From 95e7cf295e449c0aec3d7a76f01907bf300106bf Mon Sep 17 00:00:00 2001 From: "Maciej W. Rozycki" Date: Mon, 9 Sep 2013 22:36:57 +0100 Subject: [PATCH] Fix static-binary lazy FPU context allocation Long ago static startup did not parse the auxiliary vector and therefore could not get at any `AT_FPUCW' tag to check whether upon FPU context allocation the kernel would use a FPU control word setting different to that provided by the `__fpu_control' variable. Static startup therefore always initialized the FPU control word, forcing immediate FPU context allocation even for binaries that otherwise never used the FPU. As from GIT commit f8f900ecb9096ec47f5b7bb7626e29223c69061a static startup supports parsing the auxiliary vector, so now it can avoid explicit initialization of the FPU control word, just as can dynamic startup, in the usual case where the setting written to the FPU control word would be the same as the kernel uses. This defers FPU context allocation until the binary itself actually pokes at the FPU. Note that the `AT_FPUCW' tag is usually absent from the auxiliary vector in which case _FPU_DEFAULT is assumed to be the kernel default. --- ChangeLog | 22 ++++++++++++++++++++++ csu/init-first.c | 5 +---- elf/dl-support.c | 6 ++++++ math/Makefile | 11 +++++++---- math/test-fpucw-ieee-static.c | 1 + math/test-fpucw-ieee.c | 24 ++++++++++++++++++++++++ math/test-fpucw-static.c | 1 + math/test-fpucw.c | 10 +++++++--- 8 files changed, 69 insertions(+), 11 deletions(-) create mode 100644 math/test-fpucw-ieee-static.c create mode 100644 math/test-fpucw-ieee.c create mode 100644 math/test-fpucw-static.c diff --git a/ChangeLog b/ChangeLog index 9b73de5cb9..ae3a10c3f1 100644 --- a/ChangeLog +++ b/ChangeLog @@ -1,3 +1,25 @@ +2013-09-09 Maciej W. Rozycki + + * csu/init-first.c (_init): Remove the !SHARED condition around + FPU control word initialization. + * elf/dl-support.c (_dl_fpu_control): New variable. + (_dl_aux_init) : Initialize it. + * math/test-fpucw.c [!FPU_CONTROL] (FPU_CONTROL): New macro. + (main): Replace _FPU_DEFAULT with FPU_CONTROL throughout. + * math/test-fpucw-static.c: New file. + * math/test-fpucw-ieee.c: New file. + * math/test-fpucw-ieee-static.c: New file. + * math/Makefile (tests): Add `test-fpucw-ieee' and + `$(tests-static)'. + (tests-static): New variable. + [($(build-shared),yes)] ($(addprefix $(objpfx),$(tests))): Move + dependency to... + [($(build-shared),yes)] + ($(addprefix $(objpfx),$(filter-out $(tests-static),$(tests)))): + ... this. + [($(build-shared),yes)] ($(addprefix $(objpfx),$(tests-static))): + New dependency. + 2013-09-09 Allan McRae [BZ #15939] diff --git a/csu/init-first.c b/csu/init-first.c index f0ebc94b8d..b4d22ce6aa 100644 --- a/csu/init-first.c +++ b/csu/init-first.c @@ -61,11 +61,8 @@ _init (int argc, char **argv, char **envp) if (!__libc_multiple_libcs) { /* Set the FPU control word to the proper default value if the - kernel would use a different value. (In a static program we - don't have this information.) */ -#ifdef SHARED + kernel would use a different value. */ if (__fpu_control != GLRO(dl_fpu_control)) -#endif __setfpucw (__fpu_control); } diff --git a/elf/dl-support.c b/elf/dl-support.c index 5a082feb7a..2023bd031c 100644 --- a/elf/dl-support.c +++ b/elf/dl-support.c @@ -167,6 +167,9 @@ size_t _dl_phnum; uint64_t _dl_hwcap __attribute__ ((nocommon)); uint64_t _dl_hwcap2 __attribute__ ((nocommon)); +/* The value of the FPU control word the kernel will preset in hardware. */ +fpu_control_t _dl_fpu_control = _FPU_DEFAULT; + /* This is not initialized to HWCAP_IMPORTANT, matching the definition of _dl_important_hwcaps, below, where no hwcap strings are ever used. This mask is still used to mediate the lookups in the cache @@ -253,6 +256,9 @@ _dl_aux_init (ElfW(auxv_t) *av) case AT_HWCAP2: GLRO(dl_hwcap2) = (unsigned long int) av->a_un.a_val; break; + case AT_FPUCW: + GLRO(dl_fpu_control) = av->a_un.a_val; + break; #ifdef NEED_DL_SYSINFO case AT_SYSINFO: GL(dl_sysinfo) = av->a_un.a_val; diff --git a/math/Makefile b/math/Makefile index 3ed78fc9c3..a9bd49baee 100644 --- a/math/Makefile +++ b/math/Makefile @@ -87,9 +87,11 @@ long-c-yes = $(calls:=l) # Rules for the test suite. tests = test-matherr test-fenv atest-exp atest-sincos atest-exp2 basic-test \ - test-misc test-fpucw tst-definitions test-tgmath test-tgmath-ret \ - bug-nextafter bug-nexttoward bug-tgmath1 test-tgmath-int \ - test-tgmath2 test-powl tst-CMPLX tst-CMPLX2 test-snan + test-misc test-fpucw test-fpucw-ieee tst-definitions test-tgmath \ + test-tgmath-ret bug-nextafter bug-nexttoward bug-tgmath1 \ + test-tgmath-int test-tgmath2 test-powl tst-CMPLX tst-CMPLX2 test-snan \ + $(tests-static) +tests-static = test-fpucw-static test-fpucw-ieee-static # We do the `long double' tests only if this data type is available and # distinct from `double'. test-longdouble-yes = test-ldouble test-ildoubl @@ -217,7 +219,8 @@ $(objpfx)libieee.a: $(objpfx)ieee-math.o $(LN_S) $(. */ + +#define FPU_CONTROL _FPU_IEEE + +#include "test-fpucw.c" + +/* Preempt the library's definition of `__fpu_control'. */ +fpu_control_t __fpu_control = _FPU_IEEE; diff --git a/math/test-fpucw-static.c b/math/test-fpucw-static.c new file mode 100644 index 0000000000..bc1cfa8ce5 --- /dev/null +++ b/math/test-fpucw-static.c @@ -0,0 +1 @@ +#include "test-fpucw.c" diff --git a/math/test-fpucw.c b/math/test-fpucw.c index 1961a67481..ae6a2c9a71 100644 --- a/math/test-fpucw.c +++ b/math/test-fpucw.c @@ -19,6 +19,10 @@ #include #include +#ifndef FPU_CONTROL +# define FPU_CONTROL _FPU_DEFAULT +#endif + int main (void) { @@ -30,11 +34,11 @@ main (void) cw &= ~_FPU_RESERVED; - if (cw != (_FPU_DEFAULT & ~_FPU_RESERVED)) + if (cw != (FPU_CONTROL & ~_FPU_RESERVED)) printf ("control word is 0x%lx but should be 0x%lx.\n", - (long int) cw, (long int) (_FPU_DEFAULT & ~_FPU_RESERVED)); + (long int) cw, (long int) (FPU_CONTROL & ~_FPU_RESERVED)); - return cw != (_FPU_DEFAULT & ~_FPU_RESERVED); + return cw != (FPU_CONTROL & ~_FPU_RESERVED); #else return 0;