linux-kernel - Re: [PATCH] perf symbols: Don't try to find a vmlinux file when looking for kernel modules

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Date:   Mon, 2 Mar 2020 20:20:08 +0100
From:   Jiri Olsa <jolsa@...hat.com>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:     Jiri Olsa <jolsa@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Kim Phillips <kim.phillips@....com>,
        Michael Petlan <mpetlan@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Ravi Bangoria <ravi.bangoria@...ux.ibm.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] perf symbols: Don't try to find a vmlinux file when
 looking for kernel modules

On Mon, Mar 02, 2020 at 04:10:07PM -0300, Arnaldo Carvalho de Melo wrote:
> The dso->kernel value is now set to everything that is in
> machine->kmaps, but that was being used to decide if vmlinux lookup is
> needed, which ended up making that lookup be made for kernel modules,
> that now have dso->kernel set, leading to these kinds of warnings when
> running on a machine with compressed kernel modules, like fedora:31:
>     
>   [root@...e ~]# perf record -F 10000 -a sleep 2
>   [ perf record: Woken up 1 times to write data ]
>   lzma: fopen failed on vmlinux: 'No such file or directory'
>   lzma: fopen failed on /boot/vmlinux: 'No such file or directory'
>   lzma: fopen failed on /boot/vmlinux-5.5.5-200.fc31.x86_64: 'No such file or directory'
>   lzma: fopen failed on /usr/lib/debug/boot/vmlinux-5.5.5-200.fc31.x86_64: 'No such file or directory'
>   lzma: fopen failed on /lib/modules/5.5.5-200.fc31.x86_64/build/vmlinux: 'No such file or directory'
>   lzma: fopen failed on vmlinux: 'No such file or directory'
>   lzma: fopen failed on /boot/vmlinux: 'No such file or directory'
>   lzma: fopen failed on /boot/vmlinux-5.5.5-200.fc31.x86_64: 'No such file or directory'
>   lzma: fopen failed on /usr/lib/debug/boot/vmlinux-5.5.5-200.fc31.x86_64: 'No such file or directory'
>   lzma: fopen failed on /lib/modules/5.5.5-200.fc31.x86_64/build/vmlinux: 'No such file or directory'
>   lzma: fopen failed on vmlinux: 'No such file or directory'
>   lzma: fopen failed on /boot/vmlinux: 'No such file or directory'
>   lzma: fopen failed on /boot/vmlinux-5.5.5-200.fc31.x86_64: 'No such file or directory'
>   lzma: fopen failed on /usr/lib/debug/boot/vmlinux-5.5.5-200.fc31.x86_64: 'No such file or directory'
>   lzma: fopen failed on /lib/modules/5.5.5-200.fc31.x86_64/build/vmlinux: 'No such file or directory'
>   lzma: fopen failed on vmlinux: 'No such file or directory'
>   lzma: fopen failed on /boot/vmlinux: 'No such file or directory'
>   lzma: fopen failed on /boot/vmlinux-5.5.5-200.fc31.x86_64: 'No such file or directory'
>   lzma: fopen failed on /usr/lib/debug/boot/vmlinux-5.5.5-200.fc31.x86_64: 'No such file or directory'
>   lzma: fopen failed on /lib/modules/5.5.5-200.fc31.x86_64/build/vmlinux: 'No such file or directory'
>   lzma: fopen failed on vmlinux: 'No such file or directory'
>   lzma: fopen failed on /boot/vmlinux: 'No such file or directory'
>   lzma: fopen failed on /boot/vmlinux-5.5.5-200.fc31.x86_64: 'No such file or directory'
>   lzma: fopen failed on /usr/lib/debug/boot/vmlinux-5.5.5-200.fc31.x86_64: 'No such file or directory'
>   lzma: fopen failed on /lib/modules/5.5.5-200.fc31.x86_64/build/vmlinux: 'No such file or directory'
>   [ perf record: Captured and wrote 1.024 MB perf.data (1366 samples) ]
>   [root@...e ~]#
> 
> This happens when collecting the buildid, when we find samples for
> kernel modules, fix it by checking if the looked up DSO is a kernel
> module by other means.

cool, I just saw your other email and was going to check on it ;-)
ging to check on this and review

jirka

> 
> Fixes: 02213cec64bb ("perf maps: Mark module DSOs with kernel type")
> Cc: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
> Cc: Jiri Olsa <jolsa@...nel.org>
> Cc: Kim Phillips <kim.phillips@....com>
> Cc: Michael Petlan <mpetlan@...hat.com>
> Cc: Namhyung Kim <namhyung@...nel.org>
> Cc: Ravi Bangoria <ravi.bangoria@...ux.ibm.com>
> Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
> 
> ---
> 
> diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
> index 1077013d8ce2..26bc6a0096ce 100644
> --- a/tools/perf/util/symbol.c
> +++ b/tools/perf/util/symbol.c
> @@ -1622,7 +1622,12 @@ int dso__load(struct dso *dso, struct map *map)
>  		goto out;
>  	}
>  
> -	if (dso->kernel) {
> +	kmod = dso->symtab_type == DSO_BINARY_TYPE__SYSTEM_PATH_KMODULE ||
> +		dso->symtab_type == DSO_BINARY_TYPE__SYSTEM_PATH_KMODULE_COMP ||
> +		dso->symtab_type == DSO_BINARY_TYPE__GUEST_KMODULE ||
> +		dso->symtab_type == DSO_BINARY_TYPE__GUEST_KMODULE_COMP;
> +
> +	if (dso->kernel && !kmod) {
>  		if (dso->kernel == DSO_TYPE_KERNEL)
>  			ret = dso__load_kernel_sym(dso, map);
>  		else if (dso->kernel == DSO_TYPE_GUEST_KERNEL)
> @@ -1650,12 +1655,6 @@ int dso__load(struct dso *dso, struct map *map)
>  	if (!name)
>  		goto out;
>  
> -	kmod = dso->symtab_type == DSO_BINARY_TYPE__SYSTEM_PATH_KMODULE ||
> -		dso->symtab_type == DSO_BINARY_TYPE__SYSTEM_PATH_KMODULE_COMP ||
> -		dso->symtab_type == DSO_BINARY_TYPE__GUEST_KMODULE ||
> -		dso->symtab_type == DSO_BINARY_TYPE__GUEST_KMODULE_COMP;
> -
> -
>  	/*
>  	 * Read the build id if possible. This is required for
>  	 * DSO_BINARY_TYPE__BUILDID_DEBUGINFO to work
>