diff options
Diffstat (limited to 'target/linux/brcm2708/patches-4.9/950-0149-Update-vfpmodule.c.patch')
| -rw-r--r-- | target/linux/brcm2708/patches-4.9/950-0149-Update-vfpmodule.c.patch | 137 |
1 files changed, 137 insertions, 0 deletions
diff --git a/target/linux/brcm2708/patches-4.9/950-0149-Update-vfpmodule.c.patch b/target/linux/brcm2708/patches-4.9/950-0149-Update-vfpmodule.c.patch new file mode 100644 index 0000000..16d740a --- /dev/null +++ b/target/linux/brcm2708/patches-4.9/950-0149-Update-vfpmodule.c.patch @@ -0,0 +1,137 @@ +From aa00ca3b0296c40a6b5a1ad32258d5b655a28c70 Mon Sep 17 00:00:00 2001 +From: Claggy3 <stephen.maclagan@hotmail.com> +Date: Sat, 11 Feb 2017 14:00:30 +0000 +Subject: [PATCH] Update vfpmodule.c + +Christopher Alexander Tobias Schulze - May 2, 2015, 11:57 a.m. +This patch fixes a problem with VFP state save and restore related +to exception handling (panic with message "BUG: unsupported FP +instruction in kernel mode") present on VFP11 floating point units +(as used with ARM1176JZF-S CPUs, e.g. on first generation Raspberry +Pi boards). This patch was developed and discussed on + + https://github.com/raspberrypi/linux/issues/859 + +A precondition to see the crashes is that floating point exception +traps are enabled. In this case, the VFP11 might determine that a FPU +operation needs to trap at a point in time when it is not possible to +signal this to the ARM11 core any more. The VFP11 will then set the +FPEXC.EX bit and store the trapped opcode in FPINST. (In some cases, +a second opcode might have been accepted by the VFP11 before the +exception was detected and could be reported to the ARM11 - in this +case, the VFP11 also sets FPEXC.FP2V and stores the second opcode in +FPINST2.) + +If FPEXC.EX is set, the VFP11 will "bounce" the next FPU opcode issued +by the ARM11 CPU, which will be seen by the ARM11 as an undefined opcode +trap. The VFP support code examines the FPEXC.EX and FPEXC.FP2V bits +to decide what actions to take, i.e., whether to emulate the opcodes +found in FPINST and FPINST2, and whether to retry the bounced instruction. + +If a user space application has left the VFP11 in this "pending trap" +state, the next FPU opcode issued to the VFP11 might actually be the +VSTMIA operation vfp_save_state() uses to store the FPU registers +to memory (in our test cases, when building the signal stack frame). +In this case, the kernel crashes as described above. + +This patch fixes the problem by making sure that vfp_save_state() is +always entered with FPEXC.EX cleared. (The current value of FPEXC has +already been saved, so this does not corrupt the context. Clearing +FPEXC.EX has no effects on FPINST or FPINST2. Also note that many +callers already modify FPEXC by setting FPEXC.EN before invoking +vfp_save_state().) + +This patch also addresses a second problem related to FPEXC.EX: After +returning from signal handling, the kernel reloads the VFP context +from the user mode stack. However, the current code explicitly clears +both FPEXC.EX and FPEXC.FP2V during reload. As VFP11 requires these +bits to be preserved, this patch disables clearing them for VFP +implementations belonging to architecture 1. There should be no +negative side effects: the user can set both bits by executing FPU +opcodes anyway, and while user code may now place arbitrary values +into FPINST and FPINST2 (e.g., non-VFP ARM opcodes) the VFP support +code knows which instructions can be emulated, and rejects other +opcodes with "unhandled bounce" messages, so there should be no +security impact from allowing reloading FPEXC.EX and FPEXC.FP2V. + +Signed-off-by: Christopher Alexander Tobias Schulze <cat.schulze@alice-dsl.net> +--- + arch/arm/vfp/vfpmodule.c | 25 +++++++++++++++++++------ + 1 file changed, 19 insertions(+), 6 deletions(-) + +--- a/arch/arm/vfp/vfpmodule.c ++++ b/arch/arm/vfp/vfpmodule.c +@@ -179,8 +179,11 @@ static int vfp_notifier(struct notifier_ + * case the thread migrates to a different CPU. The + * restoring is done lazily. + */ +- if ((fpexc & FPEXC_EN) && vfp_current_hw_state[cpu]) ++ if ((fpexc & FPEXC_EN) && vfp_current_hw_state[cpu]) { ++ /* vfp_save_state oopses on VFP11 if EX bit set */ ++ fmxr(FPEXC, fpexc & ~FPEXC_EX); + vfp_save_state(vfp_current_hw_state[cpu], fpexc); ++ } + #endif + + /* +@@ -463,13 +466,16 @@ static int vfp_pm_suspend(void) + /* if vfp is on, then save state for resumption */ + if (fpexc & FPEXC_EN) { + pr_debug("%s: saving vfp state\n", __func__); ++ /* vfp_save_state oopses on VFP11 if EX bit set */ ++ fmxr(FPEXC, fpexc & ~FPEXC_EX); + vfp_save_state(&ti->vfpstate, fpexc); + + /* disable, just in case */ + fmxr(FPEXC, fmrx(FPEXC) & ~FPEXC_EN); + } else if (vfp_current_hw_state[ti->cpu]) { + #ifndef CONFIG_SMP +- fmxr(FPEXC, fpexc | FPEXC_EN); ++ /* vfp_save_state oopses on VFP11 if EX bit set */ ++ fmxr(FPEXC, (fpexc & ~FPEXC_EX) | FPEXC_EN); + vfp_save_state(vfp_current_hw_state[ti->cpu], fpexc); + fmxr(FPEXC, fpexc); + #endif +@@ -532,7 +538,8 @@ void vfp_sync_hwstate(struct thread_info + /* + * Save the last VFP state on this CPU. + */ +- fmxr(FPEXC, fpexc | FPEXC_EN); ++ /* vfp_save_state oopses on VFP11 if EX bit set */ ++ fmxr(FPEXC, (fpexc & ~FPEXC_EX) | FPEXC_EN); + vfp_save_state(&thread->vfpstate, fpexc | FPEXC_EN); + fmxr(FPEXC, fpexc); + } +@@ -604,6 +611,7 @@ int vfp_restore_user_hwstate(struct user + struct vfp_hard_struct *hwstate = &thread->vfpstate.hard; + unsigned long fpexc; + int err = 0; ++ u32 fpsid = fmrx(FPSID); + + /* Disable VFP to avoid corrupting the new thread state. */ + vfp_flush_hwstate(thread); +@@ -627,8 +635,12 @@ int vfp_restore_user_hwstate(struct user + /* Ensure the VFP is enabled. */ + fpexc |= FPEXC_EN; + +- /* Ensure FPINST2 is invalid and the exception flag is cleared. */ +- fpexc &= ~(FPEXC_EX | FPEXC_FP2V); ++ /* Mask FPXEC_EX and FPEXC_FP2V if not required by VFP arch */ ++ if ((fpsid & FPSID_ARCH_MASK) != (1 << FPSID_ARCH_BIT)) { ++ /* Ensure FPINST2 is invalid and the exception flag is cleared. */ ++ fpexc &= ~(FPEXC_EX | FPEXC_FP2V); ++ } ++ + hwstate->fpexc = fpexc; + + __get_user_error(hwstate->fpinst, &ufp_exc->fpinst, err); +@@ -698,7 +710,8 @@ void kernel_neon_begin(void) + cpu = get_cpu(); + + fpexc = fmrx(FPEXC) | FPEXC_EN; +- fmxr(FPEXC, fpexc); ++ /* vfp_save_state oopses on VFP11 if EX bit set */ ++ fmxr(FPEXC, fpexc & ~FPEXC_EX); + + /* + * Save the userland NEON/VFP state. Under UP, |