[PATCH v3 54/59] x86/orc: Make it callthunk aware

Peter Zijlstra
2022-09-15T11:42:24Z

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>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Josh Poimboeuf <jpoimboe@kernel.org>
---
arch/x86/include/asm/alternative.h | 5 +++++
arch/x86/kernel/callthunks.c | 13 +++++++++++++
arch/x86/kernel/unwind_orc.c | 21 ++++++++++++++++++++-
3 files changed, 38 insertions(+), 1 deletion(-)

--- a/arch/x86/include/asm/alternative.h
+++ b/arch/x86/include/asm/alternative.h
@@ -92,6 +92,7 @@ extern void callthunks_patch_builtin_cal
extern void callthunks_patch_module_calls(struct callthunk_sites *sites,
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
@@ -101,6 +102,10 @@ 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
@@ -292,6 +292,19 @@ void *callthunks_translate_call_dest(voi
return target ? : dest;
}

+bool is_callthunk(void *addr)
+{
+ unsigned int tmpl_size = SKL_TMPL_SIZE;
+ void *tmpl = skl_call_thunk_template;
+ unsigned long dest;
+
+ dest = roundup((unsigned long)addr, CONFIG_FUNCTION_ALIGNMENT);
+ if (!thunks_initialized || skip_addr((void *)dest))
+ return false;
+
+ return !bcmp((void *)(dest - tmpl_size), tmpl, tmpl_size);
+}
+
#ifdef CONFIG_MODULES
void noinline callthunks_patch_module_calls(struct callthunk_sites *cs,
struct module *mod)
--- 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