ARM: 9044/1: vfp: use undef hook for VFP support detection

BugLink: https://bugs.launchpad.net/bugs/1923214
commit 3cce9d44321e460e7c88cdec4e4537a6e9ad7c0d upstream.

Commit f77ac2e378be9dd6 ("ARM: 9030/1: entry: omit FP emulation for UND
exceptions taken in kernel mode") failed to take into account that there
is in fact a case where we relied on this code path: during boot, the
VFP detection code issues a read of FPSID, which will trigger an undef
exception on cores that lack VFP support.

So let's reinstate this logic using an undef hook which is registered
only for the duration of the initcall to vpf_init(), and which sets
VFP_arch to a non-zero value - as before - if no VFP support is present.

Fixes: f77ac2e378be9dd6 ("ARM: 9030/1: entry: omit FP emulation for UND ...")
Reported-by: "kernelci.org bot" <bot@kernelci.org>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>

diff --git a/arch/arm/vfp/entry.S b/arch/arm/vfp/entry.S
index 0186cf9da890bcab8af516b2f5234128ae3b6f38..27b0a1f27fbdf392e882d049045fd8102fe31b6e 100644 (file)
--- a/arch/arm/vfp/entry.S
+++ b/arch/arm/vfp/entry.S
@@ -37,20 +37,3 @@ ENDPROC(vfp_null_entry)
        .align  2
 .LCvfp:
        .word   vfp_vector
-
-@ This code is called if the VFP does not exist. It needs to flag the
-@ failure to the VFP initialisation code.
-
-       __INIT
-ENTRY(vfp_testing_entry)
-       dec_preempt_count_ti r10, r4
-       ldr     r0, VFP_arch_address
-       str     r0, [r0]                @ set to non-zero value
-       ret     r9                      @ we have handled the fault
-ENDPROC(vfp_testing_entry)
-
-       .align  2
-VFP_arch_address:
-       .word   VFP_arch
-
-       __FINIT

diff --git a/arch/arm/vfp/vfpmodule.c b/arch/arm/vfp/vfpmodule.c
index c3b6451c18bdae5a3f9ce1228a45fba12c4f6a4f..2cb355c1b5b71694082caa306465996efa96e532 100644 (file)
--- a/arch/arm/vfp/vfpmodule.c
+++ b/arch/arm/vfp/vfpmodule.c
@@ -32,7 +32,6 @@
 /*
  * Our undef handlers (in entry.S)
  */
-asmlinkage void vfp_testing_entry(void);
 asmlinkage void vfp_support_entry(void);
 asmlinkage void vfp_null_entry(void);
 
@@ -43,7 +42,7 @@ asmlinkage void (*vfp_vector)(void) = vfp_null_entry;
  * Used in startup: set to non-zero if VFP checks fail
  * After startup, holds VFP architecture
  */
-unsigned int VFP_arch;
+static unsigned int __initdata VFP_arch;
 
 /*
  * The pointer to the vfpstate structure of the thread which currently
@@ -437,7 +436,7 @@ static void vfp_enable(void *unused)
  * present on all CPUs within a SMP complex. Needs to be called prior to
  * vfp_init().
  */
-void vfp_disable(void)
+void __init vfp_disable(void)
 {
        if (VFP_arch) {
                pr_debug("%s: should be called prior to vfp_init\n", __func__);
@@ -707,7 +706,7 @@ static int __init vfp_kmode_exception_hook_init(void)
                register_undef_hook(&vfp_kmode_exception_hook[i]);
        return 0;
 }
-core_initcall(vfp_kmode_exception_hook_init);
+subsys_initcall(vfp_kmode_exception_hook_init);
 
 /*
  * Kernel-side NEON support functions
@@ -753,6 +752,21 @@ EXPORT_SYMBOL(kernel_neon_end);
 
 #endif /* CONFIG_KERNEL_MODE_NEON */
 
+static int __init vfp_detect(struct pt_regs *regs, unsigned int instr)
+{
+       VFP_arch = UINT_MAX;    /* mark as not present */
+       regs->ARM_pc += 4;
+       return 0;
+}
+
+static struct undef_hook vfp_detect_hook __initdata = {
+       .instr_mask     = 0x0c000e00,
+       .instr_val      = 0x0c000a00,
+       .cpsr_mask      = MODE_MASK,
+       .cpsr_val       = SVC_MODE,
+       .fn             = vfp_detect,
+};
+
 /*
  * VFP support code initialisation.
  */
@@ -773,10 +787,11 @@ static int __init vfp_init(void)
         * The handler is already setup to just log calls, so
         * we just need to read the VFPSID register.
         */
-       vfp_vector = vfp_testing_entry;
+       register_undef_hook(&vfp_detect_hook);
        barrier();
        vfpsid = fmrx(FPSID);
        barrier();
+       unregister_undef_hook(&vfp_detect_hook);
        vfp_vector = vfp_null_entry;
 
        pr_info("VFP support v0.3: ");