Adding kib@ for some input.

I have one other followup change after this that adds additional ABI-specific behavior (specifically routines for converting errno values between the native ABI and "other" ABIs). I think I like Bryan's suggestion of having an 'abi' parameter to a 'sysdecode_syscallname()' function instead of having separate functions per ABI as I've done here. I would reuse the same parameter in the errno API as well.

My question is what should that 'abi' parameter be? One approach is to simply reuse the 'sv_flags' values from the KTR_PROCCTOR record. Hmm, we don't expose sv_flags directly via kinfo_proc or another kern.proc sysctl (truss uses sv_name). Another approach is to use a dedicated enum declared in sysdecode.h and require clients to map whatever they use (sv_name or sv_flags) to the enum values. The fact that kdump doesn't currently use freebsd32 syscall names probably lends itself to this since kdump in its current form wouldn't be able to directly use sv_flags anyway.

In D4823#105084, @jhb wrote:

My question is what should that 'abi' parameter be? One approach is to simply reuse the 'sv_flags' values from the KTR_PROCCTOR record. Hmm, we don't expose sv_flags directly via kinfo_proc or another kern.proc sysctl (truss uses sv_name). Another approach is to use a dedicated enum declared in sysdecode.h and require clients to map whatever they use (sv_name or sv_flags) to the enum values. The fact that kdump doesn't currently use freebsd32 syscall names probably lends itself to this since kdump in its current form wouldn't be able to directly use sv_flags anyway.

sv_flags are not usable to you, There are SV_ABI_XXX and SV_PROC_ABI(), but they are only filled for some ABIs/sysents because programmer did not consider adding a flag or method for the specific behaviour.

I would expect that an abi structure in lib would be an equivalent of the sysent, e.g. for your purposes it probably should point to the errno names array and syscalls names array.

How to build this structure in the usermode is an interesting question, indeed. The sv_name + sv_flags is probably the most reliable way now, but it is not ideal for sure, requiring anybody to pay attention to a field that is not used by kernel for any decision. Also, kernel cannot provide the data like errno name table.

Hm, kernel could export e.g. sv_errtbl, which would allow ktrace to only know about FreeBSD errno names, by using libc syserr array ?

In D4823#105092, @kib wrote:

In D4823#105084, @jhb wrote:

My question is what should that 'abi' parameter be? One approach is to simply reuse the 'sv_flags' values from the KTR_PROCCTOR record. Hmm, we don't expose sv_flags directly via kinfo_proc or another kern.proc sysctl (truss uses sv_name). Another approach is to use a dedicated enum declared in sysdecode.h and require clients to map whatever they use (sv_name or sv_flags) to the enum values. The fact that kdump doesn't currently use freebsd32 syscall names probably lends itself to this since kdump in its current form wouldn't be able to directly use sv_flags anyway.

sv_flags are not usable to you, There are SV_ABI_XXX and SV_PROC_ABI(), but they are only filled for some ABIs/sysents because programmer did not consider adding a flag or method for the specific behaviour.

I would expect that an abi structure in lib would be an equivalent of the sysent, e.g. for your purposes it probably should point to the errno names array and syscalls names array.

How to build this structure in the usermode is an interesting question, indeed. The sv_name + sv_flags is probably the most reliable way now, but it is not ideal for sure, requiring anybody to pay attention to a field that is not used by kernel for any decision. Also, kernel cannot provide the data like errno name table.

Hm, kernel could export e.g. sv_errtbl, which would allow ktrace to only know about FreeBSD errno names, by using libc syserr array ?

Well, for now I've just moved the errno tables from truss into libsysdecode in my followup change (and then added wrapper functions to handle conversions). One nicer property of this is that I've changed truss to always print the raw errno value as the ABI sees it and then the string interpretation of that error converted to a FreeBSD errno. In that sense the new truss reports the "true" error value that the application sees (right now truss reports the converted errno value).

However, for now my question is how to describe the ABI. I think a simple enum will work for now:

enum sysdecode_abi {
    FREEBSD,
    FREEBSD32,
    LINUX,
    LINUX32,
    CLOUDABI64
};