Reinstate mpi_cmp[_ui]() and export for RSA signature verification 2012-10-08 13:50:15 +10:30
mpi-bit.c MPILIB: Provide count_leading/trailing_zeros() based on arch functions 2012-10-08 13:50:11 +10:30
mpi-cmp.c MPILIB: Fix comparison of negative MPIs 2015-01-14 16:10:12 +00:00
mpi-inline.h lib/mpi: use "static inline" instead of "extern inline" 2016-02-28 03:26:34 +08:00
mpi-internal.h lib/mpi: use "static inline" instead of "extern inline" 2016-02-28 03:26:34 +08:00
mpi-pow.c MPILIB: Provide count_leading/trailing_zeros() based on arch functions 2012-10-08 13:50:11 +10:30
mpicoder.c lib/mpi: mpi_read_raw_from_sgl(): sanitize meaning of indices 2016-04-05 20:35:51 +08:00
mpih-cmp.c
mpih-div.c Remove unused code from MPI library 2012-05-26 11:51:03 +10:00
mpih-mul.c Remove unused code from MPI library 2012-05-26 11:51:03 +10:00
mpiutil.c MPILIB: add mpi_read_buf() and mpi_get_size() helpers 2015-06-16 14:35:06 +08:00