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[src/trunk]: src/lib/libc/arch/aarch64 Decorate the aarch64 signal trampoline...



details:   https://anonhg.NetBSD.org/src/rev/b29ab904d3bd
branches:  trunk
changeset: 1015082:b29ab904d3bd
user:      kamil <kamil%NetBSD.org@localhost>
date:      Tue Oct 13 01:59:55 2020 +0000

description:
Decorate the aarch64 signal trampoline with CFI attributes easing unwinding

Now, the unwinders (in backtrace(3) and similar) can unwind properly
the stack from a signal handler.

diffstat:

 lib/libc/arch/aarch64/genassym.cf       |  32 ++++++++++++++++++++++-
 lib/libc/arch/aarch64/sys/__sigtramp2.S |  46 ++++++++++++++++++++++++++++++++-
 2 files changed, 76 insertions(+), 2 deletions(-)

diffs (118 lines):

diff -r f34a4b1a202b -r b29ab904d3bd lib/libc/arch/aarch64/genassym.cf
--- a/lib/libc/arch/aarch64/genassym.cf Tue Oct 13 01:59:32 2020 +0000
+++ b/lib/libc/arch/aarch64/genassym.cf Tue Oct 13 01:59:55 2020 +0000
@@ -1,4 +1,4 @@
-# $NetBSD: genassym.cf,v 1.2 2020/05/10 14:05:59 skrll Exp $
+# $NetBSD: genassym.cf,v 1.3 2020/10/13 01:59:55 kamil Exp $
 
 #-
 # Copyright (c) 2014 The NetBSD Foundation, Inc.
@@ -34,6 +34,36 @@
 include <setjmp.h>
 
 define _UC_REGS_X0     offsetof(ucontext_t, uc_mcontext.__gregs[_REG_X0])
+define _UC_REGS_X1     offsetof(ucontext_t, uc_mcontext.__gregs[_REG_X1])
+define _UC_REGS_X2     offsetof(ucontext_t, uc_mcontext.__gregs[_REG_X2])
+define _UC_REGS_X3     offsetof(ucontext_t, uc_mcontext.__gregs[_REG_X3])
+define _UC_REGS_X4     offsetof(ucontext_t, uc_mcontext.__gregs[_REG_X4])
+define _UC_REGS_X5     offsetof(ucontext_t, uc_mcontext.__gregs[_REG_X5])
+define _UC_REGS_X6     offsetof(ucontext_t, uc_mcontext.__gregs[_REG_X6])
+define _UC_REGS_X7     offsetof(ucontext_t, uc_mcontext.__gregs[_REG_X7])
+define _UC_REGS_X8     offsetof(ucontext_t, uc_mcontext.__gregs[_REG_X8])
+define _UC_REGS_X9     offsetof(ucontext_t, uc_mcontext.__gregs[_REG_X9])
+define _UC_REGS_X10    offsetof(ucontext_t, uc_mcontext.__gregs[_REG_X10])
+define _UC_REGS_X11    offsetof(ucontext_t, uc_mcontext.__gregs[_REG_X11])
+define _UC_REGS_X12    offsetof(ucontext_t, uc_mcontext.__gregs[_REG_X12])
+define _UC_REGS_X13    offsetof(ucontext_t, uc_mcontext.__gregs[_REG_X13])
+define _UC_REGS_X14    offsetof(ucontext_t, uc_mcontext.__gregs[_REG_X14])
+define _UC_REGS_X15    offsetof(ucontext_t, uc_mcontext.__gregs[_REG_X15])
+define _UC_REGS_X16    offsetof(ucontext_t, uc_mcontext.__gregs[_REG_X16])
+define _UC_REGS_X17    offsetof(ucontext_t, uc_mcontext.__gregs[_REG_X17])
+define _UC_REGS_X18    offsetof(ucontext_t, uc_mcontext.__gregs[_REG_X18])
+define _UC_REGS_X19    offsetof(ucontext_t, uc_mcontext.__gregs[_REG_X19])
+define _UC_REGS_X20    offsetof(ucontext_t, uc_mcontext.__gregs[_REG_X20])
+define _UC_REGS_X21    offsetof(ucontext_t, uc_mcontext.__gregs[_REG_X21])
+define _UC_REGS_X22    offsetof(ucontext_t, uc_mcontext.__gregs[_REG_X22])
+define _UC_REGS_X23    offsetof(ucontext_t, uc_mcontext.__gregs[_REG_X23])
+define _UC_REGS_X24    offsetof(ucontext_t, uc_mcontext.__gregs[_REG_X24])
+define _UC_REGS_X25    offsetof(ucontext_t, uc_mcontext.__gregs[_REG_X25])
+define _UC_REGS_X26    offsetof(ucontext_t, uc_mcontext.__gregs[_REG_X26])
+define _UC_REGS_X27    offsetof(ucontext_t, uc_mcontext.__gregs[_REG_X27])
+define _UC_REGS_X28    offsetof(ucontext_t, uc_mcontext.__gregs[_REG_X28])
+define _UC_REGS_X29    offsetof(ucontext_t, uc_mcontext.__gregs[_REG_X29])
+define _UC_REGS_X30    offsetof(ucontext_t, uc_mcontext.__gregs[_REG_X30])
 define _UC_REGS_SP     offsetof(ucontext_t, uc_mcontext.__gregs[_REG_SP])
 define _UC_REGS_PC     offsetof(ucontext_t, uc_mcontext.__gregs[_REG_PC])
 
diff -r f34a4b1a202b -r b29ab904d3bd lib/libc/arch/aarch64/sys/__sigtramp2.S
--- a/lib/libc/arch/aarch64/sys/__sigtramp2.S   Tue Oct 13 01:59:32 2020 +0000
+++ b/lib/libc/arch/aarch64/sys/__sigtramp2.S   Tue Oct 13 01:59:55 2020 +0000
@@ -1,4 +1,4 @@
-/* $NetBSD: __sigtramp2.S,v 1.1 2014/08/10 05:47:37 matt Exp $ */
+/* $NetBSD: __sigtramp2.S,v 1.2 2020/10/13 01:59:55 kamil Exp $ */
 
 /*-
  * Copyright (c) 2014 The NetBSD Foundation, Inc.
@@ -30,6 +30,7 @@
  */
 
 #include "SYS.h"
+#include "assym.h"
 
 /*
  * The ARM signal trampoline is invoked only to return from
@@ -40,11 +41,54 @@
  *             ucontext structure
  *     sp->    siginfo structure
  * and x28 points to the ucontext
+ *
+ * The unwind entry includes the one byte prior to the trampoline
+ * because the unwinder will look up (return PC - 1) while unwinding.
+ * Normally (return PC - 1) computes an address inside the call
+ * instruction that created the child frame, but here there is no call
+ * instruction so we have to manually add padding.
  */
+       .cfi_startproc simple
+       .cfi_signal_frame
+       .cfi_def_cfa x28, 0
+       .cfi_offset x0, _UC_REGS_X0
+       .cfi_offset x1, _UC_REGS_X1
+       .cfi_offset x2, _UC_REGS_X2
+       .cfi_offset x3, _UC_REGS_X3
+       .cfi_offset x4, _UC_REGS_X4
+       .cfi_offset x5, _UC_REGS_X5
+       .cfi_offset x6, _UC_REGS_X6
+       .cfi_offset x7, _UC_REGS_X7
+       .cfi_offset x8, _UC_REGS_X8
+       .cfi_offset x9, _UC_REGS_X9
+       .cfi_offset x10, _UC_REGS_X10
+       .cfi_offset x11, _UC_REGS_X11
+       .cfi_offset x12, _UC_REGS_X12
+       .cfi_offset x13, _UC_REGS_X13
+       .cfi_offset x14, _UC_REGS_X14
+       .cfi_offset x15, _UC_REGS_X15
+       .cfi_offset x16, _UC_REGS_X16
+       .cfi_offset x17, _UC_REGS_X17
+       .cfi_offset x18, _UC_REGS_X18
+       .cfi_offset x19, _UC_REGS_X19
+       .cfi_offset x20, _UC_REGS_X20
+       .cfi_offset x21, _UC_REGS_X21
+       .cfi_offset x22, _UC_REGS_X22
+       .cfi_offset x23, _UC_REGS_X23
+       .cfi_offset x24, _UC_REGS_X24
+       .cfi_offset x25, _UC_REGS_X25
+       .cfi_offset x26, _UC_REGS_X26
+       .cfi_offset x27, _UC_REGS_X27
+       .cfi_offset x28, _UC_REGS_X28
+       .cfi_offset x29, _UC_REGS_X29
+       .cfi_offset x30, _UC_REGS_X30
+       /* The unwinder will use the CFA to restore X31 (SP). */
+       nop
 ENTRY_NP(__sigtramp_siginfo_2)
        mov     x0, x28                         /* set the arg         */
        SYSTRAP(setcontext)                     /* and call setcontext */
 
        /* If that failed, exit with the error code. */
        SYSTRAP(exit)
+       .cfi_endproc
 END(__sigtramp_siginfo_2)



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