[tip: x86/entry] x86/traps: Prepare for using DEFINE_IDTENTRY

["tip-bot2 for Thomas Gleixner" <tip-bot2@linutronix.de>]

The following commit has been merged into the x86/entry branch of tip:

Commit-ID:     54367ca6ef59d0e7599b02aca8dcc7ca4fd264bd
Gitweb:        https://git.kernel.org/tip/54367ca6ef59d0e7599b02aca8dcc7ca4fd264bd
Author:        Thomas Gleixner <tglx@linutronix.de>
AuthorDate:    Tue, 25 Feb 2020 23:16:13 +01:00
Committer:     Thomas Gleixner <tglx@linutronix.de>
CommitterDate: Tue, 19 May 2020 16:03:57 +02:00

x86/traps: Prepare for using DEFINE_IDTENTRY

Prepare for using IDTENTRY to define the C exception/trap entry points. It
would be possible to glue this into the existing macro maze, but it's
simpler and better to read at the end to just make them distinct.

Provide a trivial inline helper to read the trap address and add a comment
explaining the logic behind it.

The existing macros will be removed once all instances are converted.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200505134904.556327833@linutronix.de



---
 arch/x86/kernel/traps.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index f5f4a76..3857c0f 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -205,6 +205,21 @@ static void do_error_trap(struct pt_regs *regs, long error_code, char *str,
 	}
 }
 
+/*
+ * Posix requires to provide the address of the faulting instruction for
+ * SIGILL (#UD) and SIGFPE (#DE) in the si_addr member of siginfo_t.
+ *
+ * This address is usually regs->ip, but when an uprobe moved the code out
+ * of line then regs->ip points to the XOL code which would confuse
+ * anything which analyzes the fault address vs. the unmodified binary. If
+ * a trap happened in XOL code then uprobe maps regs->ip back to the
+ * original instruction address.
+ */
+static __always_inline void __user *error_get_trap_addr(struct pt_regs *regs)
+{
+	return (void __user *)uprobe_get_trap_addr(regs);
+}
+
 #define IP ((void __user *)uprobe_get_trap_addr(regs))
 #define DO_ERROR(trapnr, signr, sicode, addr, str, name)		   \
 dotraplinkage void do_##name(struct pt_regs *regs, long error_code)	   \