On 4/22/24 10:45, Daniel Henrique Barboza wrote:
Palmer, Anup,
On 4/22/24 10:58, Clément Léger wrote:
The current semihost exception number (16) is a reserved number (range
[16-17]). The upcoming double trap specification uses that number for
the double trap exception. Since the privileged spec (Table 22) defines
ranges for custom uses change the semihosting exception number to 63
which belongs to the range [48-63] in order to avoid any future
collisions with reserved exception.
I didn't find any reference to a number for the SEMIHOST exception here:
https://github.com/riscv-non-isa/riscv-semihosting
Do we have any potential candidates? I would like to avoid, if possible, setting
RISCV_EXCP_SEMIHOST to 63 as a band-aid just to replace it later on by the real
value.
RISCV_EXCP_SEMIHOST is internal to the qemu implementation and will never be delivered to
the guest.
I suggest using a number high in the >64 reserved range which will (likely) never be used
by any implementation, including ones that *do* define implementation-specific exceptions.
Which seems more likely than not within the "implementation defined" range.
E.g. target/i386 uses 0x100+n for qemu internal exceptions.
But in any case, the number can be redefined at will and not cause
compatibility issues.
r~
