I'm testing glibc on MIPS64, little-endian, N32, O32 and N64
multilibs.
Among the NPTL test failures seen are some arising from sigsuspend
problems for N32: it blocks the wrong signals, so SIGCANCEL (SIGRTMIN)
is blocked despite glibc's carefully excluding it from sets of signals
to block. Specifically, testing suggests it blocks signal N^32
instead of signal N, so (in the example tested) blocking SIGUSR1 (17)
blocks signal 49 instead.
glibc's sigset_t uses an array of unsigned long, as does the kernel.
In both cases, signal N+1 is represented as
(1UL << (N % (8 * sizeof (unsigned long)))) in word number
(N / (8 * sizeof (unsigned long))).
Thus the N32 glibc uses an array of 32-bit words and the N64 kernel
uses an array of 64-bit words. For little-endian, the layout is the
same, with signals 1-32 in the first 4 bytes, signals 33-64 in the
second, etc.; for big-endian, userspace has that layout while in the
kernel each 8 bytes have the two halves swapped from the userspace
layout.
The N32 sigsuspend syscall uses sigset_from_compat to convert the
userspace sigset to kernel format. If __COMPAT_ENDIAN_SWAP__ is *not*
set, this uses logic of the form
set->sig[0] = compat->sig[0] | (((long)compat->sig[1]) << 32 )
to convert the userspace sigset to a kernel one. This looks correct
to me for both big and little endian, given that in userspace
compat->sig[1] will represent signals 33-64, and so will the high 32
bits of set->sig[0] in the kernel. If however __COMPAT_ENDIAN_SWAP__
*is* set, as it is for __MIPSEL__, it uses
set->sig[0] = compat->sig[1] | (((long)compat->sig[0]) << 32 );
which seems incorrect for both big and little endian, and would
explain the observed symptoms.
This code is the only use of __COMPAT_ENDIAN_SWAP__, so if incorrect
then that macro serves no purpose, in which case something like the
following patch would seem appropriate to remove it.
Signed-off-by: Joseph Myers <joseph@xxxxxxxxxxxxxxxx>
---
diff -rupN linux-2.6.17-rc6.orig/include/asm-mips/compat.h linux-2.6.17-rc6/include/asm-mips/compat.h
--- linux-2.6.17-rc6.orig/include/asm-mips/compat.h 2006-06-08 01:05:13.000000000 +0000
+++ linux-2.6.17-rc6/include/asm-mips/compat.h 2006-06-08 01:04:10.000000000 +0000
@@ -145,8 +145,5 @@ static inline void __user *compat_alloc_
return (void __user *) (regs->regs[29] - len);
}
-#if defined (__MIPSEL__)
-#define __COMPAT_ENDIAN_SWAP__ 1
-#endif
#endif /* _ASM_COMPAT_H */
diff -rupN linux-2.6.17-rc6.orig/kernel/compat.c linux-2.6.17-rc6/kernel/compat.c
--- linux-2.6.17-rc6.orig/kernel/compat.c 2006-06-08 01:05:13.000000000 +0000
+++ linux-2.6.17-rc6/kernel/compat.c 2006-06-08 01:03:47.000000000 +0000
@@ -729,17 +729,10 @@ void
sigset_from_compat (sigset_t *set, compat_sigset_t *compat)
{
switch (_NSIG_WORDS) {
-#if defined (__COMPAT_ENDIAN_SWAP__)
- case 4: set->sig[3] = compat->sig[7] | (((long)compat->sig[6]) << 32 );
- case 3: set->sig[2] = compat->sig[5] | (((long)compat->sig[4]) << 32 );
- case 2: set->sig[1] = compat->sig[3] | (((long)compat->sig[2]) << 32 );
- case 1: set->sig[0] = compat->sig[1] | (((long)compat->sig[0]) << 32 );
-#else
case 4: set->sig[3] = compat->sig[6] | (((long)compat->sig[7]) << 32 );
case 3: set->sig[2] = compat->sig[4] | (((long)compat->sig[5]) << 32 );
case 2: set->sig[1] = compat->sig[2] | (((long)compat->sig[3]) << 32 );
case 1: set->sig[0] = compat->sig[0] | (((long)compat->sig[1]) << 32 );
-#endif
}
}
--
Joseph S. Myers
joseph@xxxxxxxxxxxxxxxx
