On Mon, Mar 11, 2024 at 10:37 PM Sami Tolvanen [off-list ref] wrote:

On Mon, Mar 11, 2024 at 7:51 PM Linus Walleij [off-list ref] wrote:

quoted

On Mon, Mar 11, 2024 at 4:35 PM Sami Tolvanen [off-list ref] wrote:

quoted

On Mon, Mar 11, 2024 at 3:04 AM Ard Biesheuvel [off-list ref] wrote:

quoted

This works for some function attributes (e.g., __efiapi is used like
this), but the attribute specifier to which __nocfi resolves does not
appear to be usable in the same manner.

Best would be to annotate the asm code using
SYM_TYPED_FUNC_START/_END, so that the CFI machinery is invoked at the
call site to validate the function type of the destination.

Agreed, ideally we would annotate indirectly called assembly functions
with CFI types and avoid __nocfi wrappers.

I'm taking a stab at SYM_TYPED_FUNC_* for ARM, as we don't have them
yet.

Does the default implementation in include/linux/cfi_types.h not work
on arm for some reason?

For example I try to switch over the TLB symbols like this:

diff --git a/arch/arm/mm/proc-macros.S b/arch/arm/mm/proc-macros.S
index e43f6d716b4b..bbe47ca32e55 100644
--- a/arch/arm/mm/proc-macros.S
+++ b/arch/arm/mm/proc-macros.S

@@ -341,7 +341,7 @@ ENTRY(\name\()_cache_fns)
 .macro define_tlb_functions name:req, flags_up:req, flags_smp
        .type   \name\()_tlb_fns, #object
        .align 2
-ENTRY(\name\()_tlb_fns)
+SYM_TYPED_FUNC_START(\name\()_tlb_fns)
        .long   \name\()_flush_user_tlb_range
        .long   \name\()_flush_kern_tlb_range
        .ifnb \flags_smp

diff --git a/arch/arm/mm/tlb-v7.S b/arch/arm/mm/tlb-v7.S
index 35fd6d4f0d03..aff9d884c30d 100644
--- a/arch/arm/mm/tlb-v7.S
+++ b/arch/arm/mm/tlb-v7.S

@@ -10,6 +10,7 @@
  */
 #include <linux/init.h>
 #include <linux/linkage.h>
+#include <linux/cfi_types.h>
 #include <asm/assembler.h>
 #include <asm/asm-offsets.h>
 #include <asm/page.h>

@@ -31,7 +32,7 @@
  *     - the "Invalidate single entry" instruction will invalidate
  *       both the I and the D TLBs on Harvard-style TLBs
  */
-ENTRY(v7wbi_flush_user_tlb_range)
+SYM_TYPED_FUNC_START(v7wbi_flush_user_tlb_range)
        vma_vm_mm r3, r2                        @ get vma->vm_mm
        mmid    r3, r3                          @ get vm_mm->context.id
        dsb     ish

@@ -57,7 +58,7 @@ ENTRY(v7wbi_flush_user_tlb_range)
        blo     1b
        dsb     ish
        ret     lr
-ENDPROC(v7wbi_flush_user_tlb_range)
+SYM_FUNC_END(v7wbi_flush_user_tlb_range)

 /*
  *     v7wbi_flush_kern_tlb_range(start,end)

@@ -67,7 +68,7 @@ ENDPROC(v7wbi_flush_user_tlb_range)
  *     - start - start address (may not be aligned)
  *     - end   - end address (exclusive, may not be aligned)
  */
-ENTRY(v7wbi_flush_kern_tlb_range)
+SYM_TYPED_FUNC_START(v7wbi_flush_kern_tlb_range)
        dsb     ish
        mov     r0, r0, lsr #PAGE_SHIFT         @ align address
        mov     r1, r1, lsr #PAGE_SHIFT

@@ -86,7 +87,7 @@ ENTRY(v7wbi_flush_kern_tlb_range)
        dsb     ish
        isb
        ret     lr
-ENDPROC(v7wbi_flush_kern_tlb_range)
+SYM_FUNC_END(v7wbi_flush_kern_tlb_range)

        __INIT

Compiling results in:

  AR      vmlinux.a
  LD      vmlinux.o
  OBJCOPY modules.builtin.modinfo
  GEN     modules.builtin
  MODPOST vmlinux.symvers
  UPD     include/generated/utsversion.h
  CC      init/version-timestamp.o
  LD      .tmp_vmlinux.kallsyms1
ld.lld: error: undefined symbol: __kcfi_typeid_v7wbi_flush_user_tlb_range

quoted

quoted

referenced by arch/arm/mm/tlb-v7.o:(.text+0x0) in archive vmlinux.a

ld.lld: error: undefined symbol: __kcfi_typeid_v7wbi_flush_kern_tlb_range

quoted

quoted

referenced by tlb-v7.S:60 (/mnt/storage/linus/linux-integrator/build-vexpress/../arch/arm/mm/tlb-v7.S:60)
              arch/arm/mm/tlb-v7.o:(.text+0x40) in archive vmlinux.a

ld.lld: error: undefined symbol: __kcfi_typeid_v7wbi_tlb_fns

quoted

quoted

referenced by arch/arm/mm/tlb-v7.o:(.init.text+0x0) in archive vmlinux.a

Yours,
Linus Walleij

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