From: akpm@osdl.org Date: Sun, 25 Jun 2006 12:48:35 +0000 (-0700) Subject: [PATCH] N32 sigset and __COMPAT_ENDIAN_SWAP__ X-Git-Tag: v2.6.18-rc1~940 X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=838cd153a5250a79a302f6c5d68a4794b70c4ccb;p=linux-2.6 [PATCH] N32 sigset and __COMPAT_ENDIAN_SWAP__ 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 Signed-off-by: Ralf Baechle Cc: Arnd Bergmann Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- diff --git a/include/asm-mips/compat.h b/include/asm-mips/compat.h index 986511db54..900f472fdd 100644 --- a/include/asm-mips/compat.h +++ b/include/asm-mips/compat.h @@ -145,8 +145,5 @@ static inline void __user *compat_alloc_user_space(long len) return (void __user *) (regs->regs[29] - len); } -#if defined (__MIPSEL__) -#define __COMPAT_ENDIAN_SWAP__ 1 -#endif #endif /* _ASM_COMPAT_H */ diff --git a/kernel/compat.c b/kernel/compat.c index 2f67233243..126dee9530 100644 --- a/kernel/compat.c +++ b/kernel/compat.c @@ -730,17 +730,10 @@ 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 } }