On Sat, 23 Feb 2019 16:18:15 +0000
Peter Maydell <peter.mayd...@linaro.org> wrote:
> On Sat, 23 Feb 2019 at 16:05, Natanael Copa <nc...@alpinelinux.org> wrote:
> > I was thinking of something in the lines of:
> >
> > typedef volatile uint16_t __attribute__((__may_alias__)) volatile_uint16_t;
> > static inline int lduw_he_p(const void *ptr)
> > {
> > volatile_uint16_t r = *(volatile_uint16_t*)ptr;
> > return r;
> > }
>
> This won't correctly handle accesses with unaligned pointers,
> I'm afraid. We rely on these functions correctly working
> with pointers that are potentially unaligned.
Well, current code does not even handle access with aligned pointers,
depending on FORTIFY_SOURCE implementation.
My thinking here is that we depend on assumption that compiler will
remove the memcpy call, so maybe find other way to generate same
assembly, while still depend on compiler optimization.
I did some tests and compared the assembly output. The compiler will
generate same assembly if volatile is not used. The attribute
__may_alias__ does not seem to make any difference. So the following
function generates exactly same assembly:
static inline int lduw_he_p(const void *ptr)
{
uint16_t r = *(uint16_t*)ptr;
return r;
}
I created a script to compare on different Linux distros and
architectures. My conclusion is:
- Alpine fortify implementation is non-optimal, but technically
correct.
- `uint16_t r = *(uint16_t*)ptr;` generates the same assembly code,
regardless of fortify implementation, and is clearer on the
intention, than use of memcpy.
test.sh:
---[CUT HERE]---8<--------------------------------------------------
#!/bin/sh -x
cat > testcase.c <<EOF
#include <stdint.h>
#ifdef WITH_MEMCPY
#include <string.h>
static inline int lduw_he_p(const void *ptr)
{
uint16_t r;
memcpy(&r, ptr, sizeof(r));
return r;
}
#else
static inline int lduw_he_p(const void *ptr)
{
uint16_t r = *(uint16_t*)ptr;
return r;
}
#endif
int main(int argc, char *argv[])
{
void *p = argv;
int i;
p++; // make sure we are unaligned
i=lduw_he_p(p);
return i;
}
EOF
: ${CC:=gcc}
$CC --version
uname -m
for fortify in "-D_FORTIFY_SOURCE=2" "-U_FORTIFY_SOURCE"; do
for cflag in "-DWITH_MEMCPY" "-DWITHOUT_MEMCPY"; do
$CC $cflag $fortify $@ -o testcase$cflag testcase.c
gdb --batch -ex "disas ${func:-main}" ./testcase$cflag
done
done
---[CUT HERE]---8<--------------------------------------------------
Output on Alpine:
$ sh -x test.sh -O2
+ cat
+ : gcc
+ gcc --version
gcc (Alpine 8.2.0) 8.2.0
Copyright (C) 2018 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ uname -m
x86_64
+ gcc -DWITH_MEMCPY '-D_FORTIFY_SOURCE=2' -O2 -o testcase-DWITH_MEMCPY
testcase.c
+ gdb --batch -ex 'disas main' ./testcase-DWITH_MEMCPY
Dump of assembler code for function main:
0x0000000000001070 <+0>: sub $0x18,%rsp
0x0000000000001074 <+4>: mov %fs:0x28,%rax
0x000000000000107d <+13>: mov %rax,0x8(%rsp)
0x0000000000001082 <+18>: xor %eax,%eax
0x0000000000001084 <+20>: lea 0x6(%rsp),%rdi
0x0000000000001089 <+25>: lea 0x1(%rsi),%rax
0x000000000000108d <+29>: lea 0x2(%rdi),%rdx
0x0000000000001091 <+33>: cmp %rdx,%rax
0x0000000000001094 <+36>: jae 0x109b <main+43>
0x0000000000001096 <+38>: cmp %rdi,%rax
0x0000000000001099 <+41>: ja 0x10d0 <main+96>
0x000000000000109b <+43>: cmp %rdi,%rax
0x000000000000109e <+46>: jb 0x10c7 <main+87>
0x00000000000010a0 <+48>: mov $0x2,%edx
0x00000000000010a5 <+53>: mov %rax,%rsi
0x00000000000010a8 <+56>: callq 0x1020 <memcpy@plt>
0x00000000000010ad <+61>: movzwl 0x6(%rsp),%eax
0x00000000000010b2 <+66>: mov 0x8(%rsp),%rcx
0x00000000000010b7 <+71>: xor %fs:0x28,%rcx
0x00000000000010c0 <+80>: jne 0x10d2 <main+98>
0x00000000000010c2 <+82>: add $0x18,%rsp
0x00000000000010c6 <+86>: retq
0x00000000000010c7 <+87>: add $0x3,%rsi
0x00000000000010cb <+91>: cmp %rsi,%rdi
0x00000000000010ce <+94>: jae 0x10a0 <main+48>
0x00000000000010d0 <+96>: ud2
0x00000000000010d2 <+98>: callq 0x1030 <__stack_chk_fail@plt>
End of assembler dump.
+ gcc -DWITHOUT_MEMCPY '-D_FORTIFY_SOURCE=2' -O2 -o testcase-DWITHOUT_MEMCPY
testcase.c
+ gdb --batch -ex 'disas main' ./testcase-DWITHOUT_MEMCPY
Dump of assembler code for function main:
0x0000000000001050 <+0>: movzwl 0x1(%rsi),%eax
0x0000000000001054 <+4>: retq
End of assembler dump.
+ gcc -DWITH_MEMCPY -U_FORTIFY_SOURCE -O2 -o testcase-DWITH_MEMCPY testcase.c
+ gdb --batch -ex 'disas main' ./testcase-DWITH_MEMCPY
Dump of assembler code for function main:
0x0000000000001050 <+0>: movzwl 0x1(%rsi),%eax
0x0000000000001054 <+4>: retq
End of assembler dump.
+ gcc -DWITHOUT_MEMCPY -U_FORTIFY_SOURCE -O2 -o testcase-DWITHOUT_MEMCPY
testcase.c
+ gdb --batch -ex 'disas main' ./testcase-DWITHOUT_MEMCPY
Dump of assembler code for function main:
0x0000000000001050 <+0>: movzwl 0x1(%rsi),%eax
0x0000000000001054 <+4>: retq
End of assembler dump.
Output on Debian:
root@19c3f13c6023:~# sh -x test.sh -O2
+ cat
+ : gcc
+ gcc --version
gcc (Debian 6.3.0-18+deb9u1) 6.3.0 20170516
Copyright (C) 2016 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ uname -m
x86_64
+ gcc -DWITH_MEMCPY -D_FORTIFY_SOURCE=2 -O2 -o testcase-DWITH_MEMCPY testcase.c
+ gdb --batch -ex disas main ./testcase-DWITH_MEMCPY
Dump of assembler code for function main:
0x0000000000000530 <+0>: movzwl 0x1(%rsi),%eax
0x0000000000000534 <+4>: retq
End of assembler dump.
+ gcc -DWITHOUT_MEMCPY -D_FORTIFY_SOURCE=2 -O2 -o testcase-DWITHOUT_MEMCPY
testcase.c
+ gdb --batch -ex disas main ./testcase-DWITHOUT_MEMCPY
Dump of assembler code for function main:
0x0000000000000530 <+0>: movzwl 0x1(%rsi),%eax
0x0000000000000534 <+4>: retq
End of assembler dump.
+ gcc -DWITH_MEMCPY -U_FORTIFY_SOURCE -O2 -o testcase-DWITH_MEMCPY testcase.c
+ gdb --batch -ex disas main ./testcase-DWITH_MEMCPY
Dump of assembler code for function main:
0x0000000000000530 <+0>: movzwl 0x1(%rsi),%eax
0x0000000000000534 <+4>: retq
End of assembler dump.
+ gcc -DWITHOUT_MEMCPY -U_FORTIFY_SOURCE -O2 -o testcase-DWITHOUT_MEMCPY
testcase.c
+ gdb --batch -ex disas main ./testcase-DWITHOUT_MEMCPY
Dump of assembler code for function main:
0x0000000000000530 <+0>: movzwl 0x1(%rsi),%eax
0x0000000000000534 <+4>: retq
End of assembler dump.
root@19c3f13c6023:~#
Output on Fedora:
[root@ac68847f5bb1 ~]# sh -x test.sh -O2
+ cat
+ : gcc
+ gcc --version
gcc (GCC) 8.2.1 20181215 (Red Hat 8.2.1-6)
Copyright (C) 2018 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ uname -m
x86_64
+ for fortify in "-D_FORTIFY_SOURCE=2" "-U_FORTIFY_SOURCE"
+ for cflag in "-DWITH_MEMCPY" "-DWITHOUT_MEMCPY"
+ gcc -DWITH_MEMCPY -D_FORTIFY_SOURCE=2 -O2 -o testcase-DWITH_MEMCPY testcase.c
+ gdb --batch -ex 'disas main' ./testcase-DWITH_MEMCPY
Dump of assembler code for function main:
0x0000000000401020 <+0>: movzwl 0x1(%rsi),%eax
0x0000000000401024 <+4>: retq
End of assembler dump.
+ for cflag in "-DWITH_MEMCPY" "-DWITHOUT_MEMCPY"
+ gcc -DWITHOUT_MEMCPY -D_FORTIFY_SOURCE=2 -O2 -o testcase-DWITHOUT_MEMCPY
testcase.c
+ gdb --batch -ex 'disas main' ./testcase-DWITHOUT_MEMCPY
Dump of assembler code for function main:
0x0000000000401020 <+0>: movzwl 0x1(%rsi),%eax
0x0000000000401024 <+4>: retq
End of assembler dump.
+ for fortify in "-D_FORTIFY_SOURCE=2" "-U_FORTIFY_SOURCE"
+ for cflag in "-DWITH_MEMCPY" "-DWITHOUT_MEMCPY"
+ gcc -DWITH_MEMCPY -U_FORTIFY_SOURCE -O2 -o testcase-DWITH_MEMCPY testcase.c
+ gdb --batch -ex 'disas main' ./testcase-DWITH_MEMCPY
Dump of assembler code for function main:
0x0000000000401020 <+0>: movzwl 0x1(%rsi),%eax
0x0000000000401024 <+4>: retq
End of assembler dump.
+ for cflag in "-DWITH_MEMCPY" "-DWITHOUT_MEMCPY"
+ gcc -DWITHOUT_MEMCPY -U_FORTIFY_SOURCE -O2 -o testcase-DWITHOUT_MEMCPY
testcase.c
+ gdb --batch -ex 'disas main' ./testcase-DWITHOUT_MEMCPY
Dump of assembler code for function main:
0x0000000000401020 <+0>: movzwl 0x1(%rsi),%eax
0x0000000000401024 <+4>: retq
End of assembler dump.
Output on Alpine with clang:
$ CC=clang sh -x test.sh -O2
+ cat
+ : clang
+ clang --version
Alpine clang version 5.0.2 (tags/RELEASE_502/final) (based on LLVM 5.0.2)
Target: x86_64-alpine-linux-musl
Thread model: posix
InstalledDir: /usr/bin
+ uname -m
x86_64
+ clang -DWITH_MEMCPY '-D_FORTIFY_SOURCE=2' -O2 -o testcase-DWITH_MEMCPY
testcase.c
+ gdb --batch -ex 'disas main' ./testcase-DWITH_MEMCPY
Dump of assembler code for function main:
0x00000000000011a0 <+0>: movzwl 0x1(%rsi),%eax
0x00000000000011a4 <+4>: retq
End of assembler dump.
+ clang -DWITHOUT_MEMCPY '-D_FORTIFY_SOURCE=2' -O2 -o testcase-DWITHOUT_MEMCPY
testcase.c
+ gdb --batch -ex 'disas main' ./testcase-DWITHOUT_MEMCPY
Dump of assembler code for function main:
0x00000000000011a0 <+0>: movzwl 0x1(%rsi),%eax
0x00000000000011a4 <+4>: retq
End of assembler dump.
+ clang -DWITH_MEMCPY -U_FORTIFY_SOURCE -O2 -o testcase-DWITH_MEMCPY testcase.c
+ gdb --batch -ex 'disas main' ./testcase-DWITH_MEMCPY
Dump of assembler code for function main:
0x00000000000011a0 <+0>: movzwl 0x1(%rsi),%eax
0x00000000000011a4 <+4>: retq
End of assembler dump.
+ clang -DWITHOUT_MEMCPY -U_FORTIFY_SOURCE -O2 -o testcase-DWITHOUT_MEMCPY
testcase.c
+ gdb --batch -ex 'disas main' ./testcase-DWITHOUT_MEMCPY
Dump of assembler code for function main:
0x00000000000011a0 <+0>: movzwl 0x1(%rsi),%eax
0x00000000000011a4 <+4>: retq
End of assembler dump.
Output on alpine armv7:
$ sh -x test.sh -O2
+ cat
+ : gcc
+ gcc --version
gcc (Alpine 8.2.0) 8.2.0
Copyright (C) 2018 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ uname -m
armv8l
+ gcc -DWITH_MEMCPY '-D_FORTIFY_SOURCE=2' -O2 -o testcase-DWITH_MEMCPY
testcase.c
+ gdb --batch -ex 'disas main' ./testcase-DWITH_MEMCPY
Dump of assembler code for function main:
0x000003f8 <+0>: push {r4, r5, lr}
0x000003fa <+2>: sub sp, #12
0x000003fc <+4>: adds r3, r1, #1
0x000003fe <+6>: add r4, sp, #4
0x00000400 <+8>: cmp r3, r4
0x00000402 <+10>: add.w r0, sp, #2
0x00000406 <+14>: ite cs
0x00000408 <+16>: movcs r2, #0
0x0000040a <+18>: movcc r2, #1
0x0000040c <+20>: cmp r3, r0
0x0000040e <+22>: it ls
0x00000410 <+24>: movls r2, #0
0x00000412 <+26>: ldr r4, [pc, #52] ; (0x448 <main+80>)
0x00000414 <+28>: ldr r5, [pc, #52] ; (0x44c <main+84>)
0x00000416 <+30>: add r4, pc
0x00000418 <+32>: ldr r4, [r4, r5]
0x0000041a <+34>: ldr r5, [r4, #0]
0x0000041c <+36>: str r5, [sp, #4]
0x0000041e <+38>: cbnz r2, 0x442 <main+74>
0x00000420 <+40>: cmp r3, r0
0x00000422 <+42>: bcc.n 0x43c <main+68>
0x00000424 <+44>: mov r1, r3
0x00000426 <+46>: movs r2, #2
0x00000428 <+48>: blx 0x3b0 <memcpy@plt>
0x0000042c <+52>: ldr r2, [sp, #4]
0x0000042e <+54>: ldr r3, [r4, #0]
0x00000430 <+56>: ldrh.w r0, [sp, #2]
0x00000434 <+60>: cmp r2, r3
0x00000436 <+62>: bne.n 0x444 <main+76>
0x00000438 <+64>: add sp, #12
0x0000043a <+66>: pop {r4, r5, pc}
0x0000043c <+68>: adds r1, #3
0x0000043e <+70>: cmp r0, r1
0x00000440 <+72>: bcs.n 0x424 <main+44>
0x00000442 <+74>: udf #255 ; 0xff
0x00000444 <+76>: blx 0x3c8 <__stack_chk_fail@plt>
0x00000448 <+80>: muleq r1, lr, r11
0x0000044c <+84>: andeq r0, r0, r4, lsr #32
End of assembler dump.
+ gcc -DWITHOUT_MEMCPY '-D_FORTIFY_SOURCE=2' -O2 -o testcase-DWITHOUT_MEMCPY
testcase.c
+ gdb --batch -ex 'disas main' ./testcase-DWITHOUT_MEMCPY
Dump of assembler code for function main:
0x0000036c <+0>: ldrh.w r0, [r1, #1]
0x00000370 <+4>: bx lr
End of assembler dump.
+ gcc -DWITH_MEMCPY -U_FORTIFY_SOURCE -O2 -o testcase-DWITH_MEMCPY testcase.c
+ gdb --batch -ex 'disas main' ./testcase-DWITH_MEMCPY
Dump of assembler code for function main:
0x0000036c <+0>: ldrh.w r0, [r1, #1]
0x00000370 <+4>: bx lr
End of assembler dump.
+ gcc -DWITHOUT_MEMCPY -U_FORTIFY_SOURCE -O2 -o testcase-DWITHOUT_MEMCPY
testcase.c
+ gdb --batch -ex 'disas main' ./testcase-DWITHOUT_MEMCPY
Dump of assembler code for function main:
0x0000036c <+0>: ldrh.w r0, [r1, #1]
0x00000370 <+4>: bx lr
End of assembler dump.
Output on Alpine aarch64:
$ sh -x test.sh -O2
+ cat
+ : gcc
+ gcc --version
gcc (Alpine 8.2.0) 8.2.0
Copyright (C) 2018 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ uname -m
aarch64
+ gcc -DWITH_MEMCPY '-D_FORTIFY_SOURCE=2' -O2 -o testcase-DWITH_MEMCPY
testcase.c
+ gdb --batch -ex 'disas main' ./testcase-DWITH_MEMCPY
Dump of assembler code for function main:
0x00000000000006b0 <+0>: stp x29, x30, [sp, #-48]!
0x00000000000006b4 <+4>: add x2, x1, #0x1
0x00000000000006b8 <+8>: mov x29, sp
0x00000000000006bc <+12>: str x19, [sp, #16]
0x00000000000006c0 <+16>: adrp x19, 0x10000
0x00000000000006c4 <+20>: add x0, sp, #0x26
0x00000000000006c8 <+24>: ldr x3, [x19, #4024]
0x00000000000006cc <+28>: add x4, x0, #0x2
0x00000000000006d0 <+32>: cmp x4, x2
0x00000000000006d4 <+36>: ldr x4, [x3]
0x00000000000006d8 <+40>: str x4, [sp, #40]
0x00000000000006dc <+44>: mov x4, #0x0 // #0
0x00000000000006e0 <+48>: ccmp x0, x2, #0x2, hi // hi = pmore
0x00000000000006e4 <+52>: b.cc 0x72c <main+124> // b.lo, b.ul, b.last
0x00000000000006e8 <+56>: cmp x2, x0
0x00000000000006ec <+60>: b.cc 0x720 <main+112> // b.lo, b.ul, b.last
0x00000000000006f0 <+64>: mov x1, x2
0x00000000000006f4 <+68>: mov x2, #0x2 // #2
0x00000000000006f8 <+72>: bl 0x650 <memcpy@plt>
0x00000000000006fc <+76>: ldr x19, [x19, #4024]
0x0000000000000700 <+80>: ldrh w0, [sp, #38]
0x0000000000000704 <+84>: ldr x2, [sp, #40]
0x0000000000000708 <+88>: ldr x1, [x19]
0x000000000000070c <+92>: eor x1, x2, x1
0x0000000000000710 <+96>: cbnz x1, 0x730 <main+128>
0x0000000000000714 <+100>: ldr x19, [sp, #16]
0x0000000000000718 <+104>: ldp x29, x30, [sp], #48
0x000000000000071c <+108>: ret
0x0000000000000720 <+112>: add x1, x1, #0x3
0x0000000000000724 <+116>: cmp x0, x1
0x0000000000000728 <+120>: b.cs 0x6f0 <main+64> // b.hs, b.nlast
0x000000000000072c <+124>: brk #0x3e8
0x0000000000000730 <+128>: bl 0x670 <__stack_chk_fail@plt>
End of assembler dump.
+ gcc -DWITHOUT_MEMCPY '-D_FORTIFY_SOURCE=2' -O2 -o testcase-DWITHOUT_MEMCPY
testcase.c
+ gdb --batch -ex 'disas main' ./testcase-DWITHOUT_MEMCPY
Dump of assembler code for function main:
0x00000000000005e0 <+0>: ldurh w0, [x1, #1]
0x00000000000005e4 <+4>: ret
End of assembler dump.
+ gcc -DWITH_MEMCPY -U_FORTIFY_SOURCE -O2 -o testcase-DWITH_MEMCPY testcase.c
+ gdb --batch -ex 'disas main' ./testcase-DWITH_MEMCPY
Dump of assembler code for function main:
0x00000000000005e0 <+0>: ldurh w0, [x1, #1]
0x00000000000005e4 <+4>: ret
End of assembler dump.
+ gcc -DWITHOUT_MEMCPY -U_FORTIFY_SOURCE -O2 -o testcase-DWITHOUT_MEMCPY
testcase.c
+ gdb --batch -ex 'disas main' ./testcase-DWITHOUT_MEMCPY
Dump of assembler code for function main:
0x00000000000005e0 <+0>: ldurh w0, [x1, #1]
0x00000000000005e4 <+4>: ret
End of assembler dump.
Output on Alpine ppc64le:
$ sh -x test.sh -O2
+ cat
+ : gcc
+ gcc --version
gcc (Alpine 8.2.0) 8.2.0
Copyright (C) 2018 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ uname -m
ppc64le
+ gcc -DWITH_MEMCPY '-D_FORTIFY_SOURCE=2' -O2 -o testcase-DWITH_MEMCPY
testcase.c
+ gdb --batch -ex 'disas main' ./testcase-DWITH_MEMCPY
Dump of assembler code for function main:
0x00000000000005c0 <+0>: lhz r3,1(r4)
0x00000000000005c4 <+4>: blr
0x00000000000005c8 <+8>: .long 0x0
0x00000000000005cc <+12>: .long 0x0
0x00000000000005d0 <+16>: .long 0x0
End of assembler dump.
+ gcc -DWITHOUT_MEMCPY '-D_FORTIFY_SOURCE=2' -O2 -o testcase-DWITHOUT_MEMCPY
testcase.c
+ gdb --batch -ex 'disas main' ./testcase-DWITHOUT_MEMCPY
Dump of assembler code for function main:
0x00000000000005c0 <+0>: lhz r3,1(r4)
0x00000000000005c4 <+4>: blr
0x00000000000005c8 <+8>: .long 0x0
0x00000000000005cc <+12>: .long 0x0
0x00000000000005d0 <+16>: .long 0x0
End of assembler dump.
+ gcc -DWITH_MEMCPY -U_FORTIFY_SOURCE -O2 -o testcase-DWITH_MEMCPY testcase.c
+ gdb --batch -ex 'disas main' ./testcase-DWITH_MEMCPY
Dump of assembler code for function main:
0x00000000000005c0 <+0>: lhz r3,1(r4)
0x00000000000005c4 <+4>: blr
0x00000000000005c8 <+8>: .long 0x0
0x00000000000005cc <+12>: .long 0x0
0x00000000000005d0 <+16>: .long 0x0
End of assembler dump.
+ gcc -DWITHOUT_MEMCPY -U_FORTIFY_SOURCE -O2 -o testcase-DWITHOUT_MEMCPY
testcase.c
+ gdb --batch -ex 'disas main' ./testcase-DWITHOUT_MEMCPY
Dump of assembler code for function main:
0x00000000000005c0 <+0>: lhz r3,1(r4)
0x00000000000005c4 <+4>: blr
0x00000000000005c8 <+8>: .long 0x0
0x00000000000005cc <+12>: .long 0x0
0x00000000000005d0 <+16>: .long 0x0
End of assembler dump.
Output on Alpine s390x:
$ sh -x test.sh -O2
+ cat
+ : gcc
+ gcc --version
gcc (Alpine 8.2.0) 8.2.0
Copyright (C) 2018 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ uname -m
s390x
+ gcc -DWITH_MEMCPY '-D_FORTIFY_SOURCE=2' -O2 -o testcase-DWITH_MEMCPY
testcase.c
+ gdb --batch -ex 'disas main' ./testcase-DWITH_MEMCPY
Dump of assembler code for function main:
0x00000000000006b0 <+0>: stmg %r14,%r15,112(%r15)
0x00000000000006b6 <+6>: ear %r1,%a0
0x00000000000006ba <+10>: lay %r15,-176(%r15)
0x00000000000006c0 <+16>: sllg %r1,%r1,32
0x00000000000006c6 <+22>: ear %r1,%a1
0x00000000000006ca <+26>: la %r2,166(%r15)
0x00000000000006ce <+30>: mvc 168(8,%r15),40(%r1)
0x00000000000006d4 <+36>: la %r1,1(%r3)
0x00000000000006d8 <+40>: clgr %r1,%r2
0x00000000000006dc <+44>: jle 0x6e8 <main+56>
0x00000000000006e0 <+48>: la %r4,168(%r15)
0x00000000000006e4 <+52>: clgrtl %r1,%r4
0x00000000000006e8 <+56>: clgr %r1,%r2
0x00000000000006ec <+60>: jl 0x724 <main+116>
0x00000000000006f0 <+64>: lgr %r3,%r1
0x00000000000006f4 <+68>: lghi %r4,2
0x00000000000006f8 <+72>: brasl %r14,0x5f0 <memcpy@plt>
0x00000000000006fe <+78>: ear %r1,%a0
0x0000000000000702 <+82>: llgh %r2,166(%r15)
0x0000000000000708 <+88>: sllg %r1,%r1,32
0x000000000000070e <+94>: ear %r1,%a1
0x0000000000000712 <+98>: clc 168(8,%r15),40(%r1)
0x0000000000000718 <+104>: jne 0x730 <main+128>
0x000000000000071c <+108>: lmg %r14,%r15,288(%r15)
0x0000000000000722 <+114>: br %r14
0x0000000000000724 <+116>: la %r3,3(%r3)
0x0000000000000728 <+120>: clgrtl %r2,%r3
0x000000000000072c <+124>: j 0x6f0 <main+64>
0x0000000000000730 <+128>: brasl %r14,0x630 <__stack_chk_fail@plt>
End of assembler dump.
+ gcc -DWITHOUT_MEMCPY '-D_FORTIFY_SOURCE=2' -O2 -o testcase-DWITHOUT_MEMCPY
testcase.c
+ gdb --batch -ex 'disas main' ./testcase-DWITHOUT_MEMCPY
Dump of assembler code for function main:
0x00000000000005f8 <+0>: llgh %r2,1(%r3)
0x00000000000005fe <+6>: br %r14
End of assembler dump.
+ gcc -DWITH_MEMCPY -U_FORTIFY_SOURCE -O2 -o testcase-DWITH_MEMCPY testcase.c
+ gdb --batch -ex 'disas main' ./testcase-DWITH_MEMCPY
Dump of assembler code for function main:
0x00000000000005f8 <+0>: llgh %r2,1(%r3)
0x00000000000005fe <+6>: br %r14
End of assembler dump.
+ gcc -DWITHOUT_MEMCPY -U_FORTIFY_SOURCE -O2 -o testcase-DWITHOUT_MEMCPY
testcase.c
+ gdb --batch -ex 'disas main' ./testcase-DWITHOUT_MEMCPY
Dump of assembler code for function main:
0x00000000000005f8 <+0>: llgh %r2,1(%r3)
0x00000000000005fe <+6>: br %r14
End of assembler dump.
