[PATCH 3/7] signal/sparc: Document a conflict with SI_USER with SIGFPE
From: Eric W. Biederman
Date: Tue Jul 18 2017 - 10:19:23 EST
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 was introduced in 2.3.41 so this mess has had a long time for
people to be able to start depending on it.
As this bug has existed for 17 years already I don't know if it is
worth fixing. It is definitely worth documenting what is going
on so that no one decides to copy this bad decision.
Cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
Cc: sparclinux@xxxxxxxxxxxxxxx
Signed-off-by: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>
---
arch/sparc/include/uapi/asm/siginfo.h | 7 +++++++
arch/sparc/kernel/traps_32.c | 2 +-
arch/sparc/kernel/traps_64.c | 2 +-
3 files changed, 9 insertions(+), 2 deletions(-)
diff --git a/arch/sparc/include/uapi/asm/siginfo.h b/arch/sparc/include/uapi/asm/siginfo.h
index 2d9b79ccaa50..da2126e0c536 100644
--- a/arch/sparc/include/uapi/asm/siginfo.h
+++ b/arch/sparc/include/uapi/asm/siginfo.h
@@ -17,6 +17,13 @@
#define SI_NOINFO 32767 /* no information in siginfo_t */
/*
+ * SIGFPE si_codes
+ */
+#ifdef __KERNEL__
+#define FPE_FIXME (__SI_FAULT|0) /* Broken dup of SI_USER */
+#endif /* __KERNEL__ */
+
+/*
* SIGEMT si_codes
*/
#define EMT_TAGOVF (__SI_FAULT|1) /* tag overflow */
diff --git a/arch/sparc/kernel/traps_32.c b/arch/sparc/kernel/traps_32.c
index 466d4aed06c7..581cf35ee7e3 100644
--- a/arch/sparc/kernel/traps_32.c
+++ b/arch/sparc/kernel/traps_32.c
@@ -306,7 +306,7 @@ void do_fpe_trap(struct pt_regs *regs, unsigned long pc, unsigned long npc,
info.si_errno = 0;
info.si_addr = (void __user *)pc;
info.si_trapno = 0;
- info.si_code = __SI_FAULT;
+ info.si_code = FPE_FIXME;
if ((fsr & 0x1c000) == (1 << 14)) {
if (fsr & 0x10)
info.si_code = FPE_FLTINV;
diff --git a/arch/sparc/kernel/traps_64.c b/arch/sparc/kernel/traps_64.c
index 196ee5eb4d48..e882e128faa3 100644
--- a/arch/sparc/kernel/traps_64.c
+++ b/arch/sparc/kernel/traps_64.c
@@ -2258,7 +2258,7 @@ static void do_fpe_common(struct pt_regs *regs)
info.si_errno = 0;
info.si_addr = (void __user *)regs->tpc;
info.si_trapno = 0;
- info.si_code = __SI_FAULT;
+ info.si_code = FPE_FIXME;
if ((fsr & 0x1c000) == (1 << 14)) {
if (fsr & 0x10)
info.si_code = FPE_FLTINV;
--
2.10.1