On Wed, 30 Sep 2009 14:49:25 -0400, Takao Indoh <indou.takao@xxxxxxxxxxxxxx> wrote: >Hi all, > >When I was investigating vmcore captured by kdump, I noticed that >the backtrace was sometimes not displayed correctly. > >The cause is that pt_regs and switch_stack are not saved in the stack >when INIT comes during fsys mode. In fsys mode, r13 register does not >point task_struct of current, so pt_regs and switch_stack are not saved >because of the following code in arch/ia64/kernel/mca.c. > >static struct task_struct * >ia64_mca_modify_original_stack(struct pt_regs *regs, >(snip) > if (r13 != sos->prev_IA64_KR_CURRENT) { > msg = "inconsistent previous current and r13"; > goto no_mod; > } > >What I'd like to note here is that there is no way to know what happened >when original stack is not modified. >As I wrote above, the registers is not saved in the original stack, and >moreover, the registers in the per cpu stack are useless since they are >incomplete. We can't know why backtrace is not displayed. The only thing >we can get is the message "inconsistent previous current and r13" in the >mprintk buffer. Something problem happened? Or kernel was just in fsys >mode? We cannot know. > >Solution1: > The pt_regs in the per cpu stack are incomplete, so fill in the blanks > with the appropriate registers so that we can debug using them. > >Solution2: > Save the processor min-state(pal_min_state_area_t) somewhere. When > debugging, user can get register info from it. > >I prefer solution1 because it's easy for user to debug. The >following patch is for solution1. restore_regs(), which is new function >added by this patch, is just copying registers from pal_min_state >to pt_regs. > >Any comments would be appreciated. > >Thanks, >Takao Indoh > >Signed-off-by: Takao Indoh <indou.takao@xxxxxxxxxxxxxx> >--- > arch/ia64/kernel/mca.c | 103 +++++++++++++++++++++------------------ > 1 file changed, 56 insertions(+), 47 deletions(-) > >diff -Nurp linux-2.6.31.org/arch/ia64/kernel/mca.c linux-2.6.31/arch/ia64/kernel/mca.c >--- linux-2.6.31.org/arch/ia64/kernel/mca.c 2009-09-21 17:12:45.000000000 -0400 >+++ linux-2.6.31/arch/ia64/kernel/mca.c 2009-09-24 16:15:05.000000000 -0400 >@@ -887,6 +887,60 @@ ia64_mca_modify_comm(const struct task_s > memcpy(current->comm, comm, sizeof(current->comm)); > } > >+static void >+restore_regs(struct pt_regs *regs, const pal_min_state_area_t *ms, >+ unsigned long *nat) The name 'restore_regs' is too generic and is used in other code, 'finish_pt_regs' might be better. >+{ >+ const u64 *bank; >+ >+ /* If ipsr.ic then use pmsa_{iip,ipsr,ifs}, else use >+ * pmsa_{xip,xpsr,xfs} >+ */ >+ if (ia64_psr(regs)->ic) { >+ regs->cr_iip = ms->pmsa_iip; >+ regs->cr_ipsr = ms->pmsa_ipsr; >+ regs->cr_ifs = ms->pmsa_ifs; >+ } else { >+ regs->cr_iip = ms->pmsa_xip; >+ regs->cr_ipsr = ms->pmsa_xpsr; >+ regs->cr_ifs = ms->pmsa_xfs; >+ } >+ regs->pr = ms->pmsa_pr; >+ regs->b0 = ms->pmsa_br0; >+ regs->ar_rsc = ms->pmsa_rsc; >+ copy_reg(&ms->pmsa_gr[1-1], ms->pmsa_nat_bits, ®s->r1, nat); >+ copy_reg(&ms->pmsa_gr[2-1], ms->pmsa_nat_bits, ®s->r2, nat); >+ copy_reg(&ms->pmsa_gr[3-1], ms->pmsa_nat_bits, ®s->r3, nat); >+ copy_reg(&ms->pmsa_gr[8-1], ms->pmsa_nat_bits, ®s->r8, nat); >+ copy_reg(&ms->pmsa_gr[9-1], ms->pmsa_nat_bits, ®s->r9, nat); >+ copy_reg(&ms->pmsa_gr[10-1], ms->pmsa_nat_bits, ®s->r10, nat); >+ copy_reg(&ms->pmsa_gr[11-1], ms->pmsa_nat_bits, ®s->r11, nat); >+ copy_reg(&ms->pmsa_gr[12-1], ms->pmsa_nat_bits, ®s->r12, nat); >+ copy_reg(&ms->pmsa_gr[13-1], ms->pmsa_nat_bits, ®s->r13, nat); >+ copy_reg(&ms->pmsa_gr[14-1], ms->pmsa_nat_bits, ®s->r14, nat); >+ copy_reg(&ms->pmsa_gr[15-1], ms->pmsa_nat_bits, ®s->r15, nat); >+ if (ia64_psr(regs)->bn) >+ bank = ms->pmsa_bank1_gr; >+ else >+ bank = ms->pmsa_bank0_gr; >+ copy_reg(&bank[16-16], ms->pmsa_nat_bits, ®s->r16, nat); >+ copy_reg(&bank[17-16], ms->pmsa_nat_bits, ®s->r17, nat); >+ copy_reg(&bank[18-16], ms->pmsa_nat_bits, ®s->r18, nat); >+ copy_reg(&bank[19-16], ms->pmsa_nat_bits, ®s->r19, nat); >+ copy_reg(&bank[20-16], ms->pmsa_nat_bits, ®s->r20, nat); >+ copy_reg(&bank[21-16], ms->pmsa_nat_bits, ®s->r21, nat); >+ copy_reg(&bank[22-16], ms->pmsa_nat_bits, ®s->r22, nat); >+ copy_reg(&bank[23-16], ms->pmsa_nat_bits, ®s->r23, nat); >+ copy_reg(&bank[24-16], ms->pmsa_nat_bits, ®s->r24, nat); >+ copy_reg(&bank[25-16], ms->pmsa_nat_bits, ®s->r25, nat); >+ copy_reg(&bank[26-16], ms->pmsa_nat_bits, ®s->r26, nat); >+ copy_reg(&bank[27-16], ms->pmsa_nat_bits, ®s->r27, nat); >+ copy_reg(&bank[28-16], ms->pmsa_nat_bits, ®s->r28, nat); >+ copy_reg(&bank[29-16], ms->pmsa_nat_bits, ®s->r29, nat); >+ copy_reg(&bank[30-16], ms->pmsa_nat_bits, ®s->r30, nat); >+ copy_reg(&bank[31-16], ms->pmsa_nat_bits, ®s->r31, nat); >+} >+ > /* On entry to this routine, we are running on the per cpu stack, see > * mca_asm.h. The original stack has not been touched by this event. Some of > * the original stack's registers will be in the RBS on this stack. This stack >@@ -921,7 +975,6 @@ ia64_mca_modify_original_stack(struct pt > u64 r12 = ms->pmsa_gr[12-1], r13 = ms->pmsa_gr[13-1]; > u64 ar_bspstore = regs->ar_bspstore; > u64 ar_bsp = regs->ar_bspstore + (loadrs >> 16); >- const u64 *bank; > const char *msg; > int cpu = smp_processor_id(); > >@@ -1024,54 +1077,9 @@ ia64_mca_modify_original_stack(struct pt > p = (char *)r12 - sizeof(*regs); > old_regs = (struct pt_regs *)p; > memcpy(old_regs, regs, sizeof(*regs)); >- /* If ipsr.ic then use pmsa_{iip,ipsr,ifs}, else use >- * pmsa_{xip,xpsr,xfs} >- */ >- if (ia64_psr(regs)->ic) { >- old_regs->cr_iip = ms->pmsa_iip; >- old_regs->cr_ipsr = ms->pmsa_ipsr; >- old_regs->cr_ifs = ms->pmsa_ifs; >- } else { >- old_regs->cr_iip = ms->pmsa_xip; >- old_regs->cr_ipsr = ms->pmsa_xpsr; >- old_regs->cr_ifs = ms->pmsa_xfs; >- } >- old_regs->pr = ms->pmsa_pr; >- old_regs->b0 = ms->pmsa_br0; > old_regs->loadrs = loadrs; >- old_regs->ar_rsc = ms->pmsa_rsc; > old_unat = old_regs->ar_unat; >- copy_reg(&ms->pmsa_gr[1-1], ms->pmsa_nat_bits, &old_regs->r1, &old_unat); >- copy_reg(&ms->pmsa_gr[2-1], ms->pmsa_nat_bits, &old_regs->r2, &old_unat); >- copy_reg(&ms->pmsa_gr[3-1], ms->pmsa_nat_bits, &old_regs->r3, &old_unat); >- copy_reg(&ms->pmsa_gr[8-1], ms->pmsa_nat_bits, &old_regs->r8, &old_unat); >- copy_reg(&ms->pmsa_gr[9-1], ms->pmsa_nat_bits, &old_regs->r9, &old_unat); >- copy_reg(&ms->pmsa_gr[10-1], ms->pmsa_nat_bits, &old_regs->r10, &old_unat); >- copy_reg(&ms->pmsa_gr[11-1], ms->pmsa_nat_bits, &old_regs->r11, &old_unat); >- copy_reg(&ms->pmsa_gr[12-1], ms->pmsa_nat_bits, &old_regs->r12, &old_unat); >- copy_reg(&ms->pmsa_gr[13-1], ms->pmsa_nat_bits, &old_regs->r13, &old_unat); >- copy_reg(&ms->pmsa_gr[14-1], ms->pmsa_nat_bits, &old_regs->r14, &old_unat); >- copy_reg(&ms->pmsa_gr[15-1], ms->pmsa_nat_bits, &old_regs->r15, &old_unat); >- if (ia64_psr(old_regs)->bn) >- bank = ms->pmsa_bank1_gr; >- else >- bank = ms->pmsa_bank0_gr; >- copy_reg(&bank[16-16], ms->pmsa_nat_bits, &old_regs->r16, &old_unat); >- copy_reg(&bank[17-16], ms->pmsa_nat_bits, &old_regs->r17, &old_unat); >- copy_reg(&bank[18-16], ms->pmsa_nat_bits, &old_regs->r18, &old_unat); >- copy_reg(&bank[19-16], ms->pmsa_nat_bits, &old_regs->r19, &old_unat); >- copy_reg(&bank[20-16], ms->pmsa_nat_bits, &old_regs->r20, &old_unat); >- copy_reg(&bank[21-16], ms->pmsa_nat_bits, &old_regs->r21, &old_unat); >- copy_reg(&bank[22-16], ms->pmsa_nat_bits, &old_regs->r22, &old_unat); >- copy_reg(&bank[23-16], ms->pmsa_nat_bits, &old_regs->r23, &old_unat); >- copy_reg(&bank[24-16], ms->pmsa_nat_bits, &old_regs->r24, &old_unat); >- copy_reg(&bank[25-16], ms->pmsa_nat_bits, &old_regs->r25, &old_unat); >- copy_reg(&bank[26-16], ms->pmsa_nat_bits, &old_regs->r26, &old_unat); >- copy_reg(&bank[27-16], ms->pmsa_nat_bits, &old_regs->r27, &old_unat); >- copy_reg(&bank[28-16], ms->pmsa_nat_bits, &old_regs->r28, &old_unat); >- copy_reg(&bank[29-16], ms->pmsa_nat_bits, &old_regs->r29, &old_unat); >- copy_reg(&bank[30-16], ms->pmsa_nat_bits, &old_regs->r30, &old_unat); >- copy_reg(&bank[31-16], ms->pmsa_nat_bits, &old_regs->r31, &old_unat); >+ restore_regs(old_regs, ms, &old_unat); > > /* Next stack a struct switch_stack. mca_asm.S built a partial > * switch_stack, copy it and fill in the blanks using pt_regs and >@@ -1141,6 +1149,7 @@ ia64_mca_modify_original_stack(struct pt > no_mod: > mprintk(KERN_INFO "cpu %d, %s %s, original stack not modified\n", > smp_processor_id(), type, msg); >+ restore_regs(regs, ms, &old_unat); old_unat is undefined here. You need old_unat = regs->ar_unat; > return previous_current; > } The rest of it looks good. -- To unsubscribe from this list: send the line "unsubscribe linux-ia64" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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