From 866826b3dd41636ef6e93f036a44aa12ab99a046 Mon Sep 17 00:00:00 2001 From: "H. Peter Anvin" Date: Fri, 9 Jul 2010 21:03:13 -0700 Subject: memdisk: write a message if the RSDP is writable or not Test the RSDP for writability; print a message if it is. Signed-off-by: H. Peter Anvin --- memdisk/acpi.c | 22 ++++++++++++++++++++++ 1 file changed, 22 insertions(+) diff --git a/memdisk/acpi.c b/memdisk/acpi.c index cd0431c1..82a0808b 100644 --- a/memdisk/acpi.c +++ b/memdisk/acpi.c @@ -165,6 +165,7 @@ size_t acpi_bytes_needed(void) { struct acpi_rsdp *rsdp; struct acpi_description_header *dsdt; + bool rsdp_writable; int i, n; rsdp = find_rsdp(); @@ -173,6 +174,27 @@ size_t acpi_bytes_needed(void) return 0; } + /* Check to see if the RSDP is writable */ + if (0 && (size_t)rsdp < 0xa0000) { + rsdp_writable = true; + } else { + size_t t1, t2; + + asm volatile( + "cli ; " + "movl %2,%0 ; " + "xorl $-1,%2 ; " + "movl %2,%1 ; " + "movl %0,%2 ; " + "sti" + : "=r" (t1), "=r" (t2) + : "m" (rsdp->rsdt_addr)); + + rsdp_writable = (t1 ^ t2) == -1; + } + + printf("ACPI: RSDP is %s\n", rsdp_writable ? "writable" : "readonly"); + rsdt = (struct acpi_rsdt *)rsdp->rsdt_addr; if (is_valid_table(rsdt) != ERR_NONE) { printf("ACPI: unable to locate an ACPI RSDT\n"); -- cgit v1.2.1