tests: Rework mocking facility

Using the linker's --wrap feature has the downside that it only covers
references across object files: If foo.c defines a() and b(), with b
calling a, --wrap=a does nothing to that call.

Instead, use objcopy to mark a weak and global so it can be overridden
by another implementation, but only for files originating in src/.

That way mocks - implemented in tests/ - become the source of truth.

TEST=Had such an issue with get_log_level() in a follow-up commit, and
the mock now takes over. Also, all existing unit tests still pass.

Change-Id: I99c6d6e44ecfc73366bf464d9c51c7da3f8db388
Signed-off-by: Patrick Georgi <pgeorgi@google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/55360
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Jakub Czapiga <jacz@semihalf.com>

1 files changed, 9 insertions, 9 deletions

diff --git a/Documentation/tutorial/part3.md b/Documentation/tutorial/part3.md
index 6d147ff9a9..7cdf7d9f21 100644
--- a/Documentation/tutorial/part3.md
+++ b/Documentation/tutorial/part3.md
@@ -274,8 +274,8 @@ without changing the source code.
 
 coreboot unit test infrastructure supports overriding of functions at link time.
 This is as simple as adding a `name_of_function` to be mocked into
-<test_name>-mocks variable in Makefile.inc. The result is that every time the
-function is called, `wrap_name_of_function` will be called instead.
+<test_name>-mocks variable in Makefile.inc. The result is that the test's
+implementation of that function is called instead of coreboot's.
 
 ```eval_rst
 .. admonition:: i2c-test example
@@ -284,13 +284,13 @@ function is called, `wrap_name_of_function` will be called instead.
 
      i2c-test-mocks += platform_i2c_transfer
 
-   Now, dev can write own implementation of `platform_i2c_transfer` and define it
-   as `wrap_platform_i2c_transfer`. This implementation instead of accessing real
-   i2c bus, will write/read from fake structs.
+   Now, dev can write own implementation of `platform_i2c_transfer`. This
+   implementation instead of accessing real i2c bus, will write/read from
+   fake structs.
 
    .. code-block:: c
 
-     int __wrap_platform_i2c_transfer(unsigned int bus, struct i2c_msg *segments,
+     int platform_i2c_transfer(unsigned int bus, struct i2c_msg *segments,
              int count)
      {
      }
@@ -324,13 +324,13 @@ in which mock should have particular value, or be inside a described range.
                      I2C_M_RECV_LEN, I2C_M_NOSTART};
 
              /* Flags should always be only within supported range */
-             expect_in_set_count(__wrap_platform_i2c_transfer, segments->flags,
+             expect_in_set_count(platform_i2c_transfer, segments->flags,
                      expected_flags, -1);
 
-             expect_not_value_count(__wrap_platform_i2c_transfer, segments->buf,
+             expect_not_value_count(platform_i2c_transfer, segments->buf,
                      NULL, -1);
 
-             expect_in_range_count(__wrap_platform_i2c_transfer, count, 1, INT_MAX,
+             expect_in_range_count(platform_i2c_transfer, count, 1, INT_MAX,
                      -1);
      }