When erroring out on an DOS interrupt, print info

Print the interrupt number, AX, and CS:IP of the offending system
call.

diff --git a/core/comboot.inc b/core/comboot.inc
index b843372..abc7270 100644 (file)
--- a/core/comboot.inc
+++ b/core/comboot.inc
@@ -25,6 +25,7 @@
 %define                P_FLAGSH        byte [bp+45]
 %define                P_CS            word [bp+42]
 %define                P_IP            word [bp+40]
+%define                P_CSIP          dword [bp+40]
 %define                P_DS            word [bp+38]
 %define                P_ES            word [bp+36]
 %define                P_FS            word [bp+34]
@@ -147,16 +148,32 @@ comboot_return:   cli                     ; Don't trust anyone
 ; by the COM32 code.
 ;
 comboot_setup_api:
-               mov di,4*0x20           ; DOS interrupt vectors
-               mov eax,comboot_return  ; INT 20h = exit
+               mov di,DOSErrTramp      ; Error trampolines
+               mov cx,32
+               push cx
+               mov eax,0EB7A6A20h      ; push 20h; jmp <tramp>
+.loop1:                stosd
+               add eax,1-(4 << 16)
+               loop .loop1
+               mov byte [di-1],0E9h
+               mov ax,comboot_bogus-2
+               sub ax,di
+               stosw
+
+               mov eax,DOSErrTramp
+               pop cx                  ; CX <- 32
+               mov di,4*20h            ; DOS interrupt vectors
+               push di
+.loop2:                stosd
+               add ax,4
+               loop .loop2
+               pop di
+               mov ax,comboot_return   ; INT 20h = exit
                stosd
                mov ax,comboot_int21    ; INT 21h = DOS-compatible syscalls
                stosd
                mov ax,comboot_int22    ; INT 22h = proprietary syscalls
                stosd
-               mov ax,comboot_bogus
-               mov cx,29               ; All remaining DOS vectors
-               rep stosd
                ret
 
 ; INT 21h: generic DOS system call
@@ -194,11 +211,33 @@ comboot_resume:
                pop ds
                iret
 
-; Attempted to execute non-21h DOS system call
+comboot_bad_int21:
+               mov ax,P_AX
+               push P_CSIP
+               push 21h
+               ; Fall through
+
+; Attempted to execute invalid DOS system call
+; The interrupt number is on the stack.
 comboot_bogus: cli                     ; Don't trust anyone
+               pop edi                 ; CS:IP
+               pop dx                  ; Interrupt number
                mov cx,err_notdos
-               push enter_command
+               push comboot_bogus_tail
                jmp comboot_exit_msg
+comboot_bogus_tail:
+               xchg ax,dx
+               call writehex2          ; Interrupt number
+               mov al,' '
+               call writechr
+               xchg ax,dx
+               call writehex4          ; Function number (AX)
+               mov al,' '
+               call writechr
+               mov eax,edi
+               call writehex8          ; CS:IP of the origin
+               call crlf
+               jmp enter_command
 
 ;
 ; Generic COMBOOT return to command line code
@@ -209,7 +248,7 @@ comboot_exit:
                xor cx,cx
 comboot_exit_msg:
                pop bx                  ; Return address
-               RESET_STACK_AND_SEGS AX
+               RESET_STACK_AND_SEGS SI
                call adjust_screen      ; The COMBOOT program might have changed the screen
                jcxz .nomsg
                mov si,KernelCName
@@ -927,7 +966,7 @@ int21_table:
                int21   0Bh, comboot_checkkey
                int21   30h, comboot_checkver
                int21   4Ch, comboot_return
-               int21    -1, comboot_bogus
+               int21    -1, comboot_bad_int21
 int21_count    equ ($-int21_table)/3
 
                align 2, db 0
@@ -979,8 +1018,10 @@ feature_flags:
                db 3                    ; Have local boot, idle is noop
 feature_flags_len equ ($-feature_flags)
 
-err_notdos     db ': attempted DOS system call', CR, LF, 0
+err_notdos     db ': attempted DOS system call INT ',0
 err_comlarge   db 'COMBOOT image too large.', CR, LF, 0
 
                section .bss1
+               alignb 4
+DOSErrTramp    resd    33              ; Error trampolines
 ConfigName     resb    FILENAME_MAX

diff --git a/core/extlinux.asm b/core/extlinux.asm
index 6c2946c..1b969c7 100644 (file)
--- a/core/extlinux.asm
+++ b/core/extlinux.asm
@@ -1522,6 +1522,7 @@ getfssec:
 %include "conio.inc"           ; Console I/O
 %include "plaincon.inc"                ; writechr
 %include "writestr.inc"                ; String output
+%include "writehex.inc"                ; Hexadecimal output
 %include "configinit.inc"      ; Initialize configuration
 %include "parseconfig.inc"     ; High-level config file handling
 %include "parsecmd.inc"                ; Low-level config file handling

diff --git a/core/ldlinux.asm b/core/ldlinux.asm
index 5318c47..5823582 100644 (file)
--- a/core/ldlinux.asm
+++ b/core/ldlinux.asm
@@ -1158,7 +1158,7 @@ search_dos_dir:
                ret
 
                section .data
-               alignb 4
+               align 4, db 0
                ; Note: we have no use of the first 32 bytes (header),
                ; nor of the folloing 32 bytes (case mapping of control
                ; characters), as long as we adjust the offsets appropriately.
@@ -1681,6 +1681,7 @@ getfatsector:
 %include "conio.inc"           ; Console I/O
 %include "plaincon.inc"                ; writechr
 %include "writestr.inc"                ; String output
+%include "writehex.inc"                ; Hexadecimal output
 %include "configinit.inc"      ; Initialize configuration
 %include "parseconfig.inc"     ; High-level config file handling
 %include "parsecmd.inc"                ; Low-level config file handling