From 3b051e89da70d464a036a86d70ce2ed61c73f792 Mon Sep 17 00:00:00 2001 From: Sven Schnelle Date: Wed, 7 Apr 2021 09:20:17 +0200 Subject: s390: add support for BEAR enhancement facility The Breaking-Event-Address-Register (BEAR) stores the address of the last breaking event instruction. Breaking events are usually instructions that change the program flow - for example branches, and instructions that modify the address in the PSW like lpswe. This is useful for debugging wild branches, because one could easily figure out where the wild branch was originating from. What is problematic is that lpswe is considered a breaking event, and therefore overwrites BEAR on kernel exit. The BEAR enhancement facility adds new instructions that allow to save/restore BEAR and also an lpswey instruction that doesn't cause a breaking event. So we can save BEAR on kernel entry and restore it on exit to user space. Signed-off-by: Sven Schnelle Reviewed-by: Heiko Carstens Signed-off-by: Vasily Gorbik --- arch/s390/kernel/entry.S | 45 +++++++++++++++++++++++++++++++++++++-------- 1 file changed, 37 insertions(+), 8 deletions(-) (limited to 'arch/s390/kernel/entry.S') diff --git a/arch/s390/kernel/entry.S b/arch/s390/kernel/entry.S index 4c9b967290ae..01bae1d51113 100644 --- a/arch/s390/kernel/entry.S +++ b/arch/s390/kernel/entry.S @@ -52,6 +52,22 @@ STACK_INIT = STACK_SIZE - STACK_FRAME_OVERHEAD - __PT_SIZE _LPP_OFFSET = __LC_LPP + .macro STBEAR address + ALTERNATIVE "", ".insn s,0xb2010000,\address", 193 + .endm + + .macro LBEAR address + ALTERNATIVE "", ".insn s,0xb2000000,\address", 193 + .endm + + .macro LPSWEY address,lpswe + ALTERNATIVE "b \lpswe", ".insn siy,0xeb0000000071,\address,0", 193 + .endm + + .macro MBEAR reg + ALTERNATIVE "", __stringify(mvc __PT_LAST_BREAK(8,\reg),__LC_LAST_BREAK), 193 + .endm + .macro CHECK_STACK savearea #ifdef CONFIG_CHECK_STACK tml %r15,STACK_SIZE - CONFIG_STACK_GUARD @@ -302,6 +318,7 @@ ENTRY(system_call) BPOFF lghi %r14,0 .Lsysc_per: + STBEAR __LC_LAST_BREAK lctlg %c1,%c1,__LC_KERNEL_ASCE lg %r12,__LC_CURRENT lg %r15,__LC_KERNEL_STACK @@ -321,14 +338,16 @@ ENTRY(system_call) xgr %r11,%r11 la %r2,STACK_FRAME_OVERHEAD(%r15) # pointer to pt_regs mvc __PT_R8(64,%r2),__LC_SAVE_AREA_SYNC + MBEAR %r2 lgr %r3,%r14 brasl %r14,__do_syscall lctlg %c1,%c1,__LC_USER_ASCE mvc __LC_RETURN_PSW(16),STACK_FRAME_OVERHEAD+__PT_PSW(%r15) BPEXIT __TI_flags(%r12),_TIF_ISOLATE_BP + LBEAR STACK_FRAME_OVERHEAD+__PT_LAST_BREAK(%r15) lmg %r0,%r15,STACK_FRAME_OVERHEAD+__PT_R0(%r15) stpt __LC_EXIT_TIMER - b __LC_RETURN_LPSWE + LPSWEY __LC_RETURN_PSW,__LC_RETURN_LPSWE ENDPROC(system_call) # @@ -340,9 +359,10 @@ ENTRY(ret_from_fork) lctlg %c1,%c1,__LC_USER_ASCE mvc __LC_RETURN_PSW(16),STACK_FRAME_OVERHEAD+__PT_PSW(%r15) BPEXIT __TI_flags(%r12),_TIF_ISOLATE_BP + LBEAR STACK_FRAME_OVERHEAD+__PT_LAST_BREAK(%r15) lmg %r0,%r15,STACK_FRAME_OVERHEAD+__PT_R0(%r15) stpt __LC_EXIT_TIMER - b __LC_RETURN_LPSWE + LPSWEY __LC_RETURN_PSW,__LC_RETURN_LPSWE ENDPROC(ret_from_fork) /* @@ -382,6 +402,7 @@ ENTRY(pgm_check_handler) xc __SF_BACKCHAIN(8,%r15),__SF_BACKCHAIN(%r15) stmg %r0,%r7,__PT_R0(%r11) mvc __PT_R8(64,%r11),__LC_SAVE_AREA_SYNC + mvc __PT_LAST_BREAK(8,%r11),__LC_PGM_LAST_BREAK stmg %r8,%r9,__PT_PSW(%r11) # clear user controlled registers to prevent speculative use @@ -401,8 +422,9 @@ ENTRY(pgm_check_handler) stpt __LC_EXIT_TIMER .Lpgm_exit_kernel: mvc __LC_RETURN_PSW(16),STACK_FRAME_OVERHEAD+__PT_PSW(%r15) + LBEAR STACK_FRAME_OVERHEAD+__PT_LAST_BREAK(%r15) lmg %r0,%r15,STACK_FRAME_OVERHEAD+__PT_R0(%r15) - b __LC_RETURN_LPSWE + LPSWEY __LC_RETURN_PSW,__LC_RETURN_LPSWE # # single stepped system call @@ -412,7 +434,8 @@ ENTRY(pgm_check_handler) larl %r14,.Lsysc_per stg %r14,__LC_RETURN_PSW+8 lghi %r14,1 - lpswe __LC_RETURN_PSW # branch to .Lsysc_per + LBEAR __LC_PGM_LAST_BREAK + LPSWEY __LC_RETURN_PSW,__LC_RETURN_LPSWE # branch to .Lsysc_per ENDPROC(pgm_check_handler) /* @@ -422,6 +445,7 @@ ENDPROC(pgm_check_handler) ENTRY(\name) STCK __LC_INT_CLOCK stpt __LC_SYS_ENTER_TIMER + STBEAR __LC_LAST_BREAK BPOFF stmg %r8,%r15,__LC_SAVE_AREA_ASYNC lg %r12,__LC_CURRENT @@ -453,6 +477,7 @@ ENTRY(\name) xgr %r10,%r10 xc __PT_FLAGS(8,%r11),__PT_FLAGS(%r11) mvc __PT_R8(64,%r11),__LC_SAVE_AREA_ASYNC + MBEAR %r11 stmg %r8,%r9,__PT_PSW(%r11) tm %r8,0x0001 # coming from user space? jno 1f @@ -465,8 +490,9 @@ ENTRY(\name) lctlg %c1,%c1,__LC_USER_ASCE BPEXIT __TI_flags(%r12),_TIF_ISOLATE_BP stpt __LC_EXIT_TIMER -2: lmg %r0,%r15,__PT_R0(%r11) - b __LC_RETURN_LPSWE +2: LBEAR __PT_LAST_BREAK(%r11) + lmg %r0,%r15,__PT_R0(%r11) + LPSWEY __LC_RETURN_PSW,__LC_RETURN_LPSWE ENDPROC(\name) .endm @@ -505,6 +531,7 @@ ENTRY(mcck_int_handler) BPOFF la %r1,4095 # validate r1 spt __LC_CPU_TIMER_SAVE_AREA-4095(%r1) # validate cpu timer + LBEAR __LC_LAST_BREAK_SAVE_AREA-4095(%r1) # validate bear lmg %r0,%r15,__LC_GPREGS_SAVE_AREA-4095(%r1)# validate gprs lg %r12,__LC_CURRENT lmg %r8,%r9,__LC_MCK_OLD_PSW @@ -591,8 +618,10 @@ ENTRY(mcck_int_handler) jno 0f BPEXIT __TI_flags(%r12),_TIF_ISOLATE_BP stpt __LC_EXIT_TIMER -0: lmg %r11,%r15,__PT_R11(%r11) - b __LC_RETURN_MCCK_LPSWE +0: ALTERNATIVE "", __stringify(lghi %r12,__LC_LAST_BREAK_SAVE_AREA),193 + LBEAR 0(%r12) + lmg %r11,%r15,__PT_R11(%r11) + LPSWEY __LC_RETURN_MCCK_PSW,__LC_RETURN_MCCK_LPSWE .Lmcck_panic: /* -- cgit v1.2.3