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>

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);
      }
 

tests/Makefile.inc

@@ -17,6 +17,7 @@ coverage_dir = coverage_reports
 CMOCKA_LIB := $(cmockaobj)/src/libcmocka.so
 
 CMAKE:= cmake
+OBJCOPY?= objcopy
 
 TEST_DEFAULT_CONFIG = $(top)/configs/config.emulation_qemu_x86_i440fx
 TEST_DOTCONFIG = $(testobj)/.config
@@ -114,18 +115,21 @@ $$($(1)-config-file): $(TEST_KCONFIG_AUTOHEADER)
 
 $($(1)-objs): TEST_CFLAGS += -I$$(dir $$($(1)-config-file)) \
 	-D__$$(shell echo $$($(1)-stage) | tr '[:lower:]' '[:upper:]')__
+$($(1)-srcobjs): OBJCOPY_FLAGS += $$(foreach mock,$$($(1)-mocks),--globalize-symbol=$$(mock) --weaken-symbol=$$(mock))
 $($(1)-objs): $(testobj)/$(1)/%.o: $$$$*.c $$($(1)-config-file)
 	mkdir -p $$(dir $$@)
 	$(HOSTCC) $(HOSTCFLAGS) $$(TEST_CFLAGS) $($(1)-cflags)  -MMD \
-		-MT $$@ -c $$< -o $$@
+		-MT $$@ -c $$< -o $$@.orig
+	$(OBJCOPY) $$@.orig $$(OBJCOPY_FLAGS) $$@
 
-$($(1)-bin): TEST_LDFLAGS+= $$(foreach mock,$$($(1)-mocks),-Wl,--wrap=$$(mock))
 $($(1)-bin): $($(1)-objs) $(CMOCKA_LIB)
 	$(HOSTCC) $$^ $($(1)-cflags) $$(TEST_LDFLAGS) -o $$@
 
 endef
 
 $(foreach test, $(alltests), \
+	$(eval $(test)-srcobjs:=$(addprefix $(testobj)/$(test)/, \
+		$(patsubst %.c,%.o,$(filter src/%,$($(test)-srcs))))) \
 	$(eval $(test)-objs:=$(addprefix $(testobj)/$(test)/, \
 		$(patsubst %.c,%.o,$($(test)-srcs)))))
 $(foreach test, $(alltests), \

tests/device/i2c-test.c

@@ -30,7 +30,7 @@ i2c_ex_devs_t i2c_ex_devs[] = {
 	} },
 };
 
-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)
 {
 	int i;
@@ -77,13 +77,13 @@ static void mock_expect_params_platform_i2c_transfer(void)
 		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);
 }
 

tests/lib/coreboot_table-test.c

@@ -264,7 +264,7 @@ void cbmem_run_init_hooks(int is_recovery)
 }
 
 extern uintptr_t _cbmem_top_ptr;
-void *__wrap_cbmem_top_chipset(void)
+void *cbmem_top_chipset(void)
 {
 	return (void *)_cbmem_top_ptr;
 }

tests/lib/imd_cbmem-test.c

@@ -36,7 +36,7 @@ void cbmem_run_init_hooks(int is_recovery)
 	function_called();
 }
 
-void *__wrap_cbmem_top_chipset(void)
+void *cbmem_top_chipset(void)
 {
 	return (void *)_cbmem_top_ptr;
 }

tests/lib/spd_cache-test.c

@@ -42,14 +42,14 @@ static int teardown_spd_cache(void **state)
 }
 
 
-int __wrap_fmap_locate_area_as_rdev(const char *name, struct region_device *area)
+int fmap_locate_area_as_rdev(const char *name, struct region_device *area)
 {
 	return rdev_chain(area, &flash_rdev_rw, 0, flash_buffer_size);
 }
 
 /* This test verifies if load_spd_cache() correctly loads spd_cache pointer and size
-   from provided region_device. Memory region device is returned by
-   __wrap_fmap_locate_area_as_rdev() */
+   from provided region_device. Memory region device is returned by our
+   fmap_locate_area_as_rdev() override. */
 static void test_load_spd_cache(void **state)
 {
 	uint8_t *spd_cache;