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Support signal frame unwinding on AArch64 #348

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98 changes: 98 additions & 0 deletions build_scripts/elfutils-0.195-aarch64-signal-frame.patch
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Original file line number Diff line number Diff line change
@@ -0,0 +1,98 @@
diff --git a/backends/aarch64_unwind.c b/backends/aarch64_unwind.c
index e0a7e96..d276d92 100644
--- a/backends/aarch64_unwind.c
+++ b/backends/aarch64_unwind.c
@@ -40,16 +40,91 @@

#include "libebl_CPU.h"

+/* Linux AArch64 rt_sigreturn ABI. See kernel/vdso/sigreturn.S,
+ kernel/signal.c and include/uapi/asm/{ucontext,sigcontext}.h under:
+ https://github.com/torvalds/linux/tree/v6.6/arch/arm64
+
+ mov x8, #139 (0xd2801168) followed by svc #0 (0xd4000001) forms
+ RT_SIGRETURN_WORD on little-endian systems. The frame offsets are:
+
+ mcontext = 128 + 8 + 8 + 24 + 128 + 8 = 0x130
+ regs = 8, sp = 8 + 31 * 8 = 0x100, pc = sp + 8 = 0x108.
+ */
+#define RT_SIGRETURN_WORD UINT64_C (0xd4000001d2801168)
+#define RT_SIGFRAME_SIGCONTEXT_OFFSET 0x130
+#define SIGCONTEXT_REGS_OFFSET 0x8
+#define SIGCONTEXT_SP_OFFSET 0x100
+#define SIGCONTEXT_PC_OFFSET 0x108
+
+static bool
+unwind_signal_frame (Ebl *ebl, Dwarf_Addr pc,
+ ebl_tid_registers_t *setfunc,
+ ebl_tid_registers_get_t *getfunc,
+ ebl_pid_memory_read_t *readfunc, void *arg,
+ bool *signal_framep)
+{
+ /* Do not guess at the Linux AArch64 big-endian signal ABI here. */
+ if (ebl->data != ELFDATA2LSB)
+ return false;
+
+ /* frame_unwind.c normally passes PC - 1 for a non-activation frame. */
+ if ((pc & 3) == 3)
+ ++pc;
+ else if ((pc & 3) != 0)
+ return false;
+
+ Dwarf_Word instructions;
+ if (!readfunc (pc, &instructions, arg)
+ || instructions != RT_SIGRETURN_WORD)
+ return false;
+
+ Dwarf_Word signal_sp;
+ if (!getfunc (SP_REG, 1, &signal_sp, arg))
+ return false;
+
+ const Dwarf_Addr sigcontext
+ = signal_sp + RT_SIGFRAME_SIGCONTEXT_OFFSET;
+ Dwarf_Word registers[31];
+ Dwarf_Word saved_sp;
+ Dwarf_Word saved_pc;
+
+ /* Read the whole context before changing the tentative caller state. */
+ for (unsigned int regno = 0; regno < 31; ++regno)
+ if (!readfunc (sigcontext + SIGCONTEXT_REGS_OFFSET
+ + regno * sizeof (Dwarf_Word),
+ &registers[regno], arg))
+ return false;
+
+ if (!readfunc (sigcontext + SIGCONTEXT_SP_OFFSET, &saved_sp, arg)
+ || !readfunc (sigcontext + SIGCONTEXT_PC_OFFSET, &saved_pc, arg)
+ || saved_pc == 0
+ || saved_sp == 0
+ || (saved_sp & 15) != 0)
+ return false;
+
+ if (!setfunc (0, 31, registers, arg)
+ || !setfunc (SP_REG, 1, &saved_sp, arg)
+ || !setfunc (-1, 1, &saved_pc, arg))
+ return false;
+
+ *signal_framep = true;
+ return true;
+}
+
/* There was no CFI. Maybe we happen to have a frame pointer and can unwind from that? */

bool
-EBLHOOK(unwind) (Ebl *ebl __attribute__ ((unused)), Dwarf_Addr pc __attribute__ ((unused)),
+EBLHOOK(unwind) (Ebl *ebl, Dwarf_Addr pc,
ebl_tid_registers_t *setfunc, ebl_tid_registers_get_t *getfunc,
ebl_pid_memory_read_t *readfunc, void *arg,
- bool *signal_framep __attribute__ ((unused)))
+ bool *signal_framep)
{
Dwarf_Word fp, lr, sp;

+ if (unwind_signal_frame (ebl, pc, setfunc, getfunc, readfunc, arg,
+ signal_framep))
+ return true;
+
if (!getfunc(LR_REG, 1, &lr, arg))
return false;

11 changes: 8 additions & 3 deletions pyproject.toml
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Original file line number Diff line number Diff line change
Expand Up @@ -73,7 +73,10 @@ wheel.exclude = ["pystack/_pystack/**"]
wheel.py-api = "cp312"
metadata.version.provider = "scikit_build_core.metadata.regex"
metadata.version.input = "src/pystack/_version.py"
sdist.include = ["src/pystack/_version.py"]
sdist.include = [
"build_scripts/elfutils-0.195-aarch64-signal-frame.patch",
"src/pystack/_version.py",
]
sdist.exclude = [
".devcontainer/**",
".github/**",
Expand Down Expand Up @@ -133,13 +136,14 @@ skip = "*-musllinux_aarch64"

[tool.cibuildwheel.linux]
before-all = [
"yum install -y libzstd-devel cmake",
"yum install -y libzstd-devel cmake patch",
"yum install -y devtoolset-10-make || true", # Install a new enough GNU make on manylinux2014
"cd /",
"VERS=0.195",
"curl https://sourceware.org/elfutils/ftp/$VERS/elfutils-$VERS.tar.bz2 > ./elfutils.tar.bz2",
"tar -xf elfutils.tar.bz2",
"cd elfutils-$VERS",
"patch --batch --forward --fuzz=0 -p1 -i {package}/build_scripts/elfutils-0.195-aarch64-signal-frame.patch",
"CFLAGS='-Wno-error -g -O3' CXXFLAGS='-Wno-error -g -O3' ./configure --disable-nls --enable-libdebuginfod=dummy --disable-debuginfod --with-zstd",
'PATH="/opt/rh/devtoolset-10/root/usr/bin/:$PATH" make install', # Ensure we pick up gnu make 4.x on manylinux2014
]
Expand All @@ -157,11 +161,12 @@ before-all = [
# set the FNM_EXTMATCH macro to get the build to succeed is seen here:
# https://git.alpinelinux.org/aports/tree/main/elfutils/musl-macros.patch
"cd /",
"apk add --update argp-standalone bison bsd-compat-headers bzip2-dev flex-dev libtool linux-headers musl-fts-dev musl-libintl musl-obstack-dev xz-dev zlib-dev zstd-dev cmake",
"apk add --update argp-standalone bison bsd-compat-headers bzip2-dev flex-dev libtool linux-headers musl-fts-dev musl-libintl musl-obstack-dev patch xz-dev zlib-dev zstd-dev cmake",
"VERS=0.195",
"curl https://sourceware.org/elfutils/ftp/$VERS/elfutils-$VERS.tar.bz2 > ./elfutils.tar.bz2",
"tar -xf elfutils.tar.bz2",
"cd elfutils-$VERS",
"patch --batch --forward --fuzz=0 -p1 -i {package}/build_scripts/elfutils-0.195-aarch64-signal-frame.patch",
"CFLAGS='-Wno-error -DFNM_EXTMATCH=0 -g -O3' CXXFLAGS='-Wno-error -g -O3' ./configure --disable-nls --enable-libdebuginfod=dummy --disable-debuginfod --with-zstd",
"make install",

Expand Down