powerpc/ftrace: Add support for -mprofile-kernel ftrace ABI
The gcc switch -mprofile-kernel defines a new ABI for calling _mcount() very early in the function with minimal overhead. Although mprofile-kernel has been available since GCC 3.4, there were bugs which were only fixed recently. Currently it is known to work in GCC 4.9, 5 and 6. Additionally there are two possible code sequences generated by the flag, the first uses mflr/std/bl and the second is optimised to omit the std. Currently only gcc 6 has the optimised sequence. This patch supports both sequences. Initial work started by Vojtech Pavlik, used with permission. Key changes: - rework _mcount() to work for both the old and new ABIs. - implement new versions of ftrace_caller() and ftrace_graph_caller() which deal with the new ABI. - updates to __ftrace_make_nop() to recognise the new mcount calling sequence. - updates to __ftrace_make_call() to recognise the nop'ed sequence. - implement ftrace_modify_call(). - updates to the module loader to surpress the toc save in the module stub when calling mcount with the new ABI. Reviewed-by: Balbir Singh <bsingharora@gmail.com> Signed-off-by: Torsten Duwe <duwe@suse.de> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
Torsten Duwe
Michael Ellerman
parent
9a7841ae8d
commit
153086644f
@ -99,4 +99,25 @@ static inline unsigned long ppc_global_function_entry(void *func)
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#endif
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}
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#ifdef CONFIG_PPC64
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/*
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* Some instruction encodings commonly used in dynamic ftracing
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* and function live patching.
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*/
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/* This must match the definition of STK_GOT in <asm/ppc_asm.h> */
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#if defined(_CALL_ELF) && _CALL_ELF == 2
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#define R2_STACK_OFFSET 24
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#else
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#define R2_STACK_OFFSET 40
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#endif
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#define PPC_INST_LD_TOC (PPC_INST_LD | ___PPC_RT(__REG_R2) | \
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___PPC_RA(__REG_R1) | R2_STACK_OFFSET)
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/* usually preceded by a mflr r0 */
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#define PPC_INST_STD_LR (PPC_INST_STD | ___PPC_RS(__REG_R0) | \
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___PPC_RA(__REG_R1) | PPC_LR_STKOFF)
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#endif /* CONFIG_PPC64 */
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#endif /* _ASM_POWERPC_CODE_PATCHING_H */
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@ -46,6 +46,8 @@
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extern void _mcount(void);
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#ifdef CONFIG_DYNAMIC_FTRACE
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# define FTRACE_ADDR ((unsigned long)ftrace_caller)
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# define FTRACE_REGS_ADDR FTRACE_ADDR
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static inline unsigned long ftrace_call_adjust(unsigned long addr)
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{
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/* reloction of mcount call site is the same as the address */
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@ -58,6 +60,9 @@ struct dyn_arch_ftrace {
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#endif /* CONFIG_DYNAMIC_FTRACE */
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#endif /* __ASSEMBLY__ */
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#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
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#define ARCH_SUPPORTS_FTRACE_OPS 1
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#endif
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#endif
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#if defined(CONFIG_FTRACE_SYSCALLS) && defined(CONFIG_PPC64) && !defined(__ASSEMBLY__)
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@ -1143,8 +1143,12 @@ _GLOBAL(enter_prom)
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#ifdef CONFIG_DYNAMIC_FTRACE
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_GLOBAL(mcount)
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_GLOBAL(_mcount)
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blr
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mflr r12
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mtctr r12
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mtlr r0
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bctr
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#ifndef CC_USING_MPROFILE_KERNEL
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_GLOBAL_TOC(ftrace_caller)
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/* Taken from output of objdump from lib64/glibc */
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mflr r3
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@ -1166,6 +1170,115 @@ _GLOBAL(ftrace_graph_stub)
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ld r0, 128(r1)
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mtlr r0
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addi r1, r1, 112
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#else /* CC_USING_MPROFILE_KERNEL */
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/*
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*
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* ftrace_caller() is the function that replaces _mcount() when ftrace is
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* active.
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*
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* We arrive here after a function A calls function B, and we are the trace
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* function for B. When we enter r1 points to A's stack frame, B has not yet
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* had a chance to allocate one yet.
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*
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* Additionally r2 may point either to the TOC for A, or B, depending on
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* whether B did a TOC setup sequence before calling us.
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*
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* On entry the LR points back to the _mcount() call site, and r0 holds the
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* saved LR as it was on entry to B, ie. the original return address at the
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* call site in A.
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*
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* Our job is to save the register state into a struct pt_regs (on the stack)
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* and then arrange for the ftrace function to be called.
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*/
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_GLOBAL(ftrace_caller)
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/* Save the original return address in A's stack frame */
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std r0,LRSAVE(r1)
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/* Create our stack frame + pt_regs */
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stdu r1,-SWITCH_FRAME_SIZE(r1)
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/* Save all gprs to pt_regs */
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SAVE_8GPRS(0,r1)
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SAVE_8GPRS(8,r1)
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SAVE_8GPRS(16,r1)
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SAVE_8GPRS(24,r1)
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/* Load special regs for save below */
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mfmsr r8
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mfctr r9
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mfxer r10
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mfcr r11
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/* Get the _mcount() call site out of LR */
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mflr r7
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/* Save it as pt_regs->nip & pt_regs->link */
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std r7, _NIP(r1)
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std r7, _LINK(r1)
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/* Save callee's TOC in the ABI compliant location */
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std r2, 24(r1)
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ld r2,PACATOC(r13) /* get kernel TOC in r2 */
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addis r3,r2,function_trace_op@toc@ha
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addi r3,r3,function_trace_op@toc@l
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ld r5,0(r3)
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/* Calculate ip from nip-4 into r3 for call below */
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subi r3, r7, MCOUNT_INSN_SIZE
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/* Put the original return address in r4 as parent_ip */
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mr r4, r0
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/* Save special regs */
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std r8, _MSR(r1)
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std r9, _CTR(r1)
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std r10, _XER(r1)
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std r11, _CCR(r1)
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/* Load &pt_regs in r6 for call below */
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addi r6, r1 ,STACK_FRAME_OVERHEAD
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/* ftrace_call(r3, r4, r5, r6) */
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.globl ftrace_call
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ftrace_call:
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bl ftrace_stub
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nop
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/* Load ctr with the possibly modified NIP */
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ld r3, _NIP(r1)
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mtctr r3
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/* Restore gprs */
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REST_8GPRS(0,r1)
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REST_8GPRS(8,r1)
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REST_8GPRS(16,r1)
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REST_8GPRS(24,r1)
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/* Restore callee's TOC */
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ld r2, 24(r1)
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/* Pop our stack frame */
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addi r1, r1, SWITCH_FRAME_SIZE
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/* Restore original LR for return to B */
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ld r0, LRSAVE(r1)
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mtlr r0
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#ifdef CONFIG_FUNCTION_GRAPH_TRACER
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stdu r1, -112(r1)
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.globl ftrace_graph_call
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ftrace_graph_call:
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b ftrace_graph_stub
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_GLOBAL(ftrace_graph_stub)
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addi r1, r1, 112
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#endif
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ld r0,LRSAVE(r1) /* restore callee's lr at _mcount site */
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mtlr r0
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bctr /* jump after _mcount site */
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#endif /* CC_USING_MPROFILE_KERNEL */
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_GLOBAL(ftrace_stub)
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blr
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#else
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@ -1198,6 +1311,7 @@ _GLOBAL(ftrace_stub)
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#endif /* CONFIG_DYNAMIC_FTRACE */
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#ifdef CONFIG_FUNCTION_GRAPH_TRACER
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#ifndef CC_USING_MPROFILE_KERNEL
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_GLOBAL(ftrace_graph_caller)
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/* load r4 with local address */
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ld r4, 128(r1)
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@ -1222,6 +1336,56 @@ _GLOBAL(ftrace_graph_caller)
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addi r1, r1, 112
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blr
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#else /* CC_USING_MPROFILE_KERNEL */
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_GLOBAL(ftrace_graph_caller)
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/* with -mprofile-kernel, parameter regs are still alive at _mcount */
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std r10, 104(r1)
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std r9, 96(r1)
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std r8, 88(r1)
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std r7, 80(r1)
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std r6, 72(r1)
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std r5, 64(r1)
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std r4, 56(r1)
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std r3, 48(r1)
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/* Save callee's TOC in the ABI compliant location */
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std r2, 24(r1)
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ld r2, PACATOC(r13) /* get kernel TOC in r2 */
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mfctr r4 /* ftrace_caller has moved local addr here */
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std r4, 40(r1)
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mflr r3 /* ftrace_caller has restored LR from stack */
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subi r4, r4, MCOUNT_INSN_SIZE
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bl prepare_ftrace_return
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nop
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/*
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* prepare_ftrace_return gives us the address we divert to.
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* Change the LR to this.
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*/
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mtlr r3
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ld r0, 40(r1)
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mtctr r0
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ld r10, 104(r1)
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ld r9, 96(r1)
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ld r8, 88(r1)
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ld r7, 80(r1)
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ld r6, 72(r1)
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ld r5, 64(r1)
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ld r4, 56(r1)
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ld r3, 48(r1)
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/* Restore callee's TOC */
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ld r2, 24(r1)
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addi r1, r1, 112
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mflr r0
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std r0, LRSAVE(r1)
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bctr
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#endif /* CC_USING_MPROFILE_KERNEL */
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_GLOBAL(return_to_handler)
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/* need to save return values */
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std r4, -32(r1)
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@ -61,8 +61,11 @@ ftrace_modify_code(unsigned long ip, unsigned int old, unsigned int new)
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return -EFAULT;
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/* Make sure it is what we expect it to be */
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if (replaced != old)
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if (replaced != old) {
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pr_err("%p: replaced (%#x) != old (%#x)",
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(void *)ip, replaced, old);
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return -EINVAL;
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}
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/* replace the text with the new text */
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if (patch_instruction((unsigned int *)ip, new))
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@ -108,11 +111,13 @@ __ftrace_make_nop(struct module *mod,
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{
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unsigned long entry, ptr, tramp;
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unsigned long ip = rec->ip;
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unsigned int op;
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unsigned int op, pop;
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/* read where this goes */
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if (probe_kernel_read(&op, (void *)ip, sizeof(int)))
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if (probe_kernel_read(&op, (void *)ip, sizeof(int))) {
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pr_err("Fetching opcode failed.\n");
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return -EFAULT;
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}
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/* Make sure that that this is still a 24bit jump */
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if (!is_bl_op(op)) {
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@ -152,10 +157,42 @@ __ftrace_make_nop(struct module *mod,
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*
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* Use a b +8 to jump over the load.
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*/
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op = 0x48000008; /* b +8 */
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if (patch_instruction((unsigned int *)ip, op))
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pop = PPC_INST_BRANCH | 8; /* b +8 */
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/*
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* Check what is in the next instruction. We can see ld r2,40(r1), but
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* on first pass after boot we will see mflr r0.
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*/
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if (probe_kernel_read(&op, (void *)(ip+4), MCOUNT_INSN_SIZE)) {
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pr_err("Fetching op failed.\n");
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return -EFAULT;
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}
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if (op != PPC_INST_LD_TOC) {
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unsigned int inst;
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if (probe_kernel_read(&inst, (void *)(ip - 4), 4)) {
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pr_err("Fetching instruction at %lx failed.\n", ip - 4);
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return -EFAULT;
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}
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/* We expect either a mlfr r0, or a std r0, LRSAVE(r1) */
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if (inst != PPC_INST_MFLR && inst != PPC_INST_STD_LR) {
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pr_err("Unexpected instructions around bl _mcount\n"
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"when enabling dynamic ftrace!\t"
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"(%08x,bl,%08x)\n", inst, op);
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return -EINVAL;
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}
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/* When using -mkernel_profile there is no load to jump over */
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pop = PPC_INST_NOP;
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}
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if (patch_instruction((unsigned int *)ip, pop)) {
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pr_err("Patching NOP failed.\n");
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return -EPERM;
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}
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return 0;
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}
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@ -281,6 +318,39 @@ int ftrace_make_nop(struct module *mod,
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#ifdef CONFIG_MODULES
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#ifdef CONFIG_PPC64
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/*
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* Examine the existing instructions for __ftrace_make_call.
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* They should effectively be a NOP, and follow formal constraints,
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* depending on the ABI. Return false if they don't.
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*/
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#ifndef CC_USING_MPROFILE_KERNEL
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static int
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expected_nop_sequence(void *ip, unsigned int op0, unsigned int op1)
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{
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/*
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* We expect to see:
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*
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* b +8
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* ld r2,XX(r1)
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*
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* The load offset is different depending on the ABI. For simplicity
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* just mask it out when doing the compare.
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*/
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if ((op0 != 0x48000008) || ((op1 & 0xffff0000) != 0xe8410000))
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return 0;
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return 1;
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}
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#else
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static int
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expected_nop_sequence(void *ip, unsigned int op0, unsigned int op1)
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{
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/* look for patched "NOP" on ppc64 with -mprofile-kernel */
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if (op0 != PPC_INST_NOP)
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return 0;
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return 1;
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}
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#endif
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static int
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__ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
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{
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@ -291,17 +361,9 @@ __ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
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if (probe_kernel_read(op, ip, sizeof(op)))
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return -EFAULT;
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/*
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* We expect to see:
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*
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* b +8
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* ld r2,XX(r1)
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*
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* The load offset is different depending on the ABI. For simplicity
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* just mask it out when doing the compare.
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*/
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if ((op[0] != 0x48000008) || ((op[1] & 0xffff0000) != 0xe8410000)) {
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pr_err("Unexpected call sequence: %x %x\n", op[0], op[1]);
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if (!expected_nop_sequence(ip, op[0], op[1])) {
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pr_err("Unexpected call sequence at %p: %x %x\n",
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ip, op[0], op[1]);
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return -EINVAL;
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}
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@ -324,7 +386,16 @@ __ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
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return 0;
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}
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#else
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#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
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int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
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unsigned long addr)
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{
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return ftrace_make_call(rec, addr);
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}
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#endif
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#else /* !CONFIG_PPC64: */
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static int
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__ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
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{
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@ -42,7 +42,6 @@
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--RR. */
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#if defined(_CALL_ELF) && _CALL_ELF == 2
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#define R2_STACK_OFFSET 24
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/* An address is simply the address of the function. */
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typedef unsigned long func_desc_t;
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@ -74,7 +73,6 @@ static unsigned int local_entry_offset(const Elf64_Sym *sym)
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return PPC64_LOCAL_ENTRY_OFFSET(sym->st_other);
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}
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#else
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#define R2_STACK_OFFSET 40
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/* An address is address of the OPD entry, which contains address of fn. */
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typedef struct ppc64_opd_entry func_desc_t;
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@ -451,17 +449,60 @@ static unsigned long stub_for_addr(const Elf64_Shdr *sechdrs,
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return (unsigned long)&stubs[i];
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}
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#ifdef CC_USING_MPROFILE_KERNEL
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static bool is_early_mcount_callsite(u32 *instruction)
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{
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/*
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* Check if this is one of the -mprofile-kernel sequences.
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*/
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if (instruction[-1] == PPC_INST_STD_LR &&
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instruction[-2] == PPC_INST_MFLR)
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return true;
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if (instruction[-1] == PPC_INST_MFLR)
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return true;
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return false;
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}
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/*
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* In case of _mcount calls, do not save the current callee's TOC (in r2) into
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* the original caller's stack frame. If we did we would clobber the saved TOC
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* value of the original caller.
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*/
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static void squash_toc_save_inst(const char *name, unsigned long addr)
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{
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struct ppc64_stub_entry *stub = (struct ppc64_stub_entry *)addr;
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/* Only for calls to _mcount */
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if (strcmp("_mcount", name) != 0)
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return;
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stub->jump[2] = PPC_INST_NOP;
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}
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#else
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static void squash_toc_save_inst(const char *name, unsigned long addr) { }
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/* without -mprofile-kernel, mcount calls are never early */
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static bool is_early_mcount_callsite(u32 *instruction)
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{
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return false;
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||||
}
|
||||
#endif
|
||||
|
||||
/* We expect a noop next: if it is, replace it with instruction to
|
||||
restore r2. */
|
||||
static int restore_r2(u32 *instruction, struct module *me)
|
||||
{
|
||||
if (*instruction != PPC_INST_NOP) {
|
||||
if (is_early_mcount_callsite(instruction - 1))
|
||||
return 1;
|
||||
pr_err("%s: Expect noop after relocate, got %08x\n",
|
||||
me->name, *instruction);
|
||||
return 0;
|
||||
}
|
||||
/* ld r2,R2_STACK_OFFSET(r1) */
|
||||
*instruction = 0xe8410000 | R2_STACK_OFFSET;
|
||||
*instruction = PPC_INST_LD_TOC;
|
||||
return 1;
|
||||
}
|
||||
|
||||
@ -586,6 +627,8 @@ int apply_relocate_add(Elf64_Shdr *sechdrs,
|
||||
return -ENOENT;
|
||||
if (!restore_r2((u32 *)location + 1, me))
|
||||
return -ENOEXEC;
|
||||
|
||||
squash_toc_save_inst(strtab + sym->st_name, value);
|
||||
} else
|
||||
value += local_entry_offset(sym);
|
||||
|
||||
|
||||
Loading…
Reference in New Issue
Block a user