From: Masami Hiramatsu Date: Wed, 30 Sep 2015 16:41:33 +0000 (+0900) Subject: perf probe: Show correct source lines of probes on kmodules X-Git-Url: http://git.lede-project.org./?a=commitdiff_plain;h=9b239a12bc872f212cefbaee4d028c838abe6ff3;p=openwrt%2Fstaging%2Fblogic.git perf probe: Show correct source lines of probes on kmodules Perf probe always failed to find appropriate line numbers because of failing to find .text start address offset from debuginfo. e.g. ---- # ./perf probe -m pcspkr pcspkr_event:5 Added new events: probe:pcspkr_event (on pcspkr_event:5 in pcspkr) probe:pcspkr_event_1 (on pcspkr_event:5 in pcspkr) You can now use it in all perf tools, such as: perf record -e probe:pcspkr_event_1 -aR sleep 1 # ./perf probe -l Failed to find debug information for address ffffffffa031f006 Failed to find debug information for address ffffffffa031f016 probe:pcspkr_event (on pcspkr_event+6 in pcspkr) probe:pcspkr_event_1 (on pcspkr_event+22 in pcspkr) ---- This fixes the above issue as below. 1. Get the relative address of the symbol in .text by using map->start. 2. Adjust the address by adding the offset of .text section in the kernel module binary. With this fix, perf probe -l shows lines correctly. ---- # ./perf probe -l probe:pcspkr_event (on pcspkr_event:5@drivers/input/misc/pcspkr.c in pcspkr) probe:pcspkr_event_1 (on pcspkr_event:5@drivers/input/misc/pcspkr.c in pcspkr) ---- Reported-by: Arnaldo Carvalho de Melo Signed-off-by: Masami Hiramatsu Tested-by: Arnaldo Carvalho de Melo Cc: Jiri Olsa Cc: Namhyung Kim Cc: Wang Nan Link: http://lkml.kernel.org/r/20150930164132.3733.24643.stgit@localhost.localdomain Signed-off-by: Arnaldo Carvalho de Melo --- diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c index 5d68f68797a9..65be284823d5 100644 --- a/tools/perf/util/probe-event.c +++ b/tools/perf/util/probe-event.c @@ -137,7 +137,8 @@ static struct ref_reloc_sym *kernel_get_ref_reloc_sym(void) return kmap->ref_reloc_sym; } -static u64 kernel_get_symbol_address_by_name(const char *name, bool reloc) +static int kernel_get_symbol_address_by_name(const char *name, u64 *addr, + bool reloc, bool reladdr) { struct ref_reloc_sym *reloc_sym; struct symbol *sym; @@ -146,12 +147,14 @@ static u64 kernel_get_symbol_address_by_name(const char *name, bool reloc) /* ref_reloc_sym is just a label. Need a special fix*/ reloc_sym = kernel_get_ref_reloc_sym(); if (reloc_sym && strcmp(name, reloc_sym->name) == 0) - return (reloc) ? reloc_sym->addr : reloc_sym->unrelocated_addr; + *addr = (reloc) ? reloc_sym->addr : reloc_sym->unrelocated_addr; else { sym = __find_kernel_function_by_name(name, &map); - if (sym) - return map->unmap_ip(map, sym->start) - - ((reloc) ? 0 : map->reloc); + if (!sym) + return -ENOENT; + *addr = map->unmap_ip(map, sym->start) - + ((reloc) ? 0 : map->reloc) - + ((reladdr) ? map->start : 0); } return 0; } @@ -245,12 +248,14 @@ static void clear_probe_trace_events(struct probe_trace_event *tevs, int ntevs) static bool kprobe_blacklist__listed(unsigned long address); static bool kprobe_warn_out_range(const char *symbol, unsigned long address) { - u64 etext_addr; + u64 etext_addr = 0; + int ret; /* Get the address of _etext for checking non-probable text symbol */ - etext_addr = kernel_get_symbol_address_by_name("_etext", false); + ret = kernel_get_symbol_address_by_name("_etext", &etext_addr, + false, false); - if (etext_addr != 0 && etext_addr < address) + if (ret == 0 && etext_addr < address) pr_warning("%s is out of .text, skip it.\n", symbol); else if (kprobe_blacklist__listed(address)) pr_warning("%s is blacklisted function, skip it.\n", symbol); @@ -517,8 +522,10 @@ static int find_perf_probe_point_from_dwarf(struct probe_trace_point *tp, goto error; addr += stext; } else if (tp->symbol) { - addr = kernel_get_symbol_address_by_name(tp->symbol, false); - if (addr == 0) + /* If the module is given, this returns relative address */ + ret = kernel_get_symbol_address_by_name(tp->symbol, &addr, + false, !!tp->module); + if (ret != 0) goto error; addr += tp->offset; } @@ -1884,8 +1891,12 @@ static int find_perf_probe_point_from_map(struct probe_trace_point *tp, goto out; sym = map__find_symbol(map, addr, NULL); } else { - if (tp->symbol) - addr = kernel_get_symbol_address_by_name(tp->symbol, true); + if (tp->symbol && !addr) { + ret = kernel_get_symbol_address_by_name(tp->symbol, + &addr, true, false); + if (ret < 0) + goto out; + } if (addr) { addr += tp->offset; sym = __find_kernel_function(addr, &map); diff --git a/tools/perf/util/probe-finder.c b/tools/perf/util/probe-finder.c index 35f905f4f34c..f0708ffd5e07 100644 --- a/tools/perf/util/probe-finder.c +++ b/tools/perf/util/probe-finder.c @@ -1402,6 +1402,41 @@ int debuginfo__find_available_vars_at(struct debuginfo *dbg, return (ret < 0) ? ret : af.nvls; } +/* For the kernel module, we need a special code to get a DIE */ +static int debuginfo__get_text_offset(struct debuginfo *dbg, Dwarf_Addr *offs) +{ + int n, i; + Elf32_Word shndx; + Elf_Scn *scn; + Elf *elf; + GElf_Shdr mem, *shdr; + const char *p; + + elf = dwfl_module_getelf(dbg->mod, &dbg->bias); + if (!elf) + return -EINVAL; + + /* Get the number of relocations */ + n = dwfl_module_relocations(dbg->mod); + if (n < 0) + return -ENOENT; + /* Search the relocation related .text section */ + for (i = 0; i < n; i++) { + p = dwfl_module_relocation_info(dbg->mod, i, &shndx); + if (strcmp(p, ".text") == 0) { + /* OK, get the section header */ + scn = elf_getscn(elf, shndx); + if (!scn) + return -ENOENT; + shdr = gelf_getshdr(scn, &mem); + if (!shdr) + return -ENOENT; + *offs = shdr->sh_addr; + } + } + return 0; +} + /* Reverse search */ int debuginfo__find_probe_point(struct debuginfo *dbg, unsigned long addr, struct perf_probe_point *ppt) @@ -1410,9 +1445,16 @@ int debuginfo__find_probe_point(struct debuginfo *dbg, unsigned long addr, Dwarf_Addr _addr = 0, baseaddr = 0; const char *fname = NULL, *func = NULL, *basefunc = NULL, *tmp; int baseline = 0, lineno = 0, ret = 0; + bool reloc = false; +retry: /* Find cu die */ if (!dwarf_addrdie(dbg->dbg, (Dwarf_Addr)addr, &cudie)) { + if (!reloc && debuginfo__get_text_offset(dbg, &baseaddr) == 0) { + addr += baseaddr; + reloc = true; + goto retry; + } pr_warning("Failed to find debug information for address %lx\n", addr); ret = -EINVAL;