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Kernel+LibC: Do not return -ENAMETOOLONG from sys$readlink()

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That's not how readlink() is supposed to work: it should copy as many bytes
as fit into the buffer, and return the number of bytes copied. So do that,
but add a twist: make sys$readlink() actually return the whole size, not
the number of bytes copied. We fix up this return value in userspace, to make
LibC's readlink() behave as expected, but this will also allow other code
to allocate a buffer of just the right size.

Also, avoid an extra copy of the link target.
This commit is contained in:
Sergey Bugaev 2020-06-16 21:51:08 +03:00 • committed by Andreas Kling
parent 35329400b8
commit 47d83800e1
2 changed files with 7 additions and 6 deletions
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10
Kernel/Process.cpp
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@ -1953,11 +1953,11 @@ int Process::sys$readlink(const Syscall::SC_readlink_params* user_params)
if (contents.is_error())
return contents.error();
auto link_target = String::copy(contents.value());
if (link_target.length() > params.buffer.size)
return -ENAMETOOLONG;
copy_to_user(params.buffer.data, link_target.characters(), link_target.length());
return link_target.length();
auto& link_target = contents.value();
auto size_to_copy = min(link_target.size(), params.buffer.size);
copy_to_user(params.buffer.data, link_target.data(), size_to_copy);
// Note: we return the whole size here, not the copied size.
return link_target.size();
}
int Process::sys$chdir(const char* user_path, size_t path_length)