diff options
Diffstat (limited to 'arch/arm/boot/compressed/head.S')
| -rw-r--r-- | arch/arm/boot/compressed/head.S | 47 |
1 files changed, 29 insertions, 18 deletions
diff --git a/arch/arm/boot/compressed/head.S b/arch/arm/boot/compressed/head.S index e59d14679fb0..088b0a060876 100644 --- a/arch/arm/boot/compressed/head.S +++ b/arch/arm/boot/compressed/head.S @@ -140,7 +140,18 @@ #endif .endm - .section ".start", #alloc, #execinstr + .macro enable_cp15_barriers, reg + mrc p15, 0, \reg, c1, c0, 0 @ read SCTLR + tst \reg, #(1 << 5) @ CP15BEN bit set? + bne .L_\@ + orr \reg, \reg, #(1 << 5) @ CP15 barrier instructions + mcr p15, 0, \reg, c1, c0, 0 @ write SCTLR + ARM( .inst 0xf57ff06f @ v7+ isb ) + THUMB( isb ) +.L_\@: + .endm + + .section ".start", "ax" /* * sort out different calling conventions */ @@ -153,11 +164,23 @@ AR_CLASS( .arm ) start: .type start,#function + /* + * These 7 nops along with the 1 nop immediately below for + * !THUMB2 form 8 nops that make the compressed kernel bootable + * on legacy ARM systems that were assuming the kernel in a.out + * binary format. The boot loaders on these systems would + * jump 32 bytes into the image to skip the a.out header. + * with these 8 nops filling exactly 32 bytes, things still + * work as expected on these legacy systems. Thumb2 mode keeps + * 7 of the nops as it turns out that some boot loaders + * were patching the initial instructions of the kernel, i.e + * had started to exploit this "patch area". + */ .rept 7 __nop .endr #ifndef CONFIG_THUMB2_KERNEL - mov r0, r0 + __nop #else AR_CLASS( sub pc, pc, #3 ) @ A/R: switch to Thumb2 mode M_CLASS( nop.w ) @ M: already in Thumb2 mode @@ -808,6 +831,7 @@ __armv4_mmu_cache_on: mov pc, r12 __armv7_mmu_cache_on: + enable_cp15_barriers r11 mov r12, lr #ifdef CONFIG_MMU mrc p15, 0, r11, c0, c1, 4 @ read ID_MMFR0 @@ -1197,6 +1221,7 @@ __armv6_mmu_cache_flush: mov pc, lr __armv7_mmu_cache_flush: + enable_cp15_barriers r10 tst r4, #1 bne iflush mrc p15, 0, r10, c0, c1, 5 @ read ID_MMFR1 @@ -1261,7 +1286,7 @@ iflush: __armv5tej_mmu_cache_flush: tst r4, #1 movne pc, lr -1: mrc p15, 0, r15, c7, c14, 3 @ test,clean,invalidate D cache +1: mrc p15, 0, APSR_nzcv, c7, c14, 3 @ test,clean,invalidate D cache bne 1b mcr p15, 0, r0, c7, c5, 0 @ flush I cache mcr p15, 0, r0, c7, c10, 4 @ drain WB @@ -1435,21 +1460,7 @@ ENTRY(efi_stub_entry) @ Preserve return value of efi_entry() in r4 mov r4, r0 - - @ our cache maintenance code relies on CP15 barrier instructions - @ but since we arrived here with the MMU and caches configured - @ by UEFI, we must check that the CP15BEN bit is set in SCTLR. - @ Note that this bit is RAO/WI on v6 and earlier, so the ISB in - @ the enable path will be executed on v7+ only. - mrc p15, 0, r1, c1, c0, 0 @ read SCTLR - tst r1, #(1 << 5) @ CP15BEN bit set? - bne 0f - orr r1, r1, #(1 << 5) @ CP15 barrier instructions - mcr p15, 0, r1, c1, c0, 0 @ write SCTLR - ARM( .inst 0xf57ff06f @ v7+ isb ) - THUMB( isb ) - -0: bl cache_clean_flush + bl cache_clean_flush bl cache_off @ Set parameters for booting zImage according to boot protocol |
