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Re: PATCH: Add x32 arch_prctl support
On Tue, May 22, 2012 at 9:53 AM, Roland McGrath <roland@hack.frob.com> wrote:
>> I submitted a patch to remove x32 PTRACE_ARCH_PRCTL from
>> kernel. ?Here is a patch with only arch_prctl.c. OK to install?
>
> I'm certainly happy with the ptrace cleanup.
>
>> +/* Since x32 arch_prctl stores 32-bit base address of segment register %fs
>
> "the 32-bit ..."
> "segment registers"
>
>> + ? and %gs as unsigned 64-bit value via ARCH_GET_FS and ARCH_GET_GS, we
>
> "as an unsigned 64-bit value"
>
>> + ? use a local unsigned 64-bit variable to hold the base address and copy
>> + ? it to ADDR after arch_prctl return. ?*/
>
> "after the system call returns"
>
...
>> +weak_alias (__arch_prctl, arch_prctl)
>
> We usually don't have a blank line before a weak_alias like this.
>
Here is the updated patch. The differences are
1. Old:
0: 67 8d 97 fd ef ff ff lea -0x1003(%edi),%edx
7: 83 fa 01 cmp $0x1,%edx
a: 77 08 ja 14 <__arch_prctl+0x14>
c: 41 89 f0 mov %esi,%r8d
f: 67 8d 74 24 f8 lea -0x8(%esp),%esi
14: b8 9e 00 00 40 mov $0x4000009e,%eax
19: 0f 05 syscall
2. New
0: 67 8d 97 fd ef ff ff lea -0x1003(%edi),%edx
7: 49 89 f0 mov %rsi,%r8
a: 67 8d 74 24 f8 lea -0x8(%esp),%esi
f: b8 9e 00 00 40 mov $0x4000009e,%eax
14: 83 fa 01 cmp $0x1,%edx
17: 41 0f 47 f0 cmova %r8d,%esi
1b: 0f 05 syscall
There are no GCC warnings. OK to install?
Thanks.
--
H.J.
----
* sysdeps/unix/sysv/linux/x86_64/x32/Makefile (sysdep_routines):
Add arch_prctl.
* sysdeps/unix/sysv/linux/x86_64/x32/arch_prctl.c: New file.
diff --git a/sysdeps/unix/sysv/linux/x86_64/x32/Makefile
b/sysdeps/unix/sysv/linux/x86_64/x32/Makefile
index 5f77df7..aa78238 100644
--- a/sysdeps/unix/sysv/linux/x86_64/x32/Makefile
+++ b/sysdeps/unix/sysv/linux/x86_64/x32/Makefile
@@ -1,3 +1,7 @@
+ifeq ($(subdir),misc)
+sysdep_routines += arch_prctl
+endif
+
ifeq ($(subdir),posix)
sysdep_routines += getcpu sched_getcpu-static
endif
diff --git a/sysdeps/unix/sysv/linux/x86_64/x32/arch_prctl.c
b/sysdeps/unix/sysv/linux/x86_64/x32/arch_prctl.c
new file mode 100644
index 0000000..6933306
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/x86_64/x32/arch_prctl.c
@@ -0,0 +1,62 @@
+/* arch_prctl call for Linux/x32.
+ Copyright (C) 2012 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
+ <http://www.gnu.org/licenses/>. */
+
+#include <errno.h>
+#include <sys/prctl.h>
+#include <sys/syscall.h>
+#include <sysdep.h>
+
+/* Since x32 arch_prctl stores 32-bit base address of segment registers
+ %fs and %gs as unsigned 64-bit value via ARCH_GET_FS and ARCH_GET_GS,
+ we use an unsigned 64-bit variable to hold the base address and copy
+ it to ADDR after the system call returns. */
+
+int
+__arch_prctl (int code, uintptr_t *addr)
+{
+ int res;
+ uint64_t addr64;
+ void *prctl_arg = addr;
+
+ switch (code)
+ {
+ case ARCH_GET_FS:
+ case ARCH_GET_GS:
+ prctl_arg = &addr64;
+ break;
+ }
+
+ res = INLINE_SYSCALL (arch_prctl, 2, code, prctl_arg);
+ if (res == 0)
+ switch (code)
+ {
+ case ARCH_GET_FS:
+ case ARCH_GET_GS:
+ /* Check for a large value that overflows. */
+ if ((uintptr_t) addr64 != addr64)
+ {
+ __set_errno (EOVERFLOW);
+ return -1;
+ }
+ *addr = (uintptr_t) addr64;
+ break;
+ }
+
+ return res;
+}
+weak_alias (__arch_prctl, arch_prctl)