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Re: [Qemu-devel] [PATCH QEMU v1 1/4] multiboot: bss_end_addr can be zero
From: |
P J P |
Subject: |
Re: [Qemu-devel] [PATCH QEMU v1 1/4] multiboot: bss_end_addr can be zero |
Date: |
Wed, 7 Mar 2018 12:48:31 +0530 (IST) |
+-- On Thu, 21 Dec 2017, Jack Schwartz wrote --+
| The multiboot spec (https://www.gnu.org/software/grub/manual/multiboot/),
| section 3.1.3, allows for bss_end_addr to be zero.
|
| A zero bss_end_addr signifies there is no .bss section.
|
| Suggested-by: Daniel Kiper <address@hidden>
| Signed-off-by: Jack Schwartz <address@hidden>
| Reviewed-by: Daniel Kiper <address@hidden>
| ---
| hw/i386/multiboot.c | 18 ++++++++++--------
| 1 file changed, 10 insertions(+), 8 deletions(-)
|
| diff --git a/hw/i386/multiboot.c b/hw/i386/multiboot.c
| index c7b70c9..ff2733d 100644
| --- a/hw/i386/multiboot.c
| +++ b/hw/i386/multiboot.c
| @@ -233,12 +233,6 @@ int load_multiboot(FWCfgState *fw_cfg,
| mh_entry_addr = ldl_p(header+i+28);
|
| if (mh_load_end_addr) {
| - if (mh_bss_end_addr < mh_load_addr) {
| - fprintf(stderr, "invalid mh_bss_end_addr address\n");
| - exit(1);
| - }
| - mb_kernel_size = mh_bss_end_addr - mh_load_addr;
| -
| if (mh_load_end_addr < mh_load_addr) {
| fprintf(stderr, "invalid mh_load_end_addr address\n");
| exit(1);
| @@ -249,8 +243,16 @@ int load_multiboot(FWCfgState *fw_cfg,
| fprintf(stderr, "invalid kernel_file_size\n");
| exit(1);
| }
| - mb_kernel_size = kernel_file_size - mb_kernel_text_offset;
| - mb_load_size = mb_kernel_size;
| + mb_load_size = kernel_file_size - mb_kernel_text_offset;
| + }
| + if (mh_bss_end_addr) {
| + if (mh_bss_end_addr < (mh_load_addr + mb_load_size)) {
| + fprintf(stderr, "invalid mh_bss_end_addr address\n");
| + exit(1);
| + }
| + mb_kernel_size = mh_bss_end_addr - mh_load_addr;
| + } else {
| + mb_kernel_size = mb_load_size;
| }
|
| /* Valid if mh_flags sets MULTIBOOT_HEADER_HAS_VBE.
Looks good.
Reviewed-by: Prasad J Pandit <address@hidden>
Thank you.
--
Prasad J Pandit / Red Hat Product Security Team
47AF CE69 3A90 54AA 9045 1053 DD13 3D32 FE5B 041F
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