kernel.git/arch/arm64/kernel/entry-ftrace.S, branch linux-5.16.y

arm64: ftrace: add missing BTIs

2021-12-02T10:18:32Z

When branch target identifiers are in use, code reachable via an indirect branch requires a BTI landing pad at the branch target site. When building FTRACE_WITH_REGS atop patchable-function-entry, we miss BTIs at the start start of the `ftrace_caller` and `ftrace_regs_caller` trampolines, and when these are called from a module via a PLT (which will use a `BR X16`), we will encounter a BTI failure, e.g. | # insmod lkdtm.ko | lkdtm: No crash points registered, enable through debugfs | # echo function_graph > /sys/kernel/debug/tracing/current_tracer | # cat /sys/kernel/debug/provoke-crash/DIRECT | Unhandled 64-bit el1h sync exception on CPU0, ESR 0x34000001 -- BTI | CPU: 0 PID: 174 Comm: cat Not tainted 5.16.0-rc2-dirty #3 | Hardware name: linux,dummy-virt (DT) | pstate: 60400405 (nZCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=jc) | pc : ftrace_caller+0x0/0x3c | lr : lkdtm_debugfs_open+0xc/0x20 [lkdtm] | sp : ffff800012e43b00 | x29: ffff800012e43b00 x28: 0000000000000000 x27: ffff800012e43c88 | x26: 0000000000000000 x25: 0000000000000000 x24: ffff0000c171f200 | x23: ffff0000c27b1e00 x22: ffff0000c2265240 x21: ffff0000c23c8c30 | x20: ffff8000090ba380 x19: 0000000000000000 x18: 0000000000000000 | x17: 0000000000000000 x16: ffff80001002bb4c x15: 0000000000000000 | x14: 0000000000000000 x13: 0000000000000000 x12: 0000000000900ff0 | x11: ffff0000c4166310 x10: ffff800012e43b00 x9 : ffff8000104f2384 | x8 : 0000000000000001 x7 : 0000000000000000 x6 : 000000000000003f | x5 : 0000000000000040 x4 : ffff800012e43af0 x3 : 0000000000000001 | x2 : ffff8000090b0000 x1 : ffff0000c171f200 x0 : ffff0000c23c8c30 | Kernel panic - not syncing: Unhandled exception | CPU: 0 PID: 174 Comm: cat Not tainted 5.16.0-rc2-dirty #3 | Hardware name: linux,dummy-virt (DT) | Call trace: | dump_backtrace+0x0/0x1a4 | show_stack+0x24/0x30 | dump_stack_lvl+0x68/0x84 | dump_stack+0x1c/0x38 | panic+0x168/0x360 | arm64_exit_nmi.isra.0+0x0/0x80 | el1h_64_sync_handler+0x68/0xd4 | el1h_64_sync+0x78/0x7c | ftrace_caller+0x0/0x3c | do_dentry_open+0x134/0x3b0 | vfs_open+0x38/0x44 | path_openat+0x89c/0xe40 | do_filp_open+0x8c/0x13c | do_sys_openat2+0xbc/0x174 | __arm64_sys_openat+0x6c/0xbc | invoke_syscall+0x50/0x120 | el0_svc_common.constprop.0+0xdc/0x100 | do_el0_svc+0x84/0xa0 | el0_svc+0x28/0x80 | el0t_64_sync_handler+0xa8/0x130 | el0t_64_sync+0x1a0/0x1a4 | SMP: stopping secondary CPUs | Kernel Offset: disabled | CPU features: 0x0,00000f42,da660c5f | Memory Limit: none | ---[ end Kernel panic - not syncing: Unhandled exception ]--- Fix this by adding the required `BTI C`, as we only require these to be reachable via BL for direct calls or BR X16/X17 for PLTs. For now, these are open-coded in the function prologue, matching the style of the `__hwasan_tag_mismatch` trampoline. In future we may wish to consider adding a new SYM_CODE_START_*() variant which has an implicit BTI. When ftrace is built atop mcount, the trampolines are marked with SYM_FUNC_START(), and so get an implicit BTI. We may need to change these over to SYM_CODE_START() in future for RELIABLE_STACKTRACE, in case we need to apply special care aroud the return address being rewritten. Fixes: 97fed779f2a6 ("arm64: bti: Provide Kconfig for kernel mode BTI") Signed-off-by: Mark Rutland Cc: Catalin Marinas Cc: Mark Brown Cc: Will Deacon Reviewed-by: Mark Brown Link: https://lore.kernel.org/r/20211129135709.2274019-1-mark.rutland@arm.com Signed-off-by: Will Deacon

arm64: rename S_FRAME_SIZE to PT_REGS_SIZE

2021-01-13T15:09:06Z

S_FRAME_SIZE is the size of the pt_regs structure, no longer the size of the kernel stack frame, the name is misleading. In keeping with arm32, rename S_FRAME_SIZE to PT_REGS_SIZE. Signed-off-by: Jianlin Lv Acked-by: Mark Rutland Link: https://lore.kernel.org/r/20210112015813.2340969-1-Jianlin.Lv@arm.com Signed-off-by: Catalin Marinas

arm64: entry-ftrace.S: Update comment to indicate that x18 is live

2020-05-18T16:47:50Z

The Shadow Call Stack pointer is held in x18, so update the ftrace entry comment to indicate that it cannot be safely clobbered. Reported-by: Mark Rutland Signed-off-by: Will Deacon

arm64: entry-ftrace.S: Fix missing argument for CONFIG_FUNCTION_GRAPH_TRACER=y

2020-03-11T11:06:48Z

Missing argument of another SYM_INNER_LABEL() breaks build for CONFIG_FUNCTION_GRAPH_TRACER=y. Fixes: e2d591d29d44 ("arm64: entry-ftrace.S: Convert to modern annotations for assembly functions") Signed-off-by: Kunihiko Hayashi Signed-off-by: Catalin Marinas Acked-by: Mark Brown

arm64: ftrace: Modernise annotation of return_to_handler

2020-03-09T17:35:16Z

In an effort to clarify and simplify the annotation of assembly functions new macros have been introduced. These replace ENTRY and ENDPROC with two different annotations for normal functions and those with unusual calling conventions. return_to_handler does entertaining things with LR so doesn't follow the usual C conventions and should therefore be annotated as code rather than a function. Signed-off-by: Mark Brown Signed-off-by: Catalin Marinas

arm64: ftrace: Correct annotation of ftrace_caller assembly

2020-03-09T17:35:14Z

In an effort to clarify and simplify the annotation of assembly functions new macros have been introduced. These replace ENTRY and ENDPROC with two different annotations for normal functions and those with unusual calling conventions. The patchable function entry versions of ftrace_*_caller don't follow the usual AAPCS rules, pushing things onto the stack which they don't clean up, and therefore should be annotated as code rather than functions. Signed-off-by: Mark Brown Signed-off-by: Catalin Marinas

arm64: entry-ftrace.S: Convert to modern annotations for assembly functions

2020-03-09T17:35:12Z

In an effort to clarify and simplify the annotation of assembly functions in the kernel new macros have been introduced. These replace ENTRY and ENDPROC and also add a new annotation for static functions which previously had no ENTRY equivalent. Update the annotations in the core kernel code to the new macros. Signed-off-by: Mark Brown Signed-off-by: Catalin Marinas

arm64: ftrace: fix ifdeffery

2019-12-06T13:25:14Z

When I tweaked the ftrace entry assembly in commit: 3b23e4991fb66f6d ("arm64: implement ftrace with regs") ... my ifdeffery tweaks left ftrace_graph_caller undefined for CONFIG_DYNAMIC_FTRACE && CONFIG_FUNCTION_GRAPH_TRACER when ftrace is based on mcount. The kbuild test robot reported that this issue is detected at link time: | arch/arm64/kernel/entry-ftrace.o: In function `skip_ftrace_call': | arch/arm64/kernel/entry-ftrace.S:238: undefined reference to `ftrace_graph_caller' | arch/arm64/kernel/entry-ftrace.S:238:(.text+0x3c): relocation truncated to fit: R_AARCH64_CONDBR19 against undefined symbol | `ftrace_graph_caller' | arch/arm64/kernel/entry-ftrace.S:243: undefined reference to `ftrace_graph_caller' | arch/arm64/kernel/entry-ftrace.S:243:(.text+0x54): relocation truncated to fit: R_AARCH64_CONDBR19 against undefined symbol | `ftrace_graph_caller' This patch fixes the ifdeffery so that the mcount version of ftrace_graph_caller doesn't depend on CONFIG_DYNAMIC_FTRACE. At the same time, a redundant #else is removed from the ifdeffery for the patchable-function-entry version of ftrace_graph_caller. Fixes: 3b23e4991fb66f6d ("arm64: implement ftrace with regs") Reported-by: kbuild test robot Signed-off-by: Mark Rutland Cc: Amit Daniel Kachhap Cc: Ard Biesheuvel Cc: Mark Rutland Cc: Torsten Duwe Cc: Will Deacon Signed-off-by: Catalin Marinas

arm64: implement ftrace with regs

2019-11-06T14:17:35Z

This patch implements FTRACE_WITH_REGS for arm64, which allows a traced function's arguments (and some other registers) to be captured into a struct pt_regs, allowing these to be inspected and/or modified. This is a building block for live-patching, where a function's arguments may be forwarded to another function. This is also necessary to enable ftrace and in-kernel pointer authentication at the same time, as it allows the LR value to be captured and adjusted prior to signing. Using GCC's -fpatchable-function-entry=N option, we can have the compiler insert a configurable number of NOPs between the function entry point and the usual prologue. This also ensures functions are AAPCS compliant (e.g. disabling inter-procedural register allocation). For example, with -fpatchable-function-entry=2, GCC 8.1.0 compiles the following: | unsigned long bar(void); | | unsigned long foo(void) | { | return bar() + 1; | } ... to: | : | nop | nop | stp x29, x30, [sp, #-16]! | mov x29, sp | bl 0 | add x0, x0, #0x1 | ldp x29, x30, [sp], #16 | ret This patch builds the kernel with -fpatchable-function-entry=2, prefixing each function with two NOPs. To trace a function, we replace these NOPs with a sequence that saves the LR into a GPR, then calls an ftrace entry assembly function which saves this and other relevant registers: | mov x9, x30 | bl Since patchable functions are AAPCS compliant (and the kernel does not use x18 as a platform register), x9-x18 can be safely clobbered in the patched sequence and the ftrace entry code. There are now two ftrace entry functions, ftrace_regs_entry (which saves all GPRs), and ftrace_entry (which saves the bare minimum). A PLT is allocated for each within modules. Signed-off-by: Torsten Duwe [Mark: rework asm, comments, PLTs, initialization, commit message] Signed-off-by: Mark Rutland Reviewed-by: Amit Daniel Kachhap Reviewed-by: Ard Biesheuvel Reviewed-by: Torsten Duwe Tested-by: Amit Daniel Kachhap Tested-by: Torsten Duwe Cc: AKASHI Takahiro Cc: Catalin Marinas Cc: Josh Poimboeuf Cc: Julien Thierry Cc: Will Deacon

treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 500

2019-06-19T15:09:55Z

Based on 2 normalized pattern(s): this program is free software you can redistribute it and or modify it under the terms of the gnu general public license version 2 as published by the free software foundation this program is free software you can redistribute it and or modify it under the terms of the gnu general public license version 2 as published by the free software foundation # extracted by the scancode license scanner the SPDX license identifier GPL-2.0-only has been chosen to replace the boilerplate/reference in 4122 file(s). Signed-off-by: Thomas Gleixner Reviewed-by: Enrico Weigelt Reviewed-by: Kate Stewart Reviewed-by: Allison Randal Cc: linux-spdx@vger.kernel.org Link: https://lkml.kernel.org/r/20190604081206.933168790@linutronix.de Signed-off-by: Greg Kroah-Hartman