Re: git: 64ba1f4cf3a6 - main - rtld: Implement LD_SHOW_AUXV
Date: Sat, 13 Nov 2021 17:57:56 UTC
Jess > On 13 Nov 2021, at 17:54, Jessica Clarke <jrtc27@FreeBSD.org> wrote: > > On 13 Nov 2021, at 17:33, Konstantin Belousov <kib@FreeBSD.org> wrote: >> >> The branch main has been updated by kib: >> >> URL: https://cgit.FreeBSD.org/src/commit/?id=64ba1f4cf3a6847a1dacf4bab0409d94898fa168 >> >> commit 64ba1f4cf3a6847a1dacf4bab0409d94898fa168 >> Author: Konstantin Belousov <kib@FreeBSD.org> >> AuthorDate: 2021-11-13 01:18:13 +0000 >> Commit: Konstantin Belousov <kib@FreeBSD.org> >> CommitDate: 2021-11-13 17:33:13 +0000 >> >> rtld: Implement LD_SHOW_AUXV >> >> It dumps auxv as seen by interpreter, right before starting any user >> code. >> >> Copied from: glibc >> Sponsored by: The FreeBSD Foundation >> MFC after: 1 week >> --- >> libexec/rtld-elf/rtld.1 | 7 +++++- >> libexec/rtld-elf/rtld.c | 67 +++++++++++++++++++++++++++++++++++++++++++++++++ >> 2 files changed, 73 insertions(+), 1 deletion(-) >> >> diff --git a/libexec/rtld-elf/rtld.1 b/libexec/rtld-elf/rtld.1 >> index 187dc105667a..66aa2bdabd17 100644 >> --- a/libexec/rtld-elf/rtld.1 >> +++ b/libexec/rtld-elf/rtld.1 >> @@ -28,7 +28,7 @@ >> .\" >> .\" $FreeBSD$ >> .\" >> -.Dd August 15, 2021 >> +.Dd November 13, 2021 >> .Dt RTLD 1 >> .Os >> .Sh NAME >> @@ -309,6 +309,11 @@ will process the filtee dependencies of the loaded objects immediately, >> instead of postponing it until required. >> Normally, the filtees are opened at the time of the first symbol resolution >> from the filter object. >> +.It Ev LD_SHOW_AUXV >> +If set, causes >> +.Nm >> +to dump content of the aux vector to standard output, before passing >> +control to any user code. >> .El >> .Sh DIRECT EXECUTION MODE >> .Nm >> diff --git a/libexec/rtld-elf/rtld.c b/libexec/rtld-elf/rtld.c >> index c173c5a6e22e..0475134b0d96 100644 >> --- a/libexec/rtld-elf/rtld.c >> +++ b/libexec/rtld-elf/rtld.c >> @@ -104,6 +104,7 @@ static Obj_Entry *dlopen_object(const char *name, int fd, Obj_Entry *refobj, >> static Obj_Entry *do_load_object(int, const char *, char *, struct stat *, int); >> static int do_search_info(const Obj_Entry *obj, int, struct dl_serinfo *); >> static bool donelist_check(DoneList *, const Obj_Entry *); >> +static void dump_auxv(Elf_Auxinfo **aux_info); >> static void errmsg_restore(struct dlerror_save *); >> static struct dlerror_save *errmsg_save(void); >> static void *fill_search_info(const char *, size_t, void *); >> @@ -364,6 +365,7 @@ enum { >> LD_TRACE_LOADED_OBJECTS_FMT1, >> LD_TRACE_LOADED_OBJECTS_FMT2, >> LD_TRACE_LOADED_OBJECTS_ALL, >> + LD_SHOW_AUXV, >> }; >> >> struct ld_env_var_desc { >> @@ -396,6 +398,7 @@ static struct ld_env_var_desc ld_env_vars[] = { >> LD_ENV_DESC(TRACE_LOADED_OBJECTS_FMT1, false), >> LD_ENV_DESC(TRACE_LOADED_OBJECTS_FMT2, false), >> LD_ENV_DESC(TRACE_LOADED_OBJECTS_ALL, false), >> + LD_ENV_DESC(SHOW_AUXV, false), >> }; >> >> static const char * >> @@ -857,6 +860,9 @@ _rtld(Elf_Addr *sp, func_ptr_type *exit_proc, Obj_Entry **objp) >> if (rtld_verify_versions(&list_main) == -1 && !ld_tracing) >> rtld_die(); >> >> + if (ld_get_env_var(LD_SHOW_AUXV) != NULL) >> + dump_auxv(aux_info); >> + >> if (ld_tracing) { /* We're done */ >> trace_loaded_objects(obj_main); >> exit(0); >> @@ -6058,6 +6064,67 @@ print_usage(const char *argv0) >> " <args> Arguments to the executed process\n", argv0); >> } >> >> +#define AUXFMT(at, xfmt) [at] = { .name = #at, .fmt = xfmt } >> +static const struct auxfmt { >> + const char *name; >> + const char *fmt; >> +} auxfmts[] = { >> + AUXFMT(AT_NULL, NULL), >> + AUXFMT(AT_IGNORE, NULL), >> + AUXFMT(AT_EXECFD, "%d"), >> + AUXFMT(AT_PHDR, "%p"), >> + AUXFMT(AT_PHENT, "%u"), >> + AUXFMT(AT_PHNUM, "%u"), >> + AUXFMT(AT_PAGESZ, "%u"), >> + AUXFMT(AT_BASE, "%#lx"), >> + AUXFMT(AT_FLAGS, "%#lx"), >> + AUXFMT(AT_ENTRY, "%p"), >> + AUXFMT(AT_NOTELF, NULL), >> + AUXFMT(AT_UID, "%d"), >> + AUXFMT(AT_EUID, "%d"), >> + AUXFMT(AT_GID, "%d"), >> + AUXFMT(AT_EGID, "%d"), >> + AUXFMT(AT_EXECPATH, "%s"), >> + AUXFMT(AT_CANARY, "%p"), >> + AUXFMT(AT_CANARYLEN, "%u"), >> + AUXFMT(AT_OSRELDATE, "%u"), >> + AUXFMT(AT_NCPUS, "%u"), >> + AUXFMT(AT_PAGESIZES, "%p"), >> + AUXFMT(AT_PAGESIZESLEN, "%u"), >> + AUXFMT(AT_TIMEKEEP, "%p"), >> + AUXFMT(AT_STACKPROT, "%#x"), >> + AUXFMT(AT_EHDRFLAGS, "%#lx"), >> + AUXFMT(AT_HWCAP, "%#lx"), >> + AUXFMT(AT_HWCAP2, "%#lx"), >> + AUXFMT(AT_BSDFLAGS, "%#lx"), >> + AUXFMT(AT_ARGC, "%u"), >> + AUXFMT(AT_ARGV, "%p"), >> + AUXFMT(AT_ENVC, "%p"), >> + AUXFMT(AT_ENVV, "%p"), >> + AUXFMT(AT_PS_STRINGS, "%p"), >> + AUXFMT(AT_FXRNG, "%p"), >> +}; >> + >> +static void >> +dump_auxv(Elf_Auxinfo **aux_info) >> +{ >> + Elf_Auxinfo *auxp; >> + const struct auxfmt *fmt; >> + int i; >> + >> + for (i = 0; i < AT_COUNT; i++) { >> + auxp = aux_info[i]; >> + if (auxp == NULL) >> + continue; >> + fmt = &auxfmts[i]; >> + if (fmt->fmt == NULL) >> + continue; >> + rtld_fdprintf(STDOUT_FILENO, "%s:\t", fmt->name); >> + rtld_fdprintfx(STDOUT_FILENO, fmt->fmt, auxp->a_un.a_ptr); >> + rtld_fdprintf(STDOUT_FILENO, "\n"); > > This is undefined behaviour, breaks CHERI, and totally unnecessary. You > have a handful of cases here, just make an enum and have separate > rtld_fdprintf calls. > > Also the table itself is brittle, there’s nothing checking that the > order perfectly matches up with the defines in the header. Why not use > designated initialisers to ensure that the right values are in the > right entries (and handle the possibility that name might be NULL)? Scratch that second part, I missed the [at] = in the macro. Jess