[PATCH v7 16/19] KVM: selftests: Add helpers to read integer module params

Sean Christopherson
2023-11-08T00:32:12Z

Add helpers to read integer module params, which is painfully non-trivial
because the pain of dealing with strings in C is exacerbated by the kernel
inserting a newline.

Don't bother differentiating between int, uint, short, etc. They all fit
in an int, and KVM (thankfully) doesn't have any integer params larger
than an int.

Signed-off-by: Sean Christopherson <seanjc@google.com>
---
.../selftests/kvm/include/kvm_util_base.h | 4 ++
tools/testing/selftests/kvm/lib/kvm_util.c | 62 +++++++++++++++++--
2 files changed, 60 insertions(+), 6 deletions(-)

diff --git a/tools/testing/selftests/kvm/include/kvm_util_base.h b/tools/testing/selftests/kvm/include/kvm_util_base.h
index a18db6a7b3cf..46b71241216e 100644
--- a/tools/testing/selftests/kvm/include/kvm_util_base.h
+++ b/tools/testing/selftests/kvm/include/kvm_util_base.h
@@ -238,6 +238,10 @@ bool get_kvm_param_bool(const char *param);
bool get_kvm_intel_param_bool(const char *param);
bool get_kvm_amd_param_bool(const char *param);

+int get_kvm_param_integer(const char *param);
+int get_kvm_intel_param_integer(const char *param);
+int get_kvm_amd_param_integer(const char *param);
+
unsigned int kvm_check_cap(long cap);

static inline bool kvm_has_cap(long cap)
diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c b/tools/testing/selftests/kvm/lib/kvm_util.c
index 7a8af1821f5d..65101c7d1a1a 100644
--- a/tools/testing/selftests/kvm/lib/kvm_util.c
+++ b/tools/testing/selftests/kvm/lib/kvm_util.c
@@ -51,13 +51,13 @@ int open_kvm_dev_path_or_exit(void)
return _open_kvm_dev_path_or_exit(O_RDONLY);
}

-static bool get_module_param_bool(const char *module_name, const char *param)
+static ssize_t get_module_param(const char *module_name, const char *param,
+ void *buffer, size_t buffer_size)
{
const int path_size = 128;
char path[path_size];
- char value;
- ssize_t r;
- int fd;
+ ssize_t bytes_read;
+ int fd, r;

r = snprintf(path, path_size, "/sys/module/%s/parameters/%s",
module_name, param);
@@ -66,11 +66,46 @@ static bool get_module_param_bool(const char *module_name, const char *param)

fd = open_path_or_exit(path, O_RDONLY);

- r = read(fd, &value, 1);
- TEST_ASSERT(r == 1, "read(%s) failed", path);
+ bytes_read = read(fd, buffer, buffer_size);
+ TEST_ASSERT(bytes_read > 0, "read(%s) returned %ld, wanted %ld bytes",
+ path, bytes_read, buffer_size);

r = close(fd);
TEST_ASSERT(!r, "close(%s) failed", path);
+ return bytes_read;
+}
+
+static int get_module_param_integer(const char *module_name, const char *param)
+{
+ /*
+ * 16 bytes to hold a 64-bit value (1 byte per char), 1 byte for the
+ * NUL char, and 1 byte because the kernel sucks and inserts a newline
+ * at the end.
+ */
+ char value[16 + 1 + 1];
+ ssize_t r;
+
+ memset(value, '\0', sizeof(value));
+
+ r = get_module_param(module_name, param, value, sizeof(value));
+ TEST_ASSERT(value[r - 1] == '\n',
+ "Expected trailing newline, got char '%c'", value[r - 1]);
+
+ /*
+ * Squash the newline, otherwise atoi_paranoid() will complain about
+ * trailing non-NUL characters in the string.
+ */
+ value[r - 1] = '\0';
+ return atoi_paranoid(value);
+}
+
+static bool get_module_param_bool(const char *module_name, const char *param)
+{
+ char value;
+ ssize_t r;
+
+ r = get_module_param(module_name, param, &value, sizeof(value));
+ TEST_ASSERT_EQ(r, 1);

if (value == 'Y')
return true;
@@ -95,6 +130,21 @@ bool get_kvm_amd_param_bool(const char *param)
return get_module_param_bool("kvm_amd", param);
}

+int get_kvm_param_integer(const char *param)
+{
+ return get_module_param_integer("kvm", param);
+}
+
+int get_kvm_intel_param_integer(const char *param)
+{
+ return get_module_param_integer("kvm_intel", param);
+}
+
+int get_kvm_amd_param_integer(const char *param)
+{
+ return get_module_param_integer("kvm_amd", param);
+}
+
/*
* Capability
*
--
2.42.0.869.gea05f2083d-goog