| Message ID | 20170823142419.1811665-1-arnd@arndb.de |
|---|---|
| State | New |
| Headers | show |
Arnd Bergmann <arnd@arndb.de> writes: > gcc-8 correctly points out that reading four bytes from a pointer to a > 'char' variable is wrong > > arch/arm/kernel/vdso.c: In function 'vdso_init': > arch/arm/kernel/vdso.c:200:6: error: '__builtin_memcmp_eq' reading 4 bytes from a region of size 1 [-Werror=stringop-overflow=] > > However, in this case the variable just stands for the beginning of the > vdso and is not actually a 'char', so the code is doing what it is meant > to do. > > This uses the same approach as arm64 and x86, declaring the addresses > as char arrays. > > See also: dbbb08f500d6 ("arm64, vdso: Define vdso_{start,end} as array") > > Suggested-by: Mark Rutland <mark.rutland@arm.com> > Suggested-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> > Signed-off-by: Arnd Bergmann <arnd@arndb.de> Acked-by: Nathan Lynch <nathan_lynch@mentor.com> Thanks!
diff --git a/arch/arm/include/asm/vdso.h b/arch/arm/include/asm/vdso.h index d0295f1dd1a3..95b7a4dcd6d2 100644 --- a/arch/arm/include/asm/vdso.h +++ b/arch/arm/include/asm/vdso.h @@ -11,7 +11,7 @@ struct mm_struct; void arm_install_vdso(struct mm_struct *mm, unsigned long addr); -extern char vdso_start, vdso_end; +extern char vdso_start[], vdso_end[]; extern unsigned int vdso_total_pages; diff --git a/arch/arm/kernel/vdso.c b/arch/arm/kernel/vdso.c index a4d6dc0f2427..f401b51d06ea 100644 --- a/arch/arm/kernel/vdso.c +++ b/arch/arm/kernel/vdso.c @@ -197,13 +197,13 @@ static int __init vdso_init(void) unsigned int text_pages; int i; - if (memcmp(&vdso_start, "\177ELF", 4)) { + if (memcmp(vdso_start, "\177ELF", 4)) { pr_err("VDSO is not a valid ELF object!\n"); return -ENOEXEC; } - text_pages = (&vdso_end - &vdso_start) >> PAGE_SHIFT; - pr_debug("vdso: %i text pages at base %p\n", text_pages, &vdso_start); + text_pages = (vdso_end - vdso_start) >> PAGE_SHIFT; + pr_debug("vdso: %i text pages at base %p\n", text_pages, vdso_start); /* Allocate the VDSO text pagelist */ vdso_text_pagelist = kcalloc(text_pages, sizeof(struct page *), @@ -218,7 +218,7 @@ static int __init vdso_init(void) for (i = 0; i < text_pages; i++) { struct page *page; - page = virt_to_page(&vdso_start + i * PAGE_SIZE); + page = virt_to_page(vdso_start + i * PAGE_SIZE); vdso_text_pagelist[i] = page; } @@ -229,7 +229,7 @@ static int __init vdso_init(void) cntvct_ok = cntvct_functional(); - patch_vdso(&vdso_start); + patch_vdso(vdso_start); return 0; }
gcc-8 correctly points out that reading four bytes from a pointer to a 'char' variable is wrong arch/arm/kernel/vdso.c: In function 'vdso_init': arch/arm/kernel/vdso.c:200:6: error: '__builtin_memcmp_eq' reading 4 bytes from a region of size 1 [-Werror=stringop-overflow=] However, in this case the variable just stands for the beginning of the vdso and is not actually a 'char', so the code is doing what it is meant to do. This uses the same approach as arm64 and x86, declaring the addresses as char arrays. See also: dbbb08f500d6 ("arm64, vdso: Define vdso_{start,end} as array") Suggested-by: Mark Rutland <mark.rutland@arm.com> Suggested-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> Signed-off-by: Arnd Bergmann <arnd@arndb.de> --- arch/arm/include/asm/vdso.h | 2 +- arch/arm/kernel/vdso.c | 10 +++++----- 2 files changed, 6 insertions(+), 6 deletions(-) -- 2.9.0