[DFSan] Make dfsan_read_origin_of_first_taint public.

Makes origins easier to use with dfsan_read_label(addr, size).

Reviewed By: vitalybuka

Differential Revision: https://reviews.llvm.org/D116197

compiler-rt/include/sanitizer/dfsan_interface.h

@@ -54,6 +54,10 @@ dfsan_origin dfsan_get_origin(long data);
 /// Retrieves the label associated with the data at the given address.
 dfsan_label dfsan_read_label(const void *addr, size_t size);
 
+/// Return the origin associated with the first taint byte in the size bytes
+/// from the address addr.
+dfsan_origin dfsan_read_origin_of_first_taint(const void *addr, size_t size);
+
 /// Returns whether the given label label contains the label elem.
 int dfsan_has_label(dfsan_label label, dfsan_label elem);
 

compiler-rt/lib/dfsan/done_abilist.txt

@@ -40,6 +40,8 @@ fun:dfsan_sprint_stack_trace=uninstrumented
 fun:dfsan_sprint_stack_trace=discard
 fun:dfsan_get_origin=uninstrumented
 fun:dfsan_get_origin=custom
+fun:dfsan_read_origin_of_first_taint=uninstrumented
+fun:dfsan_read_origin_of_first_taint=discard
 fun:dfsan_get_init_origin=uninstrumented
 fun:dfsan_get_init_origin=discard
 fun:dfsan_get_track_origins=uninstrumented

compiler-rt/test/dfsan/origin_of_first_taint.c

@@ -0,0 +1,34 @@
+// RUN: %clang_dfsan -gmlt -mllvm -dfsan-track-origins=1 %s -o %t && \
+// RUN:     %run %t 2>&1 | FileCheck %s
+//
+// REQUIRES: x86_64-target-arch
+
+#include <assert.h>
+#include <sanitizer/dfsan_interface.h>
+#include <stdio.h>
+
+__attribute__((noinline)) uint64_t foo(uint64_t a, uint64_t b) { return a + b; }
+
+int main(int argc, char *argv[]) {
+  uint64_t a = 10;
+  uint64_t b = 20;
+  dfsan_set_label(8, &a, sizeof(a));
+  uint64_t c = foo(a, b);
+
+  dfsan_origin c_orig = dfsan_get_origin(c);
+  fprintf(stderr, "c_orig 0x%x\n", c_orig);
+  // CHECK: c_orig 0x[[#%x,C_ORIG:]]
+  assert(c_orig != 0);
+  dfsan_print_origin_id_trace(c_orig);
+  // CHECK: Origin value: 0x[[#%x,C_ORIG]], Taint value was created at
+
+  uint64_t d[4] = {1, 2, 3, c};
+  dfsan_origin d_orig = dfsan_read_origin_of_first_taint(d, sizeof(d));
+  fprintf(stderr, "d_orig 0x%x\n", d_orig);
+  // CHECK: d_orig 0x[[#%x,D_ORIG:]]
+  assert(d_orig != 0);
+  dfsan_print_origin_id_trace(d_orig);
+  // CHECK: Origin value: 0x[[#%x,D_ORIG]], Taint value was stored to memory at
+  // CHECK: Origin value: 0x[[#%x,C_ORIG]], Taint value was created at
+  return 0;
+}