kernel/arch/arm/boot/compressed/head.S, branch linux-rolling-stable

ARM: remove check for CONFIG_DEBUG_LL_SER3

2022-09-28T20:39:21Z

A check for CONFIG_DEBUG_LL_SER3 was added in v2.5.43. But the related symbol DEBUG_LL_SER3 was already removed in v2.5.8. This check has always evaluated to false. Remove it. Signed-off-by: Paul Bolle Signed-off-by: Geert Uytterhoeven Signed-off-by: Arnd Bergmann

ARM: 9159/1: decompressor: Avoid UNPREDICTABLE NOP encoding

2021-12-17T11:34:32Z

In the decompressor's head.S we need to start with an instruction that is some kind of NOP, but also mimics as the PE/COFF header, when the kernel is linked as an UEFI application. The clever solution here is "tstne r0, #0x4d000", which in the worst case just clobbers the condition flags, and bears the magic "MZ" signature in the lowest 16 bits. However the encoding used (0x13105a4d) is actually not valid, since bits [15:12] are supposed to be 0 (written as "(0)" in the ARM ARM). Violating this is UNPREDICTABLE, and *can* trigger an UNDEFINED exception. Common Cortex cores seem to ignore those bits, but QEMU chooses to trap, so the code goes fishing because of a missing exception handler at this point. We are just saved by the fact that commonly (with -kernel or when running from U-Boot) the "Z" bit is set, so the instruction is never executed. See [0] for more details. To make things more robust and avoid UNPREDICTABLE behaviour in the kernel code, lets replace this with a "two-instruction NOP": The first instruction is an exclusive OR, the effect of which the second instruction reverts. This does not leave any trace, neither in a register nor in the condition flags. Also it's a perfectly valid encoding. Kudos to Peter Maydell for coming up with this gem. [0] https://lore.kernel.org/qemu-devel/YTPIdbUCmwagL5%2FD@os.inf.tu-dresden.de/T/ Link: https://lore.kernel.org/linux-arm-kernel/20210908162617.104962-1-andre.przywara@arm.com/T/ Fixes: 81a0bc39ea19 ("ARM: add UEFI stub support") Signed-off-by: Andre Przywara Reported-by: Adam Lackorzynski Suggested-by: Peter Maydell Reviewed-by: Ard Biesheuvel Reviewed-by: Linus Walleij Signed-off-by: Russell King (Oracle)

ARM: 9046/1: decompressor: Do not clear SCTLR.nTLSMD for ARMv7+ cores

2021-02-01T19:42:13Z

It was observed that decompressor running on hardware implementing ARM v8.2 Load/Store Multiple Atomicity and Ordering Control (LSMAOC), say, as guest, would stuck just after: Uncompressing Linux... done, booting the kernel. The reason is that it clears nTLSMD bit when disabling caches: nTLSMD, bit [3] When ARMv8.2-LSMAOC is implemented: No Trap Load Multiple and Store Multiple to Device-nGRE/Device-nGnRE/Device-nGnRnE memory. 0b0 All memory accesses by A32 and T32 Load Multiple and Store Multiple at EL1 or EL0 that are marked at stage 1 as Device-nGRE/Device-nGnRE/Device-nGnRnE memory are trapped and generate a stage 1 Alignment fault. 0b1 All memory accesses by A32 and T32 Load Multiple and Store Multiple at EL1 or EL0 that are marked at stage 1 as Device-nGRE/Device-nGnRE/Device-nGnRnE memory are not trapped. This bit is permitted to be cached in a TLB. This field resets to 1. Otherwise: Reserved, RES1 So as effect we start getting traps we are not quite ready for. Looking into history it seems that mask used for SCTLR clear came from the similar code for ARMv4, where bit[3] is the enable/disable bit for the write buffer. That not applicable to ARMv7 and onwards, so retire that bit from the masks. Fixes: 7d09e85448dfa78e3e58186c934449aaf6d49b50 ("[ARM] 4393/2: ARMv7: Add uncompressing code for the new CPU Id format") Signed-off-by: Vladimir Murzin Signed-off-by: Russell King

ARM: 9045/1: uncompress: Validate start of physical memory against passed DTB

2021-02-01T19:42:13Z

Currently, the start address of physical memory is obtained by masking the program counter with a fixed mask of 0xf8000000. This mask value was chosen as a balance between the requirements of different platforms. However, this does require that the start address of physical memory is a multiple of 128 MiB, precluding booting Linux on platforms where this requirement is not fulfilled. Fix this limitation by validating the masked address against the memory information in the passed DTB. Only use the start address from DTB when masking would yield an out-of-range address, prefer the traditional method in all other cases. Note that this applies only to the explicitly passed DTB on modern systems, and not to a DTB appended to the kernel, or to ATAGS. The appended DTB may need to be augmented by information from ATAGS, which may need to rely on knowledge of the start address of physical memory itself. This allows to boot Linux on r7s9210/rza2mevb using the 64 MiB of SDRAM on the RZA2MEVB sub board, which is located at 0x0C000000 (CS3 space), i.e. not at a multiple of 128 MiB. Suggested-by: Nicolas Pitre Suggested-by: Ard Biesheuvel Signed-off-by: Geert Uytterhoeven Reviewed-by: Ard Biesheuvel Acked-by: Nicolas Pitre Signed-off-by: Russell King

ARM: 9039/1: assembler: generalize byte swapping macro into rev_l

2021-02-01T19:41:30Z

Take the 4 instruction byte swapping sequence from the decompressor's head.S, and turn it into a rev_l GAS macro for general use. While at it, make it use the 'rev' instruction when compiling for v6 or later. Reviewed-by: Geert Uytterhoeven Tested-by: Geert Uytterhoeven Reviewed-by: Nicolas Pitre Signed-off-by: Ard Biesheuvel Signed-off-by: Russell King

Merge tag 'for-linus' of git://git.armlinux.org.uk/~rmk/linux

2020-12-22T21:34:27Z

Pull ARM updates from Russell King: - Rework phys/virt translation - Add KASan support - Move DT out of linear map region - Use more PC-relative addressing in assembly - Remove FP emulation handling while in kernel mode - Link with '-z norelro' - remove old check for GCC <= 4.2 in ARM unwinder code - disable big endian if using clang's linker * tag 'for-linus' of git://git.armlinux.org.uk/~rmk/linux-arm: (46 commits) ARM: 9027/1: head.S: explicitly map DT even if it lives in the first physical section ARM: 9038/1: Link with '-z norelro' ARM: 9037/1: uncompress: Add OF_DT_MAGIC macro ARM: 9036/1: uncompress: Fix dbgadtb size parameter name ARM: 9035/1: uncompress: Add be32tocpu macro ARM: 9033/1: arm/smp: Drop the macro S(x,s) ARM: 9032/1: arm/mm: Convert PUD level pgtable helper macros into functions ARM: 9031/1: hyp-stub: remove unused .L__boot_cpu_mode_offset symbol ARM: 9044/1: vfp: use undef hook for VFP support detection ARM: 9034/1: __div64_32(): straighten up inline asm constraints ARM: 9030/1: entry: omit FP emulation for UND exceptions taken in kernel mode ARM: 9029/1: Make iwmmxt.S support Clang's integrated assembler ARM: 9028/1: disable KASAN in call stack capturing routines ARM: 9026/1: unwind: remove old check for GCC <= 4.2 ARM: 9025/1: Kconfig: CPU_BIG_ENDIAN depends on !LD_IS_LLD ARM: 9024/1: Drop useless cast of "u64" to "long long" ARM: 9023/1: Spelling s/mmeory/memory/ ARM: 9022/1: Change arch/arm/lib/mem*.S to use WEAK instead of .weak ARM: kvm: replace open coded VA->PA calculations with adr_l call ARM: head.S: use PC relative insn sequence to calculate PHYS_OFFSET ...

Merge branch 'devel-stable' into for-next

2020-12-21T11:19:26Z

ARM: 9037/1: uncompress: Add OF_DT_MAGIC macro

2020-12-21T11:19:21Z

The DTB magic marker is stored as a 32-bit big-endian value, and thus depends on the CPU's endianness. Add a macro to define this value in native endianness, to reduce #ifdef clutter and (future) duplication. Signed-off-by: Geert Uytterhoeven Reviewed-by: Ard Biesheuvel Reviewed-by: Nicolas Pitre Signed-off-by: Russell King

ARM: 9036/1: uncompress: Fix dbgadtb size parameter name

2020-12-21T11:19:20Z

The dbgadtb macro is passed the size of the appended DTB, not the end address. Fixes: c03e41470e901123 ("ARM: 9010/1: uncompress: Print the location of appended DTB") Signed-off-by: Geert Uytterhoeven Reviewed-by: Linus Walleij Signed-off-by: Russell King

ARM: 9035/1: uncompress: Add be32tocpu macro

2020-12-21T11:19:20Z

DTB stores all values as 32-bit big-endian integers. Add a macro to convert such values to native CPU endianness, to reduce duplication. Signed-off-by: Geert Uytterhoeven Reviewed-by: Ard Biesheuvel Reviewed-by: Nicolas Pitre Signed-off-by: Russell King