| Message ID | m3inuhma3e.fsf@oc1027705133.ibm.com |
|---|---|
| State | New |
| Headers | show |
On Wed, Aug 31, 2016 at 4:49 AM, Andreas Arnez <arnez@linux.vnet.ibm.com> wrote: > On various GNU Elf architectures, including AArch64, ARM, s390/s390x, > ppc32/64, and sparc32/64, the dynamic loader passes HWCAP as a parameter > to each ifunc resolver. Currently there is an open glibc Bugzilla that > requests this to be generalized to all architectures: > > https://sourceware.org/bugzilla/show_bug.cgi?id=19766 > > And various ifunc resolvers already rely on receiving HWCAP. Currently > GDB always calls an ifunc resolver without any arguments; thus the > resolver may receive garbage, and based on that, the resolver may decide > to return a function that is not suited for the given platform. > > This patch always passes HWCAP to ifunc resolvers, even on systems where > the dynamic loader currently behaves otherwise. The rationale is > that (1) the dynamic loader may get adjusted on those systems as well in > the future; (2) passing an unused argument should not cause a problem > with existing resolvers; and (3) the logic is much simpler without such > a distinction. Doesn't some targets pass HWCAP2 too? Thanks, Andrew > > gdb/ChangeLog: > > * elfread.c (auxv.h): New include. > (elf_gnu_ifunc_resolve_addr): Pass HWCAP to ifunc resolver. > > gdb/testsuite/ChangeLog: > > * gdb.base/gnu-ifunc-lib.c (resolver_hwcap): New external > variable declaration. > (gnu_ifunc): Add parameter hwcap. Store it in resolver_hwcap. > * gdb.base/gnu-ifunc.c (resolver_hwcap): New global variable. > * gdb.base/gnu-ifunc.exp: Add test to verify that the resolver > received HWCAP as its argument. > --- > gdb/elfread.c | 13 ++++++++++--- > gdb/testsuite/gdb.base/gnu-ifunc-lib.c | 4 +++- > gdb/testsuite/gdb.base/gnu-ifunc.c | 4 ++++ > gdb/testsuite/gdb.base/gnu-ifunc.exp | 15 +++++++++++++++ > 4 files changed, 32 insertions(+), 4 deletions(-) > > diff --git a/gdb/elfread.c b/gdb/elfread.c > index e90466b..84355cf 100644 > --- a/gdb/elfread.c > +++ b/gdb/elfread.c > @@ -46,6 +46,7 @@ > #include "gdb_bfd.h" > #include "build-id.h" > #include "location.h" > +#include "auxv.h" > > extern void _initialize_elfread (void); > > @@ -860,6 +861,8 @@ elf_gnu_ifunc_resolve_addr (struct gdbarch *gdbarch, CORE_ADDR pc) > CORE_ADDR start_at_pc, address; > struct type *func_func_type = builtin_type (gdbarch)->builtin_func_func; > struct value *function, *address_val; > + CORE_ADDR hwcap = 0; > + struct value *hwcap_val; > > /* Try first any non-intrusive methods without an inferior call. */ > > @@ -875,10 +878,14 @@ elf_gnu_ifunc_resolve_addr (struct gdbarch *gdbarch, CORE_ADDR pc) > function = allocate_value (func_func_type); > set_value_address (function, pc); > > - /* STT_GNU_IFUNC resolver functions have no parameters. FUNCTION is the > - function entry address. ADDRESS may be a function descriptor. */ > + /* STT_GNU_IFUNC resolver functions usually receive the HWCAP vector as > + parameter. FUNCTION is the function entry address. ADDRESS may be a > + function descriptor. */ > > - address_val = call_function_by_hand (function, 0, NULL); > + target_auxv_search (¤t_target, AT_HWCAP, &hwcap); > + hwcap_val = value_from_longest (builtin_type (gdbarch) > + ->builtin_unsigned_long, hwcap); > + address_val = call_function_by_hand (function, 1, &hwcap_val); > address = value_as_address (address_val); > address = gdbarch_convert_from_func_ptr_addr (gdbarch, address, > ¤t_target); > diff --git a/gdb/testsuite/gdb.base/gnu-ifunc-lib.c b/gdb/testsuite/gdb.base/gnu-ifunc-lib.c > index 8a55f60..0c0aeef 100644 > --- a/gdb/testsuite/gdb.base/gnu-ifunc-lib.c > +++ b/gdb/testsuite/gdb.base/gnu-ifunc-lib.c > @@ -16,6 +16,7 @@ > along with this program. If not, see <http://www.gnu.org/licenses/>. */ > > extern volatile int gnu_ifunc_initialized; > +extern volatile unsigned long resolver_hwcap; > extern int init_stub (int arg); > extern int final (int arg); > > @@ -24,8 +25,9 @@ typedef int (*final_t) (int arg); > asm (".type gnu_ifunc, %gnu_indirect_function"); > > final_t > -gnu_ifunc (void) > +gnu_ifunc (unsigned long hwcap) > { > + resolver_hwcap = hwcap; > if (! gnu_ifunc_initialized) > return init_stub; > else > diff --git a/gdb/testsuite/gdb.base/gnu-ifunc.c b/gdb/testsuite/gdb.base/gnu-ifunc.c > index c68866e..77dea30 100644 > --- a/gdb/testsuite/gdb.base/gnu-ifunc.c > +++ b/gdb/testsuite/gdb.base/gnu-ifunc.c > @@ -35,6 +35,10 @@ final (int arg) > > volatile int gnu_ifunc_initialized; > > +/* This stores the argument received by the ifunc resolver. */ > + > +volatile unsigned long resolver_hwcap = -1; > + > static void > gnu_ifunc_pre (void) > { > diff --git a/gdb/testsuite/gdb.base/gnu-ifunc.exp b/gdb/testsuite/gdb.base/gnu-ifunc.exp > index 097e48a9..3b2775b 100644 > --- a/gdb/testsuite/gdb.base/gnu-ifunc.exp > +++ b/gdb/testsuite/gdb.base/gnu-ifunc.exp > @@ -76,6 +76,21 @@ gdb_continue_to_breakpoint "break-at-call" ".*break-at-call.*" > > gdb_test "p gnu_ifunc (3)" " = 4" > > +# Test that the resolver received its argument. > + > +set actual_hwcap "0x0" > +set test "info auxv" > +gdb_test_multiple $test $test { > + -re "\r\n\\d+\\s+AT_HWCAP\[^\r\n\]+($hex)\r\n.*$gdb_prompt $" { > + set actual_hwcap $expect_out(1,string) > + } > + -re ".*$gdb_prompt $" { > + pass "$test (no HWCAP)" > + } > +} > + > +gdb_test "p/x resolver_hwcap" "= $actual_hwcap" "resolver received HWCAP" > + > # Test GDB will skip the gnu_ifunc resolver on first call. > > gdb_test "step" "\r\nfinal .*" > -- > 2.3.0 >
On Thu, Sep 01 2016, Andrew Pinski wrote: > On Wed, Aug 31, 2016 at 4:49 AM, Andreas Arnez <arnez@linux.vnet.ibm.com> wrote: >> On various GNU Elf architectures, including AArch64, ARM, s390/s390x, >> ppc32/64, and sparc32/64, the dynamic loader passes HWCAP as a parameter >> to each ifunc resolver. Currently there is an open glibc Bugzilla that >> requests this to be generalized to all architectures: >> >> https://sourceware.org/bugzilla/show_bug.cgi?id=19766 >> >> And various ifunc resolvers already rely on receiving HWCAP. Currently >> GDB always calls an ifunc resolver without any arguments; thus the >> resolver may receive garbage, and based on that, the resolver may decide >> to return a function that is not suited for the given platform. >> >> This patch always passes HWCAP to ifunc resolvers, even on systems where >> the dynamic loader currently behaves otherwise. The rationale is >> that (1) the dynamic loader may get adjusted on those systems as well in >> the future; (2) passing an unused argument should not cause a problem >> with existing resolvers; and (3) the logic is much simpler without such >> a distinction. > > Doesn't some targets pass HWCAP2 too? If I understand the glibc code correctly, no. The loader maintains the variables dl_hwcap and dl_hwcap2 and fills them from AT_HWCAP and AT_HWCAP2, respectively, but the ifunc resolvers only receive dl_hwcap: ./sysdeps/aarch64/dl-irel.h:33: return ((ElfW(Addr) (*) (unsigned long int)) (addr)) (GLRO(dl_hwcap)); ./sysdeps/arm/dl-irel.h:33: return ((Elf32_Addr (*) (unsigned long int)) (addr)) (GLRO(dl_hwcap)); ./sysdeps/generic/dl-irel.h:26: return ((DL_FIXUP_VALUE_TYPE (*) (void)) (addr)) (); ./sysdeps/hppa/dl-irel.h:36: return ((struct fdesc) {0, 0}); ./sysdeps/i386/dl-irel.h:32: return ((Elf32_Addr (*) (void)) (addr)) (); ./sysdeps/powerpc/powerpc32/dl-irel.h:33: return ((Elf32_Addr (*) (unsigned long int)) (addr)) (GLRO(dl_hwcap)); ./sysdeps/powerpc/powerpc64/dl-irel.h:34: return ((Elf64_Addr (*) (unsigned long int)) (addr)) (GLRO(dl_hwcap)); ./sysdeps/s390/dl-irel.h:33: return ((ElfW(Addr) (*) (unsigned long int)) (addr)) (GLRO(dl_hwcap)); ./sysdeps/sparc/sparc32/dl-irel.h:34: return ((Elf32_Addr (*) (int)) (addr)) (GLRO(dl_hwcap)); ./sysdeps/sparc/sparc64/dl-irel.h:34: return ((Elf64_Addr (*) (int)) (addr)) (GLRO(dl_hwcap)); ./sysdeps/x86_64/dl-irel.h:32: return ((ElfW(Addr) (*) (void)) (addr)) (); -- Andreas
diff --git a/gdb/elfread.c b/gdb/elfread.c index e90466b..84355cf 100644 --- a/gdb/elfread.c +++ b/gdb/elfread.c @@ -46,6 +46,7 @@ #include "gdb_bfd.h" #include "build-id.h" #include "location.h" +#include "auxv.h" extern void _initialize_elfread (void); @@ -860,6 +861,8 @@ elf_gnu_ifunc_resolve_addr (struct gdbarch *gdbarch, CORE_ADDR pc) CORE_ADDR start_at_pc, address; struct type *func_func_type = builtin_type (gdbarch)->builtin_func_func; struct value *function, *address_val; + CORE_ADDR hwcap = 0; + struct value *hwcap_val; /* Try first any non-intrusive methods without an inferior call. */ @@ -875,10 +878,14 @@ elf_gnu_ifunc_resolve_addr (struct gdbarch *gdbarch, CORE_ADDR pc) function = allocate_value (func_func_type); set_value_address (function, pc); - /* STT_GNU_IFUNC resolver functions have no parameters. FUNCTION is the - function entry address. ADDRESS may be a function descriptor. */ + /* STT_GNU_IFUNC resolver functions usually receive the HWCAP vector as + parameter. FUNCTION is the function entry address. ADDRESS may be a + function descriptor. */ - address_val = call_function_by_hand (function, 0, NULL); + target_auxv_search (¤t_target, AT_HWCAP, &hwcap); + hwcap_val = value_from_longest (builtin_type (gdbarch) + ->builtin_unsigned_long, hwcap); + address_val = call_function_by_hand (function, 1, &hwcap_val); address = value_as_address (address_val); address = gdbarch_convert_from_func_ptr_addr (gdbarch, address, ¤t_target); diff --git a/gdb/testsuite/gdb.base/gnu-ifunc-lib.c b/gdb/testsuite/gdb.base/gnu-ifunc-lib.c index 8a55f60..0c0aeef 100644 --- a/gdb/testsuite/gdb.base/gnu-ifunc-lib.c +++ b/gdb/testsuite/gdb.base/gnu-ifunc-lib.c @@ -16,6 +16,7 @@ along with this program. If not, see <http://www.gnu.org/licenses/>. */ extern volatile int gnu_ifunc_initialized; +extern volatile unsigned long resolver_hwcap; extern int init_stub (int arg); extern int final (int arg); @@ -24,8 +25,9 @@ typedef int (*final_t) (int arg); asm (".type gnu_ifunc, %gnu_indirect_function"); final_t -gnu_ifunc (void) +gnu_ifunc (unsigned long hwcap) { + resolver_hwcap = hwcap; if (! gnu_ifunc_initialized) return init_stub; else diff --git a/gdb/testsuite/gdb.base/gnu-ifunc.c b/gdb/testsuite/gdb.base/gnu-ifunc.c index c68866e..77dea30 100644 --- a/gdb/testsuite/gdb.base/gnu-ifunc.c +++ b/gdb/testsuite/gdb.base/gnu-ifunc.c @@ -35,6 +35,10 @@ final (int arg) volatile int gnu_ifunc_initialized; +/* This stores the argument received by the ifunc resolver. */ + +volatile unsigned long resolver_hwcap = -1; + static void gnu_ifunc_pre (void) { diff --git a/gdb/testsuite/gdb.base/gnu-ifunc.exp b/gdb/testsuite/gdb.base/gnu-ifunc.exp index 097e48a9..3b2775b 100644 --- a/gdb/testsuite/gdb.base/gnu-ifunc.exp +++ b/gdb/testsuite/gdb.base/gnu-ifunc.exp @@ -76,6 +76,21 @@ gdb_continue_to_breakpoint "break-at-call" ".*break-at-call.*" gdb_test "p gnu_ifunc (3)" " = 4" +# Test that the resolver received its argument. + +set actual_hwcap "0x0" +set test "info auxv" +gdb_test_multiple $test $test { + -re "\r\n\\d+\\s+AT_HWCAP\[^\r\n\]+($hex)\r\n.*$gdb_prompt $" { + set actual_hwcap $expect_out(1,string) + } + -re ".*$gdb_prompt $" { + pass "$test (no HWCAP)" + } +} + +gdb_test "p/x resolver_hwcap" "= $actual_hwcap" "resolver received HWCAP" + # Test GDB will skip the gnu_ifunc resolver on first call. gdb_test "step" "\r\nfinal .*"