4.4-stable review patch. If anyone has any objections, please let me know.
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From: Christophe Leroy christophe.leroy@c-s.fr
commit 9580b71b5a7863c24a9bd18bcd2ad759b86b1eff upstream.
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: Christophe Leroy christophe.leroy@c-s.fr Signed-off-by: Michael Ellerman mpe@ellerman.id.au Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- arch/powerpc/kernel/entry_32.S | 9 +++++++++ 1 file changed, 9 insertions(+)
--- a/arch/powerpc/kernel/entry_32.S +++ b/arch/powerpc/kernel/entry_32.S @@ -685,6 +685,9 @@ fast_exception_return: mtcr r10 lwz r10,_LINK(r11) mtlr r10 + /* Clear the exception_marker on the stack to avoid confusing stacktrace */ + li r10, 0 + stw r10, 8(r11) REST_GPR(10, r11) mtspr SPRN_SRR1,r9 mtspr SPRN_SRR0,r12 @@ -915,6 +918,9 @@ END_FTR_SECTION_IFSET(CPU_FTR_NEED_PAIRE mtcrf 0xFF,r10 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 * where exceptions are not recoverable, since taking an @@ -952,6 +958,9 @@ exc_exit_restart_end: mtlr r11 lwz r10,_CCR(r1) 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) .globl exc_exit_restart exc_exit_restart: