[patch 34/38] x86/orc: Make it callthunk aware

Thomas Gleixner
2022-07-16T23:19:49Z

From: Peter Zijlstra <peterz@infradead.org>

Callthunks addresses on the stack would confuse the ORC unwinder. Handle
them correctly and tell ORC to proceed further down the stack.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Josh Poimboeuf <jpoimboe@kernel.org>
---
arch/x86/include/asm/alternative.h | 5 +++++
arch/x86/kernel/callthunks.c | 2 +-
arch/x86/kernel/unwind_orc.c | 21 ++++++++++++++++++++-
3 files changed, 26 insertions(+), 2 deletions(-)

--- a/arch/x86/include/asm/alternative.h
+++ b/arch/x86/include/asm/alternative.h
@@ -94,6 +94,7 @@ extern void callthunks_patch_module_call
struct module *mod);
extern void callthunks_module_free(struct module *mod);
extern void *callthunks_translate_call_dest(void *dest);
+extern bool is_callthunk(void *addr);
#else
static __always_inline void callthunks_patch_builtin_calls(void) {}
static __always_inline void
@@ -104,6 +105,10 @@ static __always_inline void *callthunks_
{
return dest;
}
+static __always_inline bool is_callthunk(void *addr)
+{
+ return false;
+}
#endif

#ifdef CONFIG_SMP
--- a/arch/x86/kernel/callthunks.c
+++ b/arch/x86/kernel/callthunks.c
@@ -565,7 +565,7 @@ static bool is_module_callthunk(void *ad
return ret;
}

-static bool is_callthunk(void *addr)
+bool is_callthunk(void *addr)
{
if (builtin_layout.base <= addr &&
addr < builtin_layout.base + builtin_layout.size)
--- a/arch/x86/kernel/unwind_orc.c
+++ b/arch/x86/kernel/unwind_orc.c
@@ -131,6 +131,21 @@ static struct orc_entry null_orc_entry =
.type = UNWIND_HINT_TYPE_CALL
};

+#ifdef CONFIG_CALL_THUNKS
+static struct orc_entry *orc_callthunk_find(unsigned long ip)
+{
+ if (!is_callthunk((void *)ip))
+ return NULL;
+
+ return &null_orc_entry;
+}
+#else
+static struct orc_entry *orc_callthunk_find(unsigned long ip)
+{
+ return NULL;
+}
+#endif
+
/* Fake frame pointer entry -- used as a fallback for generated code */
static struct orc_entry orc_fp_entry = {
.type = UNWIND_HINT_TYPE_CALL,
@@ -184,7 +199,11 @@ static struct orc_entry *orc_find(unsign
if (orc)
return orc;

- return orc_ftrace_find(ip);
+ orc = orc_ftrace_find(ip);
+ if (orc)
+ return orc;
+
+ return orc_callthunk_find(ip);
}

#ifdef CONFIG_MODULES