Commit 04dabb42 authored by Heiko Carstens's avatar Heiko Carstens
Browse files

s390/bug: Implement __WARN_printf() 



This is the s390 variant of commit 5b472b6e ("x86_64/bug: Implement
__WARN_printf()"). See the x86 commit for the general idea; there are only
implementation details which are different.

With the new exception based __WARN_printf() implementation the generated
code for a simple WARN() is simplified.

For example:

void foo(int a) { WARN(a, "bar"); }

Before this change the generated code looks like this:

0000000000000210 <foo>:
 210:   c0 04 00 00 00 00       jgnop   210 <foo>
 216:   ec 26 00 06 00 7c       cgijne  %r2,0,222 <foo+0x12>
 21c:   c0 f4 00 00 00 00       jg      21c <foo+0xc>
                        21e: R_390_PC32DBL      __s390_indirect_jump_r14+0x2
 222:   eb ef f0 88 00 24       stmg    %r14,%r15,136(%r15)
 228:   b9 04 00 ef             lgr     %r14,%r15
 22c:   e3 f0 ff e8 ff 71       lay     %r15,-24(%r15)
 232:   e3 e0 f0 98 00 24       stg     %r14,152(%r15)
 238:   c0 20 00 00 00 00       larl    %r2,238 <foo+0x28>
                        23a: R_390_PC32DBL      .LC48+0x2
 23e:   c0 e5 00 00 00 00       brasl   %r14,23e <foo+0x2e>
                        240: R_390_PLT32DBL     __warn_printk+0x2
 244:   af 00 00 00             mc      0,0
 248:   eb ef f0 a0 00 04       lmg     %r14,%r15,160(%r15)
 24e:   c0 f4 00 00 00 00       jg      24e <foo+0x3e>
                        250: R_390_PC32DBL      __s390_indirect_jump_r14+0x2

With this change the generated code looks like this:

0000000000000210 <foo>:
 210:   c0 04 00 00 00 00       jgnop   210 <foo>
 216:   ec 26 00 06 00 7c       cgijne  %r2,0,222 <foo+0x12>
 21c:   c0 f4 00 00 00 00       jg      21c <foo+0xc>
                        21e: R_390_PC32DBL      __s390_indirect_jump_r14+0x2
 222:   c0 20 00 00 00 00       larl    %r2,222 <foobar+0x12>
                        224: R_390_PC32DBL      __bug_table+0x2
 228:   c0 f4 00 00 00 00       jg      228 <foobar+0x18>
                        22a: R_390_PLT32DBL     __WARN_trap+0x2

Downside is that the call trace now starts at __WARN_trap():

------------[ cut here ]------------
bar
WARNING: arch/s390/kernel/setup.c:1017 at 0x0, CPU#0: swapper/0/0
...
Krnl PSW : 0704c00180000000 000003ffe0f6a3b4 (__WARN_trap+0x4/0x10)
...
Krnl Code: 000003ffe0f6a3ac: 0707                bcr     0,%r7
           000003ffe0f6a3ae: 0707                bcr     0,%r7
          *000003ffe0f6a3b0: af000001            mc      1,0
          >000003ffe0f6a3b4: 07fe                bcr     15,%r14
           000003ffe0f6a3b6: 47000700            bc      0,1792
           000003ffe0f6a3ba: 0707                bcr     0,%r7
           000003ffe0f6a3bc: 0707                bcr     0,%r7
           000003ffe0f6a3be: 0707                bcr     0,%r7
Call Trace:
 [<000003ffe0f6a3b4>] __WARN_trap+0x4/0x10
([<000003ffe185a54c>] start_kernel+0x53c/0x5d8)
 [<000003ffe010002e>] startup_continue+0x2e/0x40

Which isn't too helpful. This can be addressed by just skipping __WARN_trap(),
which will be addressed in a later patch.

Reviewed-by: default avatarSven Schnelle <svens@linux.ibm.com>
Signed-off-by: default avatarHeiko Carstens <hca@linux.ibm.com>
parent ee44f4e7

arch/s390/include/asm/asm-prototypes.h

+1 −0
Original line number Diff line number Diff line
@@ -3,6 +3,7 @@ 


#include <linux/kvm_host.h>

#include <linux/ftrace.h>

#include <asm/bug.h>

#include <asm/fpu.h>

#include <asm/nospec-branch.h>

#include <asm-generic/asm-prototypes.h>

arch/s390/include/asm/bug.h

+56 −6
Original line number Diff line number Diff line
@@ -6,6 +6,7 @@ 
#include <linux/const.h>



#define	MONCODE_BUG	_AC(0, U)

#define	MONCODE_BUG_ARG _AC(1, U)



#ifndef __ASSEMBLER__

#if defined(CONFIG_BUG) && defined(CONFIG_CC_HAS_ASM_IMMEDIATE_STRINGS)
@@ -25,16 +26,20 @@ 
#define WARN_CONDITION_STR(cond_str) ""

#endif



#define __BUG_ENTRY(format, file, line, flags, size)			\

		"	.section __bug_table,\"aw\"\n"			\

		"1:	.long	0b - .	# bug_entry::bug_addr\n"	\

		__BUG_ENTRY_VERBOSE(format, file, line)			\

		"	.short	"flags"	# bug_entry::flags\n"		\

		"	.org	1b+"size"\n"				\

		"	.previous"



#define __BUG_ASM(cond_str, flags)					\

do {									\

	asm_inline volatile("\n"					\

		"0:	mc	%[monc](%%r0),0\n"			\

		"	.section __bug_table,\"aw\"\n"			\

		"1:	.long	0b - .	# bug_entry::bug_addr\n"	\

		__BUG_ENTRY_VERBOSE("%[frmt]", "%[file]", "%[line]")	\

		"	.short	%[flgs]	# bug_entry::flags\n"		\

		"	.org	1b+%[size]\n"				\

		"	.previous"					\

		__BUG_ENTRY("%[frmt]", "%[file]", "%[line]",		\

			    "%[flgs]", "%[size]")			\

		:							\

		: [monc] "i" (MONCODE_BUG),				\

		  [frmt] "i" (WARN_CONDITION_STR(cond_str)),		\
@@ -55,8 +60,53 @@ do { \ 
	__BUG_ASM(cond_str, BUGFLAG_WARNING | (flags));			\

} while (0)



#define __WARN_bug_entry(flags, format)					\

({									\

	struct bug_entry *bug;						\

									\

	asm_inline volatile("\n"					\

		"0:	larl	%[bug],1f\n"				\

		__BUG_ENTRY("%[frmt]", "%[file]", "%[line]",		\

			    "%[flgs]", "%[size]")			\

		: [bug] "=d" (bug)					\

		: [frmt] "i" (format),					\

		  [file] "i" (__FILE__),				\

		  [line] "i" (__LINE__),				\

		  [flgs] "i" (flags),					\

		  [size] "i" (sizeof(struct bug_entry)));		\

	bug;								\

})



/*

 * Variable Argument List (va_list) as defined in ELF Application

 * Binary Interface s390x Supplement documentation.

 */

struct arch_va_list {

	long __gpr;

	long __fpr;

	void *__overflow_arg_area;

	void *__reg_save_area;

};



struct bug_entry;

struct pt_regs;



void *__warn_args(struct arch_va_list *args, struct pt_regs *regs);

void __WARN_trap(struct bug_entry *bug, ...);



#define __WARN_print_arg(flags, format, arg...)				\

do {									\

	int __flags = (flags) | BUGFLAG_WARNING | BUGFLAG_ARGS;		\

									\

	__WARN_trap(__WARN_bug_entry(__flags, format), ## arg);		\

} while (0)



#define __WARN_printf(taint, fmt, arg...) \

	__WARN_print_arg(BUGFLAG_TAINT(taint), fmt, ## arg)



#define HAVE_ARCH_BUG

#define HAVE_ARCH_BUG_FORMAT

#define HAVE_ARCH_BUG_FORMAT_ARGS



#endif /* CONFIG_BUG && CONFIG_CC_HAS_ASM_IMMEDIATE_STRINGS */

#endif /* __ASSEMBLER__ */

arch/s390/kernel/entry.S

+11 −0
Original line number Diff line number Diff line
@@ -23,6 +23,7 @@ 
#include <asm/unistd.h>

#include <asm/page.h>

#include <asm/sigp.h>

#include <asm/bug.h>

#include <asm/irq.h>

#include <asm/fpu-insn.h>

#include <asm/setup.h>
@@ -173,6 +174,16 @@ SYM_FUNC_START(__switch_to_asm) 
	BR_EX	%r14

SYM_FUNC_END(__switch_to_asm)



#if defined(CONFIG_BUG) && defined(CONFIG_CC_HAS_ASM_IMMEDIATE_STRINGS)



SYM_FUNC_START(__WARN_trap)

	mc	MONCODE_BUG_ARG(%r0),0

	BR_EX	%r14

SYM_FUNC_END(__WARN_trap)

EXPORT_SYMBOL(__WARN_trap)



#endif /* CONFIG_BUG && CONFIG_CC_HAS_ASM_IMMEDIATE_STRINGS */



#if IS_ENABLED(CONFIG_KVM)

/*

 * __sie64a calling convention:

arch/s390/kernel/traps.c

+37 −1
Original line number Diff line number Diff line
@@ -23,6 +23,7 @@ 
#include <linux/cpu.h>

#include <linux/entry-common.h>

#include <linux/kmsan.h>

#include <linux/bug.h>

#include <asm/asm-extable.h>

#include <asm/irqflags.h>

#include <asm/ptrace.h>
@@ -220,11 +221,46 @@ static void space_switch_exception(struct pt_regs *regs) 
	do_trap(regs, SIGILL, ILL_PRVOPC, "space switch event");

}



#if defined(CONFIG_BUG) && defined(CONFIG_CC_HAS_ASM_IMMEDIATE_STRINGS)



void *__warn_args(struct arch_va_list *args, struct pt_regs *regs)

{

	struct stack_frame *stack_frame;



	/*

	 * Generate va_list from pt_regs. See ELF Application Binary Interface

	 * s390x Supplement documentation for details.

	 *

	 * - __overflow_arg_area needs to point to the parameter area, which

	 *   is right above the standard stack frame (160 bytes)

	 *

	 * - __reg_save_area needs to point to a register save area where

	 *   general registers (%r2 - %r6) can be found at offset 16. Which

	 *   means that the gprs save area of pt_regs can be used

	 *

	 * - __gpr must be set to one, since the first parameter has been

	 *   processed (pointer to bug_entry)

	 */

	stack_frame = (struct stack_frame *)regs->gprs[15];

	args->__overflow_arg_area = stack_frame + 1;

	args->__reg_save_area = regs->gprs;

	args->__gpr = 1;

	return args;

}



#endif /* CONFIG_BUG && CONFIG_CC_HAS_ASM_IMMEDIATE_STRINGS */



static void monitor_event_exception(struct pt_regs *regs)

{

	enum bug_trap_type btt;



	if (user_mode(regs))

		return;

	switch (report_bug(regs->psw.addr - (regs->int_code >> 16), regs)) {

	if (regs->monitor_code == MONCODE_BUG_ARG)

		btt = report_bug_entry((struct bug_entry *)regs->gprs[2], regs);

	else

		btt = report_bug(regs->psw.addr - (regs->int_code >> 16), regs);

	switch (btt) {

	case BUG_TRAP_TYPE_NONE:

		fixup_exception(regs);

		break;