[tip: ras/core] x86/mce: Provide method to find out the type of an exception handler

[tip-bot2 for Tony Luck]

The following commit has been merged into the ras/core branch of tip:

Commit-ID:     a05d54c41ecfa1a322b229b4e5ce50c157284f74
Gitweb:        https://git.kernel.org/tip/a05d54c41ecfa1a322b229b4e5ce50c157284f74
Author:        Tony Luck <tony.luck@xxxxxxxxx>
AuthorDate:    Tue, 06 Oct 2020 14:09:06 -07:00
Committer:     Borislav Petkov <bp@xxxxxxx>
CommitterDate: Wed, 07 Oct 2020 11:08:59 +02:00

x86/mce: Provide method to find out the type of an exception handler

Avoid a proliferation of ex_has_*_handler() functions by having just
one function that returns the type of the handler (if any).

Drop the __visible attribute for this function. It is not called
from assembler so the attribute is not necessary.

Signed-off-by: Tony Luck <tony.luck@xxxxxxxxx>
Signed-off-by: Borislav Petkov <bp@xxxxxxx>
Link: https://lkml.kernel.org/r/20201006210910.21062-3-tony.luck@xxxxxxxxx
---
 arch/x86/include/asm/extable.h     |  9 ++++++++-
 arch/x86/kernel/cpu/mce/severity.c |  5 ++++-
 arch/x86/mm/extable.c              | 12 ++++++++----
 3 files changed, 20 insertions(+), 6 deletions(-)

diff --git a/arch/x86/include/asm/extable.h b/arch/x86/include/asm/extable.h
index d8c2198..1f0cbc5 100644
--- a/arch/x86/include/asm/extable.h
+++ b/arch/x86/include/asm/extable.h
@@ -29,10 +29,17 @@ struct pt_regs;
 		(b)->handler = (tmp).handler - (delta);		\
 	} while (0)
 
+enum handler_type {
+	EX_HANDLER_NONE,
+	EX_HANDLER_FAULT,
+	EX_HANDLER_UACCESS,
+	EX_HANDLER_OTHER
+};
+
 extern int fixup_exception(struct pt_regs *regs, int trapnr,
 			   unsigned long error_code, unsigned long fault_addr);
 extern int fixup_bug(struct pt_regs *regs, int trapnr);
-extern bool ex_has_fault_handler(unsigned long ip);
+extern enum handler_type ex_get_fault_handler_type(unsigned long ip);
 extern void early_fixup_exception(struct pt_regs *regs, int trapnr);
 
 #endif
diff --git a/arch/x86/kernel/cpu/mce/severity.c b/arch/x86/kernel/cpu/mce/severity.c
index 0b072dc..c6494e6 100644
--- a/arch/x86/kernel/cpu/mce/severity.c
+++ b/arch/x86/kernel/cpu/mce/severity.c
@@ -225,10 +225,13 @@ static struct severity {
  */
 static int error_context(struct mce *m, struct pt_regs *regs)
 {
+	enum handler_type t;
+
 	if ((m->cs & 3) == 3)
 		return IN_USER;
 
-	if (mc_recoverable(m->mcgstatus) && ex_has_fault_handler(m->ip)) {
+	t = ex_get_fault_handler_type(m->ip);
+	if (mc_recoverable(m->mcgstatus) && t == EX_HANDLER_FAULT) {
 		m->kflags |= MCE_IN_KERNEL_RECOV;
 		return IN_KERNEL_RECOV;
 	}
diff --git a/arch/x86/mm/extable.c b/arch/x86/mm/extable.c
index 1d6cb07..de43525 100644
--- a/arch/x86/mm/extable.c
+++ b/arch/x86/mm/extable.c
@@ -125,17 +125,21 @@ __visible bool ex_handler_clear_fs(const struct exception_table_entry *fixup,
 }
 EXPORT_SYMBOL(ex_handler_clear_fs);
 
-__visible bool ex_has_fault_handler(unsigned long ip)
+enum handler_type ex_get_fault_handler_type(unsigned long ip)
 {
 	const struct exception_table_entry *e;
 	ex_handler_t handler;
 
 	e = search_exception_tables(ip);
 	if (!e)
-		return false;
+		return EX_HANDLER_NONE;
 	handler = ex_fixup_handler(e);
-
-	return handler == ex_handler_fault;
+	if (handler == ex_handler_fault)
+		return EX_HANDLER_FAULT;
+	else if (handler == ex_handler_uaccess)
+		return EX_HANDLER_UACCESS;
+	else
+		return EX_HANDLER_OTHER;
 }
 
 int fixup_exception(struct pt_regs *regs, int trapnr, unsigned long error_code,