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| author | Adhemerval Zanella <adhemerval.zanella@linaro.org> | 2021-06-30 10:24:09 -0300 |
|---|---|---|
| committer | Adhemerval Zanella <adhemerval.zanella@linaro.org> | 2021-12-28 08:40:38 -0300 |
| commit | 063f9ba220f434c7f30dd65c4cff17c0c458a7cf (patch) | |
| tree | 00737e23f3b48e8d8dd338f16fc8cb98f0e6c051 /elf/dl-reloc.c | |
| parent | 8c0664e2b861fd3789602cc0b0b1922b0e20cb3a (diff) | |
| download | glibc-063f9ba220f434c7f30dd65c4cff17c0c458a7cf.tar.gz glibc-063f9ba220f434c7f30dd65c4cff17c0c458a7cf.tar.xz glibc-063f9ba220f434c7f30dd65c4cff17c0c458a7cf.zip | |
elf: Avoid unnecessary slowdown from profiling with audit (BZ#15533)
The rtld-audit interfaces introduces a slowdown due to enabling profiling instrumentation (as if LD_AUDIT implied LD_PROFILE). However, instrumenting is only necessary if one of audit libraries provides PLT callbacks (la_pltenter or la_pltexit symbols). Otherwise, the slowdown can be avoided. The following patch adjusts the logic that enables profiling to iterate over all audit modules and check if any of those provides a PLT hook. To keep la_symbind to work even without PLT callbacks, _dl_fixup now calls the audit callback if the modules implements it. Co-authored-by: Alexander Monakov <amonakov@ispras.ru> Checked on x86_64-linux-gnu, i686-linux-gnu, and aarch64-linux-gnu. Reviewed-by: Florian Weimer <fweimer@redhat.com>
Diffstat (limited to 'elf/dl-reloc.c')
| -rw-r--r-- | elf/dl-reloc.c | 20 |
1 files changed, 18 insertions, 2 deletions
diff --git a/elf/dl-reloc.c b/elf/dl-reloc.c index 0d5b727c64..98a24b3b9d 100644 --- a/elf/dl-reloc.c +++ b/elf/dl-reloc.c @@ -205,12 +205,28 @@ _dl_relocate_object (struct link_map *l, struct r_scope_elem *scope[], int skip_ifunc = reloc_mode & __RTLD_NOIFUNC; #ifdef SHARED + bool consider_symbind = false; /* If we are auditing, install the same handlers we need for profiling. */ if ((reloc_mode & __RTLD_AUDIT) == 0) - consider_profiling |= GLRO(dl_audit) != NULL; + { + struct audit_ifaces *afct = GLRO(dl_audit); + for (unsigned int cnt = 0; cnt < GLRO(dl_naudit); ++cnt) + { + /* Profiling is needed only if PLT hooks are provided. */ + if (afct->ARCH_LA_PLTENTER != NULL + || afct->ARCH_LA_PLTEXIT != NULL) + consider_profiling = 1; + if (afct->symbind != NULL) + consider_symbind = true; + + afct = afct->next; + } + } #elif defined PROF /* Never use dynamic linker profiling for gprof profiling code. */ # define consider_profiling 0 +#else +# define consider_symbind 0 #endif if (l->l_relocated) @@ -272,7 +288,7 @@ _dl_relocate_object (struct link_map *l, struct r_scope_elem *scope[], ELF_DYNAMIC_RELOCATE (l, scope, lazy, consider_profiling, skip_ifunc); #ifndef PROF - if (__glibc_unlikely (consider_profiling) + if ((consider_profiling || consider_symbind) && l->l_info[DT_PLTRELSZ] != NULL) { /* Allocate the array which will contain the already found |