[xen staging] xen/ubsan: provide helper for clang's -fsanitize=function

[patchbot@xxxxxxx]

commit f38148ab093d0e5967f92062b3196d7801850548
Author:     Roger Pau Monne <roger.pau@xxxxxxxxxx>
AuthorDate: Wed Mar 12 13:35:53 2025 +0100
Commit:     Roger Pau Monne <roger.pau@xxxxxxxxxx>
CommitDate: Mon Mar 17 13:33:28 2025 +0100

    xen/ubsan: provide helper for clang's -fsanitize=function
    
    clang's -fsanitize=function relies on the presence of
    __ubsan_handle_function_type_mismatch() to print the detection of indirect
    calls of a function through a function pointer of the wrong type.
    
    Implement the helper, inspired on the llvm ubsan lib implementation.
    
    Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
    Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
 xen/common/ubsan/ubsan.c | 16 ++++++++++++++++
 xen/common/ubsan/ubsan.h |  5 +++++
 2 files changed, 21 insertions(+)

diff --git a/xen/common/ubsan/ubsan.c b/xen/common/ubsan/ubsan.c
index e99370322b..7ebe4bfc14 100644
--- a/xen/common/ubsan/ubsan.c
+++ b/xen/common/ubsan/ubsan.c
@@ -546,3 +546,19 @@ void __ubsan_handle_invalid_builtin(struct 
invalid_builtin_data *data)
 
        ubsan_epilogue(&flags);
 }
+
+void __ubsan_handle_function_type_mismatch(
+       struct function_type_mismatch_data *data, unsigned long val)
+{
+       unsigned long flags;
+
+       if (suppress_report(&data->location))
+               return;
+
+       ubsan_prologue(&data->location, &flags);
+
+       pr_err("call to function %ps through pointer to incorrect function type 
%s\n",
+               (void *)val, data->type->type_name);
+
+       ubsan_epilogue(&flags);
+}
diff --git a/xen/common/ubsan/ubsan.h b/xen/common/ubsan/ubsan.h
index 9c7f3b9b6c..8987f9d453 100644
--- a/xen/common/ubsan/ubsan.h
+++ b/xen/common/ubsan/ubsan.h
@@ -95,6 +95,11 @@ enum {
        kind_clz,
 };
 
+struct function_type_mismatch_data {
+       struct source_location location;
+       struct type_descriptor *type;
+};
+
 #if defined(CONFIG_ARCH_SUPPORTS_INT128) && defined(__SIZEOF_INT128__)
 typedef __int128 s_max;
 typedef unsigned __int128 u_max;
--
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