From e1b2624a08fae1f669d879946d5041945b4dc248 Mon Sep 17 00:00:00 2001 From: Andreas Arnez Date: Fri, 9 Sep 2016 19:59:53 +0200 Subject: [PATCH] Pass HWCAP to ifunc resolver 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. 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/ChangeLog | 5 +++++ gdb/elfread.c | 13 ++++++++++--- gdb/testsuite/ChangeLog | 9 +++++++++ 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 +++++++++++++++ 6 files changed, 46 insertions(+), 4 deletions(-) diff --git a/gdb/ChangeLog b/gdb/ChangeLog index e7cc7122d8c..b58591466a8 100644 --- a/gdb/ChangeLog +++ b/gdb/ChangeLog @@ -1,3 +1,8 @@ +2016-09-09 Andreas Arnez + + * elfread.c (auxv.h): New include. + (elf_gnu_ifunc_resolve_addr): Pass HWCAP to ifunc resolver. + 2016-09-08 Tom Tromey * remote.c (remote_notif_stop_ack, remote_wait_as) diff --git a/gdb/elfread.c b/gdb/elfread.c index e90466b00cb..84355cf032f 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/ChangeLog b/gdb/testsuite/ChangeLog index 958ec27b626..783e30fedb0 100644 --- a/gdb/testsuite/ChangeLog +++ b/gdb/testsuite/ChangeLog @@ -1,3 +1,12 @@ +2016-09-09 Andreas Arnez + + * 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. + 2016-09-06 Pedro Alves * gdb.base/new-ui-pending-input.c: New file. diff --git a/gdb/testsuite/gdb.base/gnu-ifunc-lib.c b/gdb/testsuite/gdb.base/gnu-ifunc-lib.c index 8a55f600396..0c0aeef364f 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 . */ 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 c68866ec84d..77dea30d96b 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 097e48a9a0c..3b2775b8c76 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 .*" -- 2.30.2