forked from Minki/linux
2d21889f8b
Some ftrace features are broken since commit714a8d02ca("arm64: asm: Override SYM_FUNC_START when building the kernel with BTI"). For example the function_graph tracer: $ echo function_graph > /sys/kernel/debug/tracing/current_tracer [ 36.107016] WARNING: CPU: 0 PID: 115 at kernel/trace/ftrace.c:2691 ftrace_modify_all_code+0xc8/0x14c When ftrace_modify_graph_caller() attempts to write a branch at ftrace_graph_call, it finds the "BTI J" instruction inserted by SYM_INNER_LABEL() instead of a NOP, and aborts. It turns out we don't currently need the BTI landing pads inserted by SYM_INNER_LABEL: * ftrace_call and ftrace_graph_call are only used for runtime patching of the active tracer. The patched code is not reached from a branch. * install_el2_stub is reached from a CBZ instruction, which doesn't change PSTATE.BTYPE. * __guest_exit is reached from B instructions in the hyp-entry vectors, which aren't subject to BTI checks either. Remove the BTI annotation from SYM_INNER_LABEL. Fixes:714a8d02ca("arm64: asm: Override SYM_FUNC_START when building the kernel with BTI") Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org> Reviewed-by: Mark Brown <broonie@kernel.org> Link: https://lore.kernel.org/r/20200624112253.1602786-1-jean-philippe@linaro.org Signed-off-by: Will Deacon <will@kernel.org>
64 lines
1.5 KiB
C
64 lines
1.5 KiB
C
#ifndef __ASM_LINKAGE_H
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#define __ASM_LINKAGE_H
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#define __ALIGN .align 2
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#define __ALIGN_STR ".align 2"
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#if defined(CONFIG_ARM64_BTI_KERNEL) && defined(__aarch64__)
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/*
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* Since current versions of gas reject the BTI instruction unless we
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* set the architecture version to v8.5 we use the hint instruction
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* instead.
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*/
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#define BTI_C hint 34 ;
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/*
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* When using in-kernel BTI we need to ensure that PCS-conformant assembly
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* functions have suitable annotations. Override SYM_FUNC_START to insert
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* a BTI landing pad at the start of everything.
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*/
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#define SYM_FUNC_START(name) \
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SYM_START(name, SYM_L_GLOBAL, SYM_A_ALIGN) \
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BTI_C
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#define SYM_FUNC_START_NOALIGN(name) \
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SYM_START(name, SYM_L_GLOBAL, SYM_A_NONE) \
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BTI_C
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#define SYM_FUNC_START_LOCAL(name) \
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SYM_START(name, SYM_L_LOCAL, SYM_A_ALIGN) \
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BTI_C
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#define SYM_FUNC_START_LOCAL_NOALIGN(name) \
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SYM_START(name, SYM_L_LOCAL, SYM_A_NONE) \
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BTI_C
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#define SYM_FUNC_START_WEAK(name) \
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SYM_START(name, SYM_L_WEAK, SYM_A_ALIGN) \
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BTI_C
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#define SYM_FUNC_START_WEAK_NOALIGN(name) \
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SYM_START(name, SYM_L_WEAK, SYM_A_NONE) \
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BTI_C
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#endif
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/*
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* Annotate a function as position independent, i.e., safe to be called before
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* the kernel virtual mapping is activated.
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*/
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#define SYM_FUNC_START_PI(x) \
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SYM_FUNC_START_ALIAS(__pi_##x); \
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SYM_FUNC_START(x)
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#define SYM_FUNC_START_WEAK_PI(x) \
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SYM_FUNC_START_ALIAS(__pi_##x); \
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SYM_FUNC_START_WEAK(x)
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#define SYM_FUNC_END_PI(x) \
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SYM_FUNC_END(x); \
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SYM_FUNC_END_ALIAS(__pi_##x)
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#endif
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