NAME

backtrace_pack, backtrace_unpack — convert a backtrace to and from compact formats

SYNOPSIS

#include <kern/backtrace.h>

size_t
backtrace_pack(backtrace_pack_t packing, uint8_t *dst, size_t dst_size, uintptr_t *src, unsigned int src_len);

unsigned int
backtrace_unpack(backtrace_pack_t packing, uintptr_t *dst, unsigned int dst_len, uint8_t *src, size_t src_size);

DESCRIPTION

The backtrace_pack and backtrace_unpack functions convert to and from a compact representation of a backtrace.

RETURN VALUES

The backtrace_pack() function returns the number of bytes written to the destination buffer. The backtrace_unpack() function returns the number of addresses written to the destination buffer.

FORMATS

BTP_NONE: Just copy the addresses unpacked to the destination buffer.
BTP_KERN_OFFSET_32: Subtract the kernel base address from each address so they fit in 4 bytes.

EXAMPLE

uintptr_t bt[8] = { 0 };
enum backtrace_info bti = BTI_NONE;
unsigned int len = backtrace(bt, sizeof(bt) / sizeof(bt[0]), NULL, &bti);
uint8_t bt_packed[1024] = { 0 };
size_t packed_size = backtrace_pack(BTP_KERN_OFFSET_32, bt_packed,
		sizeof(bt_packed), bt, len);
uintptr_t bt_unpacked[8] = { 0 };
unsigned int unpacked_len = backtrace_unpack(BTP_KERN_OFFSET_32, bt_unpacked,
		sizeof(bt_unpacked) / sizeof(bt_unpacked[0]), bt_packed, packed_size);
assert(len == unpacked_len);
for (unsigned int i = 0; i < len; i++) {
	assert(bt[i] == unpacked_bt[i]);
}