Re: [PATCH v3] powerpc/traps: Enhance readability for trap types

[Xiongwei Song <sxwjean@me.com>]

> On Apr 10, 2021, at 12:14 AM, Christophe Leroy <christophe.leroy@csgroup.eu> wrote:
> 
> 
> 
> Le 08/04/2021 à 16:07, Xiongwei Song a écrit :
>> From: Xiongwei Song <sxwjean@gmail.com>
>> Create a new header named traps.h, define macros to list ppc interrupt
>> types in traps.h, replace the reference of the trap hex values with these
>> macros.
>> Referred the hex number in arch/powerpc/kernel/exceptions-64e.S,
>> arch/powerpc/kernel/exceptions-64s.S and
>> arch/powerpc/include/asm/kvm_asm.h.
>> v2-v3:
>> Correct the prefix of trap macros with INTERRUPT_, the previous prefix
>> is TRAP_, which is not precise. This is suggested by Segher Boessenkool
>> and Nicholas Piggin.
>> v1-v2:
>> Define more trap macros to replace more trap hexs in code, not just for
>> the __show_regs function. This is suggested by Christophe Leroy.
>> Signed-off-by: Xiongwei Song <sxwjean@gmail.com>
>> ---
>>  arch/powerpc/include/asm/interrupt.h  |  9 +++++---
>>  arch/powerpc/include/asm/ptrace.h     |  3 ++-
>>  arch/powerpc/include/asm/traps.h      | 32 +++++++++++++++++++++++++++
>>  arch/powerpc/kernel/interrupt.c       |  3 ++-
>>  arch/powerpc/kernel/process.c         |  5 ++++-
>>  arch/powerpc/mm/book3s64/hash_utils.c |  5 +++--
>>  arch/powerpc/mm/fault.c               | 21 +++++++++++-------
>>  arch/powerpc/perf/core-book3s.c       |  5 +++--
>>  arch/powerpc/xmon/xmon.c              | 16 +++++++++++---
>>  9 files changed, 78 insertions(+), 21 deletions(-)
>>  create mode 100644 arch/powerpc/include/asm/traps.h
>> diff --git a/arch/powerpc/include/asm/interrupt.h b/arch/powerpc/include/asm/interrupt.h
>> index 7c633896d758..5ce9898bc9a6 100644
>> --- a/arch/powerpc/include/asm/interrupt.h
>> +++ b/arch/powerpc/include/asm/interrupt.h
>> @@ -8,6 +8,7 @@
>>  #include <asm/ftrace.h>
>>  #include <asm/kprobes.h>
>>  #include <asm/runlatch.h>
>> +#include <asm/traps.h>
>>    struct interrupt_state {
>>  #ifdef CONFIG_PPC_BOOK3E_64
>> @@ -59,7 +60,7 @@ static inline void interrupt_enter_prepare(struct pt_regs *regs, struct interrup
>>  		 * CT_WARN_ON comes here via program_check_exception,
>>  		 * so avoid recursion.
>>  		 */
>> -		if (TRAP(regs) != 0x700)
>> +		if (TRAP(regs) != INTERRUPT_PROGRAM)
>>  			CT_WARN_ON(ct_state() != CONTEXT_KERNEL);
>>  	}
>>  #endif
>> @@ -156,7 +157,8 @@ static inline void interrupt_nmi_enter_prepare(struct pt_regs *regs, struct inte
>>  	/* Don't do any per-CPU operations until interrupt state is fixed */
>>  #endif
>>  	/* Allow DEC and PMI to be traced when they are soft-NMI */
>> -	if (TRAP(regs) != 0x900 && TRAP(regs) != 0xf00 && TRAP(regs) != 0x260) {
>> +	if (TRAP(regs) != INTERRUPT_DECREMENTER &&
>> +	    TRAP(regs) != INTERRUPT_PERFMON) {
> 
> I think too long names hinder readability, see later for suggestions.
> 
>>  		state->ftrace_enabled = this_cpu_get_ftrace_enabled();
>>  		this_cpu_set_ftrace_enabled(0);
>>  	}
>> @@ -180,7 +182,8 @@ static inline void interrupt_nmi_exit_prepare(struct pt_regs *regs, struct inter
>>  		nmi_exit();
>>    #ifdef CONFIG_PPC64
>> -	if (TRAP(regs) != 0x900 && TRAP(regs) != 0xf00 && TRAP(regs) != 0x260)
>> +	if (TRAP(regs) != INTERRUPT_DECREMENTER &&
>> +	    TRAP(regs) != INTERRUPT_PERFMON)
>>  		this_cpu_set_ftrace_enabled(state->ftrace_enabled);
>>    #ifdef CONFIG_PPC_BOOK3S_64
>> diff --git a/arch/powerpc/include/asm/ptrace.h b/arch/powerpc/include/asm/ptrace.h
>> index f10498e1b3f6..7a17e0365d43 100644
>> --- a/arch/powerpc/include/asm/ptrace.h
>> +++ b/arch/powerpc/include/asm/ptrace.h
>> @@ -21,6 +21,7 @@
>>    #include <uapi/asm/ptrace.h>
>>  #include <asm/asm-const.h>
>> +#include <asm/traps.h>
>>    #ifndef __ASSEMBLY__
>>  struct pt_regs
>> @@ -237,7 +238,7 @@ static inline bool trap_is_unsupported_scv(struct pt_regs *regs)
>>    static inline bool trap_is_syscall(struct pt_regs *regs)
>>  {
>> -	return (trap_is_scv(regs) || TRAP(regs) == 0xc00);
>> +	return (trap_is_scv(regs) || TRAP(regs) == INTERRUPT_SYSCALL);
>>  }
>>    static inline bool trap_norestart(struct pt_regs *regs)
>> diff --git a/arch/powerpc/include/asm/traps.h b/arch/powerpc/include/asm/traps.h
>> new file mode 100644
>> index 000000000000..cb416a17097c
>> --- /dev/null
>> +++ b/arch/powerpc/include/asm/traps.h
>> @@ -0,0 +1,32 @@
>> +/* SPDX-License-Identifier: GPL-2.0 */
>> +#ifndef _ASM_PPC_TRAPS_H
>> +#define _ASM_PPC_TRAPS_H
>> +
>> +#if defined(CONFIG_BOOKE) || defined(CONFIG_4xx)
>> +#define INTERRUPT_MACHINE_CHECK   0x000
> 
> I'd prefer shorted names in order to not be obliged to split lines.
> Here are some suggestions:
> 
> INT_MCE
> 
>> +#define INTERRUPT_CRITICAL_INPUT  0x100
> 
> INT_CRIT
> 
>> +#define INTERRUPT_ALTIVEC_UNAVAIL 0x200
>> +#define INTERRUPT_PERFMON         0x260
> 
> INT_PERF
> 
>> +#define INTERRUPT_DOORBELL        0x280
>> +#define INTERRUPT_DEBUG           0xd00
>> +#elif defined(CONFIG_PPC_BOOK3S)
>> +#define INTERRUPT_SYSTEM_RESET    0x100
> 
> INT_SRESET
> 
>> +#define INTERRUPT_MACHINE_CHECK   0x200
> 
> INT_MCE
> 
>> +#define INTERRUPT_DATA_SEGMENT    0x380
> 
> INT_DSEG
> 
>> +#define INTERRUPT_INST_SEGMENT    0x480
> 
> INT_ISEG
> 
>> +#define INTERRUPT_DOORBELL        0xa00
> 
> INT_DBELL
> 
>> +#define INTERRUPT_TRACE           0xd00
> 
> INT_TRACE
> 
>> +#define INTERRUPT_H_DATA_STORAGE  0xe00
>> +#define INTERRUPT_PERFMON         0xf00
> 
> INT_PERF
> 
>> +#define INTERRUPT_H_FAC_UNAVAIL   0xf80
>> +#endif
>> +
>> +#define INTERRUPT_DATA_STORAGE    0x300
> 
> INT_DSI
> 
>> +#define INTERRUPT_INST_STORAGE    0x400
> 
> INT_ISI
> 
>> +#define INTERRUPT_ALIGNMENT       0x600
> 
> INT_ALIGN
> 
>> +#define INTERRUPT_PROGRAM         0x700
> 
> INT_PROG
> 
>> +#define INTERRUPT_FP_UNAVAIL      0x800
> 
> INT_FP_UNAVAIL
> 
>> +#define INTERRUPT_DECREMENTER     0x900
> 
> INT_DEC
> 
>> +#define INTERRUPT_SYSCALL         0xc00
> 
> INT_SYSCALL
> 
> 
>> +
>> +#endif /* _ASM_PPC_TRAPS_H */
> 
> ...
> 
>> diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c
>> index 0c0b1c2cfb49..641b3feef7ee 100644
>> --- a/arch/powerpc/mm/fault.c
>> +++ b/arch/powerpc/mm/fault.c
>> @@ -44,6 +44,7 @@
>>  #include <asm/debug.h>
>>  #include <asm/kup.h>
>>  #include <asm/inst.h>
>> +#include <asm/traps.h>
>>      /*
>> @@ -197,7 +198,7 @@ static int mm_fault_error(struct pt_regs *regs, unsigned long addr,
>>  static bool bad_kernel_fault(struct pt_regs *regs, unsigned long error_code,
>>  			     unsigned long address, bool is_write)
>>  {
>> -	int is_exec = TRAP(regs) == 0x400;
>> +	int is_exec = TRAP(regs) == INTERRUPT_INST_STORAGE;
>>    	/* NX faults set DSISR_PROTFAULT on the 8xx, DSISR_NOEXEC_OR_G on others */
>>  	if (is_exec && (error_code & (DSISR_NOEXEC_OR_G | DSISR_KEYFAULT |
>> @@ -391,7 +392,7 @@ static int ___do_page_fault(struct pt_regs *regs, unsigned long address,
>>  	struct vm_area_struct * vma;
>>  	struct mm_struct *mm = current->mm;
>>  	unsigned int flags = FAULT_FLAG_DEFAULT;
>> - 	int is_exec = TRAP(regs) == 0x400;
>> +	int is_exec = TRAP(regs) == INTERRUPT_INST_STORAGE;
>>  	int is_user = user_mode(regs);
>>  	int is_write = page_fault_is_write(error_code);
>>  	vm_fault_t fault, major = 0;
>> @@ -588,20 +589,24 @@ void __bad_page_fault(struct pt_regs *regs, int sig)
>>  	/* kernel has accessed a bad area */
>>    	switch (TRAP(regs)) {
>> -	case 0x300:
>> -	case 0x380:
>> -	case 0xe00:
>> +	case INTERRUPT_DATA_STORAGE:
>> +#ifdef CONFIG_PPC_BOOK3S
>> +	case INTERRUPT_DATA_SEGMENT:
>> +	case INTERRUPT_H_DATA_STORAGE:
>> +#endif
> 
> It would be better to avoid #ifdefs when none where necessary before.
> 
> 
>>  		pr_alert("BUG: %s on %s at 0x%08lx\n",
>>  			 regs->dar < PAGE_SIZE ? "Kernel NULL pointer dereference" :
>>  			 "Unable to handle kernel data access",
>>  			 is_write ? "write" : "read", regs->dar);
>>  		break;
>> -	case 0x400:
>> -	case 0x480:
>> +	case INTERRUPT_INST_STORAGE:
>> +#ifdef CONFIG_PPC_BOOK3S
>> +	case INTERRUPT_INST_SEGMENT:
>> +#endif
> 
> It would be better to avoid #ifdefs when none where necessary before.
> 
Good point. Will delete them.

Regards,
Xiongwei

> 
> 
>>  		pr_alert("BUG: Unable to handle kernel instruction fetch%s",
>>  			 regs->nip < PAGE_SIZE ? " (NULL pointer?)\n" : "\n");
>>  		break;
>> -	case 0x600:
>> +	case INTERRUPT_ALIGNMENT:
>>  		pr_alert("BUG: Unable to handle kernel unaligned access at 0x%08lx\n",
>>  			 regs->dar);
>>  		break;
>> diff --git a/arch/powerpc/perf/core-book3s.c b/arch/powerpc/perf/core-book3s.c
>> index 766f064f00fb..6e34f5bba232 100644
>> --- a/arch/powerpc/perf/core-book3s.c
>> +++ b/arch/powerpc/perf/core-book3s.c
>> @@ -17,6 +17,7 @@
>>  #include <asm/firmware.h>
>>  #include <asm/ptrace.h>
>>  #include <asm/code-patching.h>
>> +#include <asm/traps.h>
>>    #ifdef CONFIG_PPC64
>>  #include "internal.h"
>> @@ -168,7 +169,7 @@ static bool regs_use_siar(struct pt_regs *regs)
>>  	 * they have not been setup using perf_read_regs() and so regs->result
>>  	 * is something random.
>>  	 */
>> -	return ((TRAP(regs) == 0xf00) && regs->result);
>> +	return ((TRAP(regs) == INTERRUPT_PERFMON) && regs->result);
>>  }
>>    /*
>> @@ -347,7 +348,7 @@ static inline void perf_read_regs(struct pt_regs *regs)
>>  	 * hypervisor samples as well as samples in the kernel with
>>  	 * interrupts off hence the userspace check.
>>  	 */
>> -	if (TRAP(regs) != 0xf00)
>> +	if (TRAP(regs) != INTERRUPT_PERFMON)
>>  		use_siar = 0;
>>  	else if ((ppmu->flags & PPMU_NO_SIAR))
>>  		use_siar = 0;
>> diff --git a/arch/powerpc/xmon/xmon.c b/arch/powerpc/xmon/xmon.c
>> index bf7d69625a2e..2a4f99e64bf3 100644
>> --- a/arch/powerpc/xmon/xmon.c
>> +++ b/arch/powerpc/xmon/xmon.c
>> @@ -54,6 +54,7 @@
>>  #include <asm/code-patching.h>
>>  #include <asm/sections.h>
>>  #include <asm/inst.h>
>> +#include <asm/traps.h>
>>    #ifdef CONFIG_PPC64
>>  #include <asm/hvcall.h>
>> @@ -1769,7 +1770,12 @@ static void excprint(struct pt_regs *fp)
>>  	printf("    sp: %lx\n", fp->gpr[1]);
>>  	printf("   msr: %lx\n", fp->msr);
>>  -	if (trap == 0x300 || trap == 0x380 || trap == 0x600 || trap == 0x200) {
>> +	if (trap == INTERRUPT_DATA_STORAGE ||
>> +#ifdef CONFIG_PPC_BOOK3S
>> +	    trap == INTERRUPT_DATA_SEGMENT ||
>> +#endif
> It would be better to avoid #ifdefs when none where necessary before.
> 
> And an #ifdef in the middle of a code line is awful for readability and maintainability.
> 
>> +	    trap == INTERRUPT_ALIGNMENT ||
>> +	    trap == INTERRUPT_MACHINE_CHECK) {
>>  		printf("   dar: %lx\n", fp->dar);
>>  		if (trap != 0x380)
>>  			printf(" dsisr: %lx\n", fp->dsisr);
>> @@ -1785,7 +1791,7 @@ static void excprint(struct pt_regs *fp)
>>  		       current->pid, current->comm);
>>  	}
>>  -	if (trap == 0x700)
>> +	if (trap == INTERRUPT_PROGRAM)
>>  		print_bug_trap(fp);
>>    	printf(linux_banner);
>> @@ -1846,7 +1852,11 @@ static void prregs(struct pt_regs *fp)
>>  	printf("ctr = "REG"   xer = "REG"   trap = %4lx\n",
>>  	       fp->ctr, fp->xer, fp->trap);
>>  	trap = TRAP(fp);
>> -	if (trap == 0x300 || trap == 0x380 || trap == 0x600)
>> +	if (trap == INTERRUPT_DATA_STORAGE ||
>> +#ifdef CONFIG_PPC_BOOK3S
>> +	    trap == INTERRUPT_DATA_SEGMENT ||
>> +#endif
>> +	    trap == INTERRUPT_ALIGNMENT)
> 
> It would be better to avoid #ifdefs when none where necessary before.
> 
> And an #ifdef in the middle of a code line is awful for readability and maintainability.
> 
> 
>>  		printf("dar = "REG"   dsisr = %.8lx\n", fp->dar, fp->dsisr);
>>  }
>>