linux-kernel - Question about mmap syscall and POSIX standard on mips arch

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Date:   Thu, 18 Oct 2018 11:26:02 +0800
From:   "Hongzhi, Song" <hongzhi.song@...driver.com>
To:     <linux-kernel@...r.kernel.org>, <mm-commits@...r.kernel.org>
Subject: Question about mmap syscall and POSIX standard on mips arch

Hi all,

Ltp has a POSIX teatcase about mmap, 24-2.c.

https://github.com/linux-test-project/ltp/blob/e816127e5d8efbff5ae53e9c2292fae22f36838b/testcases/open_posix_testsuite/conformance/interfaces/mmap/24-2.c#L94

-----part of code-----

     pa = mmap(addr, len, PROT_READ | PROT_WRITE, MAP_FIXED | 
MAP_SHARED, fd,
0);
     if (pa == MAP_FAILED && errno == ENOMEM) {
         printf("Got ENOMEM: %s\nTest PASSED\n", strerror(errno));
exit(PTS_PASS);
     }

-----end----------------


Under POSIX standard, the expected errno should be ENOMEM

when the specific [addr+len] exceeds the bound of memory.


But mips returns EINVAL.

https://github.com/torvalds/linux/blob/bab5c80b211035739997ebd361a679fa85b39465/arch/mips/mm/mmap.c#L69

-------part of code-------

     if (flags & MAP_FIXED) {
         /* Even MAP_FIXED mappings must reside within TASK_SIZE */
         if (TASK_SIZE - len < addr)
             return -EINVAL;

-------end------------------


So, can we change EINVAL to ENOMEM to follow POSIX standard?


--Hongzhi