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libspl: hide global data objects

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Currently libspl is a static archive that is linked into multiple shared
objects, which then re-export its symbols. We intend to fix this soon.

For the moment though, most programs shipped with OpenZFS depend on two
or more of these shared objects, and see the same symbols twice. For
functions this is not a problem, as they do not have any mutable state
and so the linker can simply select the first one and use that for all.

For global data objects however, each shared object will have direct
(non-relocatable) references to its own instance of the symbol, such
that changes on one will not necessarily be seen by the other. While
this shouldn't be a problem in practice as these reexported interfaces
are not supposed to be used, they are technically undefined behaviour in
C (C17 6.9.2) and are reported by ASAN as a violation of C++'s "One
Definition Rule".

To fix this, we hide these globals inside their compilation units, and
add access functions and macros as appropriate to preserve the existing
API (though not ABI).

Sponsored-by: https://despairlabs.com/sponsor/
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Rob Norris <robn@despairlabs.com>
Closes #17861
This commit is contained in:
Rob Norris
2025-11-11 11:16:30 +11:00
committed by Brian Behlendorf
parent e282e98e79
commit 4d451bae8a
10 changed files with 58 additions and 52 deletions
Download Patch File Download Diff File Expand all files Collapse all files
cmd/zstream/zstream_redup.c
+2 -2
View File
@@ -191,9 +191,9 @@ zfs_redup_stream(int infd, int outfd, boolean_t verbose)
#ifdef _ILP32
uint64_t max_rde_size = SMALLEST_POSSIBLE_MAX_RDT_MB << 20;
#else
uint64_t physmem = sysconf(_SC_PHYS_PAGES) * sysconf(_SC_PAGESIZE);
uint64_t physbytes = sysconf(_SC_PHYS_PAGES) * sysconf(_SC_PAGESIZE);
uint64_t max_rde_size =
MAX((physmem * MAX_RDT_PHYSMEM_PERCENT) / 100,
MAX((physbytes * MAX_RDT_PHYSMEM_PERCENT) / 100,
SMALLEST_POSSIBLE_MAX_RDT_MB << 20);
#endif
cmd/ztest.c
+4 -15
View File
@@ -140,9 +140,9 @@
#include <sys/zfs_impl.h>
#include <sys/backtrace.h>
#include <libzpool.h>
#include <libspl.h>
static int ztest_fd_data = -1;
static int ztest_fd_rand = -1;
typedef struct ztest_shared_hdr {
uint64_t zh_hdr_size;
@@ -903,13 +903,10 @@ ztest_random(uint64_t range)
{
uint64_t r;
ASSERT3S(ztest_fd_rand, >=, 0);
if (range == 0)
return (0);
if (read(ztest_fd_rand, &r, sizeof (r)) != sizeof (r))
fatal(B_TRUE, "short read from /dev/urandom");
random_get_pseudo_bytes((uint8_t *)&r, sizeof (r));
return (r % range);
}
@@ -8146,10 +8143,8 @@ ztest_raidz_expand_run(ztest_shared_t *zs, spa_t *spa)
/* Setup a 1 MiB buffer of random data */
uint64_t bufsize = 1024 * 1024;
void *buffer = umem_alloc(bufsize, UMEM_NOFAIL);
random_get_pseudo_bytes((uint8_t *)&buffer, bufsize);
if (read(ztest_fd_rand, buffer, bufsize) != bufsize) {
fatal(B_TRUE, "short read from /dev/urandom");
}
/*
* Put some data in the pool and then attach a vdev to initiate
* reflow.
@@ -8955,13 +8950,7 @@ main(int argc, char **argv)
exit(EXIT_FAILURE);
}
/*
* Force random_get_bytes() to use /dev/urandom in order to prevent
* ztest from needlessly depleting the system entropy pool.
*/
random_path = "/dev/urandom";
ztest_fd_rand = open(random_path, O_RDONLY | O_CLOEXEC);
ASSERT3S(ztest_fd_rand, >=, 0);
libspl_init();
if (!fd_data_str) {
process_options(argc, argv);