re: port-i386/56280: Many asan tests are failing on i386

[matthew green <mrg%eterna.com.au@localhost>]

The following reply was made to PR port-i386/56280; it has been noted by GNATS.

From: matthew green <mrg%eterna.com.au@localhost>
To: gnats-bugs%netbsd.org@localhost
Cc: port-i386-maintainer%netbsd.org@localhost, gnats-admin%netbsd.org@localhost,
    netbsd-bugs%netbsd.org@localhost
Subject: re: port-i386/56280: Many asan tests are failing on i386
Date: Mon, 28 Jun 2021 18:07:26 +1000

 this is odd.  the test tries to write beyond the length
 of an array, but it gets a segv while trying to load
 stuff from the shadow i guess:
 
 Dump of assembler code for function foo:
    0x08048a08 <+0>:       push   %ebp
    0x08048a09 <+1>:       mov    %esp,%ebp
    0x08048a0b <+3>:       push   %ebx
    0x08048a0c <+4>:       sub    $0x4,%esp
    0x08048a0f <+7>:       mov    0x8(%ebp),%eax
    0x08048a12 <+10>:      shl    $0x2,%eax
    0x08048a15 <+13>:      add    $0x8049180,%eax
    0x08048a1a <+18>:      mov    %eax,%edx
    0x08048a1c <+20>:      shr    $0x3,%edx
    0x08048a1f <+23>:      add    $0x20000000,%edx
 => 0x08048a25 <+29>:      movzbl (%edx),%edx
 
 so the segv occurs before asan is able to detect the
 the write and complain normally.
 
 this occurs on amd64 with cc -m32 too.  the minimal
 version of the test is:
 
 #include <stdio.h>
 int arr[5] = {-1};
 void foo(int index) { arr[index] = 0; }
 int main(int argc, char **argv) {foo(argc + 5); printf("CHECK\n"); return 0;}
 
 and compile with -fsanitize=address on i386, or with
 -m32 on amd64.
 
 
 .mrg.