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signal/powerpc: Document conflicts with SI_USER and SIGFPE and SIGTRAP
Setting si_code to 0 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. Further use of si_code == 0 guaranteed that copy_siginfo_to_user saw a value of __SI_KILL and now sees a value of SIL_KILL with the result that uid and pid fields are copied and which might copying the si_addr field by accident but certainly not by design. Making this a very flakey implementation. Utilizing FPE_FIXME and TRAP_FIXME, siginfo_layout() will now return SIL_FAULT and the appropriate fields will be reliably copied. Possible ABI fixes includee: - Send the signal without siginfo - Don't generate a signal - Possibly assign and use an appropriate si_code - Don't handle cases which can't happen Cc: Paul Mackerras <paulus@samba.org> Cc: Kumar Gala <kumar.gala@freescale.com> Cc: Michael Ellerman <mpe@ellerman.id.au> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: linuxppc-dev@lists.ozlabs.org Ref: 9bad068c24d7 ("[PATCH] ppc32: support for e500 and 85xx") Ref: 0ed70f6105ef ("PPC32: Provide proper siginfo information on various exceptions.") History Tree: https://git.kernel.org/pub/scm/linux/kernel/git/tglx/history.git Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
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@ -18,4 +18,19 @@
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#undef NSIGTRAP
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#define NSIGTRAP 4
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/*
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* SIGFPE si_codes
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*/
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#ifdef __KERNEL__
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#define FPE_FIXME 0 /* Broken dup of SI_USER */
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#endif /* __KERNEL__ */
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/*
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* SIGTRAP si_codes
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*/
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#ifdef __KERNEL__
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#define TRAP_FIXME 0 /* Broken dup of SI_USER */
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#endif /* __KERNEL__ */
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#endif /* _ASM_POWERPC_SIGINFO_H */
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@ -917,7 +917,7 @@ void unknown_exception(struct pt_regs *regs)
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printk("Bad trap at PC: %lx, SR: %lx, vector=%lx\n",
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regs->nip, regs->msr, regs->trap);
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_exception(SIGTRAP, regs, 0, 0);
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_exception(SIGTRAP, regs, TRAP_FIXME, 0);
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exception_exit(prev_state);
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}
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@ -939,7 +939,7 @@ bail:
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void RunModeException(struct pt_regs *regs)
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{
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_exception(SIGTRAP, regs, 0, 0);
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_exception(SIGTRAP, regs, TRAP_FIXME, 0);
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}
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void single_step_exception(struct pt_regs *regs)
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@ -978,7 +978,7 @@ static void emulate_single_step(struct pt_regs *regs)
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static inline int __parse_fpscr(unsigned long fpscr)
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{
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int ret = 0;
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int ret = FPE_FIXME;
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/* Invalid operation */
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if ((fpscr & FPSCR_VE) && (fpscr & FPSCR_VX))
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@ -1929,7 +1929,7 @@ void SPEFloatingPointException(struct pt_regs *regs)
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extern int do_spe_mathemu(struct pt_regs *regs);
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unsigned long spefscr;
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int fpexc_mode;
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int code = 0;
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int code = FPE_FIXME;
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int err;
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flush_spe_to_thread(current);
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@ -1998,7 +1998,7 @@ void SPEFloatingPointRoundException(struct pt_regs *regs)
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printk(KERN_ERR "unrecognized spe instruction "
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"in %s at %lx\n", current->comm, regs->nip);
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} else {
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_exception(SIGFPE, regs, 0, regs->nip);
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_exception(SIGFPE, regs, FPE_FIXME, regs->nip);
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return;
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}
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}
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