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Subject[RFC PATCH 21/25] kvx: Add support for ftrace
Date
Add support for ftrace to kvx arch.

CC: Steven Rostedt <rostedt@goodmis.org>
CC: Masami Hiramatsu <mhiramat@kernel.org>
CC: Mark Rutland <mark.rutland@arm.com>
CC: linux-kernel@vger.kernel.org
Co-developed-by: Clement Leger <clement.leger@bootlin.com>
Signed-off-by: Clement Leger <clement.leger@bootlin.com>
Co-developed-by: Guillaume Thouvenin <gthouvenin@kalray.eu>
Signed-off-by: Guillaume Thouvenin <gthouvenin@kalray.eu>
Co-developed-by: Julian Vetter <jvetter@kalray.eu>
Signed-off-by: Julian Vetter <jvetter@kalray.eu>
Co-developed-by: Marius Gligor <mgligor@kalray.eu>
Signed-off-by: Marius Gligor <mgligor@kalray.eu>
Co-developed-by: Yann Sionneau <ysionneau@kalray.eu>
Signed-off-by: Yann Sionneau <ysionneau@kalray.eu>
---
arch/kvx/include/asm/ftrace.h | 41 ++++
arch/kvx/kernel/ftrace.c | 339 ++++++++++++++++++++++++++++++
arch/kvx/kernel/mcount.S | 340 +++++++++++++++++++++++++++++++
arch/kvx/kernel/return_address.c | 55 +++++
4 files changed, 775 insertions(+)
create mode 100644 arch/kvx/include/asm/ftrace.h
create mode 100644 arch/kvx/kernel/ftrace.c
create mode 100644 arch/kvx/kernel/mcount.S
create mode 100644 arch/kvx/kernel/return_address.c

diff --git a/arch/kvx/include/asm/ftrace.h b/arch/kvx/include/asm/ftrace.h
new file mode 100644
index 000000000000..f7bcb325d255
--- /dev/null
+++ b/arch/kvx/include/asm/ftrace.h
@@ -0,0 +1,41 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) 2017-2023 Kalray Inc.
+ * Author(s): Guillaume Thouvenin
+ * Clement Leger
+ */
+
+#ifndef _ASM_KVX_FTRACE_H
+#define _ASM_KVX_FTRACE_H
+
+#include <asm/insns_defs.h>
+
+#define INSN_MAKE_IMM64_SYLLABLE_SIZE INSN_SIZE(MAKE_IMM64)
+#define INSN_ICALL_SYLLABLE_SIZE INSN_SIZE(ICALL)
+#define INSN_IGOTO_SYLLABLE_SIZE INSN_SIZE(IGOTO)
+#define INSN_CALL_SYLLABLE_SIZE INSN_SIZE(CALL)
+#define INSN_NOP_SYLLABLE_SIZE INSN_SIZE(NOP)
+
+#define INSN_ICALL_REG_MASK 0x3f
+
+#define MCOUNT_ADDR ((unsigned long)(__mcount))
+#define MCOUNT_INSN_SIZE INSN_CALL_SYLLABLE_SIZE /* sizeof mcount call */
+
+extern void ftrace_graph_call(void);
+
+#ifdef CONFIG_DYNAMIC_FTRACE
+extern unsigned long ftrace_call_adjust(unsigned long addr);
+struct dyn_arch_ftrace {
+ unsigned int insn;
+};
+#endif
+
+extern void *return_address(unsigned int level);
+#define ftrace_return_address(n) return_address(n)
+
+#ifdef CONFIG_FUNCTION_TRACER
+extern void __mcount(void);
+#define mcount __mcount
+#endif /* CONFIG_FUNCTION_TRACER */
+
+#endif /* _ASM_KVX_FTRACE_H */
diff --git a/arch/kvx/kernel/ftrace.c b/arch/kvx/kernel/ftrace.c
new file mode 100644
index 000000000000..4c9e3ef62714
--- /dev/null
+++ b/arch/kvx/kernel/ftrace.c
@@ -0,0 +1,339 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2017-2023 Kalray Inc.
+ * Author(s): Guillaume Thouvenin
+ * Marius Gligor
+ * Clement Leger
+ */
+
+#include <linux/ftrace.h>
+#include <linux/atomic.h>
+#include <linux/stop_machine.h>
+#include <asm/insns.h>
+#include <asm/insns_defs.h>
+#include <asm/cacheflush.h>
+
+/* The longest insns we check are for the far call: make + icall */
+#define MAX_SYLLABLES_TO_CHECK (KVX_INSN_MAKE_IMM64_SIZE + INSN_ICALL_SYLLABLE_SIZE)
+
+static int read_insns_and_check(u32 *insns, u8 insns_len, u32 *addr)
+{
+ u32 insns_read[MAX_SYLLABLES_TO_CHECK];
+ int syllables = insns_len / KVX_INSN_SYLLABLE_WIDTH;
+ int i;
+
+ if (syllables > MAX_SYLLABLES_TO_CHECK) {
+ pr_err("%s: shouldn't have more than %d syllables to check\n",
+ __func__, MAX_SYLLABLES_TO_CHECK);
+ return -EINVAL;
+ }
+
+ if (kvx_insns_read(insns_read, insns_len, addr)) {
+ pr_err("%s: error when trying to read syllable\n", __func__);
+ return -EFAULT;
+ }
+
+ for (i = 0; i < syllables; i++) {
+ if (insns[i] != insns_read[i]) {
+ pr_err("%s: Instruction verification failed at PC 0x%lx\n",
+ __func__,
+ (unsigned long)addr + i * KVX_INSN_SYLLABLE_WIDTH);
+ pr_err("%s: \tExpect 0x%x\n", __func__, insns[i]);
+ pr_err("%s: \tRead 0x%x\n", __func__, insns_read[i]);
+ return -EFAULT;
+ }
+ }
+
+ return 0;
+}
+
+static int write_insns_and_check(u32 *insns, u8 insns_len, u32 *insn_addr)
+{
+ int ret;
+
+ ret = kvx_insns_write_nostop(insns, insns_len, insn_addr);
+ if (ret)
+ return ret;
+
+ /* Check that what have been written is correct. */
+ return read_insns_and_check(insns, insns_len, insn_addr);
+}
+
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,
+ unsigned long frame_pointer)
+{
+ unsigned long return_hooker = (unsigned long)&return_to_handler;
+ unsigned long old;
+
+ if (unlikely(atomic_read(&current->tracing_graph_pause)))
+ return;
+
+ old = *parent;
+ *parent = return_hooker;
+
+ if (function_graph_enter(old, self_addr, frame_pointer, NULL))
+ *parent = old;
+}
+
+#ifdef CONFIG_DYNAMIC_FTRACE
+int ftrace_enable_ftrace_graph_caller(void)
+{
+ unsigned int insn[KVX_INSN_MAKE_IMM64_SIZE + KVX_INSN_IGOTO_SIZE];
+ void *ip = (void *)ftrace_call;
+
+ KVX_INSN_MAKE_IMM64(insn, KVX_INSN_PARALLEL_EOB, KVX_REG_R32,
+ (unsigned long)&ftrace_graph_call);
+ KVX_INSN_IGOTO(&insn[KVX_INSN_MAKE_IMM64_SIZE],
+ KVX_INSN_PARALLEL_EOB,
+ KVX_REG_R32);
+
+ return write_insns_and_check(insn,
+ INSN_MAKE_IMM64_SYLLABLE_SIZE
+ + INSN_IGOTO_SYLLABLE_SIZE,
+ ip);
+}
+
+int ftrace_disable_ftrace_graph_caller(void)
+{
+ unsigned int nop;
+ void *ip = (void *)ftrace_call;
+
+ KVX_INSN_NOP(&nop, KVX_INSN_PARALLEL_EOB);
+ return write_insns_and_check(&nop,
+ INSN_NOP_SYLLABLE_SIZE,
+ ip + INSN_MAKE_IMM64_SYLLABLE_SIZE);
+}
+#endif /* CONFIG_DYNAMIC_FTRACE */
+
+#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
+
+#ifdef CONFIG_DYNAMIC_FTRACE
+struct kvx_ftrace_modify_param {
+ atomic_t cpu_ack;
+ int cpu_master;
+ int cmd;
+};
+
+static int __ftrace_modify_code_kvx(void *data)
+{
+ struct kvx_ftrace_modify_param *mp = data;
+ int no_cpus = num_online_cpus();
+ int cpu = smp_processor_id();
+
+ if (cpu == mp->cpu_master) {
+ ftrace_modify_all_code(mp->cmd);
+
+ /* Inform the other cpus that they can invalidate I-cache */
+ atomic_inc(&mp->cpu_ack);
+
+ /* param (which contains the cpu_ack counter) is allocated on the
+ * master stack: the master must wait for all other CPUs to leave
+ * this function before returning and releasing the stack
+ * allocation.
+ */
+ while (atomic_read(&mp->cpu_ack) < no_cpus)
+ cpu_relax();
+ } else {
+ /* Wait for the master cpu to finish the code modification */
+ while (atomic_read(&mp->cpu_ack) == 0)
+ cpu_relax();
+ atomic_inc(&mp->cpu_ack);
+
+ l1_inval_icache_all();
+ }
+
+ return 0;
+}
+
+void arch_ftrace_update_code(int command)
+{
+ const struct cpumask *cpumask = cpu_online_mask;
+ struct kvx_ftrace_modify_param mp = {
+ .cpu_ack = ATOMIC_INIT(0),
+ .cpu_master = smp_processor_id(),
+ .cmd = command,
+ };
+
+ stop_machine(__ftrace_modify_code_kvx, &mp, cpu_online_mask);
+}
+
+unsigned long ftrace_call_adjust(unsigned long addr)
+{
+ /*
+ * Module are using far call and kernel functions are using
+ * pcrel. If it is a call we don't need to adjust the address but
+ * if it is an icall the address is on the make. The generated code
+ * looks like:
+ *
+ * 1c: e0 00 c4 8f get $r32 = $ra
+ * 20: 00 00 84 e0 00 00 00 80 00 00 00 00 make $r33 = 0 (0x0);;
+ *
+ * 20: R_KVX_S64_LO10 __mcount
+ * 24: R_KVX_S64_UP27 __mcount
+ * 28: R_KVX_S64_EX27 __mcount
+ * 2c: 21 00 dc 0f icall $r33;;
+ *
+ * So we just need to add INSN_MAKE_IMM64_SYLLABLE_SIZE (0xc) to the
+ * address.
+ */
+ unsigned int insn;
+
+ /*
+ * The CALL is 1 syllable while the MAKE IMM64 is 3. But we just
+ * need to check that the first syllable of the MAKE IMM64 is the
+ * LO10. So finally we just need to read one syllable to adjust the
+ * call.
+ */
+ if (kvx_insns_read(&insn, KVX_INSN_SYLLABLE_WIDTH, (void *)addr)) {
+ pr_err("%s: error when trying to read syllable\n", __func__);
+ return 0;
+ }
+
+ if (IS_INSN(insn, CALL))
+ return addr;
+
+ if (IS_INSN(insn, MAKE_IMM64))
+ return addr + INSN_MAKE_IMM64_SYLLABLE_SIZE;
+
+ pr_err("%s: syllable is neither a CALL nor a MAKE\n", __func__);
+ return 0;
+}
+
+/*
+ * Do runtime patching of the active tracer.
+ * This will be modifying the assembly code at the location of the
+ * ftrace_call symbol inside of the ftrace_caller() function.
+ */
+int ftrace_update_ftrace_func(ftrace_func_t func)
+{
+ void *ip;
+ unsigned int insn[KVX_INSN_MAKE_IMM64_SIZE + KVX_INSN_ICALL_SIZE];
+
+ ip = (void *)ftrace_call;
+ KVX_INSN_MAKE_IMM64(insn, KVX_INSN_PARALLEL_EOB, KVX_REG_R32,
+ (unsigned long)func);
+ KVX_INSN_ICALL(&insn[KVX_INSN_MAKE_IMM64_SIZE],
+ KVX_INSN_PARALLEL_EOB,
+ KVX_REG_R32);
+ return write_insns_and_check(insn,
+ INSN_MAKE_IMM64_SYLLABLE_SIZE
+ + INSN_ICALL_SYLLABLE_SIZE,
+ ip);
+}
+
+/*
+ * Turn the mcount call site into a call to an arbitrary location (but
+ * typically that is ftrace_caller()) at runtime.
+ */
+int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
+{
+ void *ip = (void *)rec->ip;
+ unsigned int insn;
+ int ret;
+
+ /* Ensure that a NOP will be replaced */
+ if (kvx_insns_read(&insn, KVX_INSN_SYLLABLE_WIDTH, ip)) {
+ pr_err("%s: failed to read insn\n", __func__);
+ return -EFAULT;
+ }
+
+ if (!IS_INSN(insn, NOP)) {
+ pr_err("%s: insn 0x%x is not a NOP\n", __func__, insn);
+ return -EINVAL;
+ }
+
+ /*
+ * Now we can replace the instruction depending of what has been
+ * nopified (call or icall)
+ */
+ insn = rec->arch.insn;
+
+ if (IS_INSN(insn, CALL)) {
+ s32 pcrel = addr - (unsigned long) ip;
+ u32 insn_call;
+
+ BUG_ON(KVX_INSN_GOTO_PCREL27_CHECK(pcrel));
+ KVX_INSN_CALL(&insn_call, KVX_INSN_PARALLEL_EOB, pcrel);
+
+ return write_insns_and_check(&insn_call,
+ INSN_CALL_SYLLABLE_SIZE, ip);
+ }
+
+ if (IS_INSN(insn, ICALL)) {
+ u32 insn_make[KVX_INSN_MAKE_IMM64_SIZE];
+ u32 r = insn & INSN_ICALL_REG_MASK;
+
+ KVX_INSN_MAKE_IMM64(insn_make, KVX_INSN_PARALLEL_EOB, r, addr);
+ ret = write_insns_and_check(insn_make,
+ INSN_MAKE_IMM64_SYLLABLE_SIZE,
+ ip - INSN_MAKE_IMM64_SYLLABLE_SIZE);
+ if (ret)
+ return ret;
+
+ return write_insns_and_check(&insn,
+ INSN_ICALL_SYLLABLE_SIZE, ip);
+ }
+
+ /* It is neither a call nor an icall */
+ pr_err("%s: insn 0x%x is neither a CALL nor ICALL\n", __func__, insn);
+ return -EINVAL;
+}
+
+/*
+ * Turn the mcount call site into a nop at runtime
+ */
+int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec,
+ unsigned long addr)
+{
+ unsigned long ip = rec->ip;
+ unsigned int insn;
+ unsigned int nop;
+
+ /*
+ * Ensure that the instruction that will be replaced is a call or an
+ * icall to addr.
+ */
+ if (kvx_insns_read(&insn, KVX_INSN_SYLLABLE_WIDTH, (void *)ip)) {
+ pr_err("%s: error when trying to read syllable\n", __func__);
+ return -EFAULT;
+ }
+
+ if (IS_INSN(insn, CALL)) {
+ int pcrel = ((int)(insn & 0x7ffffff) << 5) >> 3;
+
+ if ((ip + pcrel != addr)) {
+ pr_err("%s: failed to check call addr 0x%lx != 0x%lx\n",
+ __func__, ip + pcrel, addr);
+ return -EINVAL;
+ }
+ } else if (IS_INSN(insn, ICALL)) {
+ unsigned int insn_make[KVX_INSN_MAKE_IMM64_SIZE];
+ unsigned int reg = insn & INSN_ICALL_REG_MASK;
+ int ret;
+
+ KVX_INSN_MAKE_IMM64(insn_make,
+ KVX_INSN_PARALLEL_EOB, reg,
+ addr);
+
+ ret = read_insns_and_check(insn_make,
+ INSN_MAKE_IMM64_SYLLABLE_SIZE,
+ (void *)ip -
+ INSN_MAKE_IMM64_SYLLABLE_SIZE);
+ if (ret)
+ return ret;
+ } else {
+ pr_err("%s: insn 0x%x is neither a CALL nor an ICALL\n",
+ __func__, insn);
+ return -EINVAL;
+ }
+
+ rec->arch.insn = insn;
+ KVX_INSN_NOP(&nop, KVX_INSN_PARALLEL_EOB);
+ return write_insns_and_check(&nop, INSN_NOP_SYLLABLE_SIZE, (void *)ip);
+}
+
+#endif /* CONFIG_DYNAMIC_FTRACE */
+
+/* __mcount is defined in mcount.S */
+EXPORT_SYMBOL(__mcount);
diff --git a/arch/kvx/kernel/mcount.S b/arch/kvx/kernel/mcount.S
new file mode 100644
index 000000000000..317797aeed42
--- /dev/null
+++ b/arch/kvx/kernel/mcount.S
@@ -0,0 +1,340 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) 2017-2023 Kalray Inc.
+ * Author(s): Guillaume Thouvenin
+ * Marius Gligor
+ * Clement Leger
+ */
+
+#include <linux/linkage.h>
+#include <asm/insns_defs.h>
+#include <asm/sfr_defs.h>
+
+.altmacro
+
+/*
+ * !!! The call to __mcount is special and breaks the ABI !!!
+ * It is because with dynamic ftrace the call can be replaced by any
+ * tracer and GCC cannot assume which caller registers must be saved.
+ * It's because the call is being inserted in the prologue of functions
+ * that is out of GCC knowledge.
+ * We could make this known to GCC, but then we would hit the problem of not
+ * being able to easily decide which insns are emitted and how they are
+ * bundled. So we choose to save nothing when calling __mcount and we will
+ * save all caller registers once __mcount called.
+ *
+ * Another specificity is that parameter is passed in $r32 instead of $r0.
+ *
+ * Our stack will be:
+ * 0 | $FP $RA $r15 -
+ * 32 | $r0 $r1 $r2 $r3
+ * 64 | $r4 $r5 $r6 $r7
+ * 96 | $r8 $r9 $r10 $r11
+ * 128| $r32 $r33 $r34 $r35
+ * 160| $r36 $r37 $r38 $r39
+ * 192| $r40 $r41 $r42 $r43
+ * 224| $r44 $r45 $r46 $r47
+ * 256| $r48 $r49 $r50 $r51
+ * 288| $r52 $r53 $r54 $r55
+ * 320| $r56 $r57 $r58 $r59
+ * 352| $r60 $r61 $r62 $r63
+ * 384| $r16 $r17
+ */
+
+#define STACK_OFFSET_FP 0
+#define STACK_OFFSET_RA (STACK_OFFSET_FP + 8)
+#define STACK_OFFSET_R15 (STACK_OFFSET_RA + 8)
+#define STACK_OFFSET_Q0 (STACK_OFFSET_FP + 32)
+#define STACK_OFFSET_Q4 (STACK_OFFSET_Q0 + 32)
+#define STACK_OFFSET_Q8 (STACK_OFFSET_Q4 + 32)
+#define STACK_OFFSET_Q32 (STACK_OFFSET_Q8 + 32)
+#define STACK_OFFSET_Q36 (STACK_OFFSET_Q32 + 32)
+#define STACK_OFFSET_Q40 (STACK_OFFSET_Q36 + 32)
+#define STACK_OFFSET_Q44 (STACK_OFFSET_Q40 + 32)
+#define STACK_OFFSET_Q48 (STACK_OFFSET_Q44 + 32)
+#define STACK_OFFSET_Q52 (STACK_OFFSET_Q48 + 32)
+#define STACK_OFFSET_Q56 (STACK_OFFSET_Q52 + 32)
+#define STACK_OFFSET_Q60 (STACK_OFFSET_Q56 + 32)
+#define STACK_OFFSET_P16 (STACK_OFFSET_Q60 + 32)
+#define STACK_SIZE (STACK_OFFSET_P16 + 16)
+
+#define RA_DWARF_REGNO (64 + KVX_SFR_RA)
+#define R14_DWARF_REGNO 14
+
+.macro save_all_context_but_P16
+ /*
+ * r16 and r17 are already saved. r16 is already used to store the
+ * address of the function tracer if any.
+ * so !!! USE r17 as scratch register !!!
+ */
+ get $r17 = $ra
+ sd STACK_OFFSET_FP[$r12] = $r14
+ ;;
+ .cfi_offset R14_DWARF_REGNO, -STACK_SIZE + STACK_OFFSET_FP
+ sd STACK_OFFSET_RA[$r12] = $r17
+ ;;
+ .cfi_offset RA_DWARF_REGNO, -STACK_SIZE + STACK_OFFSET_RA
+ sd STACK_OFFSET_R15[$r12] = $r15
+ ;;
+ so STACK_OFFSET_Q0[$r12] = $r0r1r2r3
+ ;;
+ so STACK_OFFSET_Q4[$r12] = $r4r5r6r7
+ ;;
+ so STACK_OFFSET_Q8[$r12] = $r8r9r10r11
+ ;;
+ so STACK_OFFSET_Q32[$r12] = $r32r33r34r35
+ ;;
+ so STACK_OFFSET_Q36[$r12] = $r36r37r38r39
+ ;;
+ so STACK_OFFSET_Q40[$r12] = $r40r41r42r43
+ ;;
+ so STACK_OFFSET_Q44[$r12] = $r44r45r46r47
+ ;;
+ so STACK_OFFSET_Q48[$r12] = $r48r49r50r51
+ ;;
+ so STACK_OFFSET_Q52[$r12] = $r52r53r54r55
+ ;;
+ so STACK_OFFSET_Q56[$r12] = $r56r57r58r59
+ ;;
+ so STACK_OFFSET_Q60[$r12] = $r60r61r62r63
+ ;;
+.endm
+
+.macro restore_all_context
+ ld $r15 = STACK_OFFSET_RA[$r12]
+ ;;
+ ld $r14 = STACK_OFFSET_FP[$r12]
+ set $ra = $r15
+ ;;
+ .cfi_restore RA_DWARF_REGNO
+ .cfi_restore R14_DWARF_REGNO
+ ld $r15 = STACK_OFFSET_R15[$r12]
+ ;;
+ lq $r16r17 = STACK_OFFSET_P16[$r12]
+ ;;
+ lo $r0r1r2r3 = STACK_OFFSET_Q0[$r12]
+ ;;
+ lo $r4r5r6r7 = STACK_OFFSET_Q4[$r12]
+ ;;
+ lo $r8r9r10r11 = STACK_OFFSET_Q8[$r12]
+ ;;
+ lo $r32r33r34r35 = STACK_OFFSET_Q32[$r12]
+ ;;
+ lo $r36r37r38r39 = STACK_OFFSET_Q36[$r12]
+ ;;
+ lo $r40r41r42r43 = STACK_OFFSET_Q40[$r12]
+ ;;
+ lo $r44r45r46r47 = STACK_OFFSET_Q44[$r12]
+ ;;
+ lo $r48r49r50r51 = STACK_OFFSET_Q48[$r12]
+ ;;
+ lo $r52r53r54r55 = STACK_OFFSET_Q52[$r12]
+ ;;
+ lo $r56r57r58r59 = STACK_OFFSET_Q56[$r12]
+ ;;
+ lo $r60r61r62r63 = STACK_OFFSET_Q60[$r12]
+ ;;
+ addd $r12 = $r12, STACK_SIZE
+ ;;
+ .cfi_def_cfa_offset 0
+.endm
+
+ENTRY(__mcount)
+.cfi_startproc
+#ifdef CONFIG_DYNAMIC_FTRACE
+ /*
+ * With dynamic ftrace mcount() is only used during boot and then all
+ * references to it will be patched out never to return. ftrace_caller
+ * is used.
+ */
+ ret
+ ;;
+#endif
+ addd $r12 = $r12, -STACK_SIZE
+ ;;
+ .cfi_def_cfa_offset STACK_SIZE
+ sq STACK_OFFSET_P16[$r12] = $r16r17
+ ;;
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+ /*
+ * Check the function pointers ftrace_graph_return
+ * (compare to ftrace_stub) and ftrace_graph_entry (compare to
+ * ftrace_graph_entry_stub). If either of those is not set to the
+ * relevant stub function, call the arch-specific function
+ * ftrace_graph_caller.
+ */
+ make $r16 = ftrace_graph_return
+ make $r17 = ftrace_graph_entry
+ ;;
+ ld $r16 = 0[$r16]
+ ;;
+ compd.eq $r16 = $r16, ftrace_stub
+ ld $r17 = 0[$r17]
+ ;;
+ /*
+ * If ftrace_graph_return is not equal to ftrace_stub ($r16 == 0) then
+ * jump to ftrace_graph_caller. Otherwise compare ftrace_graph_entry.
+ */
+ cb.deqz $r16? ftrace_graph_caller
+ compd.eq $r17 = $r17, ftrace_graph_entry_stub
+ ;;
+ /*
+ * If ftrace_graph_entry is equal to ftrace_graph_entry_stub ($r17 == 1)
+ * then jump to ftrace_graph_end. If not we continue.
+ */
+ cb.dnez $r17? ftrace_graph_end
+ ;;
+ftrace_graph_caller:
+ save_all_context_but_P16
+ ;;
+GLOBAL(ftrace_graph_call)
+ ld $r16 = 0[$r12]
+ ;;
+ addd $r0 = $r16, 0x8 /* a pointer to the frompc */
+ get $r1 = $ra /* selfpc */
+ copyd $r2 = $r16 /* FP of the function that called __mcount */
+ ;;
+ /* get the address of the bundle */
+ addd $r1 = $r1, -KVX_INSN_SYLLABLE_WIDTH
+ ;;
+ call prepare_ftrace_return
+ ;;
+ restore_all_context
+ ;;
+ ret
+ ;;
+ftrace_graph_end:
+ .cfi_def_cfa_offset STACK_SIZE
+#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
+ /*
+ * Check if function pointer ftrace_trace_function is set to
+ * ftrace_stub.
+ * If it isn't, then call that function in the same way the mcount
+ * function normally calls __mcount_internal
+ * - the first argument is the "frompc" ($r0)
+ * - the second argument is the "selfpc" ($ra - mcount size adjustement)
+ * As we don't use any callee saved registers we don't need to save
+ * them.
+ */
+ make $r16 = ftrace_trace_function
+ ;;
+ ld $r16 = 0[$r16]
+ ;;
+ /*
+ * NOTE: keep value in $r16 (the function we may call if set). See
+ * comment in save_all_context_but_P16.
+ */
+ compd.eq $r17 = $r16, ftrace_stub
+ ;;
+ /*
+ * If ftrace_trace_function is equal to ftrace_stub ($r17 == 1), there
+ * is nothing to do, so return immediately otherwise call the function
+ * in $r16 with correct parameters.
+ */
+ cb.deqz $r17? 1f
+ ;;
+ /* Only need to restore P16 */
+ lq $r16r17 = STACK_OFFSET_P16[$r12]
+ ;;
+ addd $r12 = $r12, STACK_SIZE
+ ;;
+ .cfi_def_cfa_offset 0
+ ret
+ ;;
+
+1:
+ save_all_context_but_P16
+ ;;
+ copyd $r0 = $r32
+ get $r1 = $ra
+ ;;
+ addd $r1 = $r1, -KVX_INSN_SYLLABLE_WIDTH
+ ;;
+ icall $r16
+ ;;
+ restore_all_context
+ ;;
+ ret
+ ;;
+.cfi_endproc
+ENDPROC(__mcount)
+
+/* Required by ftrace_graph_ret_addr */
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+ENTRY(return_to_handler)
+ addd $r12 = $r12, -128
+ ;;
+ so 0[$r12] = $r0r1r2r3
+ ;;
+ so 32[$r12] = $r4r5r6r7
+ ;;
+ so 64[$r12] = $r8r9r10r11
+ ;;
+ call ftrace_return_to_handler
+ ;;
+ set $ra = $r0
+ lo $r0r1r2r3 = 0[$r12]
+ ;;
+ lo $r4r5r6r7 = 32[$r12]
+ ;;
+ lo $r8r9r10r11 = 64[$r12]
+ addd $r12 = $r12, 128
+ ;;
+ ret
+ ;;
+ENDPROC(return_to_handler)
+#endif
+
+#ifdef CONFIG_DYNAMIC_FTRACE
+ENTRY(ftrace_caller)
+.cfi_startproc
+
+ addd $r12 = $r12, -STACK_SIZE
+ ;;
+ .cfi_def_cfa_offset STACK_SIZE
+ sq STACK_OFFSET_P16[$r12] = $r16r17
+ ;;
+ save_all_context_but_P16
+ ;;
+ copyd $r0 = $r32
+ get $r1 = $ra
+ ;;
+ addd $r1 = $r1, -KVX_INSN_SYLLABLE_WIDTH
+ ;;
+ goto ftrace_call
+ ;;
+.align 64
+GLOBAL(ftrace_call)
+ /*
+ * To work with module we need to use far call. So prepare the
+ * space for them:
+ * - make: 3 syllables
+ * - icall/igoto: 1 syllable
+ *
+ * We are using igoto in ftrace_enable_ftrace_graph_caller(). This is
+ * because this path is a tweak to enable function graph tracer with
+ * dynamic ftrace. We need to jump to ftrace_graph_call without updating
+ * RA and FP. Once in ftrace_graph_call we will return to the correct
+ * address from the classical path of the function graph tracer.
+ */
+ nop
+ ;;
+ nop
+ ;;
+ nop
+ ;;
+ nop
+ ;;
+ restore_all_context
+ ;;
+ ret
+ ;;
+.cfi_endproc
+ENDPROC(ftrace_caller)
+#endif // CONFIG_DYNAMIC_FTRACE
+
+ENTRY(ftrace_stub)
+ ret
+ ;;
+ENDPROC(ftrace_stub)
+
diff --git a/arch/kvx/kernel/return_address.c b/arch/kvx/kernel/return_address.c
new file mode 100644
index 000000000000..3ddf7b79662c
--- /dev/null
+++ b/arch/kvx/kernel/return_address.c
@@ -0,0 +1,55 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * derived from arch/arm64/kernel/return_address.c
+ *
+ * Copyright (C) 2017-2023 Kalray Inc.
+ * Author(s): Clement Leger
+ */
+
+#include <linux/export.h>
+#include <linux/ftrace.h>
+#include <linux/kprobes.h>
+
+#include <asm/stacktrace.h>
+
+struct return_address_data {
+ unsigned int level;
+ void *addr;
+};
+
+static bool save_return_addr(unsigned long pc, void *d)
+{
+ struct return_address_data *data = d;
+
+ /* We hit the desired level, return the address */
+ if (data->level == 0) {
+ data->addr = (void *) pc;
+ return true;
+ }
+
+ data->level--;
+ return false;
+}
+NOKPROBE_SYMBOL(save_return_addr);
+
+void *return_address(unsigned int level)
+{
+ struct return_address_data data;
+ struct stackframe frame;
+
+ /* Skip this function + caller */
+ data.level = level + 2;
+ data.addr = NULL;
+
+ start_stackframe(&frame,
+ (unsigned long) __builtin_frame_address(0),
+ (unsigned long) return_address);
+ walk_stackframe(current, &frame, save_return_addr, &data);
+
+ if (!data.level)
+ return data.addr;
+ else
+ return NULL;
+}
+EXPORT_SYMBOL_GPL(return_address);
+NOKPROBE_SYMBOL(return_address);
--
2.37.2




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