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Commit ea1b75cf authored by Eric W. Biederman's avatar Eric W. Biederman
Browse files

signal/mips: Document a conflict with SI_USER with SIGFPE 



Setting si_code to __SI_FAULT results in a userspace seeing
an si_code of 0.  This is the same si_code as SI_USER.  Posix
and common sense requires that SI_USER not be a signal specific
si_code.  As such this use of 0 for the si_code is a pretty
horribly broken ABI.

This use of of __SI_FAULT is only a decade old.  Which compared
to the other pieces of kernel code that has made this mistake
is almost yesterday.

This is probably worth fixing but I don't know mips well enough
to know what si_code to would be the proper one to use.

Cc: Ralf Baechle <ralf@linux-mips.org>
Ref: 948a34cf ("[MIPS] Maintain si_code field properly for FP exceptions")
Signed-off-by: default avatar"Eric W. Biederman" <ebiederm@xmission.com>
parent cc9f72e4

arch/mips/include/uapi/asm/siginfo.h

+7 −0
Original line number Original line Diff line number Diff line
@@ -123,4 +123,11 @@ typedef struct siginfo { 
#define SI_TIMER __SI_CODE(__SI_TIMER, -3) /* sent by timer expiration */

#define SI_TIMER __SI_CODE(__SI_TIMER, -3) /* sent by timer expiration */

#define SI_MESGQ __SI_CODE(__SI_MESGQ, -4) /* sent by real time mesq state change */

#define SI_MESGQ __SI_CODE(__SI_MESGQ, -4) /* sent by real time mesq state change */





/*

 * SIGFPE si_codes

 */

#ifdef __KERNEL__

#define FPE_FIXME	(__SI_FAULT|0)	/* Broken dup of SI_USER */

#endif /* __KERNEL__ */



#endif /* _UAPI_ASM_SIGINFO_H */
 
#endif /* _UAPI_ASM_SIGINFO_H */

arch/mips/kernel/traps.c

+1 −1
Original line number Original line Diff line number Diff line
@@ -735,7 +735,7 @@ void force_fcr31_sig(unsigned long fcr31, void __user *fault_addr, 
	else if (fcr31 & FPU_CSR_INE_X)

	else if (fcr31 & FPU_CSR_INE_X)

		si.si_code = FPE_FLTRES;

		si.si_code = FPE_FLTRES;

	else

	else

		si.si_code = __SI_FAULT;

		si.si_code = FPE_FIXME;

	force_sig_info(SIGFPE, &si, tsk);

	force_sig_info(SIGFPE, &si, tsk);

}

}