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GNU C Library master sources branch master updated. glibc-2.19-304-g7c67766
- From: willnewton at sourceware dot org
- To: glibc-cvs at sourceware dot org
- Date: 17 Apr 2014 10:41:09 -0000
- Subject: GNU C Library master sources branch master updated. glibc-2.19-304-g7c67766
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http://sourceware.org/git/gitweb.cgi?p=glibc.git;a=commitdiff;h=7c6776620db8e48fca492dbcac88d1c0f239dcde
commit 7c6776620db8e48fca492dbcac88d1c0f239dcde
Author: Will Newton <will.newton@linaro.org>
Date: Thu Mar 13 09:45:29 2014 +0000
manual/setjmp.texi: Clarify setcontext and signal handlers text
Calling setcontext from a signal handler can be done safely so
it is sufficient to note that it is not recommended.
Also mention in setcontext documentation that the behaviour of
setcontext when restoring a context created by a call to a signal
handler is unspecified.
2014-04-17 Will Newton <will.newton@linaro.org>
* manual/setjmp.texi (System V contexts): Add note that
calling setcontext on a context created by a call to a
signal handler is undefined. Update text to note that
setcontext from a signal handler is possible but not
recommended.
diff --git a/ChangeLog b/ChangeLog
index 1dd40fc..7267472 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,11 @@
2014-04-17 Will Newton <will.newton@linaro.org>
+ * manual/setjmp.texi (System V contexts): Add note that
+ calling setcontext on a context created by a call to a
+ signal handler is undefined. Update text to note that
+ setcontext from a signal handler is possible but not
+ recommended.
+
[BZ #16629]
* stdlib/tst-setcontext.c: Include signal.h.
(main): Check that the signal stack before and
diff --git a/manual/setjmp.texi b/manual/setjmp.texi
index 9446abc..ec79c26 100644
--- a/manual/setjmp.texi
+++ b/manual/setjmp.texi
@@ -396,6 +396,9 @@ time of the call. If @code{uc_link} was a null pointer the application
terminates normally with an exit status value of @code{EXIT_SUCCESS}
(@pxref{Program Termination}).
+If the context was created by a call to a signal handler or from any
+other source then the behaviour of @code{setcontext} is unspecified.
+
Since the context contains information about the stack no two threads
should use the same context at the same time. The result in most cases
would be disastrous.
@@ -483,11 +486,11 @@ and then resume where execution was stopped.
This an example how the context functions can be used to implement
co-routines or cooperative multi-threading. All that has to be done is
to call every once in a while @code{swapcontext} to continue running a
-different context. It is not allowed to do the context switching from
-the signal handler directly since neither @code{setcontext} nor
-@code{swapcontext} are functions which can be called from a signal
-handler. But setting a variable in the signal handler and checking it
-in the body of the functions which are executed is OK. Since
-@code{swapcontext} is saving the current context it is possible to have
-multiple different scheduling points in the code. Execution will always
-resume where it was left.
+different context. It is not recommended to do the context switching from
+the signal handler directly since leaving the signal handler via
+@code{setcontext} if the signal was delivered during code that was not
+asynchronous signal safe could lead to problems. Setting a variable in
+the signal handler and checking it in the body of the functions which
+are executed is a safer approach. Since @code{swapcontext} is saving the
+current context it is possible to have multiple different scheduling points
+in the code. Execution will always resume where it was left.
http://sourceware.org/git/gitweb.cgi?p=glibc.git;a=commitdiff;h=e04a4e9d2e639a7770e1c0d24ecbcf92abf6bba8
commit e04a4e9d2e639a7770e1c0d24ecbcf92abf6bba8
Author: Will Newton <will.newton@linaro.org>
Date: Tue Feb 25 14:29:32 2014 +0000
stdlib/tst-setcontext.c: Check for clobbering of signal stack
On aarch64 calling swapcontext clobbers the state of the signal
stack (BZ #16629). Check that the address and size of the signal
stack before and after the call to swapcontext remains the same.
ChangeLog:
2014-04-17 Will Newton <will.newton@linaro.org>
[BZ #16629]
* stdlib/tst-setcontext.c: Include signal.h.
(main): Check that the signal stack before and
after swapcontext is the same.
diff --git a/ChangeLog b/ChangeLog
index 55dcc2b..1dd40fc 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,6 +1,10 @@
2014-04-17 Will Newton <will.newton@linaro.org>
[BZ #16629]
+ * stdlib/tst-setcontext.c: Include signal.h.
+ (main): Check that the signal stack before and
+ after swapcontext is the same.
+
* sysdeps/unix/sysv/linux/aarch64/setcontext.S (__setcontext):
Re-implement to restore registers in user code and avoid
rt_sigreturn system call.
diff --git a/stdlib/tst-setcontext.c b/stdlib/tst-setcontext.c
index ac9deb1..55984a4 100644
--- a/stdlib/tst-setcontext.c
+++ b/stdlib/tst-setcontext.c
@@ -16,6 +16,7 @@
<http://www.gnu.org/licenses/>. */
#include <errno.h>
+#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
@@ -144,6 +145,9 @@ main (void)
atexit (check_called);
char st1[32768];
+ stack_t stack_before, stack_after;
+
+ sigaltstack(NULL, &stack_before);
puts ("making contexts");
if (getcontext (&ctx[1]) != 0)
@@ -207,6 +211,8 @@ main (void)
puts ("back at main program");
back_in_main = 1;
+ sigaltstack(NULL, &stack_after);
+
if (was_in_f1 == 0)
{
puts ("didn't reach f1");
@@ -218,6 +224,21 @@ main (void)
exit (1);
}
+ /* Check sigaltstack state is not clobbered as in BZ #16629. */
+ if (stack_before.ss_sp != stack_after.ss_sp)
+ {
+ printf ("stack ss_sp mismatch: %p %p\n",
+ stack_before.ss_sp, stack_after.ss_sp);
+ exit (1);
+ }
+
+ if (stack_before.ss_size != stack_after.ss_size)
+ {
+ printf ("stack ss_size mismatch: %zd %zd\n",
+ stack_before.ss_size, stack_after.ss_size);
+ exit (1);
+ }
+
puts ("test succeeded");
return 0;
}
http://sourceware.org/git/gitweb.cgi?p=glibc.git;a=commitdiff;h=37d350073888887637aa67dddf988d9c4b226032
commit 37d350073888887637aa67dddf988d9c4b226032
Author: Will Newton <will.newton@linaro.org>
Date: Wed Mar 12 16:14:51 2014 +0000
aarch64: Re-implement setcontext without rt_sigreturn syscall
The current implementation of setcontext uses rt_sigreturn to restore
the contents of registers. This contrasts with the way most other
architectures implement setcontext:
powerpc64, mips, tile:
Call rt_sigreturn if context was created by a call to a signal handler,
otherwise restore in user code.
powerpc32:
Call swapcontext system call and don't call sigreturn or rt_sigreturn.
x86_64, sparc, hppa, sh, ia64, m68k, s390, arm:
Only support restoring "synchronous" contexts, that is contexts
created by getcontext, and restoring in user code and don't call
sigreturn or rt_sigreturn.
alpha:
Call sigreturn (but not rt_sigreturn) in all cases to do the restore.
The text of the setcontext manpage suggests that the requirement to be
able to restore a signal handler created context has been dropped from
SUSv2:
If the context was obtained by a call to a signal handler, then old
standard text says that "program execution continues with the program
instruction following the instruction interrupted by the signal".
However, this sentence was removed in SUSv2, and the present verdict
is "the result is unspecified".
Implementing setcontext by calling rt_sigreturn unconditionally causes
problems when used with sigaltstack as in BZ #16629. On this basis it
seems that aarch64 is broken and that new ports should only support
restoring contexts created with getcontext and do not need to call
rt_sigreturn at all.
This patch re-implements the aarch64 setcontext function to restore
the context in user code in a similar manner to x86_64 and other ports.
ChangeLog:
2014-04-17 Will Newton <will.newton@linaro.org>
[BZ #16629]
* sysdeps/unix/sysv/linux/aarch64/setcontext.S (__setcontext):
Re-implement to restore registers in user code and avoid
rt_sigreturn system call.
diff --git a/ChangeLog b/ChangeLog
index b8fa520..55dcc2b 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,10 @@
+2014-04-17 Will Newton <will.newton@linaro.org>
+
+ [BZ #16629]
+ * sysdeps/unix/sysv/linux/aarch64/setcontext.S (__setcontext):
+ Re-implement to restore registers in user code and avoid
+ rt_sigreturn system call.
+
2014-04-17 Wilco <wdijkstr@arm.com>
* sysdeps/arm/math-tests.h: New file: Set ARM math-test settings.
diff --git a/NEWS b/NEWS
index ee59d33..a8a6ea8 100644
--- a/NEWS
+++ b/NEWS
@@ -11,11 +11,11 @@ Version 2.20
6804, 13347, 14770, 15347, 15514, 15804, 15894, 16002, 16198, 16284,
16348, 16349, 16357, 16362, 16447, 16532, 16545, 16574, 16599, 16600,
- 16609, 16610, 16611, 16613, 16619, 16623, 16632, 16634, 16639, 16642,
- 16648, 16649, 16670, 16674, 16677, 16680, 16683, 16689, 16695, 16701,
- 16706, 16707, 16712, 16713, 16714, 16731, 16739, 16740, 16743, 16758,
- 16759, 16760, 16770, 16786, 16789, 16799, 16800, 16815, 16824, 16831,
- 16838.
+ 16609, 16610, 16611, 16613, 16619, 16623, 16629, 16632, 16634, 16639,
+ 16642, 16648, 16649, 16670, 16674, 16677, 16680, 16683, 16689, 16695,
+ 16701, 16706, 16707, 16712, 16713, 16714, 16731, 16739, 16740, 16743,
+ 16758, 16759, 16760, 16770, 16786, 16789, 16799, 16800, 16815, 16824,
+ 16831, 16838.
* Running the testsuite no longer terminates as soon as a test fails.
Instead, a file tests.sum (xtests.sum from "make xcheck") is generated,
diff --git a/sysdeps/unix/sysv/linux/aarch64/setcontext.S b/sysdeps/unix/sysv/linux/aarch64/setcontext.S
index d220c41..f45a655 100644
--- a/sysdeps/unix/sysv/linux/aarch64/setcontext.S
+++ b/sysdeps/unix/sysv/linux/aarch64/setcontext.S
@@ -22,68 +22,108 @@
#include "ucontext_i.h"
#include "ucontext-internal.h"
-/* int setcontext (const ucontext_t *ucp) */
+/* int __setcontext (const ucontext_t *ucp)
- .text
-
-ENTRY(__setcontext)
-
- /* Create a signal frame on the stack:
-
- fp
- lr
- ...
- sp-> rt_sigframe
- */
-
- stp x29, x30, [sp, -16]!
- cfi_adjust_cfa_offset (16)
- cfi_rel_offset (x29, 0)
- cfi_rel_offset (x30, 8)
-
- mov x29, sp
- cfi_def_cfa_register (x29)
-
- /* Allocate space for the sigcontext. */
- mov w3, #((RT_SIGFRAME_SIZE + SP_ALIGN_SIZE) & SP_ALIGN_MASK)
- sub sp, sp, x3
+ Restores the machine context in UCP and thereby resumes execution
+ in that context.
- /* Compute the base address of the ucontext structure. */
- add x1, sp, #RT_SIGFRAME_UCONTEXT
+ This implementation is intended to be used for *synchronous* context
+ switches only. Therefore, it does not have to restore anything
+ other than the PRESERVED state. */
- /* Only ucontext is required in the frame, *copy* it in. */
-
-#if UCONTEXT_SIZE % 16
-#error The implementation of setcontext.S assumes sizeof(ucontext_t) % 16 == 0
-#endif
-
- mov x2, #UCONTEXT_SIZE / 16
-0:
- ldp x3, x4, [x0], #16
- stp x3, x4, [x1], #16
- sub x2, x2, 1
- cbnz x2, 0b
+ .text
- /* rt_sigreturn () -- no arguments, sp points to struct rt_sigframe. */
- mov x8, SYS_ify (rt_sigreturn)
+ENTRY (__setcontext)
+ /* Save a copy of UCP. */
+ mov x9, x0
+
+ /* Set the signal mask with
+ rt_sigprocmask (SIG_SETMASK, mask, NULL, _NSIG/8). */
+ mov x0, #SIG_SETMASK
+ add x1, x9, #UCONTEXT_SIGMASK
+ mov x2, #0
+ mov x3, #_NSIG8
+ mov x8, SYS_ify (rt_sigprocmask)
svc 0
-
- /* Ooops we failed. Recover the stack */
-
- mov sp, x29
- cfi_def_cfa_register (sp)
-
- ldp x29, x30, [sp], 16
- cfi_adjust_cfa_offset (16)
- cfi_restore (x29)
- cfi_restore (x30)
- b C_SYMBOL_NAME(__syscall_error)
-
+ cbz x0, 1f
+ b C_SYMBOL_NAME (__syscall_error)
+1:
+ /* Restore the general purpose registers. */
+ mov x0, x9
+ cfi_def_cfa (x0, 0)
+ cfi_offset (x18, oX0 + 18 * SZREG)
+ cfi_offset (x19, oX0 + 19 * SZREG)
+ cfi_offset (x20, oX0 + 20 * SZREG)
+ cfi_offset (x21, oX0 + 21 * SZREG)
+ cfi_offset (x22, oX0 + 22 * SZREG)
+ cfi_offset (x23, oX0 + 23 * SZREG)
+ cfi_offset (x24, oX0 + 24 * SZREG)
+ cfi_offset (x25, oX0 + 25 * SZREG)
+ cfi_offset (x26, oX0 + 26 * SZREG)
+ cfi_offset (x27, oX0 + 27 * SZREG)
+ cfi_offset (x28, oX0 + 28 * SZREG)
+ cfi_offset (x29, oX0 + 29 * SZREG)
+ cfi_offset (x30, oX0 + 30 * SZREG)
+
+ cfi_offset ( d8, oV0 + 8 * SZVREG)
+ cfi_offset ( d9, oV0 + 9 * SZVREG)
+ cfi_offset (d10, oV0 + 10 * SZVREG)
+ cfi_offset (d11, oV0 + 11 * SZVREG)
+ cfi_offset (d12, oV0 + 12 * SZVREG)
+ cfi_offset (d13, oV0 + 13 * SZVREG)
+ cfi_offset (d14, oV0 + 14 * SZVREG)
+ cfi_offset (d15, oV0 + 15 * SZVREG)
+ ldp x18, x19, [x0, oX0 + 18 * SZREG]
+ ldp x20, x21, [x0, oX0 + 20 * SZREG]
+ ldp x22, x23, [x0, oX0 + 22 * SZREG]
+ ldp x24, x25, [x0, oX0 + 24 * SZREG]
+ ldp x26, x27, [x0, oX0 + 26 * SZREG]
+ ldp x28, x29, [x0, oX0 + 28 * SZREG]
+ ldr x30, [x0, oX0 + 30 * SZREG]
+ ldr x2, [x0, oSP]
+ mov sp, x2
+
+ /* Check for FP SIMD context. We don't support restoring
+ contexts created by the kernel, so this context must have
+ been created by getcontext. Hence we can rely on the
+ first extension block being the FP SIMD context. */
+ add x2, x0, #oEXTENSION
+
+ mov w3, #(FPSIMD_MAGIC & 0xffff)
+ movk w3, #(FPSIMD_MAGIC >> 16), lsl #16
+ ldr w1, [x2, #oHEAD + oMAGIC]
+ cmp w1, w3
+ b.ne 2f
+
+ /* Restore the FP SIMD context. */
+ add x3, x2, #oV0 + 8 * SZVREG
+ ldp d8, d9, [x3], #2 * SZVREG
+ ldp d10, d11, [x3], #2 * SZVREG
+ ldp d12, d13, [x3], #2 * SZVREG
+ ldp d14, d15, [x3], #2 * SZVREG
+
+ add x3, x2, oFPSR
+
+ ldr w4, [x3]
+ msr fpsr, x4
+
+ ldr w4, [x3, oFPCR - oFPSR]
+ msr fpcr, x4
+
+2:
+ ldr x16, [x0, oPC]
+ /* Restore arg registers. */
+ ldp x2, x3, [x0, oX0 + 2 * SZREG]
+ ldp x4, x5, [x0, oX0 + 4 * SZREG]
+ ldp x6, x7, [x0, oX0 + 6 * SZREG]
+ ldp x0, x1, [x0, oX0 + 0 * SZREG]
+ /* Jump to the new pc value. */
+ br x16
PSEUDO_END (__setcontext)
weak_alias (__setcontext, setcontext)
-ENTRY(__startcontext)
+ENTRY (__startcontext)
mov x0, x19
cbnz x0, __setcontext
-1: b HIDDEN_JUMPTARGET(_exit)
-END(__startcontext)
+1: b HIDDEN_JUMPTARGET (_exit)
+END (__startcontext)
-----------------------------------------------------------------------
Summary of changes:
ChangeLog | 17 +++
NEWS | 10 +-
manual/setjmp.texi | 19 ++--
stdlib/tst-setcontext.c | 21 ++++
sysdeps/unix/sysv/linux/aarch64/setcontext.S | 150 ++++++++++++++++----------
5 files changed, 149 insertions(+), 68 deletions(-)
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