Assembler messages: Error: .err encountered

[Andy Whitcroft]

$ gcc -Wp,-MD,arch/arm64/kernel/.psci.o.d -nostdinc -isystem /usr/lib/gcc/aarch64-linux-gnu/4.9/include -I/usr/src/linux-headers-lbm- -I/home/apw/ubuntu-vivid2/arch/arm64/include -Iarch/arm64/include/generated -I/home/apw/ubuntu-vivid2/include -Iinclude -I/home/apw/ubuntu-vivid2/arch/arm64/include/uapi -Iarch/arm64/include/generated/uapi -I/home/apw/ubuntu-vivid2/include/uapi -Iinclude/generated/uapi -include /home/apw/ubuntu-vivid2/include/linux/kconfig.h -Iubuntu/include -I/home/apw/ubuntu-vivid2/ubuntu/include -I/home/apw/ubuntu-vivid2/arch/arm64/kernel -Iarch/arm64/kernel -D__KERNEL__ -mlittle-endian -Wall -Wundef -Wstrict-prototypes -Wno-trigraphs -fno-strict-aliasing -fno-common -Werror-implicit-function-declaration -Wno-format-security -std=gnu89 -mgeneral-regs-only -fno-delete-null-pointer-checks -O2 --param=allow-store-data-races=0 -Wframe-larger-than=1024 -fstack-protector -Wno-unused-but-set-variable -fno-omit-frame-pointer -fno-optimize-sibling-calls -fno-var-tracking-assignments -g -gdwarf-4 -pg -fno-inline-functions-called-once -Wdeclaration-after-statement -Wno-pointer-sign -fno-strict-overflow -fconserve-stack -Werror=implicit-int -Werror=strict-prototypes -Werror=date-time -DCC_HAVE_ASM_GOTO -D"KBUILD_STR(s)=#s" -D"KBUILD_BASENAME=KBUILD_STR(psci)" -D"KBUILD_MODNAME=KBUILD_STR(psci)" -c -o arch/arm64/kernel/.tmp_psci.o /home/apw/ubuntu-vivid2/arch/arm64/kernel/psci.c
/tmp/ccEayz7S.s: Assembler messages:
/tmp/ccEayz7S.s:41: Error: .err encountered
/tmp/ccEayz7S.s:42: Error: .err encountered
/tmp/ccEayz7S.s:43: Error: .err encountered
/tmp/ccEayz7S.s:101: Error: .err encountered
/tmp/ccEayz7S.s:102: Error: .err encountered
/tmp/ccEayz7S.s:103: Error: .err encountered

[Andy Whitcroft (apw)]

psci.E represents the command above with the -c switch to -E.

[Matthias Klose (doko)]

-pg triggers it

$ gcc -c -g -O2 -pg psci.i
/tmp/ccBtw9zv.s: Assembler messages:
/tmp/ccBtw9zv.s:41: Error: .err encountered
/tmp/ccBtw9zv.s:42: Error: .err encountered
/tmp/ccBtw9zv.s:43: Error: .err encountered
/tmp/ccBtw9zv.s:100: Error: .err encountered
/tmp/ccBtw9zv.s:101: Error: .err encountered
/tmp/ccBtw9zv.s:102: Error: .err encountered

[Matthias Klose (doko)]

user error, see https://bugs.linaro.org/show_bug.cgi?id=1115

[Brad Figg (brad-figg)]

This bug is missing log files that will aid in diagnosing the problem. From a terminal window please run:

apport-collect 1414002

and then change the status of the bug to 'Confirmed'.

If, due to the nature of the issue you have encountered, you are unable to run this command, please add a comment stating that fact and change the bug status to 'Confirmed'.

This change has been made by an automated script, maintained by the Ubuntu Kernel Team.

[Andy Whitcroft (apw)]

Ok. So this is actually a bad piece of assembly triggering, a piece deliberatly placed in the code to catch the compiler not placing things in the registers we expected. Basically we are assuming the ABI placement. When mcount (-pg) is enabled, the compiler adds additional code "inside" the function and all bets are off. The approved mechanism is to inform the compiler of your constraints on the variables using the below form:

int foo (int _arg)
{
    register int arg asm("r0") = _arg;
    [...]
}

[Launchpad Janitor (janitor)]

This bug was fixed in the package linux - 3.18.0-11.12

---------------
linux (3.18.0-11.12) vivid; urgency=low

  [ Leann Ogasawara ]

  * Release Tracking Bug
    - LP: #1414085

  [ Andy Whitcroft ]

  * SAUCE: arm64 -- psci tell the compiler which registers we are needing
    values in
    - LP: #1414002
 -- Leann Ogasawara <email address hidden> Fri, 23 Jan 2015 09:10:09 -0800