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Subject[PATCH 4/5] unwind, api: Add unwind interface and implementation for x86_64
Date
Adding unwind interface with x86_64 implementation.
The interface consists of following functions:

struct unw_t;
- single backtrace handle

void unw_init(struct unw_t *u);
- initialize the handle

void unw_regs(struct unw_t *u, struct pt_regs *regs);
- returns current struct pt_regs registers data

int unw_step(struct unw_t *u);
- makes single backtrace step

void unw_backtrace(void);
- runs the backtrace unwind and printk it out

The example usage is shown in unw_backtrace function.
---
arch/x86/include/asm/unwind.h | 14 +++
arch/x86/kernel/Makefile | 1 +
arch/x86/kernel/unwind_init_64.S | 31 +++++++
include/linux/unwind.h | 23 +++++
kernel/Makefile | 1 +
kernel/unwind.c | 180 ++++++++++++++++++++++++++++++++++++++
6 files changed, 250 insertions(+), 0 deletions(-)
create mode 100644 arch/x86/include/asm/unwind.h
create mode 100644 arch/x86/kernel/unwind_init_64.S
create mode 100644 include/linux/unwind.h
create mode 100644 kernel/unwind.c

diff --git a/arch/x86/include/asm/unwind.h b/arch/x86/include/asm/unwind.h
new file mode 100644
index 0000000..beab2f7
--- /dev/null
+++ b/arch/x86/include/asm/unwind.h
@@ -0,0 +1,14 @@
+#ifndef _ARCH_X86_KERNEL_UNWIND_H
+#define _ARCH_X86_KERNEL_UNWIND_H
+
+#include <asm/ptrace-abi.h>
+
+#ifdef __ASSEMBLY__
+#ifdef __i386__
+#define UNW_X86_CFA_OFF (FRAME_SIZE + 0x0)
+#else
+#define UNW_X86_64_CFA_OFF (FRAME_SIZE + 0x0)
+#endif /* __i386__ */
+#endif /* __ASSEMBLY__ */
+
+#endif /* _ARCH_X86_KERNEL_UNWIND_H */
diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
index 8a7c0ec..a77fff3 100644
--- a/arch/x86/kernel/Makefile
+++ b/arch/x86/kernel/Makefile
@@ -101,6 +101,7 @@ obj-$(CONFIG_X86_CHECK_BIOS_CORRUPTION) += check.o
obj-$(CONFIG_SWIOTLB) += pci-swiotlb.o
obj-$(CONFIG_OF) += devicetree.o
obj-$(CONFIG_UNWIND) += dwarf.o
+obj-$(CONFIG_UNWIND) += unwind_init_$(BITS).o

###
# 64 bit specific files
diff --git a/arch/x86/kernel/unwind_init_64.S b/arch/x86/kernel/unwind_init_64.S
new file mode 100644
index 0000000..4c8c9ed
--- /dev/null
+++ b/arch/x86/kernel/unwind_init_64.S
@@ -0,0 +1,31 @@
+
+#include <linux/linkage.h>
+#include <asm/ptrace-abi.h>
+#include <asm/unwind.h>
+
+ .code64
+ENTRY(unw_init)
+ /* Callee saved: RBX, RBP, R12-R15 */
+ movq %r12, R12(%rdi)
+ movq %r13, R13(%rdi)
+ movq %r14, R14(%rdi)
+ movq %r15, R15(%rdi)
+ movq %rbp, RBP(%rdi)
+ movq %rbx, RBX(%rdi)
+
+ movq %r8, R8(%rdi)
+ movq %r9, R9(%rdi)
+ movq %rdi, RDI(%rdi)
+ movq %rsi, RSI(%rdi)
+ movq %rdx, RDX(%rdi)
+ movq %rax, RAX(%rdi)
+ movq %rcx, RCX(%rdi)
+
+ leaq 8(%rsp), %rax /* exclude this call. */
+ movq %rax, UNW_X86_64_CFA_OFF(%rdi)
+ movq 0(%rsp), %rax
+ movq %rax, RIP(%rdi)
+
+ xorq %rax, %rax
+ retq
+END(unw_init)
diff --git a/include/linux/unwind.h b/include/linux/unwind.h
new file mode 100644
index 0000000..d99b028
--- /dev/null
+++ b/include/linux/unwind.h
@@ -0,0 +1,23 @@
+#ifndef UNWIND_H
+#define UNWIND_H
+
+#include <linux/ptrace.h>
+#include <asm/unwind.h>
+#include <linux/dwarf.h>
+
+struct unw_t {
+ struct pt_regs regs;
+ dwarf_word_t cfa;
+
+ /*
+ * First 2 items are touched by assembly code,
+ * do not move them.
+ */
+};
+
+void unw_init(struct unw_t *u);
+void unw_regs(struct unw_t *u, struct pt_regs *regs);
+int unw_step(struct unw_t *u);
+void unw_backtrace(void);
+
+#endif /* UNWIND_H */
diff --git a/kernel/Makefile b/kernel/Makefile
index 3ddbc72..d472f4e 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -112,6 +112,7 @@ obj-$(CONFIG_UNWIND) += dwarf-read.o
obj-$(CONFIG_UNWIND) += dwarf-cfi.o
obj-$(CONFIG_UNWIND) += dwarf-expression.o
obj-$(CONFIG_UNWIND) += dwarf-fde.o
+obj-$(CONFIG_UNWIND) += unwind.o

$(obj)/configs.o: $(obj)/config_data.h

diff --git a/kernel/unwind.c b/kernel/unwind.c
new file mode 100644
index 0000000..f5191d5
--- /dev/null
+++ b/kernel/unwind.c
@@ -0,0 +1,180 @@
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/debugfs.h>
+#include <linux/unwind.h>
+#include <linux/dwarf.h>
+#include <linux/module.h>
+#include <linux/interrupt.h>
+#include <linux/completion.h>
+
+struct table_entry {
+ int32_t start_ip_offset;
+ int32_t fde_offset;
+};
+
+static struct table_entry* table_data;
+static dwarf_word_t table_count;
+static dwarf_word_t table_base;
+
+static struct table_entry*
+lookup(dwarf_word_t ip)
+{
+ struct table_entry *fde = NULL;
+ unsigned long lo, hi, mid;
+
+ ip -= table_base;
+
+ /* Do a binary search for right entry. */
+ for (lo = 0, hi = table_count; lo < hi;)
+ {
+ mid = (lo + hi) / 2;
+ fde = table_data + mid;
+
+ if (ip < fde->start_ip_offset)
+ hi = mid;
+ else
+ lo = mid + 1;
+ }
+
+ if (hi <= 0)
+ return NULL;
+
+ fde = table_data + hi - 1;
+ return fde;
+}
+
+#ifdef CONFIG_UNWIND_EH_FRAME
+extern char __eh_frame_hdr_start[];
+extern char __eh_frame_hdr_end[];
+extern char __eh_frame_start[];
+extern char __eh_frame_end[];
+
+struct eh_frame_hdr {
+ unsigned char version;
+ unsigned char eh_frame_ptr_enc;
+ unsigned char fde_count_enc;
+ unsigned char table_enc;
+};
+
+static int __init eh_frame_init(void)
+{
+ struct eh_frame_hdr *hdr;
+ dwarf_word_t addr, eh_frame_start;
+
+ hdr = (struct eh_frame_hdr *) __eh_frame_hdr_start;
+ addr = (dwarf_word_t) (hdr + 1);
+
+ if (dwarf_read_pointer(&addr, hdr->eh_frame_ptr_enc,
+ &eh_frame_start)) {
+ printk("unwind failed to read eh_frame_start\n");
+ goto failed;
+ }
+
+ if (dwarf_read_pointer(&addr, hdr->fde_count_enc,
+ &table_count)) {
+ printk("unwind failed to read fde_count\n");
+ goto failed;
+ }
+
+ if (hdr->table_enc != (DW_EH_PE_datarel | DW_EH_PE_sdata4)) {
+ printk("unwind unexpected table_enc\n");
+ goto failed;
+ }
+
+ table_data = (struct table_entry *) addr;
+ table_base = (dwarf_word_t) hdr;
+
+ printk("unwind __eh_frame_hdr_start %p\n", __eh_frame_hdr_start);
+ printk("unwind __eh_frame_hdr_end %p\n", __eh_frame_hdr_end);
+ printk("unwind __eh_frame_start %p\n", __eh_frame_start);
+ printk("unwind __eh_frame_en %p\n", __eh_frame_end);
+ printk("unwind version %x\n", hdr->version);
+ printk("unwind eh_frame_ptr_enc %x\n", hdr->eh_frame_ptr_enc);
+ printk("unwind fde_count_enc %x\n", hdr->fde_count_enc);
+ printk("unwind table_enc %x\n", hdr->table_enc);
+ printk("unwind table_data %p\n", table_data);
+ printk("unwind table_count %llx\n", table_count);
+ printk("unwind table_base %llx\n", table_base);
+
+ printk("unwind eh_frame table initialized\n");
+ return 0;
+
+ failed:
+ printk("unwind table initialization failed\n");
+ return -EINVAL;
+}
+#endif /* CONFIG_UNWIND_EH_FRAME */
+
+static int __init unw_init_table(void)
+{
+#ifdef CONFIG_UNWIND_EH_FRAME
+ return eh_frame_init();
+#endif
+ return -EINVAL;
+}
+
+pure_initcall(unw_init_table);
+
+__weak void unw_init(struct unw_t *u)
+{
+}
+
+static void dwarf_regs_get(struct unw_t *u, struct dwarf_regs *regs)
+{
+ regs->cfa = u->cfa;
+ dwarf_regs_pt2dwarf(&u->regs, regs);
+}
+
+static void dwarf_regs_set(struct unw_t *u, struct dwarf_regs *regs)
+{
+ u->cfa = regs->cfa;
+ dwarf_regs_dwarf2pt(regs, &u->regs);
+}
+
+int unw_step(struct unw_t *u)
+{
+ struct table_entry *entry;
+ struct dwarf_fde fde;
+ struct dwarf_regs regs;
+ void *data;
+ int ret;
+
+ entry = lookup(u->regs.ip);
+ if (!entry)
+ return -EINVAL;
+
+ data = (void *) (table_base + entry->fde_offset);
+
+ ret = dwarf_fde_init(&fde, data);
+ if (ret)
+ return ret;
+
+ dwarf_regs_get(u, &regs);
+
+ ret = dwarf_fde_process(&fde, &regs);
+ if (!ret)
+ dwarf_regs_set(u, &regs);
+
+ return ret;
+}
+
+void unw_regs(struct unw_t *u, struct pt_regs *regs)
+{
+ memcpy(regs, &u->regs, sizeof(u->regs));
+}
+
+void unw_backtrace(void)
+{
+ struct unw_t unw;
+ struct pt_regs regs;
+
+ unw_init(&unw);
+
+ printk("unwind backtrace:\n");
+
+ do {
+ unw_regs(&unw, &regs);
+ printk(" [0x%lx] %pS\n", regs.ip, (void *) regs.ip);
+ } while (!unw_step(&unw));
+
+}
--
1.7.1


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