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signal/alpha: Document a conflict with SI_USER for SIGTRAP 

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.

Given that alpha is on it's last legs I don't know that it is worth
fixing this, but it is worth documenting what is going on so that
no one decides to copy this bad decision.

This was introduced during the 2.5 development cycle so this
mess has had a long time for people to be able to depend upon it.

v2: Added FPE_FIXME for alpha as Helge Deller <deller@gmx.de> pointed out
    with his alternate patch one of the cases is SIGFPE not SIGTRAP.

Cc: Helge Deller <deller@gmx.de>
Cc: Richard Henderson <rth@twiddle.net>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: Matt Turner <mattst88@gmail.com>
Cc: linux-alpha@vger.kernel.org
Acked-by: Richard Henderson <rth@twiddle.net>
History Tree: https://git.kernel.org/pub/scm/linux/kernel/git/tglx/history.git
Ref: 0a635c7a84cf ("Fill in siginfo_t.")
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
This commit is contained in:
Eric W. Biederman 2017-06-26 13:38:04 -05:00
parent 5771a8c088
commit e2bd64d92a
2 changed files with 17 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

14
arch/alpha/include/uapi/asm/siginfo.h
View File

@ -6,4 +6,18 @@
#include <asm-generic/siginfo.h>
/*
* SIGFPE si_codes
*/
#ifdef __KERNEL__
#define FPE_FIXME (__SI_FAULT|0) /* Broken dup of SI_USER */
#endif /* __KERNEL__ */
/*
* SIGTRAP si_codes
*/
#ifdef __KERNEL__
#define TRAP_FIXME (__SI_FAULT|0) /* Broken dup of SI_USER */
#endif /* __KERNEL__ */
#endif

6
arch/alpha/kernel/traps.c
View File

@ -278,7 +278,7 @@ do_entIF(unsigned long type, struct pt_regs *regs)
case 1: /* bugcheck */
info.si_signo = SIGTRAP;
info.si_errno = 0;
info.si_code = __SI_FAULT;
info.si_code = TRAP_FIXME;
info.si_addr = (void __user *) regs->pc;
info.si_trapno = 0;
send_sig_info(SIGTRAP, &info, current);
@ -318,7 +318,7 @@ do_entIF(unsigned long type, struct pt_regs *regs)
break;
case GEN_ROPRAND:
signo = SIGFPE;
code = __SI_FAULT;
code = FPE_FIXME;
break;
case GEN_DECOVF:
@ -340,7 +340,7 @@ do_entIF(unsigned long type, struct pt_regs *regs)
case GEN_SUBRNG7:
default:
signo = SIGTRAP;
code = __SI_FAULT;
code = TRAP_FIXME;
break;
}