Messages in this thread | | | Date | Thu, 30 Jan 2014 11:34:38 +0200 | From | Adrian Hunter <> | Subject | Re: [PATCH V2 9/9] perf buildid-cache: Check relocation when checking for existing kcore |
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On 29/01/14 21:14, Arnaldo Carvalho de Melo wrote: > Em Wed, Jan 29, 2014 at 04:14:44PM +0200, Adrian Hunter escreveu: >> perf buildid-cache does not make another >> copy of kcore if the buildid and modules >> match an existing copy. That does not > > Humm, what is the problem? Having the ref reloc symbol we can fix things > up, no? I.e. just using map->reloc the old kcore copy should be ok to > use, no need to replace the kcore copy in the cache. Or am I missing > something?
The current implementation works on the basis that kcore matches the perf data recorded. This is just a fix for that.
I am afraid it is that way because it meets my needs. I did not think of allowing for relocation because I need to be able to walk the code. Relocation was one of the things I was trying to avoid.
For me making a copy of kcore is far superior because it can be made to have the jump labels mostly the right way around too. e.g. run a dummy perf record while making the copy.
> > - Arnaldo > >> take into account the possibility that >> the kernel has been relocated. Extend >> the check to check if the reference >> relocation symbol matches too, otherwise >> do make a copy. >> >> Signed-off-by: Adrian Hunter <adrian.hunter@intel.com> >> --- >> tools/perf/builtin-buildid-cache.c | 33 +++++++++++++++++++++++++++++---- >> 1 file changed, 29 insertions(+), 4 deletions(-) >> >> diff --git a/tools/perf/builtin-buildid-cache.c b/tools/perf/builtin-buildid-cache.c >> index cfede86..b22dbb1 100644 >> --- a/tools/perf/builtin-buildid-cache.c >> +++ b/tools/perf/builtin-buildid-cache.c >> @@ -63,11 +63,35 @@ static int build_id_cache__kcore_dir(char *dir, size_t sz) >> return 0; >> } >> >> +static bool same_kallsyms_reloc(const char *from_dir, char *to_dir) >> +{ >> + char from[PATH_MAX]; >> + char to[PATH_MAX]; >> + const char *name; >> + u64 addr1 = 0, addr2 = 0; >> + int i; >> + >> + scnprintf(from, sizeof(from), "%s/kallsyms", from_dir); >> + scnprintf(to, sizeof(to), "%s/kallsyms", to_dir); >> + >> + for (i = 0; (name = ref_reloc_sym_names[i]) != NULL; i++) { >> + addr1 = kallsyms__get_function_start(from, name); >> + if (addr1) >> + break; >> + } >> + >> + if (name) >> + addr2 = kallsyms__get_function_start(to, name); >> + >> + return addr1 == addr2; >> +} >> + >> static int build_id_cache__kcore_existing(const char *from_dir, char *to_dir, >> size_t to_dir_sz) >> { >> char from[PATH_MAX]; >> char to[PATH_MAX]; >> + char to_subdir[PATH_MAX]; >> struct dirent *dent; >> int ret = -1; >> DIR *d; >> @@ -86,10 +110,11 @@ static int build_id_cache__kcore_existing(const char *from_dir, char *to_dir, >> continue; >> scnprintf(to, sizeof(to), "%s/%s/modules", to_dir, >> dent->d_name); >> - if (!compare_proc_modules(from, to)) { >> - scnprintf(to, sizeof(to), "%s/%s", to_dir, >> - dent->d_name); >> - strlcpy(to_dir, to, to_dir_sz); >> + scnprintf(to_subdir, sizeof(to_subdir), "%s/%s", >> + to_dir, dent->d_name); >> + if (!compare_proc_modules(from, to) && >> + same_kallsyms_reloc(from_dir, to_subdir)) { >> + strlcpy(to_dir, to_subdir, to_dir_sz); >> ret = 0; >> break; >> } >> -- >> 1.7.11.7 > >
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