Kexec command line length

[Neil Horman]

On Mon, Jan 28, 2008 at 02:37:41PM -0500, Vivek Goyal wrote:
> On Mon, Jan 28, 2008 at 12:08:11PM -0500, Neil Horman wrote:
> > Patch to clean up kexec-tools command line encoding.  It does four things:
> > 
> > 1) Move the command line out of the zero page, as per Viveks suggestion.  New
> > padding scheme places the command line starting at 4096 bytes
> > 
> > 2) Increase command line length to support maximum size of 2048 bytes
> > 
> > 3) Pull in new variables from the latest kernels struct setup_header
> > 
> > 4) Where appropriate (currently only in bzImage_load) check the cmdline_size in
> > setup header to ensure that cmdline_size isn't being violated
> > 
> > Tested by me, with successful results.
> > 
> > Regards
> > Neil
> > 
> > Signed-off-by: Neil Horman <nhorman at tuxdriver.com>
> > 
> 
> Hi Neil,
> 
> Patch looks good. Some minor nits follow.
> 
<snip>

> In general convetion for /* xxx */ seems to be that xxx represents the
> offset where that data structure starts. We might want to maintain that.
> 
Copy that.  Corrected.

<snip>
> reserved16 is now already used up in x86_linux_param_header. We might
> want to bump up the reservation number here.
> 
Yeah, good point.  Corrected. Thanks

> Ideally I would have liked to put all the 4K page in
> x86_linux_param_header and replace that definition with struct bootparam.
> But I think thats' fine for the time being. We might want to do that in 
> future as reading and mapping the code to kernel boot protocol becomes
> easy.
> 
Yeah, I had considered simply removing the x86_linux_param_header and just
inluding bootparam.h, but that becomes tricky if you're compiling for alternate
kernels, so I just left well enough alone.

New Patch attached, with youre notes incorporated.  Patch does 4 things:

1) Move the command line out of the zero page, as per Viveks suggestion.  New
   padding scheme places the command line starting at 4096 bytes

2) Increase command line length to support maximum size of 2048 bytes

3) Pull in new variables from the latest kernels struct setup_header

4) Where appropriate (currently only in bzImage_load) check the cmdline_size in
   setup header to ensure that cmdline_size isn't being violated


Regards
Neil

Signed-off-by: Neil Horman <nhorman at tuxdriver.com>


 include/x86/x86-linux.h         |   19 +++++++++++++------
 kexec/arch/i386/kexec-bzImage.c |    7 +++++++
 2 files changed, 20 insertions(+), 6 deletions(-)


diff --git a/include/x86/x86-linux.h b/include/x86/x86-linux.h
index afe66bd..e75689c 100644
--- a/include/x86/x86-linux.h
+++ b/include/x86/x86-linux.h
@@ -144,18 +144,22 @@ struct x86_linux_param_header {
 	/* 2.04+ */
 	uint32_t kernel_alignment;		/* 0x230 */
 	uint8_t  relocatable_kernel;		/* 0x234 */
-	uint8_t  reserved15[0x2d0 - 0x235];	/* 0x230 */
+	uint8_t  reserved15[3];			/* 0x235 */
+	uint32_t cmdline_size;			/* 0x238 */
+	uint32_t hardware_subarch;		/* 0x23C */
+	uint64_t hardware_subarch_data;		/* 0x240 */
+	uint8_t  reserved16[0x2d0 - 0x248];	/* 0x248 */
 #endif
 	struct e820entry e820_map[E820MAX];	/* 0x2d0 */
 						/* 0x550 */
-#define COMMAND_LINE_SIZE 256
+#define COMMAND_LINE_SIZE 2048 
 };
 
 struct x86_linux_faked_param_header {
 	struct x86_linux_param_header hdr;	/* 0x00 */
-	uint8_t reserved16[688];		/* 0x550 */
-	uint8_t command_line[COMMAND_LINE_SIZE]; /* 0x800 */
-	uint8_t reserved17[1792];		/* 0x900 - 0x1000 */
+	uint8_t reserved17[0xab0];		/* 0x550 */
+	uint8_t command_line[COMMAND_LINE_SIZE]; /* 0x1000 */
+	uint8_t reserved18[0x200];		/* 0x1800 - 0x2000 */
 };
 
 struct x86_linux_header {
@@ -206,7 +210,10 @@ struct x86_linux_header {
 #else
 	uint32_t kernel_alignment;		/* 0x230 */
 	uint8_t  relocatable_kernel;		/* 0x234 */
-	uint8_t  tail[32*1024 - 0x235];		/* 0x230 */
+	uint32_t cmdline_size;                  /* 0x235 */
+	uint32_t hardware_subarch;              /* 0x239 */
+	uint64_t hardware_subarch_data;         /* 0x23D */
+	uint8_t  tail[32*1024 - 0x245];		/* 0x245 */
 #endif
 } PACKED;
 
diff --git a/kexec/arch/i386/kexec-bzImage.c b/kexec/arch/i386/kexec-bzImage.c
index 8fde799..4f2a294 100644
--- a/kexec/arch/i386/kexec-bzImage.c
+++ b/kexec/arch/i386/kexec-bzImage.c
@@ -134,6 +134,13 @@ int do_bzImage_load(struct kexec_info *info,
 		return -1;
 	}
 
+	if (setup_header.protocol_version >= 0x0206) {
+		if (command_line_len > setup_header.cmdline_size) {
+			dbgprintf("Kernel command line too long for kernel!\n");
+			return -1;
+		}
+	}
+
 	if (setup_header.protocol_version >= 0x0205) {
 		relocatable_kernel = setup_header.relocatable_kernel;
 		dbgprintf("bzImage is relocatable\n");
/****************************************************
 * Neil Horman <nhorman at tuxdriver.com>
 * Software Engineer, Red Hat
 ****************************************************/