a1d9972e59
Perf uretprobe probes on GEP(Global Entry Point) which fails to record
all function calls via LEP(Local Entry Point). Fix that by probing on LEP.
Objdump:
00000000100005f0 <doit>:
100005f0: 02 10 40 3c lis r2,4098
100005f4: 00 7f 42 38 addi r2,r2,32512
100005f8: a6 02 08 7c mflr r0
100005fc: 10 00 01 f8 std r0,16(r1)
10000600: f8 ff e1 fb std r31,-8(r1)
Before applying patch:
$ cat /sys/kernel/debug/tracing/uprobe_events
r:probe_uprobe_test/doit /home/ravi/uprobe_test:0x00000000000005f0
After applying patch:
$ cat /sys/kernel/debug/tracing/uprobe_events
r:probe_uprobe_test/doit /home/ravi/uprobe_test:0x00000000000005f8
This is not the case with kretprobes because the kernel itself finds LEP
and probes on it.
Signed-off-by: Ravi Bangoria <ravi.bangoria@linux.vnet.ibm.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1475576865-6562-1-git-send-email-ravi.bangoria@linux.vnet.ibm.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
126 lines
3.0 KiB
C
126 lines
3.0 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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#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->uprobes && pev->point.retprobe) ||
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!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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#ifdef HAVE_LIBELF_SUPPORT
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void arch__post_process_probe_trace_events(struct perf_probe_event *pev,
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int ntevs)
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{
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struct probe_trace_event *tev;
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struct map *map;
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struct symbol *sym = NULL;
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struct rb_node *tmp;
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int i = 0;
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map = get_target_map(pev->target, pev->uprobes);
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if (!map || map__load(map) < 0)
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return;
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for (i = 0; i < ntevs; i++) {
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tev = &pev->tevs[i];
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map__for_each_symbol(map, sym, tmp) {
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if (map->unmap_ip(map, sym->start) == tev->point.address)
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arch__fix_tev_from_maps(pev, tev, map, sym);
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}
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}
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}
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#endif /* HAVE_LIBELF_SUPPORT */
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#endif
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