From: Ard Biesheuvel ard.biesheuvel@linaro.org
[ Upstream commit 06a4b6d009a1b74a6ec46c5418b46cc53a79fcb8 ]
As reported by Patrice, the header layout of the decompressor is incorrect when building for v7-M. In this case, the __nop macro resolves to 'mov r0, r0', which is emitted as a narrow encoding, resulting in the header data fields to end up at lower offsets than required.
Given the variety of targets we need to support with the same code, the startup sequence is a bit of a jumble, and uses instructions and macros whose encoding widths cannot be specified (badr), or only exist in a narrow encoding (bx)
So force the use of a wide encoding in __nop, and replace the start sequence with a simple jump to the label marking the start of code, preceded by a Thumb2 mode switch if required (using explicit wide encodings where appropriate). The label itself can be moved to the start of code [where it belongs] due to the larger range of branch instructions as compared to adr instructions.
Reported-by: Patrice CHOTARD patrice.chotard@st.com Acked-by: Nicolas Pitre nico@linaro.org Signed-off-by: Ard Biesheuvel ard.biesheuvel@linaro.org Signed-off-by: Russell King rmk+kernel@armlinux.org.uk Signed-off-by: Sasha Levin sashal@kernel.org --- arch/arm/boot/compressed/efi-header.S | 4 +--- arch/arm/boot/compressed/head.S | 17 ++++++++++------- 2 files changed, 11 insertions(+), 10 deletions(-)
diff --git a/arch/arm/boot/compressed/efi-header.S b/arch/arm/boot/compressed/efi-header.S index 9d5dc4fda3c1..3f7d1b74c5e0 100644 --- a/arch/arm/boot/compressed/efi-header.S +++ b/arch/arm/boot/compressed/efi-header.S @@ -17,14 +17,12 @@ @ there. .inst 'M' | ('Z' << 8) | (0x1310 << 16) @ tstne r0, #0x4d000 #else - mov r0, r0 + W(mov) r0, r0 #endif .endm
.macro __EFI_HEADER #ifdef CONFIG_EFI_STUB - b __efi_start - .set start_offset, __efi_start - start .org start + 0x3c @ diff --git a/arch/arm/boot/compressed/head.S b/arch/arm/boot/compressed/head.S index fc6d541549a2..2d7f2bb0d66a 100644 --- a/arch/arm/boot/compressed/head.S +++ b/arch/arm/boot/compressed/head.S @@ -130,19 +130,22 @@ start: .rept 7 __nop .endr - ARM( mov r0, r0 ) - ARM( b 1f ) - THUMB( badr r12, 1f ) - THUMB( bx r12 ) +#ifndef CONFIG_THUMB2_KERNEL + mov r0, r0 +#else + AR_CLASS( sub pc, pc, #3 ) @ A/R: switch to Thumb2 mode + M_CLASS( nop.w ) @ M: already in Thumb2 mode + .thumb +#endif + W(b) 1f
.word _magic_sig @ Magic numbers to help the loader .word _magic_start @ absolute load/run zImage address .word _magic_end @ zImage end address .word 0x04030201 @ endianness flag
- THUMB( .thumb ) -1: __EFI_HEADER - + __EFI_HEADER +1: ARM_BE8( setend be ) @ go BE8 if compiled for BE8 AR_CLASS( mrs r9, cpsr ) #ifdef CONFIG_ARM_VIRT_EXT