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126 lines
4.2 KiB
Diff
126 lines
4.2 KiB
Diff
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From aaa1a0a5912d9e5d571e5f1c6f09ceac99544ab5 Mon Sep 17 00:00:00 2001
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From: Richard Sandiford <richard.sandiford@arm.com>
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Date: Tue, 12 Sep 2023 16:07:18 +0100
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Subject: [PATCH 27/32] aarch64: Tweak stack clash boundary condition
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The AArch64 ABI says that, when stack clash protection is used,
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there can be a maximum of 1KiB of unprobed space at sp on entry
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to a function. Therefore, we need to probe when allocating
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>= guard_size - 1KiB of data (>= rather than >). This is what
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GCC does.
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If an allocation is exactly guard_size bytes, it is enough to allocate
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those bytes and probe once at offset 1024. It isn't possible to use a
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single probe at any other offset: higher would conmplicate later code,
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by leaving more unprobed space than usual, while lower would risk
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leaving an entire page unprobed. For simplicity, the code probes all
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allocations at offset 1024.
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Some register saves also act as probes. If we need to allocate
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more space below the last such register save probe, we need to
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probe the allocation if it is > 1KiB. Again, this allocation is
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then sometimes (but not always) probed at offset 1024. This sort of
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allocation is currently only used for outgoing arguments, which are
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rarely this big.
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However, the code also probed if this final outgoing-arguments
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allocation was == 1KiB, rather than just > 1KiB. This isn't
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necessary, since the register save then probes at offset 1024
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as required. Continuing to probe allocations of exactly 1KiB
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would complicate later patches.
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gcc/
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* config/aarch64/aarch64.cc (aarch64_allocate_and_probe_stack_space):
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Don't probe final allocations that are exactly 1KiB in size (after
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unprobed space above the final allocation has been deducted).
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gcc/testsuite/
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* gcc.target/aarch64/stack-check-prologue-17.c: New test.
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---
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gcc/config/aarch64/aarch64.cc | 4 +-
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.../aarch64/stack-check-prologue-17.c | 55 +++++++++++++++++++
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2 files changed, 58 insertions(+), 1 deletion(-)
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create mode 100644 gcc/testsuite/gcc.target/aarch64/stack-check-prologue-17.c
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diff --git a/gcc/config/aarch64/aarch64.cc b/gcc/config/aarch64/aarch64.cc
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index 1aa79da0673c..5cad847977a4 100644
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--- a/gcc/config/aarch64/aarch64.cc
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+++ b/gcc/config/aarch64/aarch64.cc
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@@ -9648,9 +9648,11 @@ aarch64_allocate_and_probe_stack_space (rtx temp1, rtx temp2,
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HOST_WIDE_INT guard_size
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= 1 << param_stack_clash_protection_guard_size;
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HOST_WIDE_INT guard_used_by_caller = STACK_CLASH_CALLER_GUARD;
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+ HOST_WIDE_INT byte_sp_alignment = STACK_BOUNDARY / BITS_PER_UNIT;
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+ gcc_assert (multiple_p (poly_size, byte_sp_alignment));
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HOST_WIDE_INT min_probe_threshold
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= (final_adjustment_p
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- ? guard_used_by_caller
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+ ? guard_used_by_caller + byte_sp_alignment
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: guard_size - guard_used_by_caller);
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/* When doing the final adjustment for the outgoing arguments, take into
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account any unprobed space there is above the current SP. There are
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diff --git a/gcc/testsuite/gcc.target/aarch64/stack-check-prologue-17.c b/gcc/testsuite/gcc.target/aarch64/stack-check-prologue-17.c
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new file mode 100644
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index 000000000000..0d8a25d73a24
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--- /dev/null
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+++ b/gcc/testsuite/gcc.target/aarch64/stack-check-prologue-17.c
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@@ -0,0 +1,55 @@
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+/* { dg-options "-O2 -fstack-clash-protection -fomit-frame-pointer --param stack-clash-protection-guard-size=12" } */
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+/* { dg-final { check-function-bodies "**" "" } } */
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+
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+void f(int, ...);
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+void g();
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+
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+/*
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+** test1:
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+** ...
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+** str x30, \[sp\]
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+** sub sp, sp, #1024
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+** cbnz w0, .*
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+** bl g
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+** ...
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+*/
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+int test1(int z) {
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+ __uint128_t x = 0;
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+ int y[0x400];
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+ if (z)
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+ {
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+ f(0, 0, 0, 0, 0, 0, 0, &y,
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+ x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x,
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+ x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x,
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+ x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x,
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+ x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x);
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+ }
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+ g();
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+ return 1;
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+}
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+
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+/*
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+** test2:
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+** ...
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+** str x30, \[sp\]
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+** sub sp, sp, #1040
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+** str xzr, \[sp\]
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+** cbnz w0, .*
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+** bl g
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+** ...
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+*/
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+int test2(int z) {
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+ __uint128_t x = 0;
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+ int y[0x400];
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+ if (z)
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+ {
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+ f(0, 0, 0, 0, 0, 0, 0, &y,
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+ x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x,
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+ x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x,
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+ x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x,
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+ x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x,
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+ x);
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+ }
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+ g();
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+ return 1;
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+}
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--
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2.42.0
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