1 /* SPDX-License-Identifier: GPL-2.0-or-later */
3 * Split from ftrace_64.S
6 #include <linux/magic.h>
7 #include <asm/ppc_asm.h>
8 #include <asm/asm-offsets.h>
9 #include <asm/ftrace.h>
10 #include <asm/ppc-opcode.h>
11 #include <asm/export.h>
12 #include <asm/thread_info.h>
14 #include <asm/ptrace.h>
18 * ftrace_caller()/ftrace_regs_caller() is the function that replaces _mcount()
19 * when ftrace is active.
21 * We arrive here after a function A calls function B, and we are the trace
22 * function for B. When we enter r1 points to A's stack frame, B has not yet
23 * had a chance to allocate one yet.
25 * Additionally r2 may point either to the TOC for A, or B, depending on
26 * whether B did a TOC setup sequence before calling us.
28 * On entry the LR points back to the _mcount() call site, and r0 holds the
29 * saved LR as it was on entry to B, ie. the original return address at the
32 * Our job is to save the register state into a struct pt_regs (on the stack)
33 * and then arrange for the ftrace function to be called.
35 _GLOBAL(ftrace_regs_caller)
36 /* Save the original return address in A's stack frame */
39 /* Create our stack frame + pt_regs */
40 stdu r1,-SWITCH_FRAME_SIZE(r1)
42 /* Save all gprs to pt_regs */
47 lbz r3, PACA_FTRACE_ENABLED(r13)
53 /* Save previous stack pointer (r1) */
54 addi r8, r1, SWITCH_FRAME_SIZE
57 /* Load special regs for save below */
63 /* Get the _mcount() call site out of LR */
65 /* Save it as pt_regs->nip */
67 /* Save the read LR in pt_regs->link */
70 /* Save callee's TOC in the ABI compliant location */
72 ld r2,PACATOC(r13) /* get kernel TOC in r2 */
74 addis r3,r2,function_trace_op@toc@ha
75 addi r3,r3,function_trace_op@toc@l
78 #ifdef CONFIG_LIVEPATCH
79 mr r14,r7 /* remember old NIP */
81 /* Calculate ip from nip-4 into r3 for call below */
82 subi r3, r7, MCOUNT_INSN_SIZE
84 /* Put the original return address in r4 as parent_ip */
87 /* Save special regs */
93 /* Load &pt_regs in r6 for call below */
94 addi r6, r1 ,STACK_FRAME_OVERHEAD
96 /* ftrace_call(r3, r4, r5, r6) */
97 .globl ftrace_regs_call
102 /* Load ctr with the possibly modified NIP */
105 #ifdef CONFIG_LIVEPATCH
106 cmpd r14, r3 /* has NIP been altered? */
113 /* Restore possibly modified LR */
117 /* Restore callee's TOC */
120 /* Pop our stack frame */
121 addi r1, r1, SWITCH_FRAME_SIZE
123 #ifdef CONFIG_LIVEPATCH
124 /* Based on the cmpd above, if the NIP was altered handle livepatch */
125 bne- livepatch_handler
128 ftrace_caller_common:
129 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
130 .globl ftrace_graph_call
133 _GLOBAL(ftrace_graph_stub)
136 bctr /* jump after _mcount site */
145 addi r1, r1, SWITCH_FRAME_SIZE
149 _GLOBAL(ftrace_caller)
150 /* Save the original return address in A's stack frame */
153 /* Create our stack frame + pt_regs */
154 stdu r1, -SWITCH_FRAME_SIZE(r1)
156 /* Save all gprs to pt_regs */
159 lbz r3, PACA_FTRACE_ENABLED(r13)
163 /* Get the _mcount() call site out of LR */
167 /* Save callee's TOC in the ABI compliant location */
169 ld r2, PACATOC(r13) /* get kernel TOC in r2 */
171 addis r3, r2, function_trace_op@toc@ha
172 addi r3, r3, function_trace_op@toc@l
175 /* Calculate ip from nip-4 into r3 for call below */
176 subi r3, r7, MCOUNT_INSN_SIZE
178 /* Put the original return address in r4 as parent_ip */
181 /* Set pt_regs to NULL */
184 /* ftrace_call(r3, r4, r5, r6) */
196 /* Restore callee's TOC */
199 /* Pop our stack frame */
200 addi r1, r1, SWITCH_FRAME_SIZE
202 /* Reload original LR */
206 /* Handle function_graph or go back */
207 b ftrace_caller_common
209 #ifdef CONFIG_LIVEPATCH
211 * This function runs in the mcount context, between two functions. As
212 * such it can only clobber registers which are volatile and used in
215 * We get here when a function A, calls another function B, but B has
216 * been live patched with a new function C.
219 * - we have no stack frame and can not allocate one
220 * - LR points back to the original caller (in A)
221 * - CTR holds the new NIP in C
222 * - r0, r11 & r12 are free
225 ld r12, PACA_THREAD_INFO(r13)
227 /* Allocate 3 x 8 bytes */
228 ld r11, TI_livepatch_sp(r12)
230 std r11, TI_livepatch_sp(r12)
232 /* Save toc & real LR on livepatch stack */
237 /* Store stack end marker */
238 lis r12, STACK_END_MAGIC@h
239 ori r12, r12, STACK_END_MAGIC@l
242 /* Put ctr in r12 for global entry and branch there */
247 * Now we are returning from the patched function to the original
248 * caller A. We are free to use r11, r12 and we can use r2 until we
252 ld r12, PACA_THREAD_INFO(r13)
254 ld r11, TI_livepatch_sp(r12)
256 /* Check stack marker hasn't been trashed */
257 lis r2, STACK_END_MAGIC@h
258 ori r2, r2, STACK_END_MAGIC@l
261 EMIT_BUG_ENTRY 1b, __FILE__, __LINE__ - 1, 0
263 /* Restore LR & toc from livepatch stack */
268 /* Pop livepatch stack frame */
269 ld r12, PACA_THREAD_INFO(r13)
271 std r11, TI_livepatch_sp(r12)
273 /* Return to original caller of live patched function */
275 #endif /* CONFIG_LIVEPATCH */
277 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
278 _GLOBAL(ftrace_graph_caller)
280 /* with -mprofile-kernel, parameter regs are still alive at _mcount */
290 /* Save callee's TOC in the ABI compliant location */
292 ld r2, PACATOC(r13) /* get kernel TOC in r2 */
295 mfctr r4 /* ftrace_caller has moved local addr here */
297 mflr r3 /* ftrace_caller has restored LR from stack */
298 subi r4, r4, MCOUNT_INSN_SIZE
300 bl prepare_ftrace_return
304 * prepare_ftrace_return gives us the address we divert to.
305 * Change the LR to this.
320 /* Restore callee's TOC */
327 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */