On 13 Nov 2021, at 19:06, Konstantin Belousov <kostik...@gmail.com> wrote: > On Sat, Nov 13, 2021 at 08:59:00PM +0200, Konstantin Belousov wrote: >> On Sat, Nov 13, 2021 at 06:29:24PM +0000, Jessica Clarke wrote: >>> On 13 Nov 2021, at 17:57, Jessica Clarke <jrt...@freebsd.org> wrote: >>>> >>>> On 13 Nov 2021, at 17:54, Jessica Clarke <jrt...@freebsd.org> wrote: >>>>> >>>>> On 13 Nov 2021, at 17:33, Konstantin Belousov <k...@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 <k...@freebsd.org> >>>>>> AuthorDate: 2021-11-13 01:18:13 +0000 >>>>>> Commit: Konstantin Belousov <k...@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. >>> >>> In particular, ignoring CHERI, unsigned ints are sign-extended to 64 >>> bits on MIPS and RISC-V. Thus by passing a 64-bit value but using a %u, >>> you are violating the calling convention. I can’t currently get GCC or >>> Clang to exploit the fact that varargs arguments are sign-extended, but >>> on MIPS, and RISC-V GCC (Clang is currently stupid and round-trips via >>> memory even when the va_arg calls have no branching surrounding them, >>> rather than just grabbing from the register) there is a redundant >>> sext.w that can legally be optimised out, but would be broken by this >>> calling convention violation. >> I might understand the argument that all non-pointer formats for auxv >> should be longs, i.e. %lu/%ld/%lx, but this is the only problem I see >> there. We do rely on having specific representations for addresses and >> longs, and a low-level component as rtld has full rights to exercise >> this fact, same as VM subsystem or memory allocators. >> >> In fact ELF spec exercises this as well. >> Our arches are either ILP32 or LP64. >> >>> >>> Then CHERI makes it worse because a_ptr and a_val do not have the same >>> representation, although in practice I think passing a_ptr and nothing >>> further does end up working on CHERI-RISC-V and Morello, just not >>> CHERI-MIPS due to being big-endian. > > Ok, the following should be enough for CHERI, right? > > diff --git a/libexec/rtld-elf/rtld.c b/libexec/rtld-elf/rtld.c > index 0475134b0d96..cf467ae7aacd 100644 > --- a/libexec/rtld-elf/rtld.c > +++ b/libexec/rtld-elf/rtld.c > @@ -6071,33 +6071,33 @@ static const struct auxfmt { > } auxfmts[] = { > AUXFMT(AT_NULL, NULL), > AUXFMT(AT_IGNORE, NULL), > - AUXFMT(AT_EXECFD, "%d"), > + AUXFMT(AT_EXECFD, "%ld"), > AUXFMT(AT_PHDR, "%p"), > - AUXFMT(AT_PHENT, "%u"), > - AUXFMT(AT_PHNUM, "%u"), > - AUXFMT(AT_PAGESZ, "%u"), > + AUXFMT(AT_PHENT, "%lu"), > + AUXFMT(AT_PHNUM, "%lu"), > + AUXFMT(AT_PAGESZ, "%lu"), > 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_UID, "%ld"), > + AUXFMT(AT_EUID, "%ld"), > + AUXFMT(AT_GID, "%ld"), > + AUXFMT(AT_EGID, "%ld"), > AUXFMT(AT_EXECPATH, "%s"), > AUXFMT(AT_CANARY, "%p"), > - AUXFMT(AT_CANARYLEN, "%u"), > - AUXFMT(AT_OSRELDATE, "%u"), > - AUXFMT(AT_NCPUS, "%u"), > + AUXFMT(AT_CANARYLEN, "%lu"), > + AUXFMT(AT_OSRELDATE, "%lu"), > + AUXFMT(AT_NCPUS, "%lu"), > AUXFMT(AT_PAGESIZES, "%p"), > - AUXFMT(AT_PAGESIZESLEN, "%u"), > + AUXFMT(AT_PAGESIZESLEN, "%lu"), > AUXFMT(AT_TIMEKEEP, "%p"), > - AUXFMT(AT_STACKPROT, "%#x"), > + AUXFMT(AT_STACKPROT, "%#lx"), > AUXFMT(AT_EHDRFLAGS, "%#lx"), > AUXFMT(AT_HWCAP, "%#lx"), > AUXFMT(AT_HWCAP2, "%#lx"), > AUXFMT(AT_BSDFLAGS, "%#lx"), > - AUXFMT(AT_ARGC, "%u"), > + AUXFMT(AT_ARGC, "%lu"), > AUXFMT(AT_ARGV, "%p"), > AUXFMT(AT_ENVC, "%p"), > AUXFMT(AT_ENVV, "%p"), > @@ -6105,6 +6105,15 @@ static const struct auxfmt { > AUXFMT(AT_FXRNG, "%p"), > }; > > +static bool > +is_ptr_fmt(const char *fmt) > +{ > + char last; > + > + last = fmt[strlen(fmt) - 1]; > + return (last == 'p' || last == 's'); > +} > + > static void > dump_auxv(Elf_Auxinfo **aux_info) > { > @@ -6120,7 +6129,8 @@ dump_auxv(Elf_Auxinfo **aux_info) > 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_fdprintfx(STDOUT_FILENO, fmt->fmt, is_ptr_fmt(fmt->fmt) ? > + auxp->a_un.a_ptr : auxp->a_un.a_val); > rtld_fdprintf(STDOUT_FILENO, "\n"); > } > }
That should indeed work, though I’d argue it’s still not as nice as avoiding rtld_fdprintfx entirely. Jess
