From: Daniel Wagner <dwagner@suse.de>
Date: Thu, 14 Sep 2023 08:53:20 +0000 (+0200)
Subject: nvme: introduce alloc helper with alignment support
X-Git-Tag: v2.6~27
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=fe24b9e9ecc769fa144e80ee8b31c85ff5f8f2e1;p=users%2Fsagi%2Fnvme-cli.git

nvme: introduce alloc helper with alignment support

The kernel supports since v5.2 direct mapped DMA buffers to userspace.
Up to this point a bounce buffer was involved. Because the buffers are
now directly accessed by the device, the rules of alignment also apply
for the payloads.

Introduce a helper to allocate all correctly buffers aligned.

Furthermore, ensure that the buffer is a multiple of 4k, because there
are devices on the market which will always transfer a multiple of 4k,
even if we ask for less, e.g 512 bytes. This avoid stack smashes.

Signed-off-by: Daniel Wagner <dwagner@suse.de>
---

diff --git a/nvme.c b/nvme.c
index 354c6dad..e26666b0 100644
--- a/nvme.c
+++ b/nvme.c
@@ -183,7 +183,20 @@ static const char space[51] = {[0 ... 49] = ' ', '\0'};
 
 static void *mmap_registers(nvme_root_t r, struct nvme_dev *dev);
 
-static void *__nvme_alloc(size_t len, bool *huge)
+#define ROUND_UP(N, S) ((((N) + (S) - 1) / (S)) * (S))
+
+static void *nvme_alloc(size_t len)
+{
+	size_t _len = ROUND_UP(len, 0x1000);
+	void *p;
+
+	if (posix_memalign((void *)&p, getpagesize(), _len))
+		return NULL;
+
+	memset(p, 0, _len);
+	return p;
+}
+
 static void *__nvme_alloc_huge(size_t len, bool *huge)
 {
 	void *p;