[igt-dev] [PATCH i-g-t v2] i915/gem_pread, gem_pwrite: Exercise using ourselves as the buffer

[Chris Wilson]

If we caused a fault on a GEM buffer while in the middle of trying to
write/read into that buffer, we could conceivably deadlock (e.g.
recursing on struct_mutex if we are not careful). Exercise these cases
by supplying a fresh mmap to pread/pwrite in both non-overlapping and
overlapping copies.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
---
Create a fresh handle for each pass.
---
 tests/i915/gem_pread.c  | 35 +++++++++++++++++++++++++++++++++++
 tests/i915/gem_pwrite.c | 35 +++++++++++++++++++++++++++++++++++
 2 files changed, 70 insertions(+)

diff --git a/tests/i915/gem_pread.c b/tests/i915/gem_pread.c
index 00379580c..83d878ee4 100644
--- a/tests/i915/gem_pread.c
+++ b/tests/i915/gem_pread.c
@@ -39,6 +39,38 @@
 #include <sys/time.h>
 #include "drm.h"
 
+#define MiB(x) ((x) * 1024 * 1024)
+
+typedef void *(*mmap_fn_t)(int, uint32_t, uint64_t, uint64_t, unsigned int);
+
+static void *wrap_gem_mmap__gtt(int i915, uint32_t handle,
+				uint64_t offset, uint64_t length,
+				unsigned int prot)
+{
+	return gem_mmap__gtt(i915, handle, length, prot);
+}
+
+static void pread_self(int i915)
+{
+	static const mmap_fn_t mmap_fn[] = {
+		wrap_gem_mmap__gtt,
+		gem_mmap__cpu,
+		gem_mmap__wc,
+		NULL
+	};
+	for (const mmap_fn_t *fn = mmap_fn; *fn; fn++) {
+		uint32_t handle = gem_create(i915, MiB(4));
+		void *ptr = (*fn)(i915, handle, 0, MiB(4), PROT_WRITE);
+
+		gem_read(i915, handle, 0, ptr + MiB(3), MiB(1));
+		gem_read(i915, handle, MiB(3), ptr, MiB(1));
+		gem_read(i915, handle, MiB(1), ptr + MiB(1), MiB(2));
+
+		munmap(ptr, MiB(4));
+		gem_close(i915, handle);
+	}
+}
+
 #define OBJECT_SIZE 16384
 #define LARGE_OBJECT_SIZE 1024 * 1024
 #define KGRN "\x1B[32m"
@@ -131,6 +163,9 @@ int main(int argc, char **argv)
 		}
 	}
 
+	igt_subtest("self")
+		pread_self(fd);
+
 	for (c = cache; c->level != -1; c++) {
 		igt_subtest(c->name) {
 			gem_set_caching(fd, dst, c->level);
diff --git a/tests/i915/gem_pwrite.c b/tests/i915/gem_pwrite.c
index 696bd316a..3fd0ef667 100644
--- a/tests/i915/gem_pwrite.c
+++ b/tests/i915/gem_pwrite.c
@@ -39,6 +39,38 @@
 #include <sys/time.h>
 #include "drm.h"
 
+#define MiB(x) ((x) * 1024 * 1024)
+
+typedef void *(*mmap_fn_t)(int, uint32_t, uint64_t, uint64_t, unsigned int);
+
+static void *wrap_gem_mmap__gtt(int i915, uint32_t handle,
+				uint64_t offset, uint64_t length,
+				unsigned int prot)
+{
+	return gem_mmap__gtt(i915, handle, length, prot);
+}
+
+static void pwrite_self(int i915)
+{
+	static const mmap_fn_t mmap_fn[] = {
+		wrap_gem_mmap__gtt,
+		gem_mmap__cpu,
+		gem_mmap__wc,
+		NULL
+	};
+	for (const mmap_fn_t *fn = mmap_fn; *fn; fn++) {
+		uint32_t handle = gem_create(i915, MiB(4));
+		void *ptr = (*fn)(i915, handle, 0, MiB(4), PROT_READ);
+
+		gem_write(i915, handle, 0, ptr + MiB(3), MiB(1));
+		gem_write(i915, handle, MiB(3), ptr, MiB(1));
+		gem_write(i915, handle, MiB(1), ptr + MiB(1), MiB(2));
+
+		munmap(ptr, MiB(4));
+		gem_close(i915, handle);
+	}
+}
+
 #define OBJECT_SIZE 16384
 
 #define COPY_BLT_CMD		(2<<29|0x53<<22|0x6)
@@ -258,6 +290,9 @@ int main(int argc, char **argv)
 		}
 	}
 
+	igt_subtest("self")
+		pwrite_self(fd);
+
 	for (c = cache; c->level != -1; c++) {
 		igt_subtest(c->name) {
 			gem_set_caching(fd, dst, c->level);
-- 
2.20.1