Rust strace Grate

[rennergade]

Lets create a grate that implements strace based on grate-rs: #11

For v0.1 lets omit clone/exec/exit while their routing is being fixed.

[stupendoussuperpowers]

Currently, the syscall_number in register_handler provides for an API that can map individual syscall numbers to a syscall wrapper.

This approach is limited, for example If we want to use this API for the strace grate, it would require us to individually register every syscall with a corresponding wrapper that does identical work.

This seems to be a TODO/wishlist item already.

http://github.com/Lind-Project/lind-wasm/issues/505

Ideally, we'd want something like so that we can register it like so:

register_handler(grateid, MATCH_ALL, 1, cageid, NULL);

And then, instead of the function pointer we pass in the syscall number to the dispatch function. The dispatch function can then utilize this syscall number to figure out to proceed with the syscall.

int pass_fptr_to_wt(syscall_number: uint64_t ...) {
    LOG(SYSCALL_NAMES[syscall_number], ...);
    ...
    make_syscall(syscall_number, ...);
}

[rennergade]

The logging part has to be different for each syscall right? Maybe this can be simplified in a way, can you expand on that?

[stupendoussuperpowers]

I already had a macro to log things similarly in the IMFS grate:

lind-wasm-example-grates/examples/imfs-grate/src/imfs_grate.c

Lines 41 to 69 in 62e6517

	static inline void sys_log_args(const char *name, uint64_t arg1, uint64_t arg2,
	uint64_t arg3, uint64_t arg4, uint64_t arg5,
	uint64_t arg6, int ret) {
	char buf[512];
	size_t pos = 0;
	pos += snprintf(buf + pos, sizeof(buf) - pos, "%s (", name);
	uint64_t args[6] = {arg1, arg2, arg3, arg4, arg5, arg6};
	int first = 1;
	for (int i = 0; i < 6; i++) {
	if (args[i] == 0xdeadbeefdeadbeefULL)
	continue;
	if (!first)
	pos += snprintf(buf + pos, sizeof(buf) - pos, ", ");
	pos += snprintf(buf + pos, sizeof(buf) - pos, "%llu", args[i]);
	first = 0;
	}
	snprintf(buf + pos, sizeof(buf) - pos, ") = %d\n", ret);
	fprintf(stderr, "%s", buf);
	}
	#define SYS_LOG(name, ret) \
	sys_log_args((name), arg1, arg2, arg3, arg4, arg5, arg6, (ret))

This just logs the raw values (so for e.g. the address for the string would be printed instead of the value). But we could easily add some utils to handle that.

[rennergade]

Ok I see. @drapl0n do you want to draft a PR based on match all? We can add that after the grate refactor.

[drapl0n]

For now i will register an individual handler for each syscall. Later, I can replace them with match-all.