Commit 9580b71b authored by Christophe Leroy's avatar Christophe Leroy Committed by Michael Ellerman

powerpc/32: Clear on-stack exception marker upon exception return

Clear the on-stack STACK_FRAME_REGS_MARKER on exception exit in order
to avoid confusing stacktrace like the one below.

  Call Trace:
  [c0e9dca0] [c01c42a0] print_address_description+0x64/0x2bc (unreliable)
  [c0e9dcd0] [c01c4684] kasan_report+0xfc/0x180
  [c0e9dd10] [c0895130] memchr+0x24/0x74
  [c0e9dd30] [c00a9e38] msg_print_text+0x124/0x574
  [c0e9dde0] [c00ab710] console_unlock+0x114/0x4f8
  [c0e9de40] [c00adc60] vprintk_emit+0x188/0x1c4
  --- interrupt: c0e9df00 at 0x400f330
      LR = init_stack+0x1f00/0x2000
  [c0e9de80] [c00ae3c4] printk+0xa8/0xcc (unreliable)
  [c0e9df20] [c0c27e44] early_irq_init+0x38/0x108
  [c0e9df50] [c0c15434] start_kernel+0x310/0x488
  [c0e9dff0] [00003484] 0x3484

With this patch the trace becomes:

  Call Trace:
  [c0e9dca0] [c01c42c0] print_address_description+0x64/0x2bc (unreliable)
  [c0e9dcd0] [c01c46a4] kasan_report+0xfc/0x180
  [c0e9dd10] [c0895150] memchr+0x24/0x74
  [c0e9dd30] [c00a9e58] msg_print_text+0x124/0x574
  [c0e9dde0] [c00ab730] console_unlock+0x114/0x4f8
  [c0e9de40] [c00adc80] vprintk_emit+0x188/0x1c4
  [c0e9de80] [c00ae3e4] printk+0xa8/0xcc
  [c0e9df20] [c0c27e44] early_irq_init+0x38/0x108
  [c0e9df50] [c0c15434] start_kernel+0x310/0x488
  [c0e9dff0] [00003484] 0x3484

Cc: stable@vger.kernel.org
Signed-off-by: default avatarChristophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
parent 39070a96
...@@ -730,6 +730,9 @@ fast_exception_return: ...@@ -730,6 +730,9 @@ fast_exception_return:
mtcr r10 mtcr r10
lwz r10,_LINK(r11) lwz r10,_LINK(r11)
mtlr r10 mtlr r10
/* Clear the exception_marker on the stack to avoid confusing stacktrace */
li r10, 0
stw r10, 8(r11)
REST_GPR(10, r11) REST_GPR(10, r11)
#if defined(CONFIG_PPC_8xx) && defined(CONFIG_PERF_EVENTS) #if defined(CONFIG_PPC_8xx) && defined(CONFIG_PERF_EVENTS)
mtspr SPRN_NRI, r0 mtspr SPRN_NRI, r0
...@@ -961,6 +964,9 @@ END_FTR_SECTION_IFSET(CPU_FTR_NEED_PAIRED_STWCX) ...@@ -961,6 +964,9 @@ END_FTR_SECTION_IFSET(CPU_FTR_NEED_PAIRED_STWCX)
mtcrf 0xFF,r10 mtcrf 0xFF,r10
mtlr r11 mtlr r11
/* Clear the exception_marker on the stack to avoid confusing stacktrace */
li r10, 0
stw r10, 8(r1)
/* /*
* Once we put values in SRR0 and SRR1, we are in a state * Once we put values in SRR0 and SRR1, we are in a state
* where exceptions are not recoverable, since taking an * where exceptions are not recoverable, since taking an
...@@ -997,6 +1003,9 @@ exc_exit_restart_end: ...@@ -997,6 +1003,9 @@ exc_exit_restart_end:
mtlr r11 mtlr r11
lwz r10,_CCR(r1) lwz r10,_CCR(r1)
mtcrf 0xff,r10 mtcrf 0xff,r10
/* Clear the exception_marker on the stack to avoid confusing stacktrace */
li r10, 0
stw r10, 8(r1)
REST_2GPRS(9, r1) REST_2GPRS(9, r1)
.globl exc_exit_restart .globl exc_exit_restart
exc_exit_restart: exc_exit_restart:
......
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