On Tue, 2011-10-18 at 10:49 +0900, Jung Hyun Yoo wrote:

Hi,

During looking into the source code of v_insert() function in mem_space-arm.cpp file, I found two cases where it returns improper Mem_space::Status.

Case #1 When the size parameter of v_insert() is 0x100000 (that is, section mapping is asked), and the entry in the corresponding first-level page table indicates a coarse second-level page table (that is, it’s already valid) and only the entry in the second-level table is invalid: v_insert() function returns Insert_OK status. But it seems proper to return Insert_err_exists because there is already valid entry and inserting a new entry fails.

In this case, the Page_table::walk function returns an entry in the coarse page table, not the first level, and the size check in v_insert leads to an Insert_err_exists. So this should be correct.

Case #2 When the size parameter of v_insert() is 0x1000 (that is, 4KB small page mapping is asked), and the memory allocation for creating a coarse second-level page table fails in Page_table::walk() function: v_insert() returns Insert_OK status. But it seems proper to return Insert_err_nomem because due to memory shortage inserting a new entry fails.

This case is really a bug, so I fixed it, thanks. In that case Page_table::walk returns the invalid first-level entry and an additional size check in v_insert fixes the wrong behavior.