[PATCH v2 8/9] arm64: head.S: use ordinary stack frame for __primary_switched()
From: Ard Biesheuvel <hidden>
Date: 2016-08-24 14:36:05
Subsystem:
arm64 port (aarch64 architecture), the rest · Maintainers:
Catalin Marinas, Will Deacon, Linus Torvalds
Instead of stashing the value of the link register in x28 before setting up the stack and calling into C code, create an ordinary PCS compatible stack frame so that we can push the return address onto the stack. Since exception handlers require a stack as well, assign the stach pointer register before installing the vector table. Note that this accounts for the difference between THREAD_START_SP and THREAD_SIZE, given that the stack pointer is always decremented before calling into any C code. Signed-off-by: Ard Biesheuvel <redacted> --- arch/arm64/kernel/head.S | 18 +++++++++--------- 1 file changed, 9 insertions(+), 9 deletions(-)
diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
index 27f51272de68..ad1dc61d67ac 100644
--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S@@ -415,13 +415,18 @@ ENDPROC(__create_page_tables) * * x0 = __PHYS_OFFSET */ - .set initial_sp, init_thread_union + THREAD_START_SP __primary_switched: - mov x28, lr // preserve LR + adrp x4, init_thread_union + add sp, x4, #THREAD_SIZE + msr sp_el0, x4 // Save thread_info + adr_l x8, vectors // load VBAR_EL1 with virtual msr vbar_el1, x8 // vector table address isb + stp xzr, x30, [sp, #-16]! + mov x29, sp + str_l x21, __fdt_pointer, x5 // Save FDT pointer ldr_l x4, kimage_vaddr // Save the offset between
@@ -436,11 +441,6 @@ __primary_switched: bl __pi_memset dsb ishst // Make zero page visible to PTW - adr_l sp, initial_sp, x4 - mov x4, sp - and x4, x4, #~(THREAD_SIZE - 1) - msr sp_el0, x4 // Save thread_info - mov x29, #0 #ifdef CONFIG_KASAN bl kasan_early_init #endif
@@ -452,8 +452,8 @@ __primary_switched: bl kaslr_early_init // parse FDT for KASLR options cbz x0, 0f // KASLR disabled? just proceed orr x23, x23, x0 // record KASLR offset - ret x28 // we must enable KASLR, return - // to __primary_switch() + ldp x29, x30, [sp], #16 // we must enable KASLR, return + ret // to __primary_switch() 0: #endif b start_kernel
--
2.7.4