linux-dev/arch/x86/kernel/vmlinux.lds.S, branch linus/master

x86/mm: Fix RESERVE_BRK() for older binutils

2022-06-13T08:15:04Z

With binutils 2.26, RESERVE_BRK() causes a build failure: /tmp/ccnGOKZ5.s: Assembler messages: /tmp/ccnGOKZ5.s:98: Error: missing ')' /tmp/ccnGOKZ5.s:98: Error: missing ')' /tmp/ccnGOKZ5.s:98: Error: missing ')' /tmp/ccnGOKZ5.s:98: Error: junk at end of line, first unrecognized character is `U' The problem is this line: RESERVE_BRK(early_pgt_alloc, INIT_PGT_BUF_SIZE) Specifically, the INIT_PGT_BUF_SIZE macro which (via PAGE_SIZE's use _AC()) has a "1UL", which makes older versions of the assembler unhappy. Unfortunately the _AC() macro doesn't work for inline asm. Inline asm was only needed here to convince the toolchain to add the STT_NOBITS flag. However, if a C variable is placed in a section whose name is prefixed with ".bss", GCC and Clang automatically set STT_NOBITS. In fact, ".bss..page_aligned" already relies on this trick. So fix the build failure (and simplify the macro) by allocating the variable in C. Also, add NOLOAD to the ".brk" output section clause in the linker script. This is a failsafe in case the ".bss" prefix magic trick ever stops working somehow. If there's a section type mismatch, the GNU linker will force the ".brk" output section to be STT_NOBITS. The LLVM linker will fail with a "section type mismatch" error. Note this also changes the name of the variable from .brk.##name to __brk_##name. The variable names aren't actually used anywhere, so it's harmless. Fixes: a1e2c031ec39 ("x86/mm: Simplify RESERVE_BRK()") Reported-by: Joe Damato Reported-by: Byungchul Park Signed-off-by: Josh Poimboeuf Signed-off-by: Peter Zijlstra (Intel) Tested-by: Joe Damato Link: https://lore.kernel.org/r/22d07a44c80d8e8e1e82b9a806ddc8c6bbb2606e.1654759036.git.jpoimboe@kernel.org

x86: remove the IOMMU table infrastructure

2022-04-18T05:21:10Z

The IOMMU table tries to separate the different IOMMUs into different backends, but actually requires various cross calls. Rewrite the code to do the generic swiotlb/swiotlb-xen setup directly in pci-dma.c and then just call into the IOMMU drivers. Signed-off-by: Christoph Hellwig Reviewed-by: Konrad Rzeszutek Wilk Tested-by: Boris Ostrovsky

objtool: Find unused ENDBR instructions

2022-03-15T09:32:47Z

Find all ENDBR instructions which are never referenced and stick them in a section such that the kernel can poison them, sealing the functions from ever being an indirect call target. This removes about 1-in-4 ENDBR instructions. Signed-off-by: Peter Zijlstra (Intel) Acked-by: Josh Poimboeuf Link: https://lore.kernel.org/r/20220308154319.763643193@infradead.org

x86: Remove .fixup section

2021-12-11T08:09:50Z

No moar users, kill it dead. Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Josh Poimboeuf Link: https://lore.kernel.org/r/20211110101326.201590122@infradead.org

objtool,x86: Replace alternatives with .retpoline_sites

2021-10-28T21:25:25Z

Instead of writing complete alternatives, simply provide a list of all the retpoline thunk calls. Then the kernel is free to do with them as it pleases. Simpler code all-round. Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Borislav Petkov Acked-by: Josh Poimboeuf Tested-by: Alexei Starovoitov Link: https://lore.kernel.org/r/20211026120309.850007165@infradead.org

x86/build: Fix vmlinux size check on 64-bit

2020-10-29T20:54:35Z

Commit b4e0409a36f4 ("x86: check vmlinux limits, 64-bit") added a check that the size of the 64-bit kernel is less than KERNEL_IMAGE_SIZE. The check uses (_end - _text), but this is not enough. The initial PMD used in startup_64() (level2_kernel_pgt) can only map upto KERNEL_IMAGE_SIZE from __START_KERNEL_map, not from _text, and the modules area (MODULES_VADDR) starts at KERNEL_IMAGE_SIZE. The correct check is what is currently done for 32-bit, since LOAD_OFFSET is defined appropriately for the two architectures. Just check (_end - LOAD_OFFSET) against KERNEL_IMAGE_SIZE unconditionally. Note that on 32-bit, the limit is not strict: KERNEL_IMAGE_SIZE is not really used by the main kernel. The higher the kernel is located, the less the space available for the vmalloc area. However, it is used by KASLR in the compressed stub to limit the maximum address of the kernel to a safe value. Clean up various comments to clarify that despite the name, KERNEL_IMAGE_SIZE is not a limit on the size of the kernel image, but a limit on the maximum virtual address that the image can occupy. Signed-off-by: Arvind Sankar Signed-off-by: Borislav Petkov Link: https://lkml.kernel.org/r/20201029161903.2553528-1-nivedita@alum.mit.edu

Merge tag 'core-static_call-2020-10-12' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2020-10-12T20:58:15Z

Pull static call support from Ingo Molnar: "This introduces static_call(), which is the idea of static_branch() applied to indirect function calls. Remove a data load (indirection) by modifying the text. They give the flexibility of function pointers, but with better performance. (This is especially important for cases where retpolines would otherwise be used, as retpolines can be pretty slow.) API overview: DECLARE_STATIC_CALL(name, func); DEFINE_STATIC_CALL(name, func); DEFINE_STATIC_CALL_NULL(name, typename); static_call(name)(args...); static_call_cond(name)(args...); static_call_update(name, func); x86 is supported via text patching, otherwise basic indirect calls are used, with function pointers. There's a second variant using inline code patching, inspired by jump-labels, implemented on x86 as well. The new APIs are utilized in the x86 perf code, a heavy user of function pointers, where static calls speed up the PMU handler by 4.2% (!). The generic implementation is not really excercised on other architectures, outside of the trivial test_static_call_init() self-test" * tag 'core-static_call-2020-10-12' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (21 commits) static_call: Fix return type of static_call_init tracepoint: Fix out of sync data passing by static caller tracepoint: Fix overly long tracepoint names x86/perf, static_call: Optimize x86_pmu methods tracepoint: Optimize using static_call() static_call: Allow early init static_call: Add some validation static_call: Handle tail-calls static_call: Add static_call_cond() x86/alternatives: Teach text_poke_bp() to emulate RET static_call: Add simple self-test for static calls x86/static_call: Add inline static call implementation for x86-64 x86/static_call: Add out-of-line static call implementation static_call: Avoid kprobes on inline static_call()s static_call: Add inline static call infrastructure static_call: Add basic static call infrastructure compiler.h: Make __ADDRESSABLE() symbol truly unique jump_label,module: Fix module lifetime for __jump_label_mod_text_reserved() module: Properly propagate MODULE_STATE_COMING failure module: Fix up module_notifier return values ...

x86/build: Add asserts for unwanted sections

2020-09-01T08:03:18Z

In preparation for warning on orphan sections, enforce other expected-to-be-zero-sized sections (since discarding them might hide problems with them suddenly gaining unexpected entries). Signed-off-by: Kees Cook Signed-off-by: Ingo Molnar Link: https://lore.kernel.org/r/20200821194310.3089815-25-keescook@chromium.org

x86/build: Enforce an empty .got.plt section

2020-09-01T08:03:18Z

The .got.plt section should always be zero (or filled only with the linker-generated lazy dispatch entry). Enforce this with an assert and mark the section as INFO. This is more sensitive than just blindly discarding the section. Signed-off-by: Kees Cook Signed-off-by: Ingo Molnar Link: https://lore.kernel.org/r/20200821194310.3089815-24-keescook@chromium.org

x86/static_call: Add inline static call implementation for x86-64

2020-09-01T07:58:05Z

Add the inline static call implementation for x86-64. The generated code is identical to the out-of-line case, except we move the trampoline into it's own section. Objtool uses the trampoline naming convention to detect all the call sites. It then annotates those call sites in the .static_call_sites section. During boot (and module init), the call sites are patched to call directly into the destination function. The temporary trampoline is then no longer used. [peterz: merged trampolines, put trampoline in section] Signed-off-by: Josh Poimboeuf Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Ingo Molnar Cc: Linus Torvalds Link: https://lore.kernel.org/r/20200818135804.864271425@infradead.org