On Monday, 9 November 2015 at 15:29:25 UTC, Jacob Carlborg wrote:
On 2015-11-08 19:12, bitwise wrote:
So, since binaries will not be mapped to overlapping address
spaces, I
can loop over all the binary images and find the range to
which the
argument of ___tls_get_addr() belongs, and map the pointer to
the
appropriate block of memory.
I am concerned that looping over all binary images for each
TLS access
will have performance implications, but for now, this solution
is good
enough. Later, ___tls_get_addr() can be amended to pass a
pointer to the
image from which the TLS originated, allowing constant time
lookup. I
believe Martin has already done this for linux/fbsd, but I had
time to
look at this specific issue.
Not sure if this would be too much work for the first version.
But would it be possible to, for each loaded image, register
its memory range in an associative array. Where the key is the
range the value is the image?
Hmm, when I think about, it might not help at all.
The AA is not needed. The offset of the TLS var is known at
compile time. If you look at sections_elf_shared.d you can see
the signature of __tls_get_addr, and that it takes a pointer to
the struct tls_index or something. *if* I understand correctly,
one of the two vars in that struct is the index of the image, and
the other is the offset into the imag's tls section. Not sure
where/hoe that struct is outputted though. So you would have to
figure out how to get the backend to do the same thing for OSX. I
think the image index may have to be assigned at load time, but
I'm not sure. The amount of code to actually do it should be
trivial, it's reading/interpreting the backend that will be the
problem ;)
Bit
