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[PATCH 08/10] nptl: arm: Fix Race conditions in pthread cancellation (BZ#12683)
- From: Adhemerval Zanella <adhemerval dot zanella at linaro dot org>
- To: GNU C Library <libc-alpha at sourceware dot org>
- Date: Thu, 17 Sep 2015 17:04:22 -0300
- Subject: [PATCH 08/10] nptl: arm: Fix Race conditions in pthread cancellation (BZ#12683)
- Authentication-results: sourceware.org; auth=none
This patch adds the ARM modifications required for the BZ#12683 fix.
It basically removes the enable_asynccancel/disable_asynccancel function
usage on code, provide a arch-specific symbol that contains global
markers to be used in SIGCANCEL handler.
--
* sysdeps/unix/sysv/linux/arm/syscall_cancel.S: New file.
* sysdeps/unix/sysv/linux/arm/sysdep-cancel.h (PSEUDO): Redefine
to call __syscall_cancel function for cancellable syscalls.
* sysdeps/unix/sysv/linux/arm/sysdep.h (SYSCALL_CANCEL_ERROR): Add
definition.
(SYSCALL_CANCEL_ERRNO): Likewise.
--
diff --git a/sysdeps/unix/sysv/linux/arm/syscall_cancel.S b/sysdeps/unix/sysv/linux/arm/syscall_cancel.S
new file mode 100644
index 0000000..da4b454
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/arm/syscall_cancel.S
@@ -0,0 +1,72 @@
+/* Cancellable syscall wrapper - arm version.
+ Copyright (C) 2015 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 <sysdep.h>
+
+/* long int [r0] __syscall_cancel_arch (int *cancelhandling [r0],
+ long int nr [r1],
+ long int arg1 [r2],
+ long int arg2 [r3],
+ long int arg3 [SP],
+ long int arg4 [SP+4],
+ long int arg5 [SP+8],
+ long int arg6 [SP+12]) */
+
+#ifdef __thumb2__
+ .thumb
+#endif
+ .syntax unified
+
+ENTRY (__syscall_cancel_arch)
+ .fnstart
+ mov ip,sp
+ stmfd sp!,{r4,r5,r6,lr}
+ .save {r4,r5,r6,lr}
+
+ cfi_adjust_cfa_offset (20)
+ cfi_rel_offset (lr, 16)
+
+ .globl __syscall_cancel_arch_start
+__syscall_cancel_arch_start:
+
+ /* if (*cancelhandling & CANCELED_BITMASK)
+ __syscall_do_cancel() */
+ ldr r0,[r0]
+ tst r0, #4
+ bne 1f
+
+ /* Issue a 6 argument syscall, the nr [r1] being the syscall
+ number. */
+ mov r7,r1
+ mov r0,r2
+ mov r1,r3
+ ldmfd ip,{r2,r3,r4,r5,r6}
+ svc 0x0
+
+ .globl __syscall_cancel_arch_end
+__syscall_cancel_arch_end:
+ ldmfd sp!,{r4,r5,r6,lr}
+ cfi_adjust_cfa_offset (-16);
+ bx lr
+
+1:
+ mov lr, pc
+ b __syscall_do_cancel
+ .fnend
+END (__syscall_cancel_arch)
+libc_hidden_def (__syscall_cancel_arch)
diff --git a/sysdeps/unix/sysv/linux/arm/sysdep-cancel.h b/sysdeps/unix/sysv/linux/arm/sysdep-cancel.h
index bdefa80..afbf07d 100644
--- a/sysdeps/unix/sysv/linux/arm/sysdep-cancel.h
+++ b/sysdeps/unix/sysv/linux/arm/sysdep-cancel.h
@@ -19,10 +19,17 @@
#include <tls.h>
#ifndef __ASSEMBLER__
# include <nptl/pthreadP.h>
+# include <sys/ucontext.h>
#endif
#if IS_IN (libc) || IS_IN (libpthread) || IS_IN (librt)
+# if IS_IN (libc)
+# define JMP_SYSCALL_CANCEL HIDDEN_JUMPTARGET(__syscall_cancel)
+# else
+# define JMP_SYSCALL_CANCEL __syscall_cancel(PLT)
+# endif
+
/* NOTE: We do mark syscalls with unwind annotations, for the benefit of
cancellation; but they're really only accurate at the point of the
syscall. The ARM unwind directives are not rich enough without adding
@@ -31,16 +38,10 @@
# undef PSEUDO
# define PSEUDO(name, syscall_name, args) \
.text; \
- ENTRY (__##syscall_name##_nocancel); \
- CFI_SECTIONS; \
- DO_CALL (syscall_name, args); \
- cmn r0, $4096; \
- PSEUDO_RET; \
- END (__##syscall_name##_nocancel); \
ENTRY (name); \
SINGLE_THREAD_P; \
- DOARGS_##args; \
bne .Lpseudo_cancel; \
+ DOARGS_##args; \
cfi_remember_state; \
ldr r7, =SYS_ify (syscall_name); \
swi 0x0; \
@@ -50,150 +51,36 @@
cfi_restore_state; \
.Lpseudo_cancel: \
.fnstart; /* matched by the .fnend in UNDOARGS below. */ \
- DOCARGS_##args; /* save syscall args etc. around CENABLE. */ \
- CENABLE; \
- mov ip, r0; /* put mask in safe place. */ \
- UNDOCARGS_##args; /* restore syscall args. */ \
- ldr r7, =SYS_ify (syscall_name); \
- swi 0x0; /* do the call. */ \
- mov r7, r0; /* save syscall return value. */ \
- mov r0, ip; /* get mask back. */ \
- CDISABLE; \
- mov r0, r7; /* retrieve return value. */ \
- RESTORE_LR_##args; \
- UNDOARGS_##args; \
+ push {r4, r5, lr}; \
+ .save {r4, r5, lr}; \
+ PSEUDO_CANCEL_BEFORE; \
+ ldr r0, =SYS_ify (syscall_name); \
+ PSEUDO_CANCEL_AFTER; \
+ pop {r4, r5, lr}; \
+ .fnend; \
cmn r0, $4096
-/* DOARGS pushes eight bytes on the stack for five arguments, twelve bytes for
- six arguments, and four bytes for fewer. In order to preserve doubleword
- alignment, sometimes we must save an extra register. */
-
-# define RESTART_UNWIND \
- .fnend; \
- .fnstart; \
- .save {r7}; \
- .save {lr}
-
-# define DOCARGS_0 \
- .save {r7}; \
- push {lr}; \
- cfi_adjust_cfa_offset (4); \
- cfi_rel_offset (lr, 0); \
- .save {lr}
-# define UNDOCARGS_0
-# define RESTORE_LR_0 \
- pop {lr}; \
- cfi_adjust_cfa_offset (-4); \
- cfi_restore (lr)
-
-# define DOCARGS_1 \
- .save {r7}; \
- push {r0, r1, lr}; \
- cfi_adjust_cfa_offset (12); \
- cfi_rel_offset (lr, 8); \
- .save {lr}; \
- .pad #8
-# define UNDOCARGS_1 \
- ldr r0, [sp], #8; \
- cfi_adjust_cfa_offset (-8); \
- RESTART_UNWIND
-# define RESTORE_LR_1 \
- RESTORE_LR_0
-
-# define DOCARGS_2 \
- .save {r7}; \
- push {r0, r1, lr}; \
- cfi_adjust_cfa_offset (12); \
- cfi_rel_offset (lr, 8); \
- .save {lr}; \
- .pad #8
-# define UNDOCARGS_2 \
- pop {r0, r1}; \
- cfi_adjust_cfa_offset (-8); \
- RESTART_UNWIND
-# define RESTORE_LR_2 \
- RESTORE_LR_0
-
-# define DOCARGS_3 \
- .save {r7}; \
- push {r0, r1, r2, r3, lr}; \
- cfi_adjust_cfa_offset (20); \
- cfi_rel_offset (lr, 16); \
- .save {lr}; \
- .pad #16
-# define UNDOCARGS_3 \
- pop {r0, r1, r2, r3}; \
- cfi_adjust_cfa_offset (-16); \
- RESTART_UNWIND
-# define RESTORE_LR_3 \
- RESTORE_LR_0
-
-# define DOCARGS_4 \
- .save {r7}; \
- push {r0, r1, r2, r3, lr}; \
- cfi_adjust_cfa_offset (20); \
- cfi_rel_offset (lr, 16); \
- .save {lr}; \
- .pad #16
-# define UNDOCARGS_4 \
- pop {r0, r1, r2, r3}; \
- cfi_adjust_cfa_offset (-16); \
- RESTART_UNWIND
-# define RESTORE_LR_4 \
- RESTORE_LR_0
-
-/* r4 is only stmfd'ed for correct stack alignment. */
-# define DOCARGS_5 \
- .save {r4, r7}; \
- push {r0, r1, r2, r3, r4, lr}; \
- cfi_adjust_cfa_offset (24); \
- cfi_rel_offset (lr, 20); \
- .save {lr}; \
- .pad #20
-# define UNDOCARGS_5 \
- pop {r0, r1, r2, r3}; \
- cfi_adjust_cfa_offset (-16); \
- .fnend; \
- .fnstart; \
- .save {r4, r7}; \
- .save {lr}; \
- .pad #4
-# define RESTORE_LR_5 \
- pop {r4, lr}; \
- cfi_adjust_cfa_offset (-8); \
- /* r4 will be marked as restored later. */ \
- cfi_restore (lr)
-
-# define DOCARGS_6 \
- .save {r4, r5, r7}; \
- push {r0, r1, r2, r3, lr}; \
- cfi_adjust_cfa_offset (20); \
- cfi_rel_offset (lr, 16); \
- .save {lr}; \
- .pad #16
-# define UNDOCARGS_6 \
- pop {r0, r1, r2, r3}; \
- cfi_adjust_cfa_offset (-16); \
- .fnend; \
- .fnstart; \
- .save {r4, r5, r7}; \
- .save {lr};
-# define RESTORE_LR_6 \
- RESTORE_LR_0
+# define PSEUDO_CANCEL_BEFORE \
+ .pad #20; \
+ sub sp, sp, #20; \
+ ldr r5, [sp, #32]; \
+ ldr r4, [sp, #36]; \
+ str r3, [sp]; \
+ mov r3, r2; \
+ str r5, [sp, #4]; \
+ mov r2, r1; \
+ str r4, [sp, #8]; \
+ mov r1, r0
+
+# define PSEUDO_CANCEL_AFTER \
+ bl JMP_SYSCALL_CANCEL; \
+ add sp, sp, #20
+
# if IS_IN (libpthread)
-# define CENABLE bl PLTJMP(__pthread_enable_asynccancel)
-# define CDISABLE bl PLTJMP(__pthread_disable_asynccancel)
# define __local_multiple_threads __pthread_multiple_threads
# elif IS_IN (libc)
-# define CENABLE bl PLTJMP(__libc_enable_asynccancel)
-# define CDISABLE bl PLTJMP(__libc_disable_asynccancel)
# define __local_multiple_threads __libc_multiple_threads
-# elif IS_IN (librt)
-# define CENABLE bl PLTJMP(__librt_enable_asynccancel)
-# define CDISABLE bl PLTJMP(__librt_disable_asynccancel)
-# else
-# error Unsupported library
# endif
# if IS_IN (libpthread) || IS_IN (libc)
@@ -238,4 +125,10 @@ extern int __local_multiple_threads attribute_hidden;
# define RTLD_SINGLE_THREAD_P \
__builtin_expect (THREAD_GETMEM (THREAD_SELF, \
header.multiple_threads) == 0, 1)
+
+static inline
+long int __pthread_get_ip (const struct ucontext *uc)
+{
+ return uc->uc_mcontext.arm_pc;
+}
#endif
diff --git a/sysdeps/unix/sysv/linux/arm/sysdep.h b/sysdeps/unix/sysv/linux/arm/sysdep.h
index 200f77a..6b18e34 100644
--- a/sysdeps/unix/sysv/linux/arm/sysdep.h
+++ b/sysdeps/unix/sysv/linux/arm/sysdep.h
@@ -387,6 +387,14 @@ __local_syscall_error: \
#undef INTERNAL_SYSCALL_ERRNO
#define INTERNAL_SYSCALL_ERRNO(val, err) (-(val))
+#undef SYSCALL_CANCEL_ERROR
+#define SYSCALL_CANCEL_ERROR(__val) \
+ ((unsigned int) (__val) >= 0xfffff001u)
+
+#undef SYSCALL_CANCEL_ERRNO
+#define SYSCALL_CANCEL_ERRNO(__val) \
+ (-(__val))
+
/* List of system calls which are supported as vsyscalls. */
#define HAVE_CLOCK_GETTIME_VSYSCALL 1
#define HAVE_GETTIMEOFDAY_VSYSCALL 1