Eric Lee / smarc-ti-linux-kernel

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Commit 21f585073d6347651f2262da187606fa1c4ee16d

Authored by Paul Gortmaker
Committed by Benjamin Herrenschmidt
1 parent 04c32a5168
Exists in ti-lsk-linux-4.1.y and in 10 other branches dlt-processor-sdk-linux-03.00.00.04, processor-sdk-linux-02.00.01, smarc-ti-lsk-linux-4.1.y, smarct3x-processor-sdk-04.01.00.06, smarct3x-processor-sdk-linux-02.00.01, smarct3x-processor-sdk-linux-03.00.00.04, smarct4x-800-processor-sdk-linux-02.00.01, smarct4x-processor-sdk-04.01.00.06, smarct4x-processor-sdk-linux-02.00.01, smarct4x-processor-sdk-linux-03.00.00.04

powerpc: Fix smp_processor_id() in preemptible splat in set_breakpoint 

Currently, on 8641D, which doesn't set CONFIG_HAVE_HW_BREAKPOINT
we get the following splat:

BUG: using smp_processor_id() in preemptible [00000000] code: login/1382
caller is set_breakpoint+0x1c/0xa0
CPU: 0 PID: 1382 Comm: login Not tainted 3.15.0-rc3-00041-g2aafe1a4d451 #1
Call Trace:
[decd5d80] [c0008dc4] show_stack+0x50/0x158 (unreliable)
[decd5dc0] [c03c6fa0] dump_stack+0x7c/0xdc
[decd5de0] [c01f8818] check_preemption_disabled+0xf4/0x104
[decd5e00] [c00086b8] set_breakpoint+0x1c/0xa0
[decd5e10] [c00d4530] flush_old_exec+0x2bc/0x588
[decd5e40] [c011c468] load_elf_binary+0x2ac/0x1164
[decd5ec0] [c00d35f8] search_binary_handler+0xc4/0x1f8
[decd5ef0] [c00d4ee8] do_execve+0x3d8/0x4b8
[decd5f40] [c001185c] ret_from_syscall+0x0/0x38
 --- Exception: c01 at 0xfeee554
    LR = 0xfeee7d4

The call path in this case is:

	flush_thread
	   --> set_debug_reg_defaults
	     --> set_breakpoint
	       --> __get_cpu_var

Since preemption is enabled in the cleanup of flush thread, and
there is no need to disable it, introduce the distinction between
set_breakpoint and __set_breakpoint, leaving only the flush_thread
instance as the current user of set_breakpoint.

Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

Showing 6 changed files with 17 additions and 9 deletions Side-by-side Diff

arch/powerpc/include/asm/debug.h
Diff comments   View file @ 21f5850
... ... @@ -47,6 +47,7 @@
47 47 #endif
48 48  
49 49 void set_breakpoint(struct arch_hw_breakpoint *brk);
  50 +void __set_breakpoint(struct arch_hw_breakpoint *brk);
50 51 #ifdef CONFIG_PPC_ADV_DEBUG_REGS
51 52 extern void do_send_trap(struct pt_regs *regs, unsigned long address,
52 53 unsigned long error_code, int signal_code, int brkpt);
arch/powerpc/include/asm/hw_breakpoint.h
Diff comments   View file @ 21f5850
... ... @@ -79,7 +79,7 @@
79 79 brk.address = 0;
80 80 brk.type = 0;
81 81 brk.len = 0;
82   - set_breakpoint(&brk);
  82 + __set_breakpoint(&brk);
83 83 }
84 84 extern void thread_change_pc(struct task_struct *tsk, struct pt_regs *regs);
85 85  
arch/powerpc/kernel/hw_breakpoint.c
Diff comments   View file @ 21f5850
... ... @@ -72,7 +72,7 @@
72 72 * If so, DABR will be populated in single_step_dabr_instruction().
73 73 */
74 74 if (current->thread.last_hit_ubp != bp)
75   - set_breakpoint(info);
  75 + __set_breakpoint(info);
76 76  
77 77 return 0;
78 78 }
... ... @@ -198,7 +198,7 @@
198 198  
199 199 info = counter_arch_bp(tsk->thread.last_hit_ubp);
200 200 regs->msr &= ~MSR_SE;
201   - set_breakpoint(info);
  201 + __set_breakpoint(info);
202 202 tsk->thread.last_hit_ubp = NULL;
203 203 }
204 204  
... ... @@ -284,7 +284,7 @@
284 284 if (!(info->type & HW_BRK_TYPE_EXTRANEOUS_IRQ))
285 285 perf_bp_event(bp, regs);
286 286  
287   - set_breakpoint(info);
  287 + __set_breakpoint(info);
288 288 out:
289 289 rcu_read_unlock();
290 290 return rc;
... ... @@ -316,7 +316,7 @@
316 316 if (!(info->type & HW_BRK_TYPE_EXTRANEOUS_IRQ))
317 317 perf_bp_event(bp, regs);
318 318  
319   - set_breakpoint(info);
  319 + __set_breakpoint(info);
320 320 current->thread.last_hit_ubp = NULL;
321 321  
322 322 /*
arch/powerpc/kernel/process.c
Diff comments   View file @ 21f5850
... ... @@ -496,7 +496,7 @@
496 496 return 0;
497 497 }
498 498  
499   -void set_breakpoint(struct arch_hw_breakpoint *brk)
  499 +void __set_breakpoint(struct arch_hw_breakpoint *brk)
500 500 {
501 501 __get_cpu_var(current_brk) = *brk;
502 502  
... ... @@ -506,6 +506,13 @@
506 506 set_dabr(brk);
507 507 }
508 508  
  509 +void set_breakpoint(struct arch_hw_breakpoint *brk)
  510 +{
  511 + preempt_disable();
  512 + __set_breakpoint(brk);
  513 + preempt_enable();
  514 +}
  515 +
509 516 #ifdef CONFIG_PPC64
510 517 DEFINE_PER_CPU(struct cpu_usage, cpu_usage_array);
511 518 #endif
... ... @@ -835,7 +842,7 @@
835 842 */
836 843 #ifndef CONFIG_HAVE_HW_BREAKPOINT
837 844 if (unlikely(!hw_brk_match(&__get_cpu_var(current_brk), &new->thread.hw_brk)))
838   - set_breakpoint(&new->thread.hw_brk);
  845 + __set_breakpoint(&new->thread.hw_brk);
839 846 #endif /* CONFIG_HAVE_HW_BREAKPOINT */
840 847 #endif
841 848  
arch/powerpc/kernel/signal.c
Diff comments   View file @ 21f5850
... ... @@ -134,7 +134,7 @@
134 134 */
135 135 if (current->thread.hw_brk.address &&
136 136 current->thread.hw_brk.type)
137   - set_breakpoint(&current->thread.hw_brk);
  137 + __set_breakpoint(&current->thread.hw_brk);
138 138 #endif
139 139 /* Re-enable the breakpoints for the signal stack */
140 140 thread_change_pc(current, regs);
arch/powerpc/xmon/xmon.c
Diff comments   View file @ 21f5850
... ... @@ -759,7 +759,7 @@
759 759 brk.address = dabr.address;
760 760 brk.type = (dabr.enabled & HW_BRK_TYPE_DABR) | HW_BRK_TYPE_PRIV_ALL;
761 761 brk.len = 8;
762   - set_breakpoint(&brk);
  762 + __set_breakpoint(&brk);
763 763 }
764 764 if (iabr && cpu_has_feature(CPU_FTR_IABR))
765 765 mtspr(SPRN_IABR, iabr->address