kernel.git/arch/s390/boot, branch linux-6.10.y

s390/mm: Pin identity mapping base to zero

2024-09-18T17:25:11Z

[ Upstream commit 32db401965f165f7c44447d0508097f070c8f576 ] SIE instruction performs faster when the virtual address of SIE block matches the physical one. Pin the identity mapping base to zero for the benefit of SIE and other instructions that have similar performance impact. Still, randomize the base when DEBUG_VM kernel configuration option is enabled. Suggested-by: Vasily Gorbik Reviewed-by: Christian Borntraeger Signed-off-by: Alexander Gordeev Signed-off-by: Vasily Gorbik Signed-off-by: Sasha Levin

s390/boot: Do not assume the decompressor range is reserved

2024-09-12T09:13:03Z

[ Upstream commit b798b685b42c9dbe508e59a74250d97c41bec35e ] When allocating a random memory range for .amode31 sections the minimal randomization address is 0. That does not lead to a possible overlap with the decompressor image (which also starts from 0) since by that time the image range is already reserved. Do not assume the decompressor range is reserved and always provide the minimal randomization address for .amode31 sections beyond the decompressor. That is a prerequisite for moving the lowcore memory address from NULL elsewhere. Signed-off-by: Alexander Gordeev Signed-off-by: Sven Schnelle Signed-off-by: Vasily Gorbik Signed-off-by: Sasha Levin

s390/boot: Fix KASLR base offset off by __START_KERNEL bytes

2024-08-29T15:36:06Z

[ Upstream commit 1642285e511c2a40b14e87a41aa8feace6123036 ] Symbol offsets to the KASLR base do not match symbol address in the vmlinux image. That is the result of setting the KASLR base to the beginning of .text section as result of an optimization. Revert that optimization and allocate virtual memory for the whole kernel image including __START_KERNEL bytes as per the linker script. That allows keeping the semantics of the KASLR base offset in sync with other architectures. Rename __START_KERNEL to TEXT_OFFSET, since it represents the offset of the .text section within the kernel image, rather than a virtual address. Still skip mapping TEXT_OFFSET bytes to save memory on pgtables and provoke exceptions in case an attempt to access this area is made, as no kernel symbol may reside there. In case CONFIG_KASAN is enabled the location counter might exceed the value of TEXT_OFFSET, while the decompressor linker script forcefully resets it to TEXT_OFFSET, which leads to a sections overlap link failure. Use MAX() expression to avoid that. Reported-by: Omar Sandoval Closes: https://lore.kernel.org/linux-s390/ZnS8dycxhtXBZVky@telecaster.dhcp.thefacebook.com/ Fixes: 56b1069c40c7 ("s390/boot: Rework deployment of the kernel image") Signed-off-by: Alexander Gordeev Acked-by: Vasily Gorbik Signed-off-by: Vasily Gorbik Signed-off-by: Sasha Levin

s390/boot: Avoid possible physmem_info segment corruption

2024-08-29T15:36:05Z

[ Upstream commit d7fd2941ae9a67423d1c7bee985f240e4686634f ] When physical memory for the kernel image is allocated it does not consider extra memory required for offsetting the image start to match it with the lower 20 bits of KASLR virtual base address. That might lead to kernel access beyond its memory range. Suggested-by: Vasily Gorbik Fixes: 693d41f7c938 ("s390/mm: Restore mapping of kernel image using large pages") Signed-off-by: Alexander Gordeev Acked-by: Vasily Gorbik Signed-off-by: Vasily Gorbik Signed-off-by: Sasha Levin

s390/boot: Do not adjust GOT entries for undef weak sym

2024-06-25T12:39:42Z

Since commit 778666df60f0 ("s390: compile relocatable kernel without -fPIE") and commit 00cda11d3b2e ("s390: Compile kernel with -fPIC and link with -no-pie") the kernel on s390x may have a Global Offset Table (GOT) whose entries are adjusted for KASLR in kaslr_adjust_got(). The GOT may contain entries for undefined weak symbols that resolved to zero. That is the resulting GOT entry value is zero. Adjusting those entries unconditionally in kaslr_adjust_got() is wrong. Otherwise the following sample code would erroneously assume foo to be defined, due to the adjustment changing the zero-value to a non-zero one: extern int foo __attribute__((weak)); if (*foo) /* foo is defined [or undefined and erroneously adjusted] */ The vmlinux build at commit 00cda11d3b2e ("s390: Compile kernel with -fPIC and link with -no-pie") with defconfig actually had two GOT entries for the undefined weak symbols __start_BTF and __stop_BTF: $ objdump -tw vmlinux | grep -F "*UND*" 0000000000000000 w *UND* 0000000000000000 __stop_BTF 0000000000000000 w *UND* 0000000000000000 __start_BTF $ readelf -rw vmlinux | grep -E "R_390_GOTENT +0{16}" 000000345760 2776a0000001a R_390_GOTENT 0000000000000000 __stop_BTF + 2 000000345766 2d5480000001a R_390_GOTENT 0000000000000000 __start_BTF + 2 The s390-specific vmlinux linker script sets the section start to __START_KERNEL, which is currently defined as 0x100000 on s390x. Access to lowcore is performed via a pointer of 0 and not a symbol in a section starting at 0. The first 64K are reserved for the loader on s390x. Thus it is safe to assume that __START_KERNEL will never be 0. As a result there cannot be any defined symbols resolving to zero in the kernel. Note that the first three GOT entries are reserved for the dynamic loader on s390x. [1] In the kernel they are zero. Therefore no extra handling is required to skip these. Skip adjusting GOT entries with a value of zero in kaslr_adjust_got(). While at it update the comment when a GOT exists on s390x. Since commit 00cda11d3b2e ("s390: Compile kernel with -fPIC and link with -no-pie") it no longer only exists when compiling with Clang, but also with GCC. [1]: s390x ELF ABI, section "Global Offset Table", https://github.com/IBM/s390x-abi/releases Fixes: 778666df60f0 ("s390: compile relocatable kernel without -fPIE") Reviewed-by: Ilya Leoshkevich Acked-by: Sumanth Korikkar Acked-by: Alexander Gordeev Signed-off-by: Jens Remus Signed-off-by: Alexander Gordeev

s390/mm: Restore mapping of kernel image using large pages

2024-06-11T14:20:40Z

Since physical and virtual kernel address spaces are uncoupled the kernel image is not mapped using large segment pages anymore, which is a regression. Put the kernel image at the same large segment page offset in physical memory as in virtual memory. Such approach preserves the existing number of bits of entropy used for randomization of the kernel location in virtual memory when KASLR is on. As result, the kernel is mapped using large segment pages. Fixes: c98d2ecae08f ("s390/mm: Uncouple physical vs virtual address spaces") Reported-by: Heiko Carstens Reviewed-by: Heiko Carstens Signed-off-by: Alexander Gordeev Signed-off-by: Vasily Gorbik

s390/mm: Allow large pages only for aligned physical addresses

2024-06-11T14:20:40Z

Do not allow creation of large pages against physical addresses, which itself are not aligned on the correct boundary. Failure to do so might lead to referencing wrong memory as result of the way DAT works. Fixes: c98d2ecae08f ("s390/mm: Uncouple physical vs virtual address spaces") Reviewed-by: Heiko Carstens Signed-off-by: Alexander Gordeev Signed-off-by: Vasily Gorbik

s390/boot: Remove alt_stfle_fac_list from decompressor

2024-05-16T08:17:12Z

It is nowhere used in the decompressor, therefore remove it. Fixes: 17e89e1340a3 ("s390/facilities: move stfl information from lowcore to global data") Reviewed-by: Heiko Carstens Signed-off-by: Sven Schnelle Signed-off-by: Heiko Carstens

s390: Compile kernel with -fPIC and link with -no-pie

2024-04-29T15:33:30Z

When the kernel is built with CONFIG_PIE_BUILD option enabled it uses dynamic symbols, for which the linker does not allow more than 64K number of entries. This can break features like kpatch. Hence, whenever possible the kernel is built with CONFIG_PIE_BUILD option disabled. For that support of unaligned symbols generated by linker scripts in the compiler is necessary. However, older compilers might lack such support. In that case the build process resorts to CONFIG_PIE_BUILD option-enabled build. Compile object files with -fPIC option and then link the kernel binary with -no-pie linker option. As result, the dynamic symbols are not generated and not only kpatch feature succeeds, but also the whole CONFIG_PIE_BUILD option-enabled code could be dropped. [ agordeev: Reworded the commit message ] Suggested-by: Ulrich Weigand Signed-off-by: Sumanth Korikkar Reviewed-by: Alexander Gordeev Signed-off-by: Alexander Gordeev

s390/boot: Do not rescue .vmlinux.relocs section

2024-04-17T11:38:02Z

The .vmlinux.relocs section is moved in front of the compressed kernel. The interim section rescue step is avoided as result. Suggested-by: Sumanth Korikkar Signed-off-by: Alexander Gordeev