Re: [PATCH 2/4] efi/x86: move efi bgrt init code to early init code

Nicolai Stange
2017-01-12T11:54:47Z

On Thu, Jan 12 2017, Dave Young wrote:

> -void __init efi_bgrt_init(void)
> +void __init efi_bgrt_init(struct acpi_table_header *table)
> {
> - acpi_status status;
> void *image;
> struct bmp_header bmp_header;
>
> if (acpi_disabled)
> return;
>
> - status = acpi_get_table("BGRT", 0,
> - (struct acpi_table_header **)&bgrt_tab);
> - if (ACPI_FAILURE(status))
> - return;

Not sure, but wouldn't it be safer to reverse the order of this assignment

> + bgrt_tab = *(struct acpi_table_bgrt *)table;

and this length check

> - if (bgrt_tab->header.length < sizeof(*bgrt_tab)) {
> + if (bgrt_tab.header.length < sizeof(bgrt_tab)) {
> pr_notice("Ignoring BGRT: invalid length %u (expected %zu)\n",
> - bgrt_tab->header.length, sizeof(*bgrt_tab));
> + bgrt_tab.header.length, sizeof(bgrt_tab));
> return;
> }

?

Also, from here on, all error paths should zero out
bgrt_tab.image_address (or so) to signal failure to bgrt_init():
bgrt_init() now checks for !bgrt_tab.image_address whereas before it had
tested bgrt_image and the latter used to be set at the very end of
efi_bgrt_init().

> - if (bgrt_tab->version != 1) {
> + if (bgrt_tab.version != 1) {
> pr_notice("Ignoring BGRT: invalid version %u (expected 1)\n",
> - bgrt_tab->version);
> + bgrt_tab.version);
> return;
> }
> - if (bgrt_tab->status & 0xfe) {
> + if (bgrt_tab.status & 0xfe) {
> pr_notice("Ignoring BGRT: reserved status bits are non-zero %u\n",
> - bgrt_tab->status);
> + bgrt_tab.status);
> return;
> }
> - if (bgrt_tab->image_type != 0) {
> + if (bgrt_tab.image_type != 0) {
> pr_notice("Ignoring BGRT: invalid image type %u (expected 0)\n",
> - bgrt_tab->image_type);
> + bgrt_tab.image_type);
> return;
> }
> - if (!bgrt_tab->image_address) {
> + if (!bgrt_tab.image_address) {
> pr_notice("Ignoring BGRT: null image address\n");
> return;
> }
>
> - image = memremap(bgrt_tab->image_address, sizeof(bmp_header), MEMREMAP_WB);
> + image = early_memremap(bgrt_tab.image_address, sizeof(bmp_header));
> if (!image) {
> pr_notice("Ignoring BGRT: failed to map image header memory\n");
> return;
> }
>
> memcpy(&bmp_header, image, sizeof(bmp_header));
> - memunmap(image);
> + early_memunmap(image, sizeof(bmp_header));
> if (bmp_header.id != 0x4d42) {
> pr_notice("Ignoring BGRT: Incorrect BMP magic number 0x%x (expected 0x4d42)\n",
> bmp_header.id);
> @@ -82,12 +77,5 @@ void __init efi_bgrt_init(void)
> }
> bgrt_image_size = bmp_header.size;
>
> - bgrt_image = memremap(bgrt_tab->image_address, bmp_header.size, MEMREMAP_WB);
> - if (!bgrt_image) {
> - pr_notice("Ignoring BGRT: failed to map image memory\n");
> - bgrt_image = NULL;
> - return;
> - }
> -
> - efi_mem_reserve(bgrt_tab->image_address, bgrt_image_size);
> + efi_mem_reserve(bgrt_tab.image_address, bgrt_image_size);
> }
> --- linux-x86.orig/drivers/acpi/bgrt.c
> +++ linux-x86/drivers/acpi/bgrt.c
> @@ -15,40 +15,41 @@
> #include <linux/sysfs.h>
> #include <linux/efi-bgrt.h>
>
> +static void *bgrt_image;

[...]

> @@ -84,9 +85,17 @@ static int __init bgrt_init(void)
> {
> int ret;
>
> - if (!bgrt_image)
> + if (!bgrt_tab.image_address)
> return -ENODEV;
>
> + bgrt_image = memremap(bgrt_tab.image_address, bgrt_image_size,
> + MEMREMAP_WB);
> + if (!bgrt_image) {
> + pr_notice("Ignoring BGRT: failed to map image memory\n");
> + bgrt_image = NULL;
> + return -ENOMEM;
> + }
> +
> bin_attr_image.private = bgrt_image;
> bin_attr_image.size = bgrt_image_size;
>

Thanks,

Nicolai