Commit Graph

3 Commits

Author SHA1 Message Date
Georg Sauthoff 9b51beeb2a Only pass the minimum number of syscall arguments
Previously, __internal_syscall() compiled into asm-code that unconditionally
sets the syscall argument registers a0 to a5.

For example, the instruction sequence for a exit syscall looked like
this:

    li    a0, 1   # in ther caller of exit()
    # ...         # in newlib:
    li    a1, 0   # unused arguments
    li    a2, 0
    li    a3, 0
    li    a4, 0
    li    a5, 0
    li    a7, 93  # exit syscall number

(i.e. the binary contains then 5 superfluous instructions for this
one argument syscall)

This commit changes the RISC-V syscall code such that only the required
syscall argument registers are set.

GCC detects that argc is known at compile time and thus evaluates all the
if-statements where argc is used at compile time (tested with -O2 and -Os).
2020-02-11 09:41:52 +01:00
Denis Ivanov 9e032fd939 RISC-V: Fix _sbrk, it's failed only when return value is -1.
Signed-off-by: Kito Cheng <kito.cheng@gmail.com>
2018-08-29 15:49:00 +02:00
Jim Wilson 28d5b98038 RISC-V: Moved syscalls to separate files to fix aliasing problems. 2017-12-26 12:27:52 -08:00