summaryrefslogtreecommitdiff
path: root/0197-Backport-SME-aarch64-Put-LR-save-probe-in-first-16-b.patch
diff options
context:
space:
mode:
Diffstat (limited to '0197-Backport-SME-aarch64-Put-LR-save-probe-in-first-16-b.patch')
-rw-r--r--0197-Backport-SME-aarch64-Put-LR-save-probe-in-first-16-b.patch409
1 files changed, 409 insertions, 0 deletions
diff --git a/0197-Backport-SME-aarch64-Put-LR-save-probe-in-first-16-b.patch b/0197-Backport-SME-aarch64-Put-LR-save-probe-in-first-16-b.patch
new file mode 100644
index 0000000..c848e19
--- /dev/null
+++ b/0197-Backport-SME-aarch64-Put-LR-save-probe-in-first-16-b.patch
@@ -0,0 +1,409 @@
+From ffd483dc6a2a4af495d56cf5ebdbbb3b9ca58820 Mon Sep 17 00:00:00 2001
+From: Richard Sandiford <richard.sandiford@arm.com>
+Date: Tue, 12 Sep 2023 16:05:11 +0100
+Subject: [PATCH 098/157] [Backport][SME] aarch64: Put LR save probe in first
+ 16 bytes
+
+Reference: https://gcc.gnu.org/git/?p=gcc.git;a=commit;h=fee0a18abfdd4874194abd149943fa7c77a29b7c
+
+-fstack-clash-protection uses the save of LR as a probe for the next
+allocation. The next allocation could be:
+
+* another part of the static frame, e.g. when allocating SVE save slots
+ or outgoing arguments
+
+* an alloca in the same function
+
+* an allocation made by a callee function
+
+However, when -fomit-frame-pointer is used, the LR save slot is placed
+above the other GPR save slots. It could therefore be up to 80 bytes
+above the base of the GPR save area (which is also the hard fp address).
+
+aarch64_allocate_and_probe_stack_space took this into account when
+deciding how much subsequent space could be allocated without needing
+a probe. However, it interacted badly with:
+
+ /* If doing a small final adjustment, we always probe at offset 0.
+ This is done to avoid issues when LR is not at position 0 or when
+ the final adjustment is smaller than the probing offset. */
+ else if (final_adjustment_p && rounded_size == 0)
+ residual_probe_offset = 0;
+
+which forces any allocation that is smaller than the guard page size
+to be probed at offset 0 rather than the usual offset 1024. It was
+therefore possible to construct cases in which we had:
+
+* a probe using LR at SP + 80 bytes (or some other value >= 16)
+* an allocation of the guard page size - 16 bytes
+* a probe at SP + 0
+
+which allocates guard page size + 64 consecutive unprobed bytes.
+
+This patch requires the LR probe to be in the first 16 bytes of the
+save area when stack clash protection is active. Doing it
+unconditionally would cause code-quality regressions.
+
+Putting LR before other registers prevents push/pop allocation
+when shadow call stacks are enabled, since LR is restored
+separately from the other callee-saved registers.
+
+The new comment doesn't say that the probe register is required
+to be LR, since a later patch removes that restriction.
+
+gcc/
+ * config/aarch64/aarch64.cc (aarch64_layout_frame): Ensure that
+ the LR save slot is in the first 16 bytes of the register save area.
+ Only form STP/LDP push/pop candidates if both registers are valid.
+ (aarch64_allocate_and_probe_stack_space): Remove workaround for
+ when LR was not in the first 16 bytes.
+
+gcc/testsuite/
+ * gcc.target/aarch64/stack-check-prologue-18.c: New test.
+ * gcc.target/aarch64/stack-check-prologue-19.c: Likewise.
+ * gcc.target/aarch64/stack-check-prologue-20.c: Likewise.
+---
+ gcc/config/aarch64/aarch64.cc | 72 ++++++-------
+ .../aarch64/stack-check-prologue-18.c | 100 ++++++++++++++++++
+ .../aarch64/stack-check-prologue-19.c | 100 ++++++++++++++++++
+ .../aarch64/stack-check-prologue-20.c | 3 +
+ 4 files changed, 233 insertions(+), 42 deletions(-)
+ create mode 100644 gcc/testsuite/gcc.target/aarch64/stack-check-prologue-18.c
+ create mode 100644 gcc/testsuite/gcc.target/aarch64/stack-check-prologue-19.c
+ create mode 100644 gcc/testsuite/gcc.target/aarch64/stack-check-prologue-20.c
+
+diff --git a/gcc/config/aarch64/aarch64.cc b/gcc/config/aarch64/aarch64.cc
+index ba92a23a7..1ba4c2f89 100644
+--- a/gcc/config/aarch64/aarch64.cc
++++ b/gcc/config/aarch64/aarch64.cc
+@@ -8873,26 +8873,34 @@ aarch64_layout_frame (void)
+ bool saves_below_hard_fp_p
+ = maybe_ne (frame.below_hard_fp_saved_regs_size, 0);
+ frame.bytes_below_hard_fp = offset;
++
++ auto allocate_gpr_slot = [&](unsigned int regno)
++ {
++ frame.reg_offset[regno] = offset;
++ if (frame.wb_push_candidate1 == INVALID_REGNUM)
++ frame.wb_push_candidate1 = regno;
++ else if (frame.wb_push_candidate2 == INVALID_REGNUM)
++ frame.wb_push_candidate2 = regno;
++ offset += UNITS_PER_WORD;
++ };
++
+ if (frame.emit_frame_chain)
+ {
+ /* FP and LR are placed in the linkage record. */
+- frame.reg_offset[R29_REGNUM] = offset;
+- frame.wb_push_candidate1 = R29_REGNUM;
+- frame.reg_offset[R30_REGNUM] = offset + UNITS_PER_WORD;
+- frame.wb_push_candidate2 = R30_REGNUM;
+- offset += 2 * UNITS_PER_WORD;
++ allocate_gpr_slot (R29_REGNUM);
++ allocate_gpr_slot (R30_REGNUM);
+ }
++ else if (flag_stack_clash_protection
++ && known_eq (frame.reg_offset[R30_REGNUM], SLOT_REQUIRED))
++ /* Put the LR save slot first, since it makes a good choice of probe
++ for stack clash purposes. The idea is that the link register usually
++ has to be saved before a call anyway, and so we lose little by
++ stopping it from being individually shrink-wrapped. */
++ allocate_gpr_slot (R30_REGNUM);
+
+ for (regno = R0_REGNUM; regno <= R30_REGNUM; regno++)
+ if (known_eq (frame.reg_offset[regno], SLOT_REQUIRED))
+- {
+- frame.reg_offset[regno] = offset;
+- if (frame.wb_push_candidate1 == INVALID_REGNUM)
+- frame.wb_push_candidate1 = regno;
+- else if (frame.wb_push_candidate2 == INVALID_REGNUM)
+- frame.wb_push_candidate2 = regno;
+- offset += UNITS_PER_WORD;
+- }
++ allocate_gpr_slot (regno);
+
+ poly_int64 max_int_offset = offset;
+ offset = aligned_upper_bound (offset, STACK_BOUNDARY / BITS_PER_UNIT);
+@@ -8970,10 +8978,13 @@ aarch64_layout_frame (void)
+ max_push_offset to 0, because no registers are popped at this time,
+ so callee_adjust cannot be adjusted. */
+ HOST_WIDE_INT max_push_offset = 0;
+- if (frame.wb_pop_candidate2 != INVALID_REGNUM)
+- max_push_offset = 512;
+- else if (frame.wb_pop_candidate1 != INVALID_REGNUM)
+- max_push_offset = 256;
++ if (frame.wb_pop_candidate1 != INVALID_REGNUM)
++ {
++ if (frame.wb_pop_candidate2 != INVALID_REGNUM)
++ max_push_offset = 512;
++ else
++ max_push_offset = 256;
++ }
+
+ HOST_WIDE_INT const_size, const_below_saved_regs, const_above_fp;
+ HOST_WIDE_INT const_saved_regs_size;
+@@ -9949,29 +9960,6 @@ aarch64_allocate_and_probe_stack_space (rtx temp1, rtx temp2,
+ = (final_adjustment_p
+ ? guard_used_by_caller + byte_sp_alignment
+ : guard_size - guard_used_by_caller);
+- /* When doing the final adjustment for the outgoing arguments, take into
+- account any unprobed space there is above the current SP. There are
+- two cases:
+-
+- - When saving SVE registers below the hard frame pointer, we force
+- the lowest save to take place in the prologue before doing the final
+- adjustment (i.e. we don't allow the save to be shrink-wrapped).
+- This acts as a probe at SP, so there is no unprobed space.
+-
+- - When there are no SVE register saves, we use the store of the link
+- register as a probe. We can't assume that LR was saved at position 0
+- though, so treat any space below it as unprobed. */
+- if (final_adjustment_p
+- && known_eq (frame.below_hard_fp_saved_regs_size, 0))
+- {
+- poly_int64 lr_offset = (frame.reg_offset[LR_REGNUM]
+- - frame.bytes_below_saved_regs);
+- if (known_ge (lr_offset, 0))
+- min_probe_threshold -= lr_offset.to_constant ();
+- else
+- gcc_assert (!flag_stack_clash_protection || known_eq (poly_size, 0));
+- }
+-
+ poly_int64 frame_size = frame.frame_size;
+
+ /* We should always have a positive probe threshold. */
+@@ -10151,8 +10139,8 @@ aarch64_allocate_and_probe_stack_space (rtx temp1, rtx temp2,
+ if (final_adjustment_p && rounded_size != 0)
+ min_probe_threshold = 0;
+ /* If doing a small final adjustment, we always probe at offset 0.
+- This is done to avoid issues when LR is not at position 0 or when
+- the final adjustment is smaller than the probing offset. */
++ This is done to avoid issues when the final adjustment is smaller
++ than the probing offset. */
+ else if (final_adjustment_p && rounded_size == 0)
+ residual_probe_offset = 0;
+
+diff --git a/gcc/testsuite/gcc.target/aarch64/stack-check-prologue-18.c b/gcc/testsuite/gcc.target/aarch64/stack-check-prologue-18.c
+new file mode 100644
+index 000000000..82447d20f
+--- /dev/null
++++ b/gcc/testsuite/gcc.target/aarch64/stack-check-prologue-18.c
+@@ -0,0 +1,100 @@
++/* { dg-options "-O2 -fstack-clash-protection -fomit-frame-pointer --param stack-clash-protection-guard-size=12" } */
++/* { dg-final { check-function-bodies "**" "" } } */
++
++void f(int, ...);
++void g();
++
++/*
++** test1:
++** ...
++** str x30, \[sp\]
++** sub sp, sp, #4064
++** str xzr, \[sp\]
++** cbnz w0, .*
++** bl g
++** ...
++** str x26, \[sp, #?4128\]
++** ...
++*/
++int test1(int z) {
++ __uint128_t x = 0;
++ int y[0x400];
++ if (z)
++ {
++ asm volatile ("" :::
++ "x19", "x20", "x21", "x22", "x23", "x24", "x25", "x26");
++ f(0, 0, 0, 0, 0, 0, 0, &y,
++ x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x,
++ x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x,
++ x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x,
++ x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x,
++ x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x,
++ x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x,
++ x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x,
++ x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x,
++ x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x,
++ x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x,
++ x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x,
++ x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x,
++ x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x,
++ x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x,
++ x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x,
++ x, x, x, x, x, x, x, x, x, x, x, x, x, x);
++ }
++ g();
++ return 1;
++}
++
++/*
++** test2:
++** ...
++** str x30, \[sp\]
++** sub sp, sp, #1040
++** str xzr, \[sp\]
++** cbnz w0, .*
++** bl g
++** ...
++*/
++int test2(int z) {
++ __uint128_t x = 0;
++ int y[0x400];
++ if (z)
++ {
++ asm volatile ("" :::
++ "x19", "x20", "x21", "x22", "x23", "x24", "x25", "x26");
++ f(0, 0, 0, 0, 0, 0, 0, &y,
++ x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x,
++ x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x,
++ x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x,
++ x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x,
++ x);
++ }
++ g();
++ return 1;
++}
++
++/*
++** test3:
++** ...
++** str x30, \[sp\]
++** sub sp, sp, #1024
++** cbnz w0, .*
++** bl g
++** ...
++*/
++int test3(int z) {
++ __uint128_t x = 0;
++ int y[0x400];
++ if (z)
++ {
++ asm volatile ("" :::
++ "x19", "x20", "x21", "x22", "x23", "x24", "x25", "x26");
++ f(0, 0, 0, 0, 0, 0, 0, &y,
++ x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x,
++ x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x,
++ x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x,
++ x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x);
++ }
++ g();
++ return 1;
++}
+diff --git a/gcc/testsuite/gcc.target/aarch64/stack-check-prologue-19.c b/gcc/testsuite/gcc.target/aarch64/stack-check-prologue-19.c
+new file mode 100644
+index 000000000..73ac3e4e4
+--- /dev/null
++++ b/gcc/testsuite/gcc.target/aarch64/stack-check-prologue-19.c
+@@ -0,0 +1,100 @@
++/* { dg-options "-O2 -fstack-clash-protection -fomit-frame-pointer --param stack-clash-protection-guard-size=12 -fsanitize=shadow-call-stack -ffixed-x18" } */
++/* { dg-final { check-function-bodies "**" "" } } */
++
++void f(int, ...);
++void g();
++
++/*
++** test1:
++** ...
++** str x30, \[sp\]
++** sub sp, sp, #4064
++** str xzr, \[sp\]
++** cbnz w0, .*
++** bl g
++** ...
++** str x26, \[sp, #?4128\]
++** ...
++*/
++int test1(int z) {
++ __uint128_t x = 0;
++ int y[0x400];
++ if (z)
++ {
++ asm volatile ("" :::
++ "x19", "x20", "x21", "x22", "x23", "x24", "x25", "x26");
++ f(0, 0, 0, 0, 0, 0, 0, &y,
++ x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x,
++ x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x,
++ x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x,
++ x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x,
++ x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x,
++ x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x,
++ x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x,
++ x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x,
++ x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x,
++ x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x,
++ x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x,
++ x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x,
++ x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x,
++ x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x,
++ x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x,
++ x, x, x, x, x, x, x, x, x, x, x, x, x, x);
++ }
++ g();
++ return 1;
++}
++
++/*
++** test2:
++** ...
++** str x30, \[sp\]
++** sub sp, sp, #1040
++** str xzr, \[sp\]
++** cbnz w0, .*
++** bl g
++** ...
++*/
++int test2(int z) {
++ __uint128_t x = 0;
++ int y[0x400];
++ if (z)
++ {
++ asm volatile ("" :::
++ "x19", "x20", "x21", "x22", "x23", "x24", "x25", "x26");
++ f(0, 0, 0, 0, 0, 0, 0, &y,
++ x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x,
++ x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x,
++ x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x,
++ x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x,
++ x);
++ }
++ g();
++ return 1;
++}
++
++/*
++** test3:
++** ...
++** str x30, \[sp\]
++** sub sp, sp, #1024
++** cbnz w0, .*
++** bl g
++** ...
++*/
++int test3(int z) {
++ __uint128_t x = 0;
++ int y[0x400];
++ if (z)
++ {
++ asm volatile ("" :::
++ "x19", "x20", "x21", "x22", "x23", "x24", "x25", "x26");
++ f(0, 0, 0, 0, 0, 0, 0, &y,
++ x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x,
++ x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x,
++ x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x,
++ x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x);
++ }
++ g();
++ return 1;
++}
+diff --git a/gcc/testsuite/gcc.target/aarch64/stack-check-prologue-20.c b/gcc/testsuite/gcc.target/aarch64/stack-check-prologue-20.c
+new file mode 100644
+index 000000000..690aae8df
+--- /dev/null
++++ b/gcc/testsuite/gcc.target/aarch64/stack-check-prologue-20.c
+@@ -0,0 +1,3 @@
++/* { dg-options "-O2 -fstack-protector-all -fstack-clash-protection -fomit-frame-pointer --param stack-clash-protection-guard-size=12 -fsanitize=shadow-call-stack -ffixed-x18" } */
++
++#include "stack-check-prologue-19.c"
+--
+2.33.0
+
generated by cgit v1.2.3 (git 2.25.1) at 2025-11-04 02:52:27 +0000