diff options
Diffstat (limited to 'target/linux/generic/patches-4.9/040-03-MIPS-Only-change-28-to-thread_info-if-coming-from-us.patch')
| -rw-r--r-- | target/linux/generic/patches-4.9/040-03-MIPS-Only-change-28-to-thread_info-if-coming-from-us.patch | 48 |
1 files changed, 48 insertions, 0 deletions
diff --git a/target/linux/generic/patches-4.9/040-03-MIPS-Only-change-28-to-thread_info-if-coming-from-us.patch b/target/linux/generic/patches-4.9/040-03-MIPS-Only-change-28-to-thread_info-if-coming-from-us.patch new file mode 100644 index 0000000..e13c67b --- /dev/null +++ b/target/linux/generic/patches-4.9/040-03-MIPS-Only-change-28-to-thread_info-if-coming-from-us.patch @@ -0,0 +1,48 @@ +From: Matt Redfearn <matt.redfearn@imgtec.com> +Date: Mon, 19 Dec 2016 14:20:58 +0000 +Subject: [PATCH] MIPS: Only change $28 to thread_info if coming from user + mode + +The SAVE_SOME macro is used to save the execution context on all +exceptions. +If an exception occurs while executing user code, the stack is switched +to the kernel's stack for the current task, and register $28 is switched +to point to the current_thread_info, which is at the bottom of the stack +region. +If the exception occurs while executing kernel code, the stack is left, +and this change ensures that register $28 is not updated. This is the +correct behaviour when the kernel can be executing on the separate irq +stack, because the thread_info will not be at the base of it. + +With this change, register $28 is only switched to it's kernel +conventional usage of the currrent thread info pointer at the point at +which execution enters kernel space. Doing it on every exception was +redundant, but OK without an IRQ stack, but will be erroneous once that +is introduced. + +Signed-off-by: Matt Redfearn <matt.redfearn@imgtec.com> +Reviewed-by: Maciej W. Rozycki <macro@imgtec.com> +--- + +--- a/arch/mips/include/asm/stackframe.h ++++ b/arch/mips/include/asm/stackframe.h +@@ -216,12 +216,19 @@ + LONG_S $25, PT_R25(sp) + LONG_S $28, PT_R28(sp) + LONG_S $31, PT_R31(sp) ++ ++ /* Set thread_info if we're coming from user mode */ ++ mfc0 k0, CP0_STATUS ++ sll k0, 3 /* extract cu0 bit */ ++ bltz k0, 9f ++ + ori $28, sp, _THREAD_MASK + xori $28, _THREAD_MASK + #ifdef CONFIG_CPU_CAVIUM_OCTEON + .set mips64 + pref 0, 0($28) /* Prefetch the current pointer */ + #endif ++9: + .set pop + .endm + |