0b3c2264ae
ppc64le functions have a Global Entry Point (GEP) and a Local Entry Point (LEP). While placing a probe, we always prefer the LEP since it catches function calls through both the GEP and the LEP. In order to do this, we fixup the function entry points during elf symbol table lookup to point to the LEPs. This works, but breaks 'perf test kallsyms' since the symbols loaded from the symbol table (pointing to the LEP) do not match the symbols in kallsyms. To fix this, we do not adjust all the symbols during symbol table load. Instead, we note down st_other in a newly introduced arch-specific member of perf symbol structure, and later use this to adjust the probe trace point. Reported-by: Michael Ellerman <mpe@ellerman.id.au> Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com> Acked-by: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Acked-by: Balbir Singh <bsingharora@gmail.com> Cc: Mark Wielaard <mjw@redhat.com> Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Thiago Jung Bauermann <bauerman@linux.vnet.ibm.com> Cc: linuxppc-dev@lists.ozlabs.org Link: http://lkml.kernel.org/r/6be7c2b17e370100c2f79dd444509df7929bdd3e.1460451721.git.naveen.n.rao@linux.vnet.ibm.com Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
104 lines
2.5 KiB
C
104 lines
2.5 KiB
C
/*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License, version 2, as
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* published by the Free Software Foundation.
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*
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* Copyright (C) 2015 Naveen N. Rao, IBM Corporation
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*/
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#include "debug.h"
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#include "symbol.h"
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#include "map.h"
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#include "probe-event.h"
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#ifdef HAVE_LIBELF_SUPPORT
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bool elf__needs_adjust_symbols(GElf_Ehdr ehdr)
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{
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return ehdr.e_type == ET_EXEC ||
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ehdr.e_type == ET_REL ||
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ehdr.e_type == ET_DYN;
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}
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#endif
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#if !defined(_CALL_ELF) || _CALL_ELF != 2
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int arch__choose_best_symbol(struct symbol *syma,
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struct symbol *symb __maybe_unused)
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{
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char *sym = syma->name;
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/* Skip over any initial dot */
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if (*sym == '.')
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sym++;
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/* Avoid "SyS" kernel syscall aliases */
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if (strlen(sym) >= 3 && !strncmp(sym, "SyS", 3))
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return SYMBOL_B;
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if (strlen(sym) >= 10 && !strncmp(sym, "compat_SyS", 10))
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return SYMBOL_B;
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return SYMBOL_A;
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}
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/* Allow matching against dot variants */
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int arch__compare_symbol_names(const char *namea, const char *nameb)
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{
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/* Skip over initial dot */
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if (*namea == '.')
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namea++;
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if (*nameb == '.')
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nameb++;
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return strcmp(namea, nameb);
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}
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#endif
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#if defined(_CALL_ELF) && _CALL_ELF == 2
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bool arch__prefers_symtab(void)
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{
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return true;
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}
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#ifdef HAVE_LIBELF_SUPPORT
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void arch__sym_update(struct symbol *s, GElf_Sym *sym)
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{
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s->arch_sym = sym->st_other;
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}
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#endif
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#define PPC64LE_LEP_OFFSET 8
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void arch__fix_tev_from_maps(struct perf_probe_event *pev,
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struct probe_trace_event *tev, struct map *map,
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struct symbol *sym)
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{
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int lep_offset;
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/*
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* When probing at a function entry point, we normally always want the
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* LEP since that catches calls to the function through both the GEP and
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* the LEP. Hence, we would like to probe at an offset of 8 bytes if
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* the user only specified the function entry.
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*
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* However, if the user specifies an offset, we fall back to using the
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* GEP since all userspace applications (objdump/readelf) show function
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* disassembly with offsets from the GEP.
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*
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* In addition, we shouldn't specify an offset for kretprobes.
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*/
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if (pev->point.offset || pev->point.retprobe || !map || !sym)
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return;
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lep_offset = PPC64_LOCAL_ENTRY_OFFSET(sym->arch_sym);
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if (map->dso->symtab_type == DSO_BINARY_TYPE__KALLSYMS)
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tev->point.offset += PPC64LE_LEP_OFFSET;
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else if (lep_offset) {
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if (pev->uprobes)
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tev->point.address += lep_offset;
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else
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tev->point.offset += lep_offset;
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}
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}
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#endif
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