Messages in this thread Patch in this message | | | From | Yauheni Kaliuta <> | Subject | [RFC PATCH] gcc-9: workaround array bounds warning on boot_params cleaning | Date | Tue, 6 Aug 2019 19:30:34 +0300 |
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The code is supposed to clear several fields in the structure with memset() and it produces the warning:
In file included from arch/x86/kernel/head64.c:17: In function ‘memset’, inlined from ‘sanitize_boot_params’ at ./arch/x86/include/asm/bootparam_utils.h:40:3, inlined from ‘copy_bootdata’ at arch/x86/kernel/head64.c:391:2: ./include/linux/string.h:344:9: warning: ‘__builtin_memset’ offset [197, 448] from the object at ‘boot_params’ is out of the bounds of referenced subobject ‘ext_ramdisk_image’ with type ‘unsigned int’ at offset 192 [-Warray-bounds] 344 | return __builtin_memset(p, c, size); | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
since gcc is aware of the field sizes of the structure.
Blind gcc treating the structure as a byte array and calculate positions with offsetof().
Suggested-by: Ed Kellett <e@kellett.im> Signed-off-by: Yauheni Kaliuta <yauheni.kaliuta@redhat.com> --- arch/x86/include/asm/bootparam_utils.h | 14 ++++++++------ 1 file changed, 8 insertions(+), 6 deletions(-)
diff --git a/arch/x86/include/asm/bootparam_utils.h b/arch/x86/include/asm/bootparam_utils.h index 101eb944f13c..16e567a08b54 100644 --- a/arch/x86/include/asm/bootparam_utils.h +++ b/arch/x86/include/asm/bootparam_utils.h @@ -37,12 +37,14 @@ static void sanitize_boot_params(struct boot_params *boot_params) if (boot_params->sentinel) { /* fields in boot_params are left uninitialized, clear them */ boot_params->acpi_rsdp_addr = 0; - memset(&boot_params->ext_ramdisk_image, 0, - (char *)&boot_params->efi_info - - (char *)&boot_params->ext_ramdisk_image); - memset(&boot_params->kbd_status, 0, - (char *)&boot_params->hdr - - (char *)&boot_params->kbd_status); + memset((u8 *)boot_params + offsetof(struct boot_params, ext_ramdisk_image), + 0, + offsetof(struct boot_params, efi_info) - + offsetof(struct boot_params, ext_ramdisk_image)); + memset((u8 *)boot_params + offsetof(struct boot_params, _pad7[0]), + 0, + offsetof(struct boot_params, edd_mbr_sig_buffer[0]) - + offsetof(struct boot_params, _pad7[0])); memset(&boot_params->_pad7[0], 0, (char *)&boot_params->edd_mbr_sig_buffer[0] - (char *)&boot_params->_pad7[0]); -- 2.22.0
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