137 lines
5 KiB
Text
137 lines
5 KiB
Text
Index: libavutil/aarch64/asm.S
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--- libavutil/aarch64/asm.S.orig
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+++ libavutil/aarch64/asm.S
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@@ -36,6 +36,125 @@
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# define __has_feature(x) 0
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#endif
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+
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+/* Support macros for
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+ * - Armv8.3-A Pointer Authentication and
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+ * - Armv8.5-A Branch Target Identification
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+ * features which require emitting a .note.gnu.property section with the
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+ * appropriate architecture-dependent feature bits set.
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+ *
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+ * |AARCH64_SIGN_LINK_REGISTER| and |AARCH64_VALIDATE_LINK_REGISTER| expand to
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+ * PACIxSP and AUTIxSP, respectively. |AARCH64_SIGN_LINK_REGISTER| should be
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+ * used immediately before saving the LR register (x30) to the stack.
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+ * |AARCH64_VALIDATE_LINK_REGISTER| should be used immediately after restoring
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+ * it. Note |AARCH64_SIGN_LINK_REGISTER|'s modifications to LR must be undone
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+ * with |AARCH64_VALIDATE_LINK_REGISTER| before RET. The SP register must also
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+ * have the same value at the two points. For example:
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+ *
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+ * .global f
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+ * f:
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+ * AARCH64_SIGN_LINK_REGISTER
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+ * stp x29, x30, [sp, #-96]!
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+ * mov x29, sp
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+ * ...
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+ * ldp x29, x30, [sp], #96
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+ * AARCH64_VALIDATE_LINK_REGISTER
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+ * ret
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+ *
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+ * |AARCH64_VALID_CALL_TARGET| expands to BTI 'c'. Either it, or
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+ * |AARCH64_SIGN_LINK_REGISTER|, must be used at every point that may be an
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+ * indirect call target. In particular, all symbols exported from a file must
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+ * begin with one of these macros. For example, a leaf function that does not
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+ * save LR can instead use |AARCH64_VALID_CALL_TARGET|:
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+ *
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+ * .globl return_zero
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+ * return_zero:
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+ * AARCH64_VALID_CALL_TARGET
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+ * mov x0, #0
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+ * ret
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+ *
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+ * A non-leaf function which does not immediately save LR may need both macros
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+ * because |AARCH64_SIGN_LINK_REGISTER| appears late. For example, the function
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+ * may jump to an alternate implementation before setting up the stack:
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+ *
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+ * .globl with_early_jump
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+ * with_early_jump:
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+ * AARCH64_VALID_CALL_TARGET
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+ * cmp x0, #128
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+ * b.lt .Lwith_early_jump_128
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+ * AARCH64_SIGN_LINK_REGISTER
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+ * stp x29, x30, [sp, #-96]!
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+ * mov x29, sp
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+ * ...
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+ * ldp x29, x30, [sp], #96
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+ * AARCH64_VALIDATE_LINK_REGISTER
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+ * ret
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+ *
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+ * .Lwith_early_jump_128:
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+ * ...
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+ * ret
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+ *
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+ * These annotations are only required with indirect calls. Private symbols that
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+ * are only the target of direct calls do not require annotations. Also note
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+ * that |AARCH64_VALID_CALL_TARGET| is only valid for indirect calls (BLR), not
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+ * indirect jumps (BR). Indirect jumps in assembly are supported through
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+ * |AARCH64_VALID_JUMP_TARGET|. Landing Pads which shall serve for jumps and
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+ * calls can be created using |AARCH64_VALID_JUMP_CALL_TARGET|.
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+ *
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+ * Although not necessary, it is safe to use these macros in 32-bit ARM
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+ * assembly. This may be used to simplify dual 32-bit and 64-bit files.
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+ *
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+ * References:
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+ * - "ELF for the Arm® 64-bit Architecture"
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+ * https: *github.com/ARM-software/abi-aa/blob/master/aaelf64/aaelf64.rst
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+ * - "Providing protection for complex software"
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+ * https://developer.arm.com/architectures/learn-the-architecture/providing-protection-for-complex-software
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+ */
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+#if defined(__ARM_FEATURE_BTI_DEFAULT) && (__ARM_FEATURE_BTI_DEFAULT == 1)
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+# define GNU_PROPERTY_AARCH64_BTI (1 << 0) // Has BTI
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+# define AARCH64_VALID_CALL_TARGET hint #34 // BTI 'c'
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+# define AARCH64_VALID_JUMP_TARGET hint #38 // BTI 'j'
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+#else
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+# define GNU_PROPERTY_AARCH64_BTI 0 // No BTI
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+# define AARCH64_VALID_CALL_TARGET
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+# define AARCH64_VALID_JUMP_TARGET
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+#endif
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+
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+#if defined(__ARM_FEATURE_PAC_DEFAULT)
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+# if ((__ARM_FEATURE_PAC_DEFAULT & (1 << 0)) != 0) // authentication using key A
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+# define AARCH64_SIGN_LINK_REGISTER paciasp
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+# define AARCH64_VALIDATE_LINK_REGISTER autiasp
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+# elif ((__ARM_FEATURE_PAC_DEFAULT & (1 << 1)) != 0) // authentication using key B
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+# define AARCH64_SIGN_LINK_REGISTER pacibsp
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+# define AARCH64_VALIDATE_LINK_REGISTER autibsp
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+# else
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+# error Pointer authentication defines no valid key!
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+# endif
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+# if ((__ARM_FEATURE_PAC_DEFAULT & (1 << 2)) != 0)
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+# error Authentication of leaf functions is enabled but not supported in FFmpeg!
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+# endif
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+# define GNU_PROPERTY_AARCH64_PAC (1 << 1)
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+#else
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+# define GNU_PROPERTY_AARCH64_PAC 0
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+# define AARCH64_SIGN_LINK_REGISTER
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+# define AARCH64_VALIDATE_LINK_REGISTER
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+#endif
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+
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+
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+#if (GNU_PROPERTY_AARCH64_BTI != 0 || GNU_PROPERTY_AARCH64_PAC != 0)
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+ .pushsection .note.gnu.property, "a"
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+ .balign 8
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+ .long 4
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+ .long 0x10
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+ .long 0x5
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+ .asciz "GNU"
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+ .long 0xc0000000 /* GNU_PROPERTY_AARCH64_FEATURE_1_AND */
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+ .long 4
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+ .long (GNU_PROPERTY_AARCH64_BTI | GNU_PROPERTY_AARCH64_PAC)
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+ .long 0
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+ .popsection
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+#endif
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+
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.macro function name, export=0, align=2
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.macro endfunc
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ELF .size \name, . - \name
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@@ -49,6 +168,7 @@ FUNC .endfunc
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ELF .type EXTERN_ASM\name, %function
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FUNC .func EXTERN_ASM\name
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EXTERN_ASM\name:
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+ AARCH64_VALID_CALL_TARGET
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.else
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ELF .type \name, %function
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FUNC .func \name
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