91e0fc0bf4
gcc-8.1 for xtensa miscompiles uClibc dynamic linker due to gcc PR
target/65416. The build completes successfully, but the binary is
non-functional because the following fragment in the _dl_get_ready_to_run
in ld-uClibc.so overwrites register spill area on stack causing register
corruption in the previous call frame and a subsequent crash:
419f: f0c1b2 addi a11, a1, -16
41a2: 1ba9 s32i.n a10, a11, 4
41a4: 0bc9 s32i.n a12, a11, 0
41a6: 5127f2 l32i a15, a7, 0x144
41a9: 1765b2 s32i a11, a5, 92
41ac: 4e2782 l32i a8, a7, 0x138
41af: 146af2 s32i a15, a10, 80
41b2: 001b10 movsp a1, a11
The crash terminates the init process and causes kernel panic.
The fix prevents reordering of movsp opcode and any access to the stack
frame memory and is applicable to all existing gcc versions.
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
102 lines
3.0 KiB
Diff
102 lines
3.0 KiB
Diff
From 87fda0741d210727672cba5e54a37a189e8ac04e Mon Sep 17 00:00:00 2001
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From: Max Filippov <jcmvbkbc@gmail.com>
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Date: Sun, 17 Jun 2018 21:18:39 -0700
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Subject: [PATCH] xtensa: fix PR target/65416
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The issue is caused by reordering of stack pointer update after stack
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space allocation with instructions that write to the allocated stack
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space. In windowed ABI register spill area for the previous call frame
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is located just below the stack pointer and may be reloaded back into
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the register file on movsp.
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Implement allocate_stack pattern for windowed ABI configuration and
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insert an instruction that prevents reordering of frame memory access
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and stack pointer update.
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gcc/
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2018-06-19 Max Filippov <jcmvbkbc@gmail.com>
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* config/xtensa/xtensa.md (UNSPEC_FRAME_BLOCKAGE): New unspec
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constant.
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(allocate_stack, frame_blockage, *frame_blockage): New patterns.
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Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
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Backported from: r261755
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---
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gcc/config/xtensa/xtensa.md | 46 +++++++++++++++++++++++++++++++++++++++++++++
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1 file changed, 46 insertions(+)
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diff --git a/gcc/config/xtensa/xtensa.md b/gcc/config/xtensa/xtensa.md
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index 84967dbedc08..209f839cfb0f 100644
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--- a/gcc/config/xtensa/xtensa.md
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+++ b/gcc/config/xtensa/xtensa.md
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@@ -38,6 +38,7 @@
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(UNSPEC_MEMW 11)
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(UNSPEC_LSETUP_START 12)
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(UNSPEC_LSETUP_END 13)
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+ (UNSPEC_FRAME_BLOCKAGE 14)
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(UNSPECV_SET_FP 1)
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(UNSPECV_ENTRY 2)
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@@ -1676,6 +1677,32 @@
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;; Miscellaneous instructions.
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+;; In windowed ABI stack pointer adjustment must happen before any access
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+;; to the space allocated on stack is allowed, otherwise register spill
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+;; area may be clobbered. That's what frame blockage is supposed to enforce.
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+
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+(define_expand "allocate_stack"
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+ [(set (match_operand 0 "nonimmed_operand")
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+ (minus (reg A1_REG) (match_operand 1 "add_operand")))
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+ (set (reg A1_REG)
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+ (minus (reg A1_REG) (match_dup 1)))]
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+ "TARGET_WINDOWED_ABI"
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+{
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+ if (CONST_INT_P (operands[1]))
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+ {
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+ rtx neg_op0 = GEN_INT (-INTVAL (operands[1]));
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+ emit_insn (gen_addsi3 (stack_pointer_rtx, stack_pointer_rtx, neg_op0));
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+ }
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+ else
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+ {
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+ emit_insn (gen_subsi3 (stack_pointer_rtx, stack_pointer_rtx,
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+ operands[1]));
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+ }
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+ emit_move_insn (operands[0], virtual_stack_dynamic_rtx);
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+ emit_insn (gen_frame_blockage ());
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+ DONE;
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+})
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+
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(define_expand "prologue"
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[(const_int 0)]
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""
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@@ -1767,6 +1794,25 @@
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[(set_attr "length" "0")
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(set_attr "type" "nop")])
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+;; Do not schedule instructions accessing memory before this point.
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+
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+(define_expand "frame_blockage"
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+ [(set (match_dup 0)
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+ (unspec:BLK [(match_dup 1)] UNSPEC_FRAME_BLOCKAGE))]
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+ ""
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+{
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+ operands[0] = gen_rtx_MEM (BLKmode, gen_rtx_SCRATCH (Pmode));
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+ MEM_VOLATILE_P (operands[0]) = 1;
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+ operands[1] = stack_pointer_rtx;
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+})
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+
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+(define_insn "*frame_blockage"
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+ [(set (match_operand:BLK 0 "" "")
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+ (unspec:BLK [(match_operand:SI 1 "" "")] UNSPEC_FRAME_BLOCKAGE))]
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+ ""
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+ ""
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+ [(set_attr "length" "0")])
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+
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(define_insn "trap"
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[(trap_if (const_int 1) (const_int 0))]
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""
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--
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2.11.0
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