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powerpc64: Set up thread register for _dl_relocate_static_pie

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libgcc ifunc resolvers that access hwcap via a field in the tcb can't
be called until the thread pointer is set up.  Other ifunc resolvers
might need access to at_platform.  This patch sets up a fake thread
pointer early to a copy of tcbhead_t.  hwcapinfo.c already had local
variables for hwcap and at_platform, replace them with an entire
tcbhead_t.  It's not that large and this way we easily ensure hwcap
and at_platform are at the same relative offsets as they are in the
real thread block.

The patch also conditionally disables part of tst-tlsifunc-static,
"bar address read from IFUNC resolver is incorrect".  We can't get a
proper address for a thread variable before glibc initialises tls.

Reviewed-by: Tulio Magno Quites Machado Filho <tuliom@linux.ibm.com>
This commit is contained in:
Alan Modra 2022-01-24 07:58:18 +10:30
parent d6efcc118e
commit 31a9bc8c55
6 changed files with 33 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
sysdeps/powerpc/hwcapinfo.c
View File

@ -20,8 +20,7 @@
#include <shlib-compat.h>
#include <dl-procinfo.h>
uint64_t __tcb_hwcap __attribute__ ((visibility ("hidden")));
uint32_t __tcb_platform __attribute__ ((visibility ("hidden")));
tcbhead_t __tcb __attribute__ ((visibility ("hidden")));
/* This function parses the HWCAP/HWCAP2 fields, adding the previous supported
ISA bits, as well as converting the AT_PLATFORM string to a number. This
@ -34,7 +33,7 @@ __tcb_parse_hwcap_and_convert_at_platform (void)
uint64_t h1, h2;
/* Read AT_PLATFORM string from auxv and convert it to a number. */
__tcb_platform = _dl_string_platform (GLRO (dl_platform));
__tcb.at_platform = _dl_string_platform (GLRO (dl_platform));
/* Read HWCAP and HWCAP2 from auxv. */
h1 = GLRO (dl_hwcap);
@ -66,8 +65,7 @@ __tcb_parse_hwcap_and_convert_at_platform (void)
/* Consolidate both HWCAP and HWCAP2 into a single doubleword so that
we can read both in a single load later. */
__tcb_hwcap = h2;
__tcb_hwcap = (h1 << 32) | __tcb_hwcap;
__tcb.hwcap = (h1 << 32) | (h2 & 0xffffffff);
}
#if IS_IN (rtld)

3
sysdeps/powerpc/hwcapinfo.h
View File

@ -21,8 +21,7 @@
#ifndef HWCAPINFO_H
# define HWCAPINFO_H
extern uint64_t __tcb_hwcap attribute_hidden;
extern uint32_t __tcb_platform attribute_hidden;
extern tcbhead_t __tcb attribute_hidden;
extern void __tcb_parse_hwcap_and_convert_at_platform (void);

8
sysdeps/powerpc/nptl/tls.h
View File

@ -45,8 +45,6 @@
#ifndef __ASSEMBLER__
# include <hwcapinfo.h>
/* Get system call information. */
# include <sysdep.h>
@ -100,6 +98,8 @@ typedef struct
dtv_t *dtv;
} tcbhead_t;
# include <hwcapinfo.h>
/* This is the size of the initial TCB. */
# define TLS_INIT_TCB_SIZE 0
@ -137,8 +137,8 @@ typedef struct
# define TLS_INIT_TP(tcbp) \
({ \
__thread_register = (void *) (tcbp) + TLS_TCB_OFFSET; \
THREAD_SET_HWCAP (__tcb_hwcap); \
THREAD_SET_AT_PLATFORM (__tcb_platform); \
THREAD_SET_HWCAP (__tcb.hwcap); \
THREAD_SET_AT_PLATFORM (__tcb.at_platform); \
NULL; \
})

21
sysdeps/powerpc/powerpc64/dl-machine.h
View File

@ -559,6 +559,27 @@ elf_machine_plt_value (struct link_map *map, const Elf64_Rela *reloc,
#define ARCH_LA_PLTEXIT ppc64v2_gnu_pltexit
#endif
#if ENABLE_STATIC_PIE && !defined SHARED && !IS_IN (rtld)
#include <libc-diag.h>
#include <tcb-offsets.h>
/* Set up r13 for _dl_relocate_static_pie so that libgcc ifuncs that
normally access the tcb copy of hwcap will see __tcb.hwcap. */
static inline void __attribute__ ((always_inline))
ppc_init_fake_thread_pointer (void)
{
DIAG_PUSH_NEEDS_COMMENT;
/* We are playing pointer tricks. Silence gcc warning. */
DIAG_IGNORE_NEEDS_COMMENT (4.9, "-Warray-bounds");
__thread_register = (char *) &__tcb.hwcap - TCB_HWCAP;
DIAG_POP_NEEDS_COMMENT;
}
#define ELF_MACHINE_BEFORE_RTLD_RELOC(map, dynamic_info) \
ppc_init_fake_thread_pointer ();
#endif /* ENABLE_STATIC_PIE && !defined SHARED && !IS_IN (rtld) */
#endif /* dl_machine_h */
#ifdef RESOLVE_MAP

1
sysdeps/powerpc/tst-tlsifunc-static.c
View File

@ -16,4 +16,5 @@
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
#define TST_TLSIFUNC_STATIC 1
#include "tst-tlsifunc.c"

3
sysdeps/powerpc/tst-tlsifunc.c
View File

@ -101,11 +101,14 @@ do_test (void)
if (&bar == bar_ptr)
printf ("PASS: bar address read from IFUNC resolver is correct.\n");
#if !defined TST_TLSIFUNC_STATIC || !defined PIC \
|| !defined PI_STATIC_AND_HIDDEN
else
{
printf ("FAIL: bar address read from IFUNC resolver is incorrect.\n");
ret = 1;
}
#endif
if (tcb_test ())
printf ("PASS: tcb_test IFUNC resolver called once.\n");