Hello world,
I'd like to know how to set a global conditional breakpoint (that will be evaluated after any instruction) that will break when EAX value is equal to a specific string (EAX->value == ASCII("string_to_break_on")?

I think, that this isn't possible. You must specify where You can sen BP. You can trace program with log & then set BP.
You can right click -> Search for -> All command -> mov eax, const
Seach too for: inc eax, dec eax, pop eax ...
In Foud commands window right click -> Set log breakpoint on every command ->
Condition: eax==0
Pause program: On condition

Look to older post in which are answers from oh me anon. He has very useful tips.

thanks joe
well the search function in this board at present is not optimum
and tbd it seems cant find what is messed up

so to answer

use ctrl+t and type string [eax] == "your preferred string" int the condition is true box and hit ctrl+ f11 (trace into it will stop when the condition is true

for example

you have this code
00401000 >MOV EAX, 4DC9C0 ; ASCII "hello"
00401005 PUSH EAX
00401006 POP ECX ; OLLYDBG.004DC9C0
00401007 PUSH EAX
00401008 JMP SHORT 0040100C ; 0040100C
0040100A DB 4F ; CHAR 'O'
0040100B DB 4B ; CHAR 'K'
0040100C JMP SHORT 00401000 ; <ModuleEntryPoint>


now this is an infinite loop and eax will always contain the string "hello"

if you specify this as condition
STRING [EAX] == "hello" & eip != 401000 & eip != 401005

you will see it will stop according tho the condition like this
look at the address the stops are always in 401006

Log data
Address Message
00401006 Conditional pause: STRING [EAX] == "hello" & eip != 401000 & eip != 401005
00401007 Conditional pause: STRING [EAX] == "hello" & eip != 401000 & eip != 401005
00401008 Conditional pause: STRING [EAX] == "hello" & eip != 401000 & eip != 401005
0040100C Conditional pause: STRING [EAX] == "hello" & eip != 401000 & eip != 401005
00401006 Conditional pause: STRING [EAX] == "hello" & eip != 401000 & eip != 401005
00401007 Conditional pause: STRING [EAX] == "hello" & eip != 401000 & eip != 401005
00401008 Conditional pause: STRING [EAX] == "hello" & eip != 401000 & eip != 401005
0040100C Conditional pause: STRING [EAX] == "hello" & eip != 401000 & eip != 401005
00401006 Conditional pause: STRING [EAX] == "hello" & eip != 401000 & eip != 401005
00401007 Conditional pause: STRING [EAX] == "hello" & eip != 401000 & eip != 401005
00401008 Conditional pause: STRING [EAX] == "hello" & eip != 401000 & eip != 401005
0040100C Conditional pause: STRING [EAX] == "hello" & eip != 401000 & eip != 401005
00401006 Conditional pause: STRING [EAX] == "hello" & eip != 401000 & eip != 401005
00401007 Conditional pause: STRING [EAX] == "hello" & eip != 401000 & eip != 401005
00401008 Conditional pause: STRING [EAX] == "hello" & eip != 401000 & eip != 401005
0040100C Conditional pause: STRING [EAX] == "hello" & eip != 401000 & eip != 401005
00401006 Conditional pause: STRING [EAX] == "hello" & eip != 401000 & eip != 401005

have fun