3.17-stable review patch. If anyone has any objections, please let me know.
------------------ From: Mark Rutland <[email protected]> commit 9b0b26580a753d4d6bdd2b8b4ca9a8f3f2d39065 upstream. While efi-entry.S mentions that efi_entry() will have relocated the kernel image, it actually means that efi_entry will have placed a copy of the kernel in the appropriate location, and until this is branched to at the end of efi_entry.S, all instructions are executed from the original image. Thus while the flush in efi_entry.S does ensure that the copy is visible to noncacheable accesses, it does not guarantee that this is true for the image instructions are being executed from. This could have disasterous effects when the MMU and caches are disabled if the image has not been naturally evicted to the PoC. Additionally, due to a missing dsb following the ic ialluis, the new kernel image is not necessarily clean in the I-cache when it is branched to, with similar potentially disasterous effects. This patch adds additional flushing to ensure that the currently executing stub text is flushed to the PoC and is thus visible to noncacheable accesses. As it is placed after the instructions cache maintenance for the new image and __flush_dcache_area already contains a dsb, we do not need to add a separate barrier to ensure completion of the icache maintenance. Comments are updated to clarify the situation with regard to the two images and the maintenance required for both. Fixes: 3c7f255039a2ad6ee1e3890505caf0d029b22e29 Signed-off-by: Mark Rutland <[email protected]> Acked-by: Joel Schopp <[email protected]> Reviewed-by: Roy Franz <[email protected]> Tested-by: Tom Lendacky <[email protected]> Cc: Ard Biesheuvel <[email protected]> Cc: Ian Campbell <[email protected]> Cc: Leif Lindholm <[email protected]> Cc: Mark Salter <[email protected]> Cc: Will Deacon <[email protected]> Signed-off-by: Catalin Marinas <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]> --- arch/arm64/kernel/efi-entry.S | 27 +++++++++++++++++++++------ 1 file changed, 21 insertions(+), 6 deletions(-) --- a/arch/arm64/kernel/efi-entry.S +++ b/arch/arm64/kernel/efi-entry.S @@ -54,18 +54,17 @@ ENTRY(efi_stub_entry) b.eq efi_load_fail /* - * efi_entry() will have relocated 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. + * 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 mov x21, x0 /* - * Flush dcache covering current runtime addresses - * of kernel text/data. Then flush all of icache. + * Calculate size of the kernel Image (same for original and copy). */ adrp x1, _text add x1, x1, #:lo12:_text @@ -73,9 +72,24 @@ ENTRY(efi_stub_entry) add x2, x2, #:lo12:_edata sub x1, x2, x1 + /* + * Flush the copied Image to the PoC, and ensure it is not shadowed by + * stale icache entries from before relocation. + */ bl __flush_dcache_area ic ialluis + /* + * 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. + */ + adr x0, efi_stub_entry + adr x1, efi_stub_entry_end + sub x1, x1, x0 + bl __flush_dcache_area + /* Turn off Dcache and MMU */ mrs x0, CurrentEL cmp x0, #CurrentEL_EL2 @@ -105,4 +119,5 @@ efi_load_fail: ldp x29, x30, [sp], #32 ret +efi_stub_entry_end: ENDPROC(efi_stub_entry) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
