$ xref data

On this page

Usage
Arguments and options
Examples
A string in read-only data
The same bytes as a hex dump
Zero-initialised data
An address outside the binary
Reading the output
Limits
Provenance

Read typed values at a virtual address of the binary: the address is mapped through the load segments (ELF PT_LOAD, Mach-O segments) and each element is printed with its address. Use it when pseudo-C or assembly loads from a constant address (a table indexed by some value, a string, a constant) and you want the values without writing an ELF reader.

Usage

xref data [OPTIONS] --as <AS_TYPE> <VA>

Arguments and options

Arguments

<VA>

Virtual address to read from (0x... hex or decimal).

Options

--as <AS_TYPE>

Data type to read (f64, f32, u64, u32, u16, u8, i64, i32, i16, i8, bytes, str) [possible values: f64, f32, u64, u32, u16, u8, i64, i32, i16, i8, bytes, str].

--count <COUNT>

Number of elements to read (byte count for bytes; default 1, or 64 for bytes).

--max-len <MAX_LEN>

Maximum string length to read up to the first NUL (default 256).

default 256

Examples

A string in read-only data

0x492c0b is the string ripgrep's statistics serializer passes (see card). The serializer slices it by length, so the bytes after the first key belong to the next keys:

Command

$ xref -b rg data 0x492c0b --as str

Output

0x492c0b  str  "elapsedsearchessearches_with_matchbytes_searchedbytes_printedmatched_linesmatchesbeginendmatchcontextstartnanoshumanPoisonError\n"

stderr

xref: load 2.5ms, total 2.5ms

The same bytes as a hex dump

Command

$ xref -b rg data 0x492c0b --as bytes --count 32

Output

0x492c0b  65 6c 61 70 73 65 64 73 65 61 72 63 68 65 73 73
0x492c1b  65 61 72 63 68 65 73 5f 77 69 74 68 5f 6d 61 74

stderr

xref: load 2.4ms, total 2.4ms

Zero-initialised data

0x84a560 is past the file-backed part of ripgrep's writable segment, so the values are zero in the file and marked (bss):

Command

$ xref -b rg data 0x84a560 --as u64 --count 2

Output

0x84a560  u64  0  (bss)
0x84a568  u64  0  (bss)

stderr

xref: load 1.9ms, total 1.9ms

An address outside the binary

Command

$ xref -b rg data 0x900000 --as f64

(no stdout)

Exit status 1.

stderr

xref: VA 0x900000 is outside all segments; nearest segment is 0x785af0..0x896148 (permissions: ?w- (read bit not recorded))

Reading the output

One line per element: address, type, value. f64 and f32 use the shortest form that reads back the same value (1.0, 1e19).
str reads up to the first NUL byte and prints the text escaped. If no NUL is found within --max-len bytes, the line says the text was capped.
bytes prints 16 bytes per line with the address of the line.
(bss) marks values past the file-backed part of a segment. The file holds no bytes for them, so they read as zero; at run time the program may have changed them.
A range that runs past the end of its segment is cut there, with a line saying so.
An address outside every segment is an error that names the nearest segment. The read permission is printed as ? because xref does not record it.

Limits

Values are what the file holds. Data the dynamic loader relocates at start (pointers in .data.rel.ro, .got) reads as its addend or zero here; use refs to follow such pointers, or live memscan on a running process for run-time values.
--count is limited to 65,536 elements, or 1 MiB for bytes.

Provenance

Recorded with a development build of xref after 0.4.0 on Linux x86-64, on rg = ripgrep 14.1.1 (official stripped release). Output is unchanged except that whitespace at the end of each line and empty lines at the end of the output are removed; long outputs are cut where marked.

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