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23a4d7fd34
The return from the ftrace_stub, _mcount, ftrace_caller and
return_to_handler functions is done with "br %r14" and "br %r1".
These are indirect branches as well and need to use execute
trampolines for CONFIG_EXPOLINE=y.
The ftrace_caller function is a special case as it returns to the
start of a function and may only use %r0 and %r1. For a pre z10
machine the standard execute trampoline uses a LARL + EX to do
this, but this requires *two* registers in the range %r1..%r15.
To get around this the 'br %r1' located in the lowcore is used,
then the EX instruction does not need an address register.
But the lowcore trick may only be used for pre z14 machines,
with noexec=on the mapping for the first page may not contain
instructions. The solution for that is an ALTERNATIVE in the
expoline THUNK generated by 'GEN_BR_THUNK %r1' to switch to
EXRL, this relies on the fact that a machine that supports
noexec=on has EXRL as well.
Cc: stable@vger.kernel.org # 4.16
Fixes: f19fbd5ed6 ("s390: introduce execute-trampolines for branches")
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
91 lines
2.1 KiB
ArmAsm
91 lines
2.1 KiB
ArmAsm
/* SPDX-License-Identifier: GPL-2.0 */
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/*
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* Copyright IBM Corp. 2008, 2009
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*
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* Author(s): Heiko Carstens <heiko.carstens@de.ibm.com>,
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*
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*/
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#include <linux/linkage.h>
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#include <asm/asm-offsets.h>
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#include <asm/ftrace.h>
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#include <asm/nospec-insn.h>
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#include <asm/ptrace.h>
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#include <asm/export.h>
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GEN_BR_THUNK %r1
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GEN_BR_THUNK %r14
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.section .kprobes.text, "ax"
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ENTRY(ftrace_stub)
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BR_EX %r14
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#define STACK_FRAME_SIZE (STACK_FRAME_OVERHEAD + __PT_SIZE)
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#define STACK_PTREGS (STACK_FRAME_OVERHEAD)
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#define STACK_PTREGS_GPRS (STACK_PTREGS + __PT_GPRS)
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#define STACK_PTREGS_PSW (STACK_PTREGS + __PT_PSW)
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ENTRY(_mcount)
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BR_EX %r14
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EXPORT_SYMBOL(_mcount)
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ENTRY(ftrace_caller)
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.globl ftrace_regs_caller
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.set ftrace_regs_caller,ftrace_caller
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lgr %r1,%r15
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#ifndef CC_USING_HOTPATCH
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aghi %r0,MCOUNT_RETURN_FIXUP
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#endif
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aghi %r15,-STACK_FRAME_SIZE
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stg %r1,__SF_BACKCHAIN(%r15)
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stg %r1,(STACK_PTREGS_GPRS+15*8)(%r15)
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stg %r0,(STACK_PTREGS_PSW+8)(%r15)
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stmg %r2,%r14,(STACK_PTREGS_GPRS+2*8)(%r15)
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#ifdef CONFIG_HAVE_MARCH_Z196_FEATURES
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aghik %r2,%r0,-MCOUNT_INSN_SIZE
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lgrl %r4,function_trace_op
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lgrl %r1,ftrace_trace_function
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#else
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lgr %r2,%r0
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aghi %r2,-MCOUNT_INSN_SIZE
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larl %r4,function_trace_op
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lg %r4,0(%r4)
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larl %r1,ftrace_trace_function
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lg %r1,0(%r1)
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#endif
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lgr %r3,%r14
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la %r5,STACK_PTREGS(%r15)
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BASR_EX %r14,%r1
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#ifdef CONFIG_FUNCTION_GRAPH_TRACER
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# The j instruction gets runtime patched to a nop instruction.
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# See ftrace_enable_ftrace_graph_caller.
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ENTRY(ftrace_graph_caller)
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j ftrace_graph_caller_end
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lg %r2,(STACK_PTREGS_GPRS+14*8)(%r15)
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lg %r3,(STACK_PTREGS_PSW+8)(%r15)
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brasl %r14,prepare_ftrace_return
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stg %r2,(STACK_PTREGS_GPRS+14*8)(%r15)
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ftrace_graph_caller_end:
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.globl ftrace_graph_caller_end
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#endif
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lg %r1,(STACK_PTREGS_PSW+8)(%r15)
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lmg %r2,%r15,(STACK_PTREGS_GPRS+2*8)(%r15)
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BR_EX %r1
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#ifdef CONFIG_FUNCTION_GRAPH_TRACER
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ENTRY(return_to_handler)
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stmg %r2,%r5,32(%r15)
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lgr %r1,%r15
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aghi %r15,-STACK_FRAME_OVERHEAD
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stg %r1,__SF_BACKCHAIN(%r15)
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brasl %r14,ftrace_return_to_handler
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aghi %r15,STACK_FRAME_OVERHEAD
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lgr %r14,%r2
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lmg %r2,%r5,32(%r15)
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BR_EX %r14
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#endif
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