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authorLinus Torvalds <torvalds@linux-foundation.org>2019-09-22 09:39:09 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2019-09-22 09:39:09 -0700
commit8808cf8cbc4da1ceef9307fba7e499563908c211 (patch)
tree4048db33e1c347bc2a8a89b8f79d9fcf88bc6f2d /arch/arm/boot
parent5c6bd5de3c2e5bc8a17451e281ed2613375a7fd5 (diff)
parent79bdcb202a35bf2701779afafa0db07e2852d46b (diff)
downloadlinux-8808cf8cbc4da1ceef9307fba7e499563908c211.tar.bz2
Merge tag 'for-linus' of git://git.armlinux.org.uk/~rmk/linux-arm
Pull ARM updates from Russell King: - fix various clang build and cppcheck issues - switch ARM to use new common outgoing-CPU-notification code - add some additional explanation about the boot code - kbuild "make clean" fixes - get rid of another "(____ptrval____)", this time for the VDSO code - avoid treating cache maintenance faults as a write - add a frame pointer unwinder implementation for clang - add EDAC support for Aurora L2 cache - improve robustness of adjust_lowmem_bounds() finding the bounds of lowmem. - add reset control for AMBA primecell devices * tag 'for-linus' of git://git.armlinux.org.uk/~rmk/linux-arm: (24 commits) ARM: 8906/1: drivers/amba: add reset control to amba bus probe ARM: 8905/1: Emit __gnu_mcount_nc when using Clang 10.0.0 or newer ARM: 8904/1: skip nomap memblocks while finding the lowmem/highmem boundary ARM: 8903/1: ensure that usable memory in bank 0 starts from a PMD-aligned address ARM: 8891/1: EDAC: armada_xp: Add support for more SoCs ARM: 8888/1: EDAC: Add driver for the Marvell Armada XP SDRAM and L2 cache ECC ARM: 8892/1: EDAC: Add missing debugfs_create_x32 wrapper ARM: 8890/1: l2x0: add marvell,ecc-enable property for aurora ARM: 8889/1: dt-bindings: document marvell,ecc-enable binding ARM: 8886/1: l2x0: support parity-enable/disable on aurora ARM: 8885/1: aurora-l2: add defines for parity and ECC registers ARM: 8887/1: aurora-l2: add prefix to MAX_RANGE_SIZE ARM: 8902/1: l2c: move cache-aurora-l2.h to asm/hardware ARM: 8900/1: UNWINDER_FRAME_POINTER implementation for Clang ARM: 8898/1: mm: Don't treat faults reported from cache maintenance as writes ARM: 8896/1: VDSO: Don't leak kernel addresses ARM: 8895/1: visit mach-* and plat-* directories when cleaning ARM: 8894/1: boot: Replace open-coded nop with macro ARM: 8893/1: boot: Explain the 8 nops ARM: 8876/1: fix O= building with CONFIG_FPE_FASTFPE ...
Diffstat (limited to 'arch/arm/boot')
-rw-r--r--arch/arm/boot/compressed/head.S14
1 files changed, 13 insertions, 1 deletions
diff --git a/arch/arm/boot/compressed/head.S b/arch/arm/boot/compressed/head.S
index e59d14679fb0..93dffed0ac6e 100644
--- a/arch/arm/boot/compressed/head.S
+++ b/arch/arm/boot/compressed/head.S
@@ -153,11 +153,23 @@
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