The registers are part of a user area stored in the context structure used by the scheduler. This structure can be manipulated to get and set the values of those registers, and, for example, on Intel hosts, it is possible to directly manipulate DR0-DR7 hardware registers to set hardware breakpoints.
There are different commands to get values of registers. For the General Purpose ones use:
[0x4A13B8C0]> dr
r15 = 0x00000000
r14 = 0x00000000
r13 = 0x00000000
r12 = 0x00000000
rbp = 0x00000000
rbx = 0x00000000
r11 = 0x00000000
r10 = 0x00000000
r9 = 0x00000000
r8 = 0x00000000
rax = 0x00000000
rcx = 0x00000000
rdx = 0x00000000
rsi = 0x00000000
rdi = 0x00000000
oeax = 0x0000003b
rip = 0x7f20bf5df630
rsp = 0x7fff515923c0
[0x7f0f2dbae630]> dr rip ; get value of 'rip'
0x7f0f2dbae630
[0x4A13B8C0]> dr rip = esp ; set 'rip' as esp
Interaction between a plugin and the core is done by commands returning radare instructions. This is used, for example, to set flags in the core to set values of registers.
[0x7f0f2dbae630]> dr* ; Appending '*' will show radare commands
f r15 1 0x0
f r14 1 0x0
f r13 1 0x0
f r12 1 0x0
f rbp 1 0x0
f rbx 1 0x0
f r11 1 0x0
f r10 1 0x0
f r9 1 0x0
f r8 1 0x0
f rax 1 0x0
f rcx 1 0x0
f rdx 1 0x0
f rsi 1 0x0
f rdi 1 0x0
f oeax 1 0x3b
f rip 1 0x7fff73557940
f rflags 1 0x200
f rsp 1 0x7fff73557940
[0x4A13B8C0]> .dr* ; include common register values in flags
An old copy of registers is stored all the time to keep track of the changes done during execution of a program being analyzed. This old copy can be accessed with oregs.
