Disable floating point code/linking when possible.
Unless heap profiling is enabled, disable floating point code and don't
link with libm. This, in combination with e.g. EXTRA_CFLAGS=-mno-sse on
x64 systems, makes it possible to completely disable floating point
register use. Some versions of glibc neglect to save/restore
caller-saved floating point registers during dynamic lazy symbol
loading, and the symbol loading code uses whatever malloc the
application happens to have linked/loaded with, the result being
potential floating point register corruption.
diff --git a/ChangeLog b/ChangeLog
index 90ab107..34d017e 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -9,6 +9,13 @@
* 3.5.0 (XXX)
Bug fixes:
+ - Unless heap profiling is enabled, disable floating point code and don't link
+ with libm. This, in combination with e.g. EXTRA_CFLAGS=-mno-sse on x64
+ systems, makes it possible to completely disable floating point register
+ use. Some versions of glibc neglect to save/restore caller-saved floating
+ point registers during dynamic lazy symbol loading, and the symbol loading
+ code uses whatever malloc the application happens to have linked/loaded
+ with, the result being potential floating point register corruption.
- Change the default private namespace prefix from empty to je_, and change
--with-private-namespace-prefix so that it prepends an additional prefix
rather than replacing je_. This reduces the likelihood of applications
diff --git a/configure.ac b/configure.ac
index 7f0fecc..1103cc7 100644
--- a/configure.ac
+++ b/configure.ac
@@ -356,11 +356,6 @@
AC_SUBST([AROUT])
AC_SUBST([CC_MM])
-if test "x$abi" != "xpecoff"; then
- dnl Heap profiling uses the log(3) function.
- LIBS="$LIBS -lm"
-fi
-
JE_COMPILABLE([__attribute__ syntax],
[static __attribute__((unused)) void foo(void){}],
[],
@@ -774,6 +769,12 @@
AC_MSG_ERROR([Heap profiling requires TLS]);
fi
force_tls="1"
+
+ if test "x$abi" != "xpecoff"; then
+ dnl Heap profiling uses the log(3) function.
+ LIBS="$LIBS -lm"
+ fi
+
AC_DEFINE([JEMALLOC_PROF], [ ])
fi
AC_SUBST([enable_prof])
diff --git a/include/jemalloc/internal/prof.h b/include/jemalloc/internal/prof.h
index 119a5b1..38a761b 100644
--- a/include/jemalloc/internal/prof.h
+++ b/include/jemalloc/internal/prof.h
@@ -320,6 +320,20 @@
JEMALLOC_INLINE void
prof_sample_threshold_update(prof_tdata_t *prof_tdata)
{
+ /*
+ * The body of this function is compiled out unless heap profiling is
+ * enabled, so that it is possible to compile jemalloc with floating
+ * point support completely disabled. Avoiding floating point code is
+ * important on memory-constrained systems, but it also enables a
+ * workaround for versions of glibc that don't properly save/restore
+ * floating point registers during dynamic lazy symbol loading (which
+ * internally calls into whatever malloc implementation happens to be
+ * integrated into the application). Note that some compilers (e.g.
+ * gcc 4.8) may use floating point registers for fast memory moves, so
+ * jemalloc must be compiled with such optimizations disabled (e.g.
+ * -mno-sse) in order for the workaround to be complete.
+ */
+#ifdef JEMALLOC_PROF
uint64_t r;
double u;
@@ -349,6 +363,7 @@
prof_tdata->threshold = (uint64_t)(log(u) /
log(1.0 - (1.0 / (double)((uint64_t)1U << opt_lg_prof_sample))))
+ (uint64_t)1U;
+#endif
}
JEMALLOC_INLINE prof_ctx_t *