Date: Sat, 13 Nov 2021 19:10:54 +0000 From: Jessica Clarke <jrtc27@freebsd.org> To: Konstantin Belousov <kostikbel@gmail.com> Cc: "src-committers@freebsd.org" <src-committers@freebsd.org>, "dev-commits-src-all@freebsd.org" <dev-commits-src-all@freebsd.org>, "dev-commits-src-main@freebsd.org" <dev-commits-src-main@freebsd.org> Subject: Re: git: 64ba1f4cf3a6 - main - rtld: Implement LD_SHOW_AUXV Message-ID: <BF2534B3-7A3A-4006-9105-5AACDD728AA4@freebsd.org> In-Reply-To: <A76167C8-7A1D-41C2-A9F2-A3A2D990A4BA@freebsd.org> References: <202111131733.1ADHXekX049248@gitrepo.freebsd.org> <37FC39AA-925D-4D75-8E0A-EA14E846E3A6@freebsd.org> <110784F6-3A7A-4F27-AAEB-E9B5A8F7CF0E@freebsd.org> <2450270B-CB98-43D0-B3BE-3C6D02F9B6FD@freebsd.org> <YZAK7b8PzqlaS85b@kib.kiev.ua> <YZAMvZdyEsxXodm0@kib.kiev.ua> <A76167C8-7A1D-41C2-A9F2-A3A2D990A4BA@freebsd.org>
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On 13 Nov 2021, at 19:09, Jessica Clarke <jrtc27@freebsd.org> wrote: >=20 > On 13 Nov 2021, at 19:06, Konstantin Belousov <kostikbel@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 <jrtc27@FreeBSD.org> = wrote: >>>>>=20 >>>>> On 13 Nov 2021, at 17:54, Jessica Clarke <jrtc27@FreeBSD.org> = wrote: >>>>>>=20 >>>>>> On 13 Nov 2021, at 17:33, Konstantin Belousov <kib@FreeBSD.org> = wrote: >>>>>>>=20 >>>>>>> The branch main has been updated by kib: >>>>>>>=20 >>>>>>> URL: = https://cgit.FreeBSD.org/src/commit/?id=3D64ba1f4cf3a6847a1dacf4bab0409d94= 898fa168 >>>>>>>=20 >>>>>>> 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 >>>>>>>=20 >>>>>>> rtld: Implement LD_SHOW_AUXV >>>>>>>=20 >>>>>>> It dumps auxv as seen by interpreter, right before starting any = user >>>>>>> code. >>>>>>>=20 >>>>>>> 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(-) >>>>>>>=20 >>>>>>> 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, >>>>>>> }; >>>>>>>=20 >>>>>>> struct ld_env_var_desc { >>>>>>> @@ -396,6 +398,7 @@ static struct ld_env_var_desc ld_env_vars[] = =3D { >>>>>>> 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), >>>>>>> }; >>>>>>>=20 >>>>>>> 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) =3D=3D -1 && !ld_tracing) >>>>>>> rtld_die(); >>>>>>>=20 >>>>>>> + if (ld_get_env_var(LD_SHOW_AUXV) !=3D 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); >>>>>>> } >>>>>>>=20 >>>>>>> +#define AUXFMT(at, xfmt) [at] =3D { .name =3D #at, .fmt = =3D xfmt } >>>>>>> +static const struct auxfmt { >>>>>>> + const char *name; >>>>>>> + const char *fmt; >>>>>>> +} auxfmts[] =3D { >>>>>>> + 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 =3D 0; i < AT_COUNT; i++) { >>>>>>> + auxp =3D aux_info[i]; >>>>>>> + if (auxp =3D=3D NULL) >>>>>>> + continue; >>>>>>> + fmt =3D &auxfmts[i]; >>>>>>> + if (fmt->fmt =3D=3D 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"); >>>>>>=20 >>>>>> 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. >>>>=20 >>>> 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=E2=80=99t 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. >>>=20 >>> In fact ELF spec exercises this as well. >>> Our arches are either ILP32 or LP64. >>>=20 >>>>=20 >>>> 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. >>=20 >> Ok, the following should be enough for CHERI, right? >>=20 >> 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[] =3D { >> 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"), >> }; >>=20 >> +static bool >> +is_ptr_fmt(const char *fmt) >> +{ >> + char last; >> + >> + last =3D fmt[strlen(fmt) - 1]; >> + return (last =3D=3D 'p' || last =3D=3D 's'); >> +} >> + >> static void >> dump_auxv(Elf_Auxinfo **aux_info) >> { >> @@ -6120,7 +6129,8 @@ dump_auxv(Elf_Auxinfo **aux_info) >> if (fmt->fmt =3D=3D 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"); >> } >> } >=20 > That should indeed work, though I=E2=80=99d argue it=E2=80=99s still = not as nice as > avoiding rtld_fdprintfx entirely. Wait, no, it doesn=E2=80=99t, the ternary means both operands need to = have the same type, so you end up implicitly casting the long to a pointer. You need a real if and two different rtld_fdprintfx calls (or just do it as I=E2=80=99ve suggested). Jess
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