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signal/mips: Document a conflict with SI_USER with SIGFPE

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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: 948a34cf39 ("[MIPS] Maintain si_code field properly for FP exceptions")
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
This commit is contained in:
Eric W. Biederman 2017-06-26 16:16:17 -05:00
parent cc9f72e474
commit ea1b75cf91
2 changed files with 8 additions and 1 deletions
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7
arch/mips/include/uapi/asm/siginfo.h
View File

@ -123,4 +123,11 @@ typedef struct siginfo {
#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 */
/*
* SIGFPE si_codes
*/
#ifdef __KERNEL__
#define FPE_FIXME (__SI_FAULT|0) /* Broken dup of SI_USER */
#endif /* __KERNEL__ */
#endif /* _UAPI_ASM_SIGINFO_H */

2
arch/mips/kernel/traps.c
View File

@ -735,7 +735,7 @@ void force_fcr31_sig(unsigned long fcr31, void __user *fault_addr,
else if (fcr31 & FPU_CSR_INE_X)
si.si_code = FPE_FLTRES;
else
si.si_code = __SI_FAULT;
si.si_code = FPE_FIXME;
force_sig_info(SIGFPE, &si, tsk);
}