[Xen-devel] [PATCH 2/2] xen/ubsan: Support for -fsanitise=builtin

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

This fixes the UBSAN build for GCC 8 and later.  The sanitiser checks for
passing 0 to the ctz()/clz() builtins.

Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
CC: Jan Beulich <JBeulich@xxxxxxxx>
CC: Wei Liu <wl@xxxxxxx>
CC: Roger Pau Monné <roger.pau@xxxxxxxxxx>
CC: Stefano Stabellini <sstabellini@xxxxxxxxxx>
CC: Julien Grall <julien.grall@xxxxxxx>
---
 xen/common/ubsan/ubsan.c | 21 +++++++++++++++++++++
 xen/common/ubsan/ubsan.h |  9 +++++++++
 2 files changed, 30 insertions(+)

diff --git a/xen/common/ubsan/ubsan.c b/xen/common/ubsan/ubsan.c
index 50a4e14fac..e75f614fa7 100644
--- a/xen/common/ubsan/ubsan.c
+++ b/xen/common/ubsan/ubsan.c
@@ -518,3 +518,24 @@ void __ubsan_handle_pointer_overflow(struct 
pointer_overflow_data *data,
 
        ubsan_epilogue(&flags);
 }
+
+void __ubsan_handle_invalid_builtin(struct invalid_builtin_data *data)
+{
+       unsigned long flags;
+       const char *fn;
+
+       if (suppress_report(&data->location))
+               return;
+
+       ubsan_prologue(&data->location, &flags);
+
+       switch (data->kind) {
+       case kind_ctz: fn = "ctz"; break;
+       case kind_clz: fn = "clz"; break;
+       default: fn = "<UNKNOWN>"; break;
+       }
+
+       pr_err("passing zero to %s(), which is not a valid argument\n", fn);
+
+       ubsan_epilogue(&flags);
+}
diff --git a/xen/common/ubsan/ubsan.h b/xen/common/ubsan/ubsan.h
index 2710cd423e..a3159040fe 100644
--- a/xen/common/ubsan/ubsan.h
+++ b/xen/common/ubsan/ubsan.h
@@ -84,6 +84,15 @@ struct pointer_overflow_data {
        struct source_location location;
 };
 
+struct invalid_builtin_data {
+       struct source_location location;
+       unsigned char kind;
+};
+enum {
+       kind_ctz,
+       kind_clz,
+};
+
 #if defined(CONFIG_ARCH_SUPPORTS_INT128) && defined(__SIZEOF_INT128__)
 typedef __int128 s_max;
 typedef unsigned __int128 u_max;
-- 
2.11.0


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