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Message-ID: <20061011163356.GA2022@mailshack.com> Date: Wed, 11 Oct 2006 18:33:56 +0200 From: Alexander van Heukelum <heukelum@...lshack.com> To: linux-kernel@...r.kernel.org, Andrew Morton <akpm@...l.org> Cc: Venkatesh Pallipadi <venkatesh.pallipadi@...el.com>, Linus Torvalds <torvalds@...l.org>, "Eric W. Biederman" <ebiederm@...ssion.com>, John Coffman <johninsd@....rr.com> Subject: [PATCH] Remove lilo-loads-only-five-sectors-of-zImage-fixup from setup.S Hi! The real-mode kernel (on i386 and x86_64) checks if the bootloader loaded it correctly. Apparantly, very old versions of LILO disregarded the setupsects field in the bootsector and always just loaded the first five sectors. If the kernel is compiled as a zImage, the real-mode kernel is able to rectify the situation. At least it was, until the code to do so was moved to the eighth sector in order to make space for more E820 entries (commit: f9ba70535dc12d9eb57d466a2ecd749e16eca866). This occured on 1 May 2005 and as far as I know, noone has complained yet. This patch removes the checks for the signature and the fixup code completely. Comments? Which bootloaders are still in use? Kill zImage? Alexander If acceptable as-is: Signed-off-by: Alexander van Heukelum <heukelum@...lshack.com> --- arch/i386/boot/setup.S | 68 +++++----------------------------------------- arch/x86_64/boot/setup.S | 64 ++++--------------------------------------- 2 files changed, 13 insertions(+), 119 deletions(-) diff --git a/arch/i386/boot/setup.S b/arch/i386/boot/setup.S index 3aec453..cd354b2 100644 --- a/arch/i386/boot/setup.S +++ b/arch/i386/boot/setup.S @@ -52,8 +52,8 @@ #include <linux/compile.h> #include <asm/boot.h> #include <asm/e820.h> #include <asm/page.h> - -/* Signature words to ensure LILO loaded us right */ + +/* Signature words to mark the end of the real-mode kernel */ #define SIG1 0xAA55 #define SIG2 0x5A5A @@ -179,17 +179,7 @@ # Reset the disk controller. int $0x13 #endif -# Set %ds = %cs, we know that SETUPSEG = %cs at this point - movw %cs, %ax # aka SETUPSEG - movw %ax, %ds -# Check signature at end of setup - cmpw $SIG1, setup_sig1 - jne bad_sig - - cmpw $SIG2, setup_sig2 - jne bad_sig - - jmp good_sig1 + jmp test_loader # Routine to print asciiz string at ds:si prtstr: @@ -220,52 +210,7 @@ prtchr: pushw %ax beep: movb $0x07, %al jmp prtchr -no_sig_mess: .string "No setup signature found ..." - -good_sig1: - jmp good_sig - -# We now have to find the rest of the setup code/data -bad_sig: - movw %cs, %ax # SETUPSEG - subw $DELTA_INITSEG, %ax # INITSEG - movw %ax, %ds - xorb %bh, %bh - movb (497), %bl # get setup sect from bootsect - subw $4, %bx # LILO loads 4 sectors of setup - shlw $8, %bx # convert to words (1sect=2^8 words) - movw %bx, %cx - shrw $3, %bx # convert to segment - addw $SYSSEG, %bx - movw %bx, %cs:start_sys_seg -# Move rest of setup code/data to here - movw $2048, %di # four sectors loaded by LILO - subw %si, %si - pushw %cs - popw %es - movw $SYSSEG, %ax - movw %ax, %ds - rep - movsw - movw %cs, %ax # aka SETUPSEG - movw %ax, %ds - cmpw $SIG1, setup_sig1 - jne no_sig - - cmpw $SIG2, setup_sig2 - jne no_sig - - jmp good_sig - -no_sig: - lea no_sig_mess, %si - call prtstr - -no_sig_loop: - hlt - jmp no_sig_loop - -good_sig: +test_loader: movw %cs, %ax # aka SETUPSEG subw $DELTA_INITSEG, %ax # aka INITSEG movw %ax, %ds @@ -281,8 +226,9 @@ # Check if an old loader tries to load a popw %ds # die. lea loader_panic_mess, %si call prtstr - - jmp no_sig_loop +bad_loader: + hlt + jmp bad_loader loader_panic_mess: .string "Wrong loader, giving up..." diff --git a/arch/x86_64/boot/setup.S b/arch/x86_64/boot/setup.S index c3bfd22..5542c59 100644 --- a/arch/x86_64/boot/setup.S +++ b/arch/x86_64/boot/setup.S @@ -52,7 +52,7 @@ #include <asm/boot.h> #include <asm/e820.h> #include <asm/page.h> -/* Signature words to ensure LILO loaded us right */ +/* Signature words to mark the end of the real-mode kernel */ #define SIG1 0xAA55 #define SIG2 0x5A5A @@ -175,17 +175,7 @@ # Reset the disk controller. int $0x13 #endif -# Set %ds = %cs, we know that SETUPSEG = %cs at this point - movw %cs, %ax # aka SETUPSEG - movw %ax, %ds -# Check signature at end of setup - cmpw $SIG1, setup_sig1 - jne bad_sig - - cmpw $SIG2, setup_sig2 - jne bad_sig - - jmp good_sig1 + jmp test_loader # Routine to print asciiz string at ds:si prtstr: @@ -216,51 +206,7 @@ prtchr: beep: movb $0x07, %al jmp prtchr -no_sig_mess: .string "No setup signature found ..." - -good_sig1: - jmp good_sig - -# We now have to find the rest of the setup code/data -bad_sig: - movw %cs, %ax # SETUPSEG - subw $DELTA_INITSEG, %ax # INITSEG - movw %ax, %ds - xorb %bh, %bh - movb (497), %bl # get setup sect from bootsect - subw $4, %bx # LILO loads 4 sectors of setup - shlw $8, %bx # convert to words (1sect=2^8 words) - movw %bx, %cx - shrw $3, %bx # convert to segment - addw $SYSSEG, %bx - movw %bx, %cs:start_sys_seg -# Move rest of setup code/data to here - movw $2048, %di # four sectors loaded by LILO - subw %si, %si - movw %cs, %ax # aka SETUPSEG - movw %ax, %es - movw $SYSSEG, %ax - movw %ax, %ds - rep - movsw - movw %cs, %ax # aka SETUPSEG - movw %ax, %ds - cmpw $SIG1, setup_sig1 - jne no_sig - - cmpw $SIG2, setup_sig2 - jne no_sig - - jmp good_sig - -no_sig: - lea no_sig_mess, %si - call prtstr - -no_sig_loop: - jmp no_sig_loop - -good_sig: +test_loader: movw %cs, %ax # aka SETUPSEG subw $DELTA_INITSEG, %ax # aka INITSEG movw %ax, %ds @@ -277,7 +223,9 @@ # Check if an old loader tries to load a lea loader_panic_mess, %si call prtstr - jmp no_sig_loop +bad_loader: + hlt + jmp bad_loader loader_panic_mess: .string "Wrong loader, giving up..." -- 1.4.1 - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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