[v2] Linux: Consolidate auxiliary vector parsing (redo)
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Commit Message
And optimize it slightly.
This is commit 8c8510ab2790039e58995ef3a22309582413d3ff revised.
In _dl_aux_init in elf/dl-support.c, use an explicit loop
and -fno-tree-loop-distribute-patterns to avoid memset.
Reviewed-by: Szabolcs Nagy <szabolcs.nagy@arm.com>
---
v2: Fix #include ordering in sysdeps/unix/sysv/linux/dl-sysdep.c
to address s390x build failure with certain kernel header versions.
elf/Makefile | 5 ++
elf/dl-support.c | 85 +++-----------------
sysdeps/unix/sysv/linux/alpha/dl-auxv.h | 18 ++---
sysdeps/unix/sysv/linux/dl-parse_auxv.h | 61 ++++++++++++++
sysdeps/unix/sysv/linux/dl-sysdep.c | 114 ++++++++-------------------
sysdeps/unix/sysv/linux/powerpc/dl-auxv.h | 14 +---
sysdeps/unix/sysv/linux/powerpc/dl-support.c | 4 +
7 files changed, 118 insertions(+), 183 deletions(-)
Comments
On Feb 14 2022, Florian Weimer via Libc-alpha wrote:
> diff --git a/sysdeps/unix/sysv/linux/dl-parse_auxv.h b/sysdeps/unix/sysv/linux/dl-parse_auxv.h
> new file mode 100644
> index 0000000000..b3d82f6994
> --- /dev/null
> +++ b/sysdeps/unix/sysv/linux/dl-parse_auxv.h
> @@ -0,0 +1,61 @@
> +/* Parse the Linux auxiliary vector.
> + Copyright (C) 1995-2022 Free Software Foundation, Inc.
> + This file is part of the GNU C Library.
> +
> + The GNU C Library is free software; you can redistribute it and/or
> + modify it under the terms of the GNU Lesser General Public
> + License as published by the Free Software Foundation; either
> + version 2.1 of the License, or (at your option) any later version.
> +
> + The GNU C Library is distributed in the hope that it will be useful,
> + but WITHOUT ANY WARRANTY; without even the implied warranty of
> + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
> + Lesser General Public License for more details.
> +
> + You should have received a copy of the GNU Lesser General Public
> + License along with the GNU C Library; if not, see
> + <https://www.gnu.org/licenses/>. */
> +
> +#include <elf.h>
> +#include <entry.h>
> +#include <fpu_control.h>
> +#include <ldsodefs.h>
> +#include <link.h>
> +
> +typedef ElfW(Addr) dl_parse_auxv_t[AT_MINSIGSTKSZ + 1];
> +
> +/* Copy the auxiliary vector into AUX_VALUES and set up GLRO
s/AUX/AUXV/
@@ -160,6 +160,11 @@ ifeq (yes,$(have-loop-to-function))
CFLAGS-rtld.c += -fno-tree-loop-distribute-patterns
endif
+ifeq (yes,$(have-loop-to-function))
+# Likewise, during static library startup, memset is not yet available.
+CFLAGS-dl-support.c = -fno-tree-loop-distribute-patterns
+endif
+
# Compile rtld itself without stack protection.
# Also compile all routines in the static library that are elided from
# the shared libc because they are in libc.a in the same way.
@@ -44,6 +44,7 @@
#include <dl-vdso-setup.h>
#include <dl-auxv.h>
#include <dl-find_object.h>
+#include <array_length.h>
extern char *__progname;
char **_dl_argv = &__progname; /* This is checked for some error messages. */
@@ -240,93 +241,25 @@ __rtld_lock_define_initialized_recursive (, _dl_load_tls_lock)
#ifdef HAVE_AUX_VECTOR
+#include <dl-parse_auxv.h>
+
int _dl_clktck;
void
_dl_aux_init (ElfW(auxv_t) *av)
{
- int seen = 0;
- uid_t uid = 0;
- gid_t gid = 0;
-
#ifdef NEED_DL_SYSINFO
/* NB: Avoid RELATIVE relocation in static PIE. */
GL(dl_sysinfo) = DL_SYSINFO_DEFAULT;
#endif
_dl_auxv = av;
- for (; av->a_type != AT_NULL; ++av)
- switch (av->a_type)
- {
- case AT_PAGESZ:
- if (av->a_un.a_val != 0)
- GLRO(dl_pagesize) = av->a_un.a_val;
- break;
- case AT_CLKTCK:
- GLRO(dl_clktck) = av->a_un.a_val;
- break;
- case AT_PHDR:
- GL(dl_phdr) = (const void *) av->a_un.a_val;
- break;
- case AT_PHNUM:
- GL(dl_phnum) = av->a_un.a_val;
- break;
- case AT_PLATFORM:
- GLRO(dl_platform) = (void *) av->a_un.a_val;
- break;
- case AT_HWCAP:
- GLRO(dl_hwcap) = (unsigned long int) av->a_un.a_val;
- break;
- 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;
- break;
-#endif
-#ifdef NEED_DL_SYSINFO_DSO
- case AT_SYSINFO_EHDR:
- GL(dl_sysinfo_dso) = (void *) av->a_un.a_val;
- break;
-#endif
- case AT_UID:
- uid ^= av->a_un.a_val;
- seen |= 1;
- break;
- case AT_EUID:
- uid ^= av->a_un.a_val;
- seen |= 2;
- break;
- case AT_GID:
- gid ^= av->a_un.a_val;
- seen |= 4;
- break;
- case AT_EGID:
- gid ^= av->a_un.a_val;
- seen |= 8;
- break;
- case AT_SECURE:
- seen = -1;
- __libc_enable_secure = av->a_un.a_val;
- __libc_enable_secure_decided = 1;
- break;
- case AT_RANDOM:
- _dl_random = (void *) av->a_un.a_val;
- break;
- case AT_MINSIGSTKSZ:
- _dl_minsigstacksize = av->a_un.a_val;
- break;
- DL_PLATFORM_AUXV
- }
- if (seen == 0xf)
- {
- __libc_enable_secure = uid != 0 || gid != 0;
- __libc_enable_secure_decided = 1;
- }
+ dl_parse_auxv_t auxv_values;
+ /* Use an explicit initialization loop here because memset may not
+ be available yet. */
+ for (int i = 0; i < array_length (auxv_values); ++i)
+ auxv_values[i] = 0;
+ _dl_parse_auxv (av, auxv_values);
}
#endif
@@ -20,16 +20,8 @@
extern long __libc_alpha_cache_shape[4];
-#define DL_PLATFORM_AUXV \
- case AT_L1I_CACHESHAPE: \
- __libc_alpha_cache_shape[0] = av->a_un.a_val; \
- break; \
- case AT_L1D_CACHESHAPE: \
- __libc_alpha_cache_shape[1] = av->a_un.a_val; \
- break; \
- case AT_L2_CACHESHAPE: \
- __libc_alpha_cache_shape[2] = av->a_un.a_val; \
- break; \
- case AT_L3_CACHESHAPE: \
- __libc_alpha_cache_shape[3] = av->a_un.a_val; \
- break;
+#define DL_PLATFORM_AUXV \
+ __libc_alpha_cache_shape[0] = auxv_values[AT_L1I_CACHESHAPE]; \
+ __libc_alpha_cache_shape[1] = auxv_values[AT_L1D_CACHESHAPE]; \
+ __libc_alpha_cache_shape[2] = auxv_values[AT_L2_CACHESHAPE]; \
+ __libc_alpha_cache_shape[3] = auxv_values[AT_L3_CACHESHAPE];
new file mode 100644
@@ -0,0 +1,61 @@
+/* Parse the Linux auxiliary vector.
+ Copyright (C) 1995-2022 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <https://www.gnu.org/licenses/>. */
+
+#include <elf.h>
+#include <entry.h>
+#include <fpu_control.h>
+#include <ldsodefs.h>
+#include <link.h>
+
+typedef ElfW(Addr) dl_parse_auxv_t[AT_MINSIGSTKSZ + 1];
+
+/* Copy the auxiliary vector into AUX_VALUES and set up GLRO
+ variables. */
+static inline
+void _dl_parse_auxv (ElfW(auxv_t) *av, dl_parse_auxv_t auxv_values)
+{
+ auxv_values[AT_ENTRY] = (ElfW(Addr)) ENTRY_POINT;
+ auxv_values[AT_PAGESZ] = EXEC_PAGESIZE;
+ auxv_values[AT_FPUCW] = _FPU_DEFAULT;
+
+ /* NB: Default to a constant CONSTANT_MINSIGSTKSZ. */
+ _Static_assert (__builtin_constant_p (CONSTANT_MINSIGSTKSZ),
+ "CONSTANT_MINSIGSTKSZ is constant");
+ auxv_values[AT_MINSIGSTKSZ] = CONSTANT_MINSIGSTKSZ;
+
+ for (; av->a_type != AT_NULL; av++)
+ if (av->a_type <= AT_MINSIGSTKSZ)
+ auxv_values[av->a_type] = av->a_un.a_val;
+
+ GLRO(dl_pagesize) = auxv_values[AT_PAGESZ];
+ __libc_enable_secure = auxv_values[AT_SECURE];
+ GLRO(dl_platform) = (void *) auxv_values[AT_PLATFORM];
+ GLRO(dl_hwcap) = auxv_values[AT_HWCAP];
+ GLRO(dl_hwcap2) = auxv_values[AT_HWCAP2];
+ GLRO(dl_clktck) = auxv_values[AT_CLKTCK];
+ GLRO(dl_fpu_control) = auxv_values[AT_FPUCW];
+ _dl_random = (void *) auxv_values[AT_RANDOM];
+ GLRO(dl_minsigstacksize) = auxv_values[AT_MINSIGSTKSZ];
+ GLRO(dl_sysinfo_dso) = (void *) auxv_values[AT_SYSINFO_EHDR];
+#ifdef NEED_DL_SYSINFO
+ if (GLRO(dl_sysinfo_dso) != NULL)
+ GLRO(dl_sysinfo) = auxv_values[AT_SYSINFO];
+#endif
+
+ DL_PLATFORM_AUXV
+}
@@ -18,15 +18,14 @@
#include <_itoa.h>
#include <assert.h>
-#include <dl-hwcap-check.h>
+#include <dl-auxv.h>
#include <dl-osinfo.h>
+#include <dl-parse_auxv.h>
#include <dl-procinfo.h>
#include <dl-tunables.h>
#include <elf.h>
-#include <entry.h>
#include <errno.h>
#include <fcntl.h>
-#include <fpu_control.h>
#include <ldsodefs.h>
#include <libc-internal.h>
#include <libintl.h>
@@ -43,10 +42,9 @@
#include <unistd.h>
#include <dl-machine.h>
+#include <dl-hwcap-check.h>
#ifdef SHARED
-# include <dl-auxv.h>
-
extern char **_environ attribute_hidden;
extern char _end[] attribute_hidden;
@@ -64,20 +62,20 @@ void *_dl_random attribute_relro = NULL;
# define DL_STACK_END(cookie) ((void *) (cookie))
#endif
-ElfW(Addr)
-_dl_sysdep_start (void **start_argptr,
- void (*dl_main) (const ElfW(Phdr) *phdr, ElfW(Word) phnum,
- ElfW(Addr) *user_entry, ElfW(auxv_t) *auxv))
+/* Arguments passed to dl_main. */
+struct dl_main_arguments
{
- const ElfW(Phdr) *phdr = NULL;
- ElfW(Word) phnum = 0;
+ const ElfW(Phdr) *phdr;
+ ElfW(Word) phnum;
ElfW(Addr) user_entry;
- ElfW(auxv_t) *av;
-#ifdef NEED_DL_SYSINFO
- uintptr_t new_sysinfo = 0;
-#endif
+};
- __libc_stack_end = DL_STACK_END (start_argptr);
+/* Separate function, so that dl_main can be called without the large
+ array on the stack. */
+static void
+_dl_sysdep_parse_arguments (void **start_argptr,
+ struct dl_main_arguments *args)
+{
_dl_argc = (intptr_t) *start_argptr;
_dl_argv = (char **) (start_argptr + 1); /* Necessary aliasing violation. */
_environ = _dl_argv + _dl_argc + 1;
@@ -89,75 +87,26 @@ _dl_sysdep_start (void **start_argptr,
break;
}
- user_entry = (ElfW(Addr)) ENTRY_POINT;
- GLRO(dl_platform) = NULL; /* Default to nothing known about the platform. */
+ dl_parse_auxv_t auxv_values = { 0, };
+ _dl_parse_auxv (GLRO(dl_auxv), auxv_values);
- /* NB: Default to a constant CONSTANT_MINSIGSTKSZ. */
- _Static_assert (__builtin_constant_p (CONSTANT_MINSIGSTKSZ),
- "CONSTANT_MINSIGSTKSZ is constant");
- GLRO(dl_minsigstacksize) = CONSTANT_MINSIGSTKSZ;
+ args->phdr = (const ElfW(Phdr) *) auxv_values[AT_PHDR];
+ args->phnum = auxv_values[AT_PHNUM];
+ args->user_entry = auxv_values[AT_ENTRY];
+}
- for (av = GLRO(dl_auxv); av->a_type != AT_NULL; av++)
- switch (av->a_type)
- {
- case AT_PHDR:
- phdr = (void *) av->a_un.a_val;
- break;
- case AT_PHNUM:
- phnum = av->a_un.a_val;
- break;
- case AT_PAGESZ:
- GLRO(dl_pagesize) = av->a_un.a_val;
- break;
- case AT_ENTRY:
- user_entry = av->a_un.a_val;
- break;
- case AT_SECURE:
- __libc_enable_secure = av->a_un.a_val;
- break;
- case AT_PLATFORM:
- GLRO(dl_platform) = (void *) av->a_un.a_val;
- break;
- case AT_HWCAP:
- GLRO(dl_hwcap) = (unsigned long int) av->a_un.a_val;
- break;
- case AT_HWCAP2:
- GLRO(dl_hwcap2) = (unsigned long int) av->a_un.a_val;
- break;
- case AT_CLKTCK:
- GLRO(dl_clktck) = 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:
- new_sysinfo = av->a_un.a_val;
- break;
-#endif
- case AT_SYSINFO_EHDR:
- GLRO(dl_sysinfo_dso) = (void *) av->a_un.a_val;
- break;
- case AT_RANDOM:
- _dl_random = (void *) av->a_un.a_val;
- break;
- case AT_MINSIGSTKSZ:
- GLRO(dl_minsigstacksize) = av->a_un.a_val;
- break;
- DL_PLATFORM_AUXV
- }
+ElfW(Addr)
+_dl_sysdep_start (void **start_argptr,
+ void (*dl_main) (const ElfW(Phdr) *phdr, ElfW(Word) phnum,
+ ElfW(Addr) *user_entry, ElfW(auxv_t) *auxv))
+{
+ __libc_stack_end = DL_STACK_END (start_argptr);
+
+ struct dl_main_arguments dl_main_args;
+ _dl_sysdep_parse_arguments (start_argptr, &dl_main_args);
dl_hwcap_check ();
-#ifdef NEED_DL_SYSINFO
- if (new_sysinfo != 0)
- {
- /* Only set the sysinfo value if we also have the vsyscall DSO. */
- if (GLRO(dl_sysinfo_dso) != 0)
- GLRO(dl_sysinfo) = new_sysinfo;
- }
-#endif
-
__tunables_init (_environ);
/* Initialize DSO sorting algorithm after tunables. */
@@ -188,8 +137,9 @@ _dl_sysdep_start (void **start_argptr,
if (__builtin_expect (__libc_enable_secure, 0))
__libc_check_standard_fds ();
- (*dl_main) (phdr, phnum, &user_entry, GLRO(dl_auxv));
- return user_entry;
+ (*dl_main) (dl_main_args.phdr, dl_main_args.phnum,
+ &dl_main_args.user_entry, GLRO(dl_auxv));
+ return dl_main_args.user_entry;
}
void
@@ -16,15 +16,5 @@
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
-#include <ldsodefs.h>
-
-#if IS_IN (libc) && !defined SHARED
-int GLRO(dl_cache_line_size);
-#endif
-
-/* Scan the Aux Vector for the "Data Cache Block Size" entry and assign it
- to dl_cache_line_size. */
-#define DL_PLATFORM_AUXV \
- case AT_DCACHEBSIZE: \
- GLRO(dl_cache_line_size) = av->a_un.a_val; \
- break;
+#define DL_PLATFORM_AUXV \
+ GLRO(dl_cache_line_size) = auxv_values[AT_DCACHEBSIZE];
new file mode 100644
@@ -0,0 +1,4 @@
+#include <elf/dl-support.c>
+
+/* Populated from the auxiliary vector. */
+int _dl_cache_line_size;