On 14/11/2023 13:21, Kevin Brodsky wrote:
On 14/11/2023 13:06, Kevin Brodsky wrote:
On 13/11/2023 19:51, Teo Couprie Diaz wrote:
[...]
- /*
* The start of the string should always be properly aligned, but* its representable length might be different. Get the representable* length by using the same length that was used during allocation:* the length of the original string.* This takes into account the padding due to length change, but not that* for alignment. Thus we might not end up at the start of the next arg.* If not, we will need to take a slow* path to go through the padding.Nit: the text could be rewrapped (we end up with two short lines at the end).
*/- len = cheri_representable_length(len);
+#if (ELF_COMPAT == 0)
- str_ptr = cheri_perms_and(str_ptr,
(CHERI_PERM_GLOBAL | CHERI_PERM_STORE | CHERI_PERM_LOAD));- str_ptr = cheri_bounds_set_exact(str_ptr, len);
+#endif
- if (elf_stack_put_user(str_ptr, stack_item++))
return -EFAULT;- /*
* If right after the end of the argument length we have a zero,* that means the argument alignment was adjusted in order to create a* representable capability in purecap, even if we are not loading a* purecap binary. This padding is added at the end, so find the real* end by going through the padding.*/- for (pad_len = 0; len + pad_len < MAX_ARG_STRLEN; pad_len++) {
if (get_user(c, ustr + len + pad_len))return -EFAULT;if (c != '\0')break;- }
- ustr += pad_len;
- len += pad_len;
In fact I'm realising that things are even simpler: ustr doesn't need to be incremented (this has no effect, and it's now done in create_elf_tables()), and as a result we can do away with pad_len too:
for (; len < MAX_ARG_STRLEN; len++) { if (get_user(c, ustr + len)) return -EFAULT; if (c != '\0') break; }
I can amend that too if it makes sense.
Oh, yeah you're absolutely right. It makes it very clear what's going on and simplifies it fairly well.
Happy for you to make the change. (Which skews the patch even more towards being "mostly comments" :) )
Téo
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