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MIPS, Tracing: Clean up ftrace_make_nop()
This moves the comments out of ftrace_make_nop() and cleans it. At the same time, a macro MCOUNT_OFFSET_INSNS is defined for sharing with the next patch. Signed-off-by: Wu Zhangjin <wuzhangjin@gmail.com> Cc: Steven Rostedt <srostedt@redhat.com> Cc: linux-mips@linux-mips.org Patchwork: https://patchwork.linux-mips.org/patch/2008/ Signed-off-by: Ralf Baechle <ralf@duck.linux-mips.net>
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2816e32596
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7f21a60968
1 changed files with 38 additions and 32 deletions
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@ -24,8 +24,6 @@
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#define JAL 0x0c000000 /* jump & link: ip --> ra, jump to target */
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#define ADDR_MASK 0x03ffffff /* op_code|addr : 31...26|25 ....0 */
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#define INSN_B_1F_4 0x10000004 /* b 1f; offset = 4 */
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#define INSN_B_1F_5 0x10000005 /* b 1f; offset = 5 */
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#define INSN_NOP 0x00000000 /* nop */
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#define INSN_JAL(addr) \
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((unsigned int)(JAL | (((addr) >> 2) & ADDR_MASK)))
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@ -84,6 +82,42 @@ static int ftrace_modify_code(unsigned long ip, unsigned int new_code)
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return 0;
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}
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/*
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* The details about the calling site of mcount on MIPS
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*
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* 1. For kernel:
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*
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* move at, ra
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* jal _mcount --> nop
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*
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* 2. For modules:
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*
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* 2.1 For KBUILD_MCOUNT_RA_ADDRESS and CONFIG_32BIT
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*
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* lui v1, hi_16bit_of_mcount --> b 1f (0x10000005)
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* addiu v1, v1, low_16bit_of_mcount
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* move at, ra
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* move $12, ra_address
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* jalr v1
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* sub sp, sp, 8
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* 1: offset = 5 instructions
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* 2.2 For the Other situations
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*
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* lui v1, hi_16bit_of_mcount --> b 1f (0x10000004)
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* addiu v1, v1, low_16bit_of_mcount
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* move at, ra
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* jalr v1
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* nop | move $12, ra_address | sub sp, sp, 8
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* 1: offset = 4 instructions
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*/
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#if defined(KBUILD_MCOUNT_RA_ADDRESS) && defined(CONFIG_32BIT)
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#define MCOUNT_OFFSET_INSNS 5
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#else
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#define MCOUNT_OFFSET_INSNS 4
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#endif
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#define INSN_B_1F (0x10000000 | MCOUNT_OFFSET_INSNS)
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int ftrace_make_nop(struct module *mod,
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struct dyn_ftrace *rec, unsigned long addr)
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{
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@ -94,36 +128,8 @@ int ftrace_make_nop(struct module *mod,
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* If ip is in kernel space, no long call, otherwise, long call is
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* needed.
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*/
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if (in_kernel_space(ip)) {
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/*
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* move at, ra
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* jal _mcount --> nop
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*/
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new = INSN_NOP;
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} else {
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#if defined(KBUILD_MCOUNT_RA_ADDRESS) && defined(CONFIG_32BIT)
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/*
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* lui v1, hi_16bit_of_mcount --> b 1f (0x10000005)
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* addiu v1, v1, low_16bit_of_mcount
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* move at, ra
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* move $12, ra_address
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* jalr v1
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* sub sp, sp, 8
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* 1: offset = 5 instructions
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*/
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new = INSN_B_1F_5;
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#else
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/*
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* lui v1, hi_16bit_of_mcount --> b 1f (0x10000004)
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* addiu v1, v1, low_16bit_of_mcount
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* move at, ra
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* jalr v1
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* nop | move $12, ra_address | sub sp, sp, 8
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* 1: offset = 4 instructions
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*/
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new = INSN_B_1F_4;
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#endif
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}
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new = in_kernel_space(ip) ? INSN_NOP : INSN_B_1F;
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return ftrace_modify_code(ip, new);
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}
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