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Date: Fri, 20 Apr 2018 09:11:05 +0900 From: Namhyung Kim <namhyung@...nel.org> To: Kim Phillips <kim.phillips@....com> Cc: Ard Biesheuvel <ard.biesheuvel@...aro.org>, Will Deacon <will.deacon@....com>, Arnaldo Carvalho de Melo <acme@...nel.org>, Jiri Olsa <jolsa@...hat.com>, Ingo Molnar <mingo@...nel.org>, Peter Zijlstra <a.p.zijlstra@...llo.nl>, Jiri Olsa <jolsa@...nel.org>, LKML <linux-kernel@...r.kernel.org>, kernel-team@....com Subject: Re: [PATCH] perf tools: set kernel end address properly On Thu, Apr 19, 2018 at 06:33:13PM -0500, Kim Phillips wrote: > On Thu, 19 Apr 2018 11:54:24 +0900 > Namhyung Kim <namhyung@...nel.org> wrote: > > > On Wed, Apr 18, 2018 at 07:37:59PM -0500, Kim Phillips wrote: > > > diff --git a/tools/perf/arch/arm64/util/sym-handling.c b/tools/perf/arch/arm64/util/sym-handling.c > > > index 0051b1ee8450..5c4a2e208bbc 100644 > > > --- a/tools/perf/arch/arm64/util/sym-handling.c > > > +++ b/tools/perf/arch/arm64/util/sym-handling.c > > > @@ -20,3 +20,16 @@ bool elf__needs_adjust_symbols(GElf_Ehdr ehdr) > > > ehdr.e_type == ET_DYN; > > > } > > > #endif > > > + > > > +const char *arch__normalize_symbol_name(const char *name) > > > +{ > > > + /* > > > + * arm64 kernels compensating for a CPU erratum can put up a > > > + * module_emit_adrp_veneer in place of a module_emit_plt_entry > > > + */ > > > + if (name && strlen(name) >= 23 && > > > + !strncmp(name, "module_emit_adrp_veneer", 23)) > > > + return "module_emit_plt_entry"; > > > + > > > + return name; > > > +} > > > > I don't know it's always preferable or just for the test. It it's the > > latter it may be better to move it to the test code. > > AFACT, the veneer is a moniker and doesn't technically exist, and > shouldn't be being looked-up. Both chunks of this diff are needed to > pass perf test 1: this chunk above is because in > arch__normalize_symbol_name(), we squash the perf test 1's "<veneer> > not in *kallsyms*" problem, and in the below chunk, we prevent it > coming up when the test code iterates over the *vmlinux* symbols. I.e. > we need to prevent the veneer from coming up in both kallsyms *and* > vmlinux. > > > > diff --git a/tools/perf/tests/vmlinux-kallsyms.c b/tools/perf/tests/vmlinux-kallsyms.c > > > index 1e5adb65632a..07064e76947d 100644 > > > --- a/tools/perf/tests/vmlinux-kallsyms.c > > > +++ b/tools/perf/tests/vmlinux-kallsyms.c > > > @@ -163,6 +163,29 @@ int test__vmlinux_matches_kallsyms(struct test *test __maybe_unused, int subtest > > > > > > continue; > > > } > > > + } else if (pair) { > > > + s64 skew = mem_start - UM(pair->start); > > > + struct map *kmap = map_groups__find(&kallsyms.kmaps, type, mem_start); > > > + struct map *vmap = map_groups__find(&vmlinux.kmaps, type, mem_start); > > > + > > > + /* > > > + * arm64 kernels compensating for a CPU erratum can put up a > > > + * module_emit_adrp_veneer in place of a module_emit_plt_entry > > > + */ > > > + if (llabs(skew) < page_size) > > > > It seems that we needs to check it's the ARM64 at least. If it's a > > OK. > > > rare case we might need to add more paranoid checks. > > It's certainly rare: Adding the authors of the veneer to cc for > comments: > > Will, Ard, how probable are veneer-style symbols such as the > one introduced in commit a257e0257 "arm64/kernel: don't ban ADRP to > work around Cortex-A53 erratum #843419" to happen again in the future? > > I would have thought WARNing on within-a-pagesize would be OK, > Namhyung. Are you suggesting checking instead for a hardcoded veneer > symbol string? Anything to prevent false-negatives (possibly on other archs). Thanks, Namhyung > > Thanks, > > Kim > > > > + { > > > + pr_debug("NO ERR FOR SKEW %ld: %#" PRIx64 ": diff start addr v: %s k: %#" PRIx64 " %s\n", > > > + skew, mem_start, sym->name, UM(pair->start), pair->name); > > > + continue; > > > + } > > > + > > > + pr_debug("ERR : %#" PRIx64 ": diff start addr v: %s k: %#" PRIx64 " %s\n", > > > + mem_start, sym->name, UM(pair->start), pair->name); > > > + > > > + if (kmap && vmap) { > > > + pr_debug(" : map v: %s k: %s\n", > > > + vmap->dso->short_name, kmap->dso->short_name); > > > + } > > > } else > > > pr_debug("ERR : %#" PRIx64 ": %s not on kallsyms\n", > > > mem_start, sym->name);
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