x86/entry: Unbreak __irqentry_text_start/end magic

The entry rework moved interrupt entry code from the irqentry to the
noinstr section which made the irqentry section empty.

This breaks boundary checks which rely on the __irqentry_text_start/end
markers to find out whether a function in a stack trace is
interrupt/exception entry code. This affects the function graph tracer and
filter_irq_stacks().

As the IDT entry points are all sequentialy emitted this is rather simple
to unbreak by injecting __irqentry_text_start/end as global labels.

To make this work correctly:

  - Remove the IRQENTRY_TEXT section from the x86 linker script
  - Define __irqentry so it breaks the build if it's used
  - Adjust the entry mirroring in PTI
  - Remove the redundant kprobes and unwinder bound checks

Reported-by: Qian Cai <cai@lca.pw>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 1 insertions, 7 deletions

diff --git a/arch/x86/kernel/unwind_frame.c b/arch/x86/kernel/unwind_frame.c
index 54226110bc7f..722a85f3b2dd 100644
--- a/arch/x86/kernel/unwind_frame.c
+++ b/arch/x86/kernel/unwind_frame.c
@@ -74,13 +74,7 @@ static bool in_entry_code(unsigned long ip)
 {
 	char *addr = (char *)ip;
 
-	if (addr >= __entry_text_start && addr < __entry_text_end)
-		return true;
-
-	if (addr >= __irqentry_text_start && addr < __irqentry_text_end)
-		return true;
-
-	return false;
+	return addr >= __entry_text_start && addr < __entry_text_end;
 }
 
 static inline unsigned long *last_frame(struct unwind_state *state)