This patch preallocates the intermediate page table entries so that
all that is needed to setup a fixmap is to fill in the appropriate
pte.
By doing this modern hardware that uses memory mapped access can be
talked to early in boot through a fixmap.
Allowing USB debugging and the like.
Signed-off-by: Eric W. Biederman <[EMAIL PROTECTED]>
---
arch/x86_64/kernel/head.S | 14 +++++++++++++-
1 files changed, 13 insertions(+), 1 deletions(-)
diff --git a/arch/x86_64/kernel/head.S b/arch/x86_64/kernel/head.S
index 1fab487..1b704c4 100644
--- a/arch/x86_64/kernel/head.S
+++ b/arch/x86_64/kernel/head.S
@@ -74,6 +74,9 @@ startup_64:
addq %rbp, level3_ident_pgt + 0(%rip)
addq %rbp, level3_kernel_pgt + (510*8)(%rip)
+ addq %rbp, level3_kernel_pgt + (511*8)(%rip)
+
+ addq %rbp, level2_fixmap_pgt + (506*8)(%rip)
/* Add an Identity mapping if I am above 1G */
leaq _text(%rip), %rdi
@@ -314,7 +317,16 @@ NEXT_PAGE(level3_kernel_pgt)
.fill 510,8,0
/* (2^48-(2*1024*1024*1024)-((2^39)*511))/(2^30) = 510 */
.quad level2_kernel_pgt - __START_KERNEL_map + _KERNPG_TABLE
- .fill 1,8,0
+ .quad level2_fixmap_pgt - __START_KERNEL_map + _KERNPG_TABLE +
_PAGE_USER
+
+NEXT_PAGE(level2_fixmap_pgt)
+ .fill 506,8,0
+ .quad level1_fixmap_pgt - __START_KERNEL_map + _KERNPG_TABLE +
_PAGE_USER
+ /* 8MB reserved for vsyscalls + a 2MB hole = 4 + 1 entries */
+ .fill 5,8,0
+
+NEXT_PAGE(level1_fixmap_pgt)
+ .fill 512,8,0
NEXT_PAGE(level2_ident_pgt)
/* Since I easily can, map the first 1G.
--
1.5.1.1.181.g2de0
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