kernel/arch/s390/boot/boot.h, branch linux-6.2.y

s390/boot: fix mem_detect extended area allocation

2023-03-10T08:28:16Z

[ Upstream commit 22476f47b6b7fb7d066c71f67ebc11892adb0849 ] Allocation of mem_detect extended area was not considered neither in commit 9641b8cc733f ("s390/ipl: read IPL report at early boot") nor in commit b2d24b97b2a9 ("s390/kernel: add support for kernel address space layout randomization (KASLR)"). As a result mem_detect extended theoretically may overlap with ipl report or randomized kernel image position. But as mem_detect code will allocate extended area only upon exceeding 255 online regions (which should alternate with offline memory regions) it is not seen in practice. To make sure mem_detect extended area does not overlap with ipl report or randomized kernel position extend usage of "safe_addr". Make initrd handling and mem_detect extended area allocation code move it further right and make KASLR takes in into consideration as well. Fixes: 9641b8cc733f ("s390/ipl: read IPL report at early boot") Fixes: b2d24b97b2a9 ("s390/kernel: add support for kernel address space layout randomization (KASLR)") Reviewed-by: Alexander Gordeev Signed-off-by: Vasily Gorbik Signed-off-by: Heiko Carstens Signed-off-by: Sasha Levin

s390/boot: cleanup decompressor header files

2023-03-10T08:28:16Z

[ Upstream commit 9c3205b2b062420c26b33924b910880889acf832 ] Move declarations to appropriate header files. Instead of cryptic casting directly assign struct vmlinux_info type to _vmlinux_info linker script variable - wich it actually is. Reviewed-by: Heiko Carstens Signed-off-by: Alexander Gordeev Signed-off-by: Heiko Carstens Stable-dep-of: 22476f47b6b7 ("s390/boot: fix mem_detect extended area allocation") Signed-off-by: Sasha Levin

s390/boot: convert initial lowcore to C

2022-05-06T18:45:15Z

Convert initial lowcore to C and use proper defines and structures to initialize it. This should make the z/VM ipl procedure a bit less magic. Acked-by: Peter Oberparleiter Reviewed-by: Vasily Gorbik Signed-off-by: Heiko Carstens

s390/boot: move dma sections from decompressor to decompressed kernel

2021-07-27T07:39:17Z

This change simplifies the task of making the decompressor relocatable. The decompressor's image contains special DMA sections between _sdma and _edma. This DMA segment is loaded at boot as part of the decompressor and then simply handed over to the decompressed kernel. The decompressor itself never uses it in any way. The primary reason for this is the need to keep the aforementioned DMA segment below 2GB which is required by architecture, and because the decompressor is always loaded at a fixed low physical address, it is guaranteed that the DMA region will not cross the 2GB memory limit. If the DMA region had been placed in the decompressed kernel, then KASLR would make this guarantee impossible to fulfill or it would be restricted to the first 2GB of memory address space. This commit moves all DMA sections between _sdma and _edma from the decompressor's image to the decompressed kernel's image. The complete DMA region is placed in the init section of the decompressed kernel and immediately relocated below 2GB at start-up before it is needed by other parts of the decompressed kernel. The relocation of the DMA region happens even if the decompressed kernel is already located below 2GB in order to keep the first implementation simple. The relocation should not have any noticeable impact on boot time because the DMA segment is only a couple of pages. After relocating the DMA sections, the kernel has to fix all references which point into it. In order to automate this, place all variables pointing into the DMA sections in a special .dma.refs section. All such variables must be defined using the new __dma_ref macro. Only variables containing addresses within the DMA sections must be placed in the new .dma.refs section. Furthermore, move the initialization of control registers from the decompressor to the decompressed kernel because some control registers reference tables that must be placed in the DMA data section to guarantee that their addresses are below 2G. Because the decompressed kernel relocates the DMA sections at startup, the content of control registers CR2, CR5 and CR15 must be updated with new addresses after the relocation. The decompressed kernel initializes all control registers early at boot and then updates the content of CR2, CR5 and CR15 as soon as the DMA relocation has occurred. This practically reverts the commit a80313ff91ab ("s390/kernel: introduce .dma sections"). Signed-off-by: Alexander Egorenkov Acked-by: Heiko Carstens Signed-off-by: Heiko Carstens

s390/boot: move sclp early buffer from fixed address in asm to C

2021-07-27T07:39:15Z

To make the decompressor relocatable, the early SCLP buffer with a fixed address must be replaced with a relocatable C buffer of the according size and alignment as required by SCLP. Introduce a new function sclp_early_set_buffer() into the SCLP driver which enables the decompressor to change the SCLP early buffer at any time. This will be useful when the decompressor becomes fully relocatable and might need to change the SCLP early buffer to one with an address < 2G as required by SCLP because it was loaded at an address >= 2G. Signed-off-by: Alexander Egorenkov Acked-by: Heiko Carstens Signed-off-by: Heiko Carstens

s390/boot: make stacks part of the decompressor's image

2021-07-27T07:39:13Z

Instead of using constant addresses for the normal and dump-info stacks, allocate both stacks in the decompressor's image and load the stack register in a position-independent manner. This will allow loading and entering the decompressor at an arbitrary memory address without corrupting the content at the fixed addresses used until now for both stacks. This is one of the prerequisites for being able to kexec the decompressor from its load address without relocating it first. Signed-off-by: Alexander Egorenkov Acked-by: Heiko Carstens Reviewed-by: Vasily Gorbik Signed-off-by: Heiko Carstens

s390/boot: move all linker symbol declarations from c to h files

2021-07-27T07:39:12Z

To prevent multiple incompatible declarations of symbols and to catch such mistakes at compile time. Signed-off-by: Alexander Egorenkov Acked-by: Heiko Carstens Acked-by: Vasily Gorbik Signed-off-by: Heiko Carstens

s390: setup kernel memory layout early

2021-06-18T14:41:19Z

Currently there are two separate places where kernel memory layout has to be known and adjusted: 1. early kasan setup. 2. paging setup later. Those 2 places had to be kept in sync and adjusted to reflect peculiar technical details of one another. With additional factors which influence kernel memory layout like ultravisor secure storage limit, complexity of keeping two things in sync grew up even more. Besides that if we look forward towards creating identity mapping and enabling DAT before jumping into uncompressed kernel - that would also require full knowledge of and control over kernel memory layout. So, de-duplicate and move kernel memory layout setup logic into the decompressor. Reviewed-by: Alexander Gordeev Signed-off-by: Vasily Gorbik

s390/decompressor: add stacktrace support

2020-11-20T18:19:11Z

Decompressor works on a single statically allocated stack. Stacktrace implementation with -mbackchain just takes few lines of code. Linux version 5.10.0-rc3-22793-g0f84a355b776-dirty (gor@tuxmaker) #27 SMP PREEMPT Mon Nov 9 17:30:18 CET 2020 Kernel fault: interruption code 0005 ilc:2 PSW : 0000000180000000 0000000000012f92 (parse_boot_command_line+0x27a/0x46c) R:0 T:0 IO:0 EX:0 Key:0 M:0 W:0 P:0 AS:0 CC:0 PM:0 RI:0 EA:3 GPRS: 0000000000000000 00ffffffffffffff 0000000000000000 000000000001a62c 000000000000bf60 0000000000000000 00000000000003c0 0000000000000000 0000000000000080 000000000002322d 000000007f29ef20 0000000000efd018 000000000311c000 0000000000010070 0000000000012f82 000000000000bea8 Call Trace: (sp:000000000000bea8 [<000000000002016e>] 000000000002016e) sp:000000000000bf18 [<0000000000012408>] startup_kernel+0x88/0x2fc sp:000000000000bf60 [<00000000000100c4>] startup_normal+0xb0/0xb0 Reviewed-by: Alexander Egorenkov Signed-off-by: Vasily Gorbik Signed-off-by: Heiko Carstens

s390/decompressor: add decompressor_printk

2020-11-20T18:19:11Z

The decompressor does not have any special debug means. Running the kernel under qemu with gdb is helpful but tedious exercise if done repeatedly. It is also not applicable to debugging under LPAR and z/VM. One special thing which stands out is a working sclp_early_printk, which could be used once the kernel switches to 64-bit addressing mode. But sclp_early_printk does not provide any string formating capabilities. Formatting and printing string without printk-alike function is a not fun. The lack of printk-alike function means people would save up on testing and introduce more bugs. So, finally, provide decompressor_printk function, which fits on one screen and trades features for simplicity. It only supports "%s", "%x" and "%lx" specifiers and zero padding for hex values. Reviewed-by: Alexander Egorenkov Signed-off-by: Vasily Gorbik Signed-off-by: Heiko Carstens