freebsd-skq/lib/libkvm/kvm_nlist.3
jhb ab35544b83 Add support to libkvm for reading vmcores from other architectures.
- Add a kvaddr_type to represent kernel virtual addresses instead of
  unsigned long.
- Add a struct kvm_nlist which is a stripped down version of struct nlist
  that uses kvaddr_t for n_value.
- Add a kvm_native() routine that returns true if an open kvm descriptor
  is for a native kernel and memory image.
- Add a kvm_open2() function similar to kvm_openfiles().  It drops the
  unused 'swapfile' argument and adds a new function pointer argument for
  a symbol resolving function.  Native kernels still use _fdnlist() from
  libc to resolve symbols if a resolver function is not supplied, but cross
  kernels require a resolver.
- Add a kvm_nlist2() function similar to kvm_nlist() except that it uses
  struct kvm_nlist instead of struct nlist.
- Add a kvm_read2() function similar to kvm_read() except that it uses
  kvaddr_t instead of unsigned long for the kernel virtual address.
- Add a new kvm_arch switch of routines needed by a vmcore backend.
  Each backend is responsible for implementing kvm_read2() for a given
  vmcore format.
- Use libelf to read headers from ELF kernels and cores (except for
  powerpc cores).
- Add internal helper routines for the common page offset hash table used
  by the minidump backends.
- Port all of the existing kvm backends to implement a kvm_arch switch and
  to be cross-friendly by using private constants instead of ones that
  vary by platform (e.g. PAGE_SIZE).  Static assertions are present when
  a given backend is compiled natively to ensure the private constants
  match the real ones.
- Enable all of the existing vmcore backends on all platforms.  This means
  that libkvm on any platform should be able to perform KVA translation
  and read data from a vmcore of any platform.

Tested on:	amd64, i386, sparc64 (marius)
Differential Revision:	https://reviews.freebsd.org/D3341
2015-11-27 18:58:26 +00:00

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3.6 KiB
Groff

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.\" @(#)kvm_nlist.3 8.1 (Berkeley) 6/4/93
.\" $FreeBSD$
.\"
.Dd November 27, 2015
.Dt KVM_NLIST 3
.Os
.Sh NAME
.Nm kvm_nlist ,
.Nm kvm_nlist2
.Nd retrieve symbol table names from a kernel image
.Sh LIBRARY
.Lb libkvm
.Sh SYNOPSIS
.In kvm.h
.In nlist.h
.Ft int
.Fn kvm_nlist "kvm_t *kd" "struct nlist *nl"
.Ft int
.Fn kvm_nlist2 "kvm_t *kd" "struct kvm_nlist *nl"
.Sh DESCRIPTION
The
.Fn kvm_nlist
function retrieves the symbol table entries indicated by the name list argument
.Fa \&nl .
This argument points to an array of nlist structures, terminated by
an entry whose
.Fa n_name
field is
.Dv NULL
(see
.Xr nlist 3 ) .
Each symbol is looked up using the
.Fa n_name
field, and if found, the
corresponding
.Fa n_type
and
.Fa n_value
fields are filled in.
These fields are set
to 0 if the symbol is not found.
.Pp
The
.Xr kldsym 2
system call is used to locate symbols in live kernels.
This is a less than perfect
emulation of the nlist values but has the advantage of being aware of kernel
modules and is reasonably fast.
.Pp
The
.Fn kvm_nlist2
function retrieves the symbol table entries indicated by the name list argument
.Fa nl .
This argument points to an array of
.Vt "struct kvm_nlist"
structures,
terminated by an entry whose
.Fa n_name
field is
.Dv NULL
These structures are similar to the nlist structures used by
.Fn kvm_nlist
except that the
.Fa n_value
field uses a different type
.Pq Vt kvaddr_t
to avoid truncation when examining non-native kernel images.
.Sh RETURN VALUES
The
.Fn kvm_nlist
and
.Fn kvm_nlist2
functions return the number of invalid entries found.
If the kernel symbol table was unreadable, -1 is returned.
.Sh SEE ALSO
.Xr kldsym 2 ,
.Xr kvm 3 ,
.Xr kvm_close 3 ,
.Xr kvm_getargv 3 ,
.Xr kvm_getenvv 3 ,
.Xr kvm_geterr 3 ,
.Xr kvm_getprocs 3 ,
.Xr kvm_native 3 ,
.Xr kvm_open 3 ,
.Xr kvm_openfiles 3 ,
.Xr kvm_read 3 ,
.Xr kvm_write 3