On Tue, Nov 09, 2021 at 05:45:44PM +0100, Ard Biesheuvel wrote:
quoted hunk ↗ jump to hunk
diff --git a/include/linux/static_call_types.h b/include/linux/static_call_types.h
index 5a00b8b2cf9f..0bb36294cce7 100644
--- a/include/linux/static_call_types.h
+++ b/include/linux/static_call_types.h
@@ -32,15 +32,20 @@
struct static_call_site {
s32 addr;
s32 key;
+ s32 tramp;
};
I can't say I'm thrilled at growing this thing, but the cleanup is nice.
Perhaps we can increase alignment on struct static_call_key and instead
frob it in .key still?
quoted hunk ↗ jump to hunk
#define DECLARE_STATIC_CALL(name, func) \
- extern struct static_call_key STATIC_CALL_KEY(name); \
+ extern __weak struct static_call_key STATIC_CALL_KEY(name); \
extern typeof(func) STATIC_CALL_TRAMP(name);
I'm a little bit confused on how this actually works. What does a __weak
extern data symbol do?
A __weak function definition would create a module local instance of the
function barring a strong override.
But what does a __weak extern do?
quoted hunk ↗ jump to hunk
diff --git a/kernel/static_call.c b/kernel/static_call.c
index 43ba0b1e0edb..360cc3cd0fbf 100644
--- a/kernel/static_call.c
+++ b/kernel/static_call.c
@@ -366,18 +366,18 @@ static int static_call_add_module(struct module *mod)
* means modules are allowed to call static_call_update() on
* it.
*
- * Otherwise, the key isn't exported, and 'addr' points to the
+ * Otherwise, the key isn't exported, and 'tramp' points to the
* trampoline so we need to lookup the key.
*
* We go through this dance to prevent crazy modules from
* abusing sensitive static calls.
*/
- if (!kernel_text_address(addr))
+ if (addr)
continue;
This seems to imply that the __weak extern symbol gets resolved to 0 at
module link time.
quoted hunk ↗ jump to hunk
- key = tramp_key_lookup(addr);
+ key = tramp_key_lookup((unsigned long)offset_to_ptr(&site->tramp));
if (!key) {
- pr_warn("Failed to fixup __raw_static_call() usage at: %ps\n",
+ pr_warn("Failed to fixup static_call() usage at: %ps\n",
static_call_addr(site));
return -EINVAL;
}
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