In message <202507021341.562dfueh023...@gitrepo.freebsd.org>, Mark Johnston
wri
tes:
> The branch main has been updated by markj:
>
> URL: https://cgit.FreeBSD.org/src/commit/?id=aefae931820fe1e93a31855296851029
> 8c7941a0
>
> commit aefae931820fe1e93a318552968510298c7941a0
> Author: Mark Johnston <ma...@freebsd.org>
> AuthorDate: 2025-07-02 13:34:47 +0000
> Commit: Mark Johnston <ma...@freebsd.org>
> CommitDate: 2025-07-02 13:34:47 +0000
>
> linker: Improve handling of ifuncs when fetching symbol metadata
>
> When looking up symbol values, we map ifunc symbols to the value
> returned by the resolver. However, the returned symbol size is still
> that of the resolver. Be consistent and provide the size of the
> implementation symbol as well.
>
> This fixes an inconsistency in dtrace's FBT provider, which enumerates
> all function symbols and disassembles their values, using the symbol
> size as the bound for the disassembly loop. In particular, for ifuncs,
> we were not creating return probes.
>
> Reviewed by: kib
> MFC after: 2 weeks
> Sponsored by: Innovate UK
> Differential Revision: https://reviews.freebsd.org/D50683
> ---
> sys/kern/link_elf.c | 38 ++++++++++++++++++++++++++++++++++----
> sys/kern/link_elf_obj.c | 31 +++++++++++++++++++++++++++++--
> 2 files changed, 63 insertions(+), 6 deletions(-)
>
> diff --git a/sys/kern/link_elf.c b/sys/kern/link_elf.c
> index 53af1e164980..bbebadc4c395 100644
> --- a/sys/kern/link_elf.c
> +++ b/sys/kern/link_elf.c
> @@ -1628,6 +1628,30 @@ link_elf_lookup_debug_symbol_ctf(linker_file_t lf, con
> st char *name,
> return (i < ef->ddbsymcnt ? link_elf_ctf_get_ddb(lf, lc) : ENOENT);
> }
>
> +static void
> +link_elf_ifunc_symbol_value(linker_file_t lf, caddr_t *valp, size_t *sizep)
> +{
> + c_linker_sym_t sym;
> + elf_file_t ef;
> + const Elf_Sym *es;
> + caddr_t val;
> + long off;
> +
> + val = *valp;
> + ef = (elf_file_t)lf;
> +
> + /* Provide the value and size of the target symbol, if available. */
> + val = ((caddr_t (*)(void))val)();
> + if (link_elf_search_symbol(lf, val, &sym, &off) == 0 && off == 0) {
> + es = (const Elf_Sym *)sym;
> + *valp = (caddr_t)ef->address + es->st_value;
> + *sizep = es->st_size;
> + } else {
> + *valp = val;
> + *sizep = 0;
> + }
> +}
> +
> static int
> link_elf_symbol_values1(linker_file_t lf, c_linker_sym_t sym,
> linker_symval_t *symval, bool see_local)
> @@ -1635,6 +1659,7 @@ link_elf_symbol_values1(linker_file_t lf, c_linker_sym_
> t sym,
> elf_file_t ef;
> const Elf_Sym *es;
> caddr_t val;
> + size_t size;
>
> ef = (elf_file_t)lf;
> es = (const Elf_Sym *)sym;
> @@ -1644,9 +1669,11 @@ link_elf_symbol_values1(linker_file_t lf, c_linker_sym
> _t sym,
> symval->name = ef->strtab + es->st_name;
> val = (caddr_t)ef->address + es->st_value;
> if (ELF_ST_TYPE(es->st_info) == STT_GNU_IFUNC)
> - val = ((caddr_t (*)(void))val)();
> + link_elf_ifunc_symbol_value(lf, &val, &size);
> + else
> + size = es->st_size;
> symval->value = val;
> - symval->size = es->st_size;
> + symval->size = size;
> return (0);
> }
> return (ENOENT);
> @@ -1668,6 +1695,7 @@ link_elf_debug_symbol_values(linker_file_t lf, c_linker
> _sym_t sym,
> elf_file_t ef = (elf_file_t)lf;
> const Elf_Sym *es = (const Elf_Sym *)sym;
> caddr_t val;
> + size_t size;
>
> if (link_elf_symbol_values1(lf, sym, symval, true) == 0)
> return (0);
> @@ -1678,9 +1706,11 @@ link_elf_debug_symbol_values(linker_file_t lf, c_linke
> r_sym_t sym,
> symval->name = ef->ddbstrtab + es->st_name;
> val = (caddr_t)ef->address + es->st_value;
> if (ELF_ST_TYPE(es->st_info) == STT_GNU_IFUNC)
> - val = ((caddr_t (*)(void))val)();
> + link_elf_ifunc_symbol_value(lf, &val, &size);
> + else
> + size = es->st_size;
> symval->value = val;
> - symval->size = es->st_size;
> + symval->size = size;
> return (0);
> }
> return (ENOENT);
> diff --git a/sys/kern/link_elf_obj.c b/sys/kern/link_elf_obj.c
> index 02fd4caffcd9..3d18aed2b1c0 100644
> --- a/sys/kern/link_elf_obj.c
> +++ b/sys/kern/link_elf_obj.c
> @@ -1510,6 +1510,30 @@ link_elf_lookup_debug_symbol_ctf(linker_file_t lf, con
> st char *name,
> return (link_elf_ctf_get_ddb(lf, lc));
> }
>
> +static void
> +link_elf_ifunc_symbol_value(linker_file_t lf, caddr_t *valp, size_t *sizep)
> +{
> + c_linker_sym_t sym;
> + elf_file_t ef;
> + const Elf_Sym *es;
> + caddr_t val;
> + long off;
> +
> + val = *valp;
> + ef = (elf_file_t)lf;
> +
> + /* Provide the value and size of the target symbol, if available. */
> + val = ((caddr_t (*)(void))val)();
> + if (link_elf_search_symbol(lf, val, &sym, &off) == 0 && off == 0) {
> + es = (const Elf_Sym *)sym;
> + *valp = (caddr_t)ef->address + es->st_value;
> + *sizep = es->st_size;
> + } else {
> + *valp = val;
> + *sizep = 0;
> + }
> +}
> +
> static int
> link_elf_symbol_values1(linker_file_t lf, c_linker_sym_t sym,
> linker_symval_t *symval, bool see_local)
> @@ -1517,6 +1541,7 @@ link_elf_symbol_values1(linker_file_t lf, c_linker_sym_
> t sym,
> elf_file_t ef;
> const Elf_Sym *es;
> caddr_t val;
> + size_t size;
>
> ef = (elf_file_t) lf;
> es = (const Elf_Sym*) sym;
> @@ -1527,9 +1552,11 @@ link_elf_symbol_values1(linker_file_t lf, c_linker_sym
> _t sym,
> symval->name = ef->ddbstrtab + es->st_name;
> val = (caddr_t)es->st_value;
> if (ELF_ST_TYPE(es->st_info) == STT_GNU_IFUNC)
> - val = ((caddr_t (*)(void))val)();
> + link_elf_ifunc_symbol_value(lf, &val, &size);
> + else
> + size = es->st_size;
> symval->value = val;
> - symval->size = es->st_size;
> + symval->size = size;
> return (0);
> }
> return (ENOENT);
>
This commit may have caused a panic loading linux.ko.
#0 __curthread () at /opt/src/git-src/sys/amd64/include/pcpu_aux.h:57
#1 doadump (textdump=textdump@entry=1)
at /opt/src/git-src/sys/kern/kern_shutdown.c:399
#2 0xffffffff806fad1e in kern_reboot (howto=260)
at /opt/src/git-src/sys/kern/kern_shutdown.c:519
#3 0xffffffff806fb247 in vpanic (fmt=0xffffffff80b2e000 "%s",
ap=ap@entry=0xfffffe008c8e2450)
at /opt/src/git-src/sys/kern/kern_shutdown.c:974
#4 0xffffffff806fb073 in panic (fmt=<unavailable>)
at /opt/src/git-src/sys/kern/kern_shutdown.c:887
#5 0xffffffff80aa8e7a in trap_fatal (frame=<optimized out>,
eva=<optimized out>) at /opt/src/git-src/sys/amd64/amd64/trap.c:974
#6 0xffffffff80aa8e7a in trap_pfault (frame=0xfffffe008c8e24d0,
usermode=false, signo=<optimized out>, ucode=<optimized out>)
#7 <signal handler called>
#8 fbt_provide_module_function (lf=lf@entry=0xfffff80126035900,
symindx=symindx@entry=753, symval=symval@entry=0xfffffe008c8e25f0,
opaque=opaque@entry=0xfffffe008c8e2640)
at /opt/src/git-src/sys/cddl/dev/fbt/x86/fbt_isa.c:205
#9 0xffffffff80ac870d in link_elf_each_function_nameval (
file=0xfffff80126035900,
callback=0xffffffff81d916a0 <fbt_provide_module_function>,
opaque=0xfffffe008c8e2640) at /opt/src/git-src/sys/kern/link_elf_obj.c:1
685
--Type <RET> for more, q to quit, c to continue without paging--c
#10 0xffffffff81d9035f in fbt_provide_module (arg=<optimized out>,
lf=0xfffff80126035900) at /opt/src/git-src/sys/cddl/dev/fbt/fbt.c:221
#11 0xffffffff81cc87fb in dtrace_module_loaded (ctl=0xfffff80126035900)
at /opt/src/git-src/sys/cddl/contrib/opensolaris/uts/common/dtrace/dtrac
e.c:16709
#12 dtrace_kld_load (arg=<optimized out>, lf=0xfffff80126035900)
at /opt/src/git-src/sys/cddl/contrib/opensolaris/uts/common/dtrace/dtrac
e.c:16894
#13 0xffffffff806c4ecb in linker_load_file (
filename=0xfffff80054e6d500 "/boot/kernel/linux.ko",
result=<optimized out>) at /opt/src/git-src/sys/kern/kern_linker.c:518
#14 linker_load_module (kldname=kldname@entry=0x0,
modname=0xfffff8005437c800 "linux", parent=parent@entry=0x0,
verinfo=verinfo@entry=0x0, lfpp=lfpp@entry=0xfffffe008c8e2da0)
at /opt/src/git-src/sys/kern/kern_linker.c:2292
#15 0xffffffff806c69f5 in kern_kldload (td=td@entry=0xfffff8005ce3c780,
file=file@entry=0xfffff8005437c800 "linux",
fileid=fileid@entry=0xfffffe008c8e2de4)
at /opt/src/git-src/sys/kern/kern_linker.c:1236
#16 0xffffffff806c6b09 in sys_kldload (td=0xfffff8005ce3c780,
uap=0xfffff8005ce3cba8) at /opt/src/git-src/sys/kern/kern_linker.c:1259
#17 0xffffffff80aa97d6 in syscallenter (td=0xfffff8005ce3c780)
at /opt/src/git-src/sys/amd64/amd64/../../kern/subr_syscall.c:193
#18 amd64_syscall (td=0xfffff8005ce3c780, traced=0)
at /opt/src/git-src/sys/amd64/amd64/trap.c:1215
#19 <signal handler called>
#20 0x00000ce63ecf8c3a in ?? ()
--
Cheers,
Cy Schubert <cy.schub...@cschubert.com>
FreeBSD UNIX: <c...@freebsd.org> Web: https://FreeBSD.org
NTP: <c...@nwtime.org> Web: https://nwtime.org
e**(i*pi)+1=0
