Commit 60fbb3e4 authored by Adrian Hunter's avatar Adrian Hunter Committed by Arnaldo Carvalho de Melo
Browse files

perf symbols: Allow for .plt without header 



A static executable can have a .plt due to the presence of IFUNCs.  In
that case the .plt does not have a header. Check for whether there is a
header by comparing the number of entries to the number of relocation
entries.

Reviewed-by: default avatarNamhyung Kim <namhyung@kernel.org>
Signed-off-by: default avatarAdrian Hunter <adrian.hunter@intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Link: https://lore.kernel.org/r/20230131131625.6964-7-adrian.hunter@intel.com


Signed-off-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
parent b7dbc0be

tools/perf/util/symbol-elf.c

+15 −1
Original line number Diff line number Diff line
@@ -489,6 +489,7 @@ int dso__synthesize_plt_symbols(struct dso *dso, struct symsrc *ss) 
	Elf *elf;

	int nr = 0, err = -1;

	struct rel_info ri = { .is_rela = false };

	bool lazy_plt;



	elf = ss->elf;

	ehdr = ss->ehdr;
@@ -523,8 +524,10 @@ int dso__synthesize_plt_symbols(struct dso *dso, struct symsrc *ss) 
		plt_sym->end = plt_sym->start + shdr_plt.sh_size;

		/* Use .plt.sec offset */

		plt_offset = plt_sec_shdr.sh_offset;

		lazy_plt = false;

	} else {

		plt_offset = shdr_plt.sh_offset + plt_header_size;

		plt_offset = shdr_plt.sh_offset;

		lazy_plt = true;

	}



	scn_dynsym = ss->dynsym;
@@ -577,6 +580,17 @@ int dso__synthesize_plt_symbols(struct dso *dso, struct symsrc *ss) 


	ri.is_rela = shdr_rel_plt.sh_type == SHT_RELA;



	if (lazy_plt) {

		/*

		 * Assume a .plt with the same number of entries as the number

		 * of relocation entries is not lazy and does not have a header.

		 */

		if (ri.nr_entries * plt_entry_size == shdr_plt.sh_size)

			dso__delete_symbol(dso, plt_sym);

		else

			plt_offset += plt_header_size;

	}



	/*

	 * x86 doesn't insert IFUNC relocations in .plt order, so sort to get

	 * back in order.