From c9343637d6b265127dfe37cd7e09eb6feac03032 Mon Sep 17 00:00:00 2001 From: Vasily Gorbik Date: Thu, 12 Nov 2020 15:54:47 +0100 Subject: s390/ftrace: assume -mhotpatch or -mrecord-mcount always available Currently the kernel minimal compiler requirement is gcc 4.9 or clang 10.0.1. * gcc -mhotpatch option is supported since 4.8. * A combination of -pg -mrecord-mcount -mnop-mcount -mfentry flags is supported since gcc 9 and since clang 10. Drop support for old -pg function prologues. Which leaves binary compatible -mhotpatch / -mnop-mcount -mfentry prologues in a form: brcl 0,0 Which are also do not require initial nop optimization / conversion and presence of _mcount symbol. Signed-off-by: Vasily Gorbik Reviewed-by: Heiko Carstens Signed-off-by: Heiko Carstens --- arch/s390/include/asm/ftrace.h | 31 +++++++-------------- arch/s390/kernel/ftrace.c | 63 ++++++++++-------------------------------- arch/s390/kernel/mcount.S | 8 ------ scripts/recordmcount.pl | 3 -- 4 files changed, 24 insertions(+), 81 deletions(-) diff --git a/arch/s390/include/asm/ftrace.h b/arch/s390/include/asm/ftrace.h index 68d362f8d6c1..695c61989f97 100644 --- a/arch/s390/include/asm/ftrace.h +++ b/arch/s390/include/asm/ftrace.h @@ -2,16 +2,9 @@ #ifndef _ASM_S390_FTRACE_H #define _ASM_S390_FTRACE_H +#define HAVE_FUNCTION_GRAPH_RET_ADDR_PTR #define ARCH_SUPPORTS_FTRACE_OPS 1 - -#if defined(CC_USING_HOTPATCH) || defined(CC_USING_NOP_MCOUNT) #define MCOUNT_INSN_SIZE 6 -#else -#define MCOUNT_INSN_SIZE 24 -#define MCOUNT_RETURN_FIXUP 18 -#endif - -#define HAVE_FUNCTION_GRAPH_RET_ADDR_PTR #ifndef __ASSEMBLY__ @@ -22,7 +15,6 @@ #define ftrace_return_address(n) __builtin_return_address(n) #endif -void _mcount(void); void ftrace_caller(void); extern char ftrace_graph_caller_end; @@ -30,12 +22,20 @@ extern unsigned long ftrace_plt; struct dyn_arch_ftrace { }; -#define MCOUNT_ADDR ((unsigned long)_mcount) +#define MCOUNT_ADDR 0 #define FTRACE_ADDR ((unsigned long)ftrace_caller) #define KPROBE_ON_FTRACE_NOP 0 #define KPROBE_ON_FTRACE_CALL 1 +struct module; +struct dyn_ftrace; +/* + * Either -mhotpatch or -mnop-mcount is used - no explicit init is required + */ +static inline int ftrace_init_nop(struct module *mod, struct dyn_ftrace *rec) { return 0; } +#define ftrace_init_nop ftrace_init_nop + static inline unsigned long ftrace_call_adjust(unsigned long addr) { return addr; @@ -49,28 +49,17 @@ struct ftrace_insn { static inline void ftrace_generate_nop_insn(struct ftrace_insn *insn) { #ifdef CONFIG_FUNCTION_TRACER -#if defined(CC_USING_HOTPATCH) || defined(CC_USING_NOP_MCOUNT) /* brcl 0,0 */ insn->opc = 0xc004; insn->disp = 0; -#else - /* jg .+24 */ - insn->opc = 0xc0f4; - insn->disp = MCOUNT_INSN_SIZE / 2; -#endif #endif } static inline int is_ftrace_nop(struct ftrace_insn *insn) { #ifdef CONFIG_FUNCTION_TRACER -#if defined(CC_USING_HOTPATCH) || defined(CC_USING_NOP_MCOUNT) if (insn->disp == 0) return 1; -#else - if (insn->disp == MCOUNT_INSN_SIZE / 2) - return 1; -#endif #endif return 0; } diff --git a/arch/s390/kernel/ftrace.c b/arch/s390/kernel/ftrace.c index b388e87a08bf..ebc1284a618b 100644 --- a/arch/s390/kernel/ftrace.c +++ b/arch/s390/kernel/ftrace.c @@ -22,56 +22,26 @@ #include "entry.h" /* - * The mcount code looks like this: - * stg %r14,8(%r15) # offset 0 - * larl %r1,<&counter> # offset 6 - * brasl %r14,_mcount # offset 12 - * lg %r14,8(%r15) # offset 18 - * Total length is 24 bytes. Only the first instruction will be patched - * by ftrace_make_call / ftrace_make_nop. - * The enabled ftrace code block looks like this: + * To generate function prologue either gcc's hotpatch feature (since gcc 4.8) + * or a combination of -pg -mrecord-mcount -mnop-mcount -mfentry flags + * (since gcc 9 / clang 10) is used. + * In both cases the original and also the disabled function prologue contains + * only a single six byte instruction and looks like this: + * > brcl 0,0 # offset 0 + * To enable ftrace the code gets patched like above and afterwards looks + * like this: * > brasl %r0,ftrace_caller # offset 0 - * larl %r1,<&counter> # offset 6 - * brasl %r14,_mcount # offset 12 - * lg %r14,8(%r15) # offset 18 + * + * The instruction will be patched by ftrace_make_call / ftrace_make_nop. * The ftrace function gets called with a non-standard C function call ABI * where r0 contains the return address. It is also expected that the called * function only clobbers r0 and r1, but restores r2-r15. * For module code we can't directly jump to ftrace caller, but need a * trampoline (ftrace_plt), which clobbers also r1. - * The return point of the ftrace function has offset 24, so execution - * continues behind the mcount block. - * The disabled ftrace code block looks like this: - * > jg .+24 # offset 0 - * larl %r1,<&counter> # offset 6 - * brasl %r14,_mcount # offset 12 - * lg %r14,8(%r15) # offset 18 - * The jg instruction branches to offset 24 to skip as many instructions - * as possible. - * In case we use gcc's hotpatch feature the original and also the disabled - * function prologue contains only a single six byte instruction and looks - * like this: - * > brcl 0,0 # offset 0 - * To enable ftrace the code gets patched like above and afterwards looks - * like this: - * > brasl %r0,ftrace_caller # offset 0 */ unsigned long ftrace_plt; -static inline void ftrace_generate_orig_insn(struct ftrace_insn *insn) -{ -#if defined(CC_USING_HOTPATCH) || defined(CC_USING_NOP_MCOUNT) - /* brcl 0,0 */ - insn->opc = 0xc004; - insn->disp = 0; -#else - /* stg r14,8(r15) */ - insn->opc = 0xe3e0; - insn->disp = 0xf0080024; -#endif -} - int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr, unsigned long addr) { @@ -85,15 +55,10 @@ int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec, if (copy_from_kernel_nofault(&old, (void *) rec->ip, sizeof(old))) return -EFAULT; - if (addr == MCOUNT_ADDR) { - /* Initial code replacement */ - ftrace_generate_orig_insn(&orig); - ftrace_generate_nop_insn(&new); - } else { - /* Replace ftrace call with a nop. */ - ftrace_generate_call_insn(&orig, rec->ip); - ftrace_generate_nop_insn(&new); - } + /* Replace ftrace call with a nop. */ + ftrace_generate_call_insn(&orig, rec->ip); + ftrace_generate_nop_insn(&new); + /* Verify that the to be replaced code matches what we expect. */ if (memcmp(&orig, &old, sizeof(old))) return -EINVAL; diff --git a/arch/s390/kernel/mcount.S b/arch/s390/kernel/mcount.S index 7458dcfd6464..faf64c2f90f5 100644 --- a/arch/s390/kernel/mcount.S +++ b/arch/s390/kernel/mcount.S @@ -33,11 +33,6 @@ ENDPROC(ftrace_stub) #define TRACED_FUNC_FRAME_SIZE STACK_FRAME_OVERHEAD #endif -ENTRY(_mcount) - BR_EX %r14 -ENDPROC(_mcount) -EXPORT_SYMBOL(_mcount) - ENTRY(ftrace_caller) .globl ftrace_regs_caller .set ftrace_regs_caller,ftrace_caller @@ -46,9 +41,6 @@ ENTRY(ftrace_caller) ipm %r14 # don't put any instructions sllg %r14,%r14,16 # clobbering CC before this point lgr %r1,%r15 -#if !(defined(CC_USING_HOTPATCH) || defined(CC_USING_NOP_MCOUNT)) - aghi %r0,MCOUNT_RETURN_FIXUP -#endif # allocate stack frame for ftrace_caller to contain traced function aghi %r15,-TRACED_FUNC_FRAME_SIZE stg %r1,__SF_BACKCHAIN(%r15) diff --git a/scripts/recordmcount.pl b/scripts/recordmcount.pl index 3f77a5d695c1..56c801502b9a 100755 --- a/scripts/recordmcount.pl +++ b/scripts/recordmcount.pl @@ -254,9 +254,6 @@ if ($arch eq "x86_64") { if ($cc =~ /-DCC_USING_HOTPATCH/) { $mcount_regex = "^\\s*([0-9a-fA-F]+):\\s*c0 04 00 00 00 00\\s*brcl\\s*0,[0-9a-f]+ <([^\+]*)>\$"; $mcount_adjust = 0; - } else { - $mcount_regex = "^\\s*([0-9a-fA-F]+):\\s*R_390_(PC|PLT)32DBL\\s+_mcount\\+0x2\$"; - $mcount_adjust = -14; } $alignment = 8; $type = ".quad"; -- cgit