Re: [PATCH 4/6] sysroot: delay adding sysroot path to module name in case of non absolute executable

[David Smith <dsmith at redhat dot com>]

Sigh. I had just made your patch changes by hand, and somehow I
reversed the last one. Commit a71465872 fixes that, and adds a small
cosmetic fix to path_remove_sysroot().

On Mon, Mar 19, 2018 at 8:54 AM, David Smith <dsmith@redhat.com> wrote:
> Checked in as commit 4ffecddf5. Thanks.
>
> On Mon, Mar 5, 2018 at 11:37 AM, Victor Kamensky <kamensky@cisco.com> wrote:
>> Current stap code adds sysroot prematurely for probes that specify
>> non absolute path name, i.e like "foo", so when find_executable called
>> it receives full path as <sysroot>/foo and find_executable does not
>> search PATH while applying sysroot.
>>
>> Fix delays adding sysroot till path inside of sysroot is searched first.
>>
>> Also fix missing sysroot addition in glob expansion case.
>>
>> Note in case of sysroot cross compile environment it is highly recommended
>> to pass --sysenv=PATH=xxx:yyy and --sysenv=LD_LIBRARY_PATH=zzz to use
>> search path appropriate for target system, rather then host setting on
>> system where stap runs.
>>
>> Here are steps how to reproduce the issue. Note <sysroot> is produced by
>> yocto poky build.
>>
>> [kamensky@coreos-lnx2 tests]$ cat mkdir2.stp
>> probe process("mkdir.coreutils").function("*").call {
>>   printf ("%s -> %s\n", thread_indent(1), ppfunc())
>> }
>> probe process("mkdir.coreutils").function("*").return {
>>   printf ("%s <- %s\n", thread_indent(-1), ppfunc())
>> }
>> [kamensky@coreos-lnx2 tests]$ ls /home/wd8/yocto/20180128/build_x86_64/tmp/work/intel_corei7_64-poky-linux/kdevel-console-devel-image/1.0-r0/rootfs/bin/mkdir.coreutils
>> /home/wd8/yocto/20180128/build_x86_64/tmp/work/intel_corei7_64-poky-linux/kdevel-console-devel-image/1.0-r0/rootfs/bin/mkdir.coreutils
>> [kamensky@coreos-lnx2 tests]$ ls /home/wd8/yocto/20180128/build_x86_64/tmp/work/intel_corei7_64-poky-linux/kdevel-console-devel-image/1.0-r0/rootfs/bin/.debug/mkdir.coreutils
>> /home/wd8/yocto/20180128/build_x86_64/tmp/work/intel_corei7_64-poky-linux/kdevel-console-devel-image/1.0-r0/rootfs/bin/.debug/mkdir.coreutils
>> [kamensky@coreos-lnx2 tests]$ /home/wd8/systemtap/20180208_2/packages/bin/stap --sysroot=/home/wd8/yocto/20180128/build_x86_64/tmp/work/intel_corei7_64-poky-linux/kdevel-console-devel-image/1.0-r0/rootfs -a x86_64 -r 4.9.78-yocto-standard -B CROSS_COMPILE=x86_64-poky-linux- --sysenv=PATH=/usr/bin:/bin:/usr/sbin:/sbin --sysenv=LD_LIBRARY_PATH=/lib:/usr/lib -v -p4 -m mkdir2 mkdir2.stp
>> Pass 1: parsed user script and 480 library scripts using 230196virt/93536res/5448shr/88624data kb, in 330usr/30sys/364real ms.
>> semantic error: resolution failed in DWARF builder
>>
>> semantic error: while resolving probe point: identifier 'process' at mkdir2.stp:1:7
>>         source: probe process("mkdir.coreutils").function("*").call {
>>                       ^
>>
>> semantic error: no match
>>
>> semantic error: resolution failed in DWARF builder
>>
>> semantic error: while resolving probe point: identifier 'process' at :4:7
>>         source: probe process("mkdir.coreutils").function("*").return {
>>                       ^
>>
>> semantic error: no match
>>
>> Pass 2: analyzed script: 0 probes, 0 functions, 0 embeds, 0 globals using 233496virt/97032res/5520shr/91924data kb, in 20usr/0sys/25real ms.
>> Pass 2: analysis failed.  [man error::pass2]
>>
>> Under strace it shows that stap is not trying to lookup mkdir.coreutils
>> inside of sysroot accoring to PATH that was passed through --sysenv:
>>
>> 16048 openat(AT_FDCWD, "/home/wd8/yocto/20180128/build_x86_64/tmp/work/intel_corei7_64-poky-linux/kdevel-console-devel-image/1.0-r0/rootfs/mkdir.coreutils", O_RDONLY) = -1 ENOENT (No such file or directory)
>>
>> i.e it rather just tries <sysroot> + "mkdir.coreutils"
>>
>> After the fix veried that that above example able to find mkdir.coreutils
>> executable in sysroot and corresponding symbols
>>
>> Also verified that glob matching in sysroot works too for example for
>> this test case:
>>
>> [kamensky@coreos-lnx2 tests]$ cat mkdir3.stp
>> probe process("/bin/mkdi*").function("*").call {
>>   printf ("%s -> %s\n", thread_indent(1), ppfunc())
>> }
>> probe process("/bin/mkdi*").function("*").return {
>>   printf ("%s <- %s\n", thread_indent(-1), ppfunc())
>> }
>>
>> Signed-off-by: Victor Kamensky <kamensky@cisco.com>
>> ---
>>  tapsets.cxx | 8 ++++----
>>  1 file changed, 4 insertions(+), 4 deletions(-)
>>
>> diff --git a/tapsets.cxx b/tapsets.cxx
>> index 28296b14f..c664df0f9 100644
>> --- a/tapsets.cxx
>> +++ b/tapsets.cxx
>> @@ -746,7 +746,7 @@ base_query::base_query(dwflpp & dw, literal_map_t const & params):
>>                pid_val = 0;
>>                get_string_param(params, TOK_PROCESS, module_val);
>>              }
>> -          module_val = find_executable (module_val, "", sess.sysenv);
>> +          module_val = find_executable (module_val, sess.sysroot, sess.sysenv);
>>            if (!is_fully_resolved(module_val, "", sess.sysenv))
>>              throw SEMANTIC_ERROR(_F("cannot find executable '%s'",
>>                                      module_val.to_string().c_str()));
>> @@ -8293,7 +8293,6 @@ dwarf_builder::build(systemtap_session & sess,
>>              }
>>            else
>>              {
>> -              module_name = (string)sess.sysroot + (string)module_name;
>>                filled_parameters[TOK_PROCESS] = new literal_string(module_name);
>>              }
>>          }
>> @@ -8327,7 +8326,7 @@ dwarf_builder::build(systemtap_session & sess,
>>            assert (lit);
>>
>>            // Evaluate glob here, and call derive_probes recursively with each match.
>> -          const auto& globs = glob_executable (module_name);
>> +          const auto& globs = glob_executable (sess.sysroot + string(module_name));
>>            unsigned results_pre = finished_results.size();
>>            for (auto it = globs.begin(); it != globs.end(); ++it)
>>              {
>> @@ -8418,7 +8417,8 @@ dwarf_builder::build(systemtap_session & sess,
>>
>>        // PR13338: unquote glob results
>>        module_name = unescape_glob_chars (module_name);
>> -      user_path = find_executable (module_name, "", sess.sysenv); // canonicalize it
>> +      user_path = find_executable (module_name, sess.sysroot,
>> +                                  sess.sysenv); // canonicalize it
>>        if (!is_fully_resolved(user_path, "", sess.sysenv))
>>          throw SEMANTIC_ERROR(_F("cannot find executable '%s'",
>>                                  user_path.to_string().c_str()));
>> --
>> 2.14.3
>>
>
>
>
> --
> David Smith
> Associate Manager
> Red Hat



-- 
David Smith
Associate Manager
Red Hat