[tip: x86/core] x86/orc: Make it callthunk aware

tip-bot2 for Peter Zijlstra
2022-10-17T14:54:28Z

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

Commit-ID: 396e0b8e09e86440c2119d12c2101110d3cd5bf9
Gitweb: https://git.kernel.org/tip/396e0b8e09e86440c2119d12c2101110d3cd5bf9
Author: Peter Zijlstra <peterz@infradead.org>
AuthorDate: Thu, 15 Sep 2022 13:11:33 +02:00
Committer: Peter Zijlstra <peterz@infradead.org>
CommitterDate: Mon, 17 Oct 2022 16:41:17 +02:00

x86/orc: Make it callthunk aware

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>
Link: https://lore.kernel.org/r/20220915111148.511637628@infradead.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(-)

diff --git a/arch/x86/include/asm/alternative.h b/arch/x86/include/asm/alternative.h
index 07ac257..4b8cd25 100644
--- a/arch/x86/include/asm/alternative.h
+++ b/arch/x86/include/asm/alternative.h
@@ -92,6 +92,7 @@ extern void callthunks_patch_builtin_calls(void);
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_translate_call_dest(void *dest)
{
return dest;
}
+static __always_inline bool is_callthunk(void *addr)
+{
+ return false;
+}
#endif

#ifdef CONFIG_SMP
diff --git a/arch/x86/kernel/callthunks.c b/arch/x86/kernel/callthunks.c
index 0710036..7f97881 100644
--- a/arch/x86/kernel/callthunks.c
+++ b/arch/x86/kernel/callthunks.c
@@ -293,6 +293,19 @@ void *callthunks_translate_call_dest(void *dest)
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)
diff --git a/arch/x86/kernel/unwind_orc.c b/arch/x86/kernel/unwind_orc.c
index 0ea57da..cfac2b5 100644
--- a/arch/x86/kernel/unwind_orc.c
+++ b/arch/x86/kernel/unwind_orc.c
@@ -136,6 +136,21 @@ 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,
@@ -189,7 +204,11 @@ static struct orc_entry *orc_find(unsigned long ip)
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