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authorArd Biesheuvel <ardb@kernel.org>2020-02-17 14:44:37 +0300
committerArd Biesheuvel <ardb@kernel.org>2020-02-23 01:37:37 +0300
commit9f9223778ef385e79dc67f5ee48ee4c1fb757f6b (patch)
tree82aab113bd4467d603dc317435832205ac1e7c74 /arch/arm64/kernel/efi-entry.S
parente951a1f427f2312e17b4e0f485e60068ca1423bb (diff)
downloadlinux-9f9223778ef385e79dc67f5ee48ee4c1fb757f6b.tar.xz
efi/libstub/arm: Make efi_entry() an ordinary PE/COFF entrypoint
Expose efi_entry() as the PE/COFF entrypoint directly, instead of jumping into a wrapper that fiddles with stack buffers and other stuff that the compiler is much better at. The only reason this code exists is to obtain a pointer to the base of the image, but we can get the same value from the loaded_image protocol, which we already need for other reasons anyway. Update the return type as well, to make it consistent with what is required for a PE/COFF executable entrypoint. Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Diffstat (limited to 'arch/arm64/kernel/efi-entry.S')
-rw-r--r--arch/arm64/kernel/efi-entry.S86
1 files changed, 17 insertions, 69 deletions
diff --git a/arch/arm64/kernel/efi-entry.S b/arch/arm64/kernel/efi-entry.S
index 304d5b02ca67..4cfd03c35c49 100644
--- a/arch/arm64/kernel/efi-entry.S
+++ b/arch/arm64/kernel/efi-entry.S
@@ -10,81 +10,35 @@
#include <asm/assembler.h>
-#define EFI_LOAD_ERROR 0x8000000000000001
-
__INIT
- /*
- * We arrive here from the EFI boot manager with:
- *
- * * CPU in little-endian mode
- * * MMU on with identity-mapped RAM
- * * Icache and Dcache on
- *
- * We will most likely be running from some place other than where
- * we want to be. The kernel image wants to be placed at TEXT_OFFSET
- * from start of RAM.
- */
-ENTRY(entry)
- /*
- * Create a stack frame to save FP/LR with extra space
- * for image_addr variable passed to efi_entry().
- */
- stp x29, x30, [sp, #-32]!
- mov x29, sp
-
- /*
- * Call efi_entry to do the real work.
- * x0 and x1 are already set up by firmware. Current runtime
- * address of image is calculated and passed via *image_addr.
- *
- * unsigned long efi_entry(void *handle,
- * efi_system_table_t *sys_table,
- * unsigned long *image_addr) ;
- */
- adr_l x8, _text
- add x2, sp, 16
- str x8, [x2]
- bl efi_entry
- cmn x0, #1
- b.eq efi_load_fail
-
+ENTRY(efi_enter_kernel)
/*
* efi_entry() will have copied the kernel image if necessary and we
- * return here with device tree address in x0 and the kernel entry
- * point stored at *image_addr. Save those values in registers which
- * are callee preserved.
- */
- mov x20, x0 // DTB address
- ldr x0, [sp, #16] // relocated _text address
- ldr w21, =stext_offset
- add x21, x0, x21
-
- /*
- * Calculate size of the kernel Image (same for original and copy).
+ * end up here with device tree address in x1 and the kernel entry
+ * point stored in x0. Save those values in registers which are
+ * callee preserved.
*/
- adr_l x1, _text
- adr_l x2, _edata
- sub x1, x2, x1
+ mov x19, x0 // relocated Image address
+ mov x20, x1 // DTB address
/*
* Flush the copied Image to the PoC, and ensure it is not shadowed by
* stale icache entries from before relocation.
*/
+ ldr w1, =kernel_size
bl __flush_dcache_area
ic ialluis
+ dsb sy
/*
- * Ensure that the rest of this function (in the original Image) is
- * visible when the caches are disabled. The I-cache can't have stale
- * entries for the VA range of the current image, so no maintenance is
- * necessary.
+ * Jump across, into the copy of the image that we just cleaned
+ * to the PoC, so that we can safely disable the MMU and caches.
*/
- adr x0, entry
- adr x1, entry_end
- sub x1, x1, x0
- bl __flush_dcache_area
-
+ ldr w0, .Ljmp
+ sub x0, x19, w0, sxtw
+ br x0
+0:
/* Turn off Dcache and MMU */
mrs x0, CurrentEL
cmp x0, #CurrentEL_EL2
@@ -109,12 +63,6 @@ ENTRY(entry)
mov x1, xzr
mov x2, xzr
mov x3, xzr
- br x21
-
-efi_load_fail:
- mov x0, #EFI_LOAD_ERROR
- ldp x29, x30, [sp], #32
- ret
-
-entry_end:
-ENDPROC(entry)
+ b stext
+ENDPROC(efi_enter_kernel)
+.Ljmp: .long _text - 0b