diff mbox series

[v2,17/35] brcmfmac: pcie: Provide a buffer of random bytes to the device

Message ID 20220104072658.69756-18-marcan@marcan.st
State New
Headers show
Series brcmfmac: Support Apple T2 and M1 platforms | expand

Commit Message

Hector Martin Jan. 4, 2022, 7:26 a.m. UTC 
Newer Apple firmwares on chipsets without a hardware RNG require the
host to provide a buffer of 256 random bytes to the device on
initialization. This buffer is present immediately before NVRAM,
suffixed by a footer containing a magic number and the buffer length.

This won't affect chips/firmwares that do not use this feature, so do it
unconditionally.

Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Hector Martin <marcan@marcan.st>
---
 .../broadcom/brcm80211/brcmfmac/pcie.c        | 30 +++++++++++++++++++
 1 file changed, 30 insertions(+)

Comments

Arend van Spriel Jan. 10, 2022, 9:11 a.m. UTC | #1 
On 1/4/2022 8:26 AM, Hector Martin wrote:
> Newer Apple firmwares on chipsets without a hardware RNG require the
> host to provide a buffer of 256 random bytes to the device on
> initialization. This buffer is present immediately before NVRAM,
> suffixed by a footer containing a magic number and the buffer length.
> 
> This won't affect chips/firmwares that do not use this feature, so do it
> unconditionally.

Not sure what the general opinion is here, but pulling random bytes for 
naught seems wasteful to me. So if there is a way of knowing it is 
needed please make it conditional.

Reviewed-by: Arend van Spriel <arend.vanspriel@broadcom.com>
> Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
> Signed-off-by: Hector Martin <marcan@marcan.st>
> ---
>   .../broadcom/brcm80211/brcmfmac/pcie.c        | 30 +++++++++++++++++++
>   1 file changed, 30 insertions(+)
diff mbox series

Patch

diff --git a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/pcie.c b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/pcie.c
index cc76f00724e6..a8cccfbea20b 100644
--- a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/pcie.c
+++ b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/pcie.c
@@ -12,6 +12,7 @@ 
 #include <linux/interrupt.h>
 #include <linux/bcma/bcma.h>
 #include <linux/sched.h>
+#include <linux/random.h>
 #include <asm/unaligned.h>
 
 #include <soc.h>
@@ -1662,6 +1663,13 @@  brcmf_pcie_init_share_ram_info(struct brcmf_pciedev_info *devinfo,
 	return 0;
 }
 
+struct brcmf_random_seed_footer {
+	__le32 length;
+	__le32 magic;
+};
+
+#define BRCMF_RANDOM_SEED_MAGIC		0xfeedc0de
+#define BRCMF_RANDOM_SEED_LENGTH	0x100
 
 static int brcmf_pcie_download_fw_nvram(struct brcmf_pciedev_info *devinfo,
 					const struct firmware *fw, void *nvram,
@@ -1693,11 +1701,33 @@  static int brcmf_pcie_download_fw_nvram(struct brcmf_pciedev_info *devinfo,
 	brcmf_pcie_write_ram32(devinfo, devinfo->ci->ramsize - 4, 0);
 
 	if (nvram) {
+		size_t rand_len = BRCMF_RANDOM_SEED_LENGTH;
+		struct brcmf_random_seed_footer footer = {
+			.length = cpu_to_le32(rand_len),
+			.magic = cpu_to_le32(BRCMF_RANDOM_SEED_MAGIC),
+		};
+		void *randbuf;
+
 		brcmf_dbg(PCIE, "Download NVRAM %s\n", devinfo->nvram_name);
 		address = devinfo->ci->rambase + devinfo->ci->ramsize -
 			  nvram_len;
 		brcmf_pcie_copy_mem_todev(devinfo, address, nvram, nvram_len);
 		brcmf_fw_nvram_free(nvram);
+
+		/* Some Apple chips/firmwares expect a buffer of random data
+		 * to be present before NVRAM
+		 */
+		brcmf_dbg(PCIE, "Download random seed\n");
+
+		address -= sizeof(footer);
+		brcmf_pcie_copy_mem_todev(devinfo, address, &footer,
+					  sizeof(footer));
+
+		address -= rand_len;
+		randbuf = kzalloc(rand_len, GFP_KERNEL);
+		get_random_bytes(randbuf, rand_len);
+		brcmf_pcie_copy_mem_todev(devinfo, address, randbuf, rand_len);
+		kfree(randbuf);
 	} else {
 		brcmf_dbg(PCIE, "No matching NVRAM file found %s\n",
 			  devinfo->nvram_name);