Bug 1889516

This bug was originally filled in:  
  https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97060

let's track it for fedora, because the affected gcc is now in fedora 32.

---
We are missing expected declaration tag - DW_AT_declaration : 1 for function
in debug info data.

The problem we see is:

 - fs/init.c calls vfs_getattr function
 - vfs_getattr is defined outside the fs/init.c
 - once compiled, debug info data for vfs_getattr should contain declaration
   tag - DW_AT_declaration : 1, but it's missing

gcc version: gcc (GCC) 10.2.1 20200826 (Red Hat 10.2.1-3)

Unfortunately the issue can be so far reproduced only inside container,
I tried to narrow it down to single fs/init.o object.

Following steps create fs/init.o binary in kernel tree within the container:

# podman image pull registry.gitlab.com/cki-project/containers/builder-rawhide:latest
# podman image list
# podman run -it <ID> /bin/bash
# git clone https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git --depth 1
# curl https://xci32.lab.eng.rdu2.redhat.com/cki-project/cki-pipeline/-/jobs/974002/artifacts/raw/artifacts/kernel-bpf-next-x86_64-cd04b04de119a222c83936f7e9dbd46a650cb688.config -o bpf-next/.config
# cd bpf-next/

# make oldconfig # might need some ENTERs
# make fs/ -j

# gcc -Wp,-MMD,fs/.init.o.d -nostdinc -isystem /usr/lib/gcc/x86_64-redhat-linux/10/include -I./arch/x86/include -I./arch/x86/include/generated  -I./include -I./arch/x86/include/uapi -I./arch/x86/include/generated/uapi -I./include/uapi -I./include/generated/uapi -include ./include/linux/kconfig.h -include ./include/linux/compiler_types.h -D__KERNEL__ -Wall -Wundef -Werror=strict-prototypes -Wno-trigraphs -fno-strict-aliasing -fno-common -fshort-wchar -fno-PIE -Werror=implicit-function-declaration -Werror=implicit-int -Wno-format-security -std=gnu89 -mno-sse -mno-mmx -mno-sse2 -mno-3dnow -mno-avx -m64 -falign-jumps=1 -falign-loops=1 -mno-80387 -mno-fp-ret-in-387 -mpreferred-stack-boundary=3 -mskip-rax-setup -mtune=generic -mno-red-zone -mcmodel=kernel -Wno-sign-compare -fno-asynchronous-unwind-tables -mindirect-branch=thunk-extern -mindirect-branch-register -fno-jump-tables -fno-delete-null-pointer-checks -Wno-frame-address -Wno-format-truncation -Wno-format-overflow -Wno-address-of-packed-member -O2 -fno-allow-store-data-races -Wframe-larger-than=2048 -fstack-protector -Wno-unused-but-set-variable -Wimplicit-fallthrough -Wno-unused-const-variable -fno-var-tracking-assignments -g -pg -mrecord-mcount -mfentry -DCC_USING_FENTRY -flive-patching=inline-clone -Wdeclaration-after-statement -Wvla -Wno-pointer-sign -Wno-stringop-truncation -Wno-zero-length-bounds -Wno-array-bounds -Wno-stringop-overflow -Wno-restrict -Wno-maybe-uninitialized -fno-strict-overflow -fno-merge-all-constants -fmerge-constants -fno-stack-check -fconserve-stack -Werror=date-time -Werror=incompatible-pointer-types -Werror=designated-init -fmacro-prefix-map=./= -fcf-protection=none -Wno-packed-not-aligned    -DKBUILD_MODFILE='"fs/init"' -DKBUILD_BASENAME='"init"' -DKBUILD_MODNAME='"init"' -c -o fs/init.o fs/init.c

# readelf --debug fs/init.o
...
 <1><9145>: Abbrev Number: 46 (DW_TAG_subprogram)
    <9146>   DW_AT_external    : 1
    <9146>   DW_AT_name        : (indirect string, offset: 0x531c): vfs_getattr
    <914a>   DW_AT_decl_file   : 7
    <914b>   DW_AT_decl_line   : 3148
    <914d>   DW_AT_decl_column : 12
    <914e>   DW_AT_prototyped  : 1
    <914e>   DW_AT_type        : <0xa9>
    <9152>   DW_AT_sibling     : <0x916b>
 <2><9156>: Abbrev Number: 3 (DW_TAG_formal_parameter)
    <9157>   DW_AT_type        : <0x3573>
 <2><915b>: Abbrev Number: 3 (DW_TAG_formal_parameter)
    <915c>   DW_AT_type        : <0x893a>
 <2><9160>: Abbrev Number: 3 (DW_TAG_formal_parameter)
    <9161>   DW_AT_type        : <0x111>
 <2><9165>: Abbrev Number: 3 (DW_TAG_formal_parameter)
    <9166>   DW_AT_type        : <0x4c>


When we link the final kernel binary the debug info data contains multiple records for vfs_getattr,
and neither has 'declaration' tag and it confuses pahole tool that uses this data to get function
records and skips declarations.

The problem is for more functions, vfs_getattr is just one example.