Re: [PATCH] tools/perf: Fix powerpc gap between kernel end and module start

[Arnaldo Carvalho de Melo <acme@kernel.org>]

Em Tue, Feb 02, 2021 at 04:02:36PM +0530, Athira Rajeev escreveu:
> 
> 
>     On 18-Jan-2021, at 3:51 PM, kajoljain <kjain@linux.ibm.com> wrote:
> 
> 
> 
>     On 1/12/21 3:08 PM, Jiri Olsa wrote:
> 
>         On Mon, Dec 28, 2020 at 09:14:14PM -0500, Athira Rajeev wrote:
> 
>         SNIP
> 
> 
>             c000000002799370 b backtrace_flag
>             c000000002799378 B radix_tree_node_cachep
>             c000000002799380 B __bss_stop
>             c0000000027a0000 B _end
>             c008000003890000 t icmp_checkentry      [ip_tables]
>             c008000003890038 t ipt_alloc_initial_table      [ip_tables]
>             c008000003890468 T ipt_do_table [ip_tables]
>             c008000003890de8 T ipt_unregister_table_pre_exit        [ip_tables]
>             ...
> 
>             Perf calls function symbols__fixup_end() which sets the end of
>             symbol
>             to 0xc008000003890000, which is the next address and this is the
>             start
>             address of first module (icmp_checkentry in above) which will make
>             the
>             huge symbol size of 0x80000010f0000.
> 
>             After symbols__fixup_end:
>             symbols__fixup_end: sym->name: _end, sym->start:
>             0xc0000000027a0000,
>             sym->end: 0xc008000003890000
> 
>             On powerpc, kernel text segment is located at 0xc000000000000000
>             whereas the modules are located at very high memory addresses,
>             0xc00800000xxxxxxx. Since the gap between end of kernel text
>             segment
>             and beginning of first module's address is high, histogram
>             allocation
>             using calloc fails.
> 
>             Fix this by detecting the kernel's last symbol and limiting
>             the range of last kernel symbol to pagesize.
> 
> 
>     Patch looks good to me.
> 
>     Tested-By: Kajol Jain<kjain@linux.ibm.com>
> 
>     Thanks,
>     Kajol Jain
> 
> 
>             Signed-off-by: Athira Rajeev<atrajeev@linux.vnet.ibm.com>
> 
> 
>         I can't test, but since the same approach works for arm and s390,
>         this also looks ok
> 
>         Acked-by: Jiri Olsa <jolsa@redhat.com>
> 
>         thanks,
>         jirka
> 
> 
> Hi Arnaldo,
> 
> Can you please help review this patch and merge if this looks good..

Thanks, collected the Tested-by from Kajol and the Acked-by from Jiri
and applied to my local tree for testing, then up to my perf/core
branch.

- Arnaldo