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nptl: add rtld_hidden_proto to __rseq_size and __rseq_offset 

This allows accessing the internal aliases of __rseq_size and
__rseq_offset from ld.so without ifdefs and avoids dynamic symbol
binding at run time for both variables.

Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Reviewed-by: Florian Weimer <fweimer@redhat.com>
This commit is contained in:
Michael Jeanson 2024-11-20 22:28:07 +00:00
parent 304221775c
commit be440f6c38
2 changed files with 28 additions and 15 deletions
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27
sysdeps/unix/sysv/linux/dl-rseq-symbols.S
View File

@ -27,14 +27,18 @@
/* Some targets define a macro to denote the zero register. */ /* Some targets define a macro to denote the zero register. */
#undef zero #undef zero
/* Define 2 symbols: '__rseq_size' is public const and '_rseq_size' (an /* Define 3 symbols: '__rseq_size' is public const and then '_rseq_size' and
alias of '__rseq_size') is hidden and writable for internal use by the '__GI___rseq_size' (both aliases of '__rseq_size') are hidden, '_rseq_size'
dynamic linker which will initialize the value both symbols point to is writable for internal use by the dynamic linker which will initialize
before copy relocations take place. */ the value the symbols point to before copy relocations take place. */
.globl __rseq_size .globl __rseq_size
.type __rseq_size, %object .type __rseq_size, %object
.size __rseq_size, 4 .size __rseq_size, 4
.hidden __GI___rseq_size
.globl __GI___rseq_size
.type __GI___rseq_size, %object
.size __GI___rseq_size, 4
.hidden _rseq_size .hidden _rseq_size
.globl _rseq_size .globl _rseq_size
.type _rseq_size, %object .type _rseq_size, %object
@ -42,17 +46,23 @@
.section .data.rel.ro .section .data.rel.ro
.balign 4 .balign 4
__rseq_size: __rseq_size:
__GI___rseq_size:
_rseq_size: _rseq_size:
.zero 4 .zero 4
/* Define 2 symbols: '__rseq_offset' is public const and '_rseq_offset' (an /* Define 3 symbols: '__rseq_offset' is public const and then '_rseq_offset'
alias of '__rseq_offset') is hidden and writable for internal use by the and '__GI___rseq_offset' (both aliases of '__rseq_offset') are hidden,
dynamic linker which will initialize the value both symbols point to '_rseq_offset' is writable for internal use by the dynamic linker which will
before copy relocations take place. */ initialize the value the symbols point to before copy relocations take
place. */
.globl __rseq_offset .globl __rseq_offset
.type __rseq_offset, %object .type __rseq_offset, %object
.size __rseq_offset, RSEQ_OFFSET_SIZE .size __rseq_offset, RSEQ_OFFSET_SIZE
.hidden __GI___rseq_offset
.globl __GI___rseq_offset
.type __GI___rseq_offset, %object
.size __GI___rseq_offset, RSEQ_OFFSET_SIZE
.hidden _rseq_offset .hidden _rseq_offset
.globl _rseq_offset .globl _rseq_offset
.type _rseq_offset, %object .type _rseq_offset, %object
@ -60,5 +70,6 @@ _rseq_size:
.section .data.rel.ro .section .data.rel.ro
.balign RSEQ_OFFSET_SIZE .balign RSEQ_OFFSET_SIZE
__rseq_offset: __rseq_offset:
__GI___rseq_offset:
_rseq_offset: _rseq_offset:
.zero RSEQ_OFFSET_SIZE .zero RSEQ_OFFSET_SIZE

16
sysdeps/unix/sysv/linux/rseq-internal.h
View File

@ -24,6 +24,7 @@
#include <stdbool.h> #include <stdbool.h>
#include <stdio.h> #include <stdio.h>
#include <sys/rseq.h> #include <sys/rseq.h>
#include <ldsodefs.h>
/* Minimum size of the rseq area allocation required by the syscall. The /* Minimum size of the rseq area allocation required by the syscall. The
actually used rseq feature size may be less (20 bytes initially). */ actually used rseq feature size may be less (20 bytes initially). */
@ -52,19 +53,20 @@ extern unsigned int _rseq_size attribute_hidden;
In .data.relro but not yet write-protected. */ In .data.relro but not yet write-protected. */
extern ptrdiff_t _rseq_offset attribute_hidden; extern ptrdiff_t _rseq_offset attribute_hidden;
/* We want to use rtld_hidden_proto in order to call the internal aliases
of __rseq_size and __rseq_offset from ld.so. This avoids dynamic symbol
binding at run time for both variables. */
rtld_hidden_proto (__rseq_size)
rtld_hidden_proto (__rseq_offset)
#ifdef RSEQ_SIG #ifdef RSEQ_SIG
static inline bool static inline bool
rseq_register_current_thread (struct pthread *self, bool do_rseq) rseq_register_current_thread (struct pthread *self, bool do_rseq)
{ {
if (do_rseq) if (do_rseq)
{ {
unsigned int size; unsigned int size = __rseq_size;
#if IS_IN (rtld)
/* Use the hidden symbol in ld.so. */
size = _rseq_size;
#else
size = __rseq_size;
#endif
if (size < RSEQ_AREA_SIZE_INITIAL) if (size < RSEQ_AREA_SIZE_INITIAL)
/* The initial implementation used only 20 bytes out of 32, /* The initial implementation used only 20 bytes out of 32,
but still expected size 32. */ but still expected size 32. */