From 694cfd87b0c8a48af2f1afb225563571c0b975c4 Mon Sep 17 00:00:00 2001 From: "Ronald G. Minnich" Date: Sat, 25 Apr 2020 18:10:21 -0700 Subject: x86/setup: Add an initrdmem= option to specify initrd physical address Add the initrdmem option: initrdmem=ss[KMG],nn[KMG] which is used to specify the physical address of the initrd, almost always an address in FLASH. Also add code for x86 to use the existing phys_init_start and phys_init_size variables in the kernel. This is useful in cases where a kernel and an initrd is placed in FLASH, but there is no firmware file system structure in the FLASH. One such situation occurs when unused FLASH space on UEFI systems has been reclaimed by, e.g., taking it from the Management Engine. For example, on many systems, the ME is given half the FLASH part; not only is 2.75M of an 8M part unused; but 10.75M of a 16M part is unused. This space can be used to contain an initrd, but need to tell Linux where it is. This space is "raw": due to, e.g., UEFI limitations: it can not be added to UEFI firmware volumes without rebuilding UEFI from source or writing a UEFI device driver. It can be referenced only as a physical address and size. At the same time, if a kernel can be "netbooted" or loaded from GRUB or syslinux, the option of not using the physical address specification should be available. Then, it is easy to boot the kernel and provide an initrd; or boot the the kernel and let it use the initrd in FLASH. In practice, this has proven to be very helpful when integrating Linux into FLASH on x86. Hence, the most flexible and convenient path is to enable the initrdmem command line option in a way that it is the last choice tried. For example, on the DigitalLoggers Atomic Pi, an image into FLASH can be burnt in with a built-in command line which includes: initrdmem=0xff968000,0x200000 which specifies a location and size. [ bp: Massage commit message, make it passive. ] [akpm@linux-foundation.org: coding style fixes] Signed-off-by: Ronald G. Minnich Signed-off-by: Andrew Morton Signed-off-by: Borislav Petkov Reviewed-by: H. Peter Anvin (Intel) Link: http://lkml.kernel.org/r/CAP6exYLK11rhreX=6QPyDQmW7wPHsKNEFtXE47pjx41xS6O7-A@mail.gmail.com Link: https://lkml.kernel.org/r/20200426011021.1cskg0AGd%akpm@linux-foundation.org --- init/do_mounts_initrd.c | 13 ++++++++++++- 1 file changed, 12 insertions(+), 1 deletion(-) (limited to 'init') diff --git a/init/do_mounts_initrd.c b/init/do_mounts_initrd.c index dab8b1151b56..d72beda824aa 100644 --- a/init/do_mounts_initrd.c +++ b/init/do_mounts_initrd.c @@ -28,7 +28,7 @@ static int __init no_initrd(char *str) __setup("noinitrd", no_initrd); -static int __init early_initrd(char *p) +static int __init early_initrdmem(char *p) { phys_addr_t start; unsigned long size; @@ -43,6 +43,17 @@ static int __init early_initrd(char *p) } return 0; } +early_param("initrdmem", early_initrdmem); + +/* + * This is here as the initrd keyword has been in use since 11/2018 + * on ARM, PowerPC, and MIPS. + * It should not be; it is reserved for bootloaders. + */ +static int __init early_initrd(char *p) +{ + return early_initrdmem(p); +} early_param("initrd", early_initrd); static int init_linuxrc(struct subprocess_info *info, struct cred *new) -- cgit v1.2.3