Subject: Re: [PATCH v3 2/7] perf probe/ppc: Fix symbol fixup issues due to ELF type

From: Arnaldo Carvalho de Melo <[email-masked]>
Date: Tue, 28 Apr 2015 10:48:28 -0300

Em Tue, Apr 28, 2015 at 05:35:35PM +0530, Naveen N. Rao escreveu:
> If using the symbol table, symbol addresses are not being fixed up
> properly, resulting in probes being placed at wrong addresses:
> 
>   # perf probe do_fork
>   Added new event:
>     probe:do_fork        (on do_fork)
> 
>   You can now use it in all perf tools, such as:
> 
> 	  perf record -e probe:do_fork -aR sleep 1
> 
>   # cat /sys/kernel/debug/tracing/kprobe_events
>   p:probe/do_fork _text+635952
>   # printf "%x" 635952
>   9b430
>   # grep do_fork /boot/System.map
>   c0000000000ab430 T .do_fork
> 
> Fix by checking for ELF type ET_DYN used by ppc64 kernels.
> 
> Signed-off-by: Naveen N. Rao <[email-masked]>
> Reviewed-by: Srikar Dronamraju <[email-masked]>

This one looks great, Are you keeping the Reviewed by from a previous
patch? Or has Srikar reissued it? Srikar?

- Arnaldo
> ---
> Changes:
> - Introduce arch helper to limit change to ppc.
> 
>  tools/perf/arch/powerpc/util/Build          |  1 +
>  tools/perf/arch/powerpc/util/sym-handling.c | 19 +++++++++++++++++++
>  tools/perf/util/symbol-elf.c                |  8 ++++++--
>  tools/perf/util/symbol.h                    |  4 ++++
>  4 files changed, 30 insertions(+), 2 deletions(-)
>  create mode 100644 tools/perf/arch/powerpc/util/sym-handling.c
> 
> diff --git a/tools/perf/arch/powerpc/util/Build b/tools/perf/arch/powerpc/util/Build
> index 0af6e9b..7b8b0d1 100644
> --- a/tools/perf/arch/powerpc/util/Build
> +++ b/tools/perf/arch/powerpc/util/Build
> @@ -1,4 +1,5 @@
>  libperf-y += header.o
> +libperf-y += sym-handling.o
>  
>  libperf-$(CONFIG_DWARF) += dwarf-regs.o
>  libperf-$(CONFIG_DWARF) += skip-callchain-idx.o
> diff --git a/tools/perf/arch/powerpc/util/sym-handling.c b/tools/perf/arch/powerpc/util/sym-handling.c
> new file mode 100644
> index 0000000..c9de001
> --- /dev/null
> +++ b/tools/perf/arch/powerpc/util/sym-handling.c
> @@ -0,0 +1,19 @@
> +/*
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License, version 2, as
> + * published by the Free Software Foundation.
> + *
> + * Copyright (C) 2015 Naveen N. Rao, IBM Corporation
> + */
> +
> +#include "debug.h"
> +#include "symbol.h"
> +
> +#ifdef HAVE_LIBELF_SUPPORT
> +bool elf__needs_adjust_symbols(GElf_Ehdr ehdr)
> +{
> +	return ehdr.e_type == ET_EXEC ||
> +	       ehdr.e_type == ET_REL ||
> +	       ehdr.e_type == ET_DYN;
> +}
> +#endif
> diff --git a/tools/perf/util/symbol-elf.c b/tools/perf/util/symbol-elf.c
> index ac09c60..7f5d237 100644
> --- a/tools/perf/util/symbol-elf.c
> +++ b/tools/perf/util/symbol-elf.c
> @@ -630,6 +630,11 @@ void symsrc__destroy(struct symsrc *ss)
>  	close(ss->fd);
>  }
>  
> +bool __weak elf__needs_adjust_symbols(GElf_Ehdr ehdr)
> +{
> +	return ehdr.e_type == ET_EXEC || ehdr.e_type == ET_REL;
> +}
> +
>  int symsrc__init(struct symsrc *ss, struct dso *dso, const char *name,
>  		 enum dso_binary_type type)
>  {
> @@ -712,8 +717,7 @@ int symsrc__init(struct symsrc *ss, struct dso *dso, const char *name,
>  						     ".gnu.prelink_undo",
>  						     NULL) != NULL);
>  	} else {
> -		ss->adjust_symbols = ehdr.e_type == ET_EXEC ||
> -				     ehdr.e_type == ET_REL;
> +		ss->adjust_symbols = elf__needs_adjust_symbols(ehdr);
>  	}
>  
>  	ss->name   = strdup(name);
> diff --git a/tools/perf/util/symbol.h b/tools/perf/util/symbol.h
> index 0956150..8cb0af4 100644
> --- a/tools/perf/util/symbol.h
> +++ b/tools/perf/util/symbol.h
> @@ -303,4 +303,8 @@ int setup_list(struct strlist **list, const char *list_str,
>  int setup_intlist(struct intlist **list, const char *list_str,
>  		  const char *list_name);
>  
> +#ifdef HAVE_LIBELF_SUPPORT
> +bool elf__needs_adjust_symbols(GElf_Ehdr ehdr);
> +#endif
> +
>  #endif /* __PERF_SYMBOL */
> -- 
> 2.3.5