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Howlett" , Vlastimil Babka , Lorenzo Stoakes , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Huacai Chen , WANG Xuerui , Russell King , Thomas Bogendoerfer , "James E.J. Bottomley" , Helge Deller , Alexander Gordeev , Gerald Schaefer , Heiko Carstens , Vasily Gorbik , Christian Borntraeger , Sven Schnelle , Yoshinori Sato , Rich Felker , John Paul Adrian Glaubitz , "David S. Miller" , Andreas Larsson , Shuah Khan , Alexandre Ghiti Cc: linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, Palmer Dabbelt , linux-riscv@lists.infradead.org, linux-arm-kernel@lists.infradead.org, linuxppc-dev@lists.ozlabs.org, linux-mm@kvack.org, loongarch@lists.linux.dev, linux-mips@vger.kernel.org, linux-parisc@vger.kernel.org, linux-s390@vger.kernel.org, linux-sh@vger.kernel.org, sparclinux@vger.kernel.org, linux-kselftest@vger.kernel.org, Charlie Jenkins X-Mailer: b4 0.13.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=2933; i=charlie@rivosinc.com; h=from:subject:message-id; bh=/49vITxLNj+RJRh4dWyqxf17jS8h791m43d/wmsbi4g=; b=owGbwMvMwCHWx5hUnlvL8Y3xtFoSQ9q5XfH5mu/c9Rrzlz8/vq1gj25AnkDItFvB5j/EjQ7d2 dgpWufVUcrCIMbBICumyMJzrYG59Y5+2VHRsgkwc1iZQIYwcHEKwERiehj+Oxm+8In6am8suLjK Qbj6ukzK61nfEx9q7X3ecc3HVutSBcP/QCmOFDVPG+uvAsGmtk+sN15sO6WrIvn+0Hvj8ITPYtt ZAA== X-Developer-Key: i=charlie@rivosinc.com; a=openpgp; fpr=7D834FF11B1D8387E61C776FFB10D1F27D6B1354 Add support for MAP_BELOW_HINT to mmap by restricting high_limit to addr when the flag is enabled. Signed-off-by: Charlie Jenkins --- arch/x86/kernel/sys_x86_64.c | 25 ++++++++++++++++++++++--- 1 file changed, 22 insertions(+), 3 deletions(-) diff --git a/arch/x86/kernel/sys_x86_64.c b/arch/x86/kernel/sys_x86_64.c index 01d7cd85ef97..fa16b38f3702 100644 --- a/arch/x86/kernel/sys_x86_64.c +++ b/arch/x86/kernel/sys_x86_64.c @@ -86,7 +86,7 @@ SYSCALL_DEFINE6(mmap, unsigned long, addr, unsigned long, len, return ksys_mmap_pgoff(addr, len, prot, flags, fd, off >> PAGE_SHIFT); } -static void find_start_end(unsigned long addr, unsigned long flags, +static void find_start_end(unsigned long addr, unsigned long len, unsigned long flags, unsigned long *begin, unsigned long *end) { if (!in_32bit_syscall() && (flags & MAP_32BIT)) { @@ -106,10 +106,14 @@ static void find_start_end(unsigned long addr, unsigned long flags, } *begin = get_mmap_base(1); + if (in_32bit_syscall()) *end = task_size_32bit(); else *end = task_size_64bit(addr > DEFAULT_MAP_WINDOW); + + if (flags & MAP_BELOW_HINT) + *end = MIN(*end, addr + len); } static inline unsigned long stack_guard_placement(vm_flags_t vm_flags) @@ -132,7 +136,7 @@ arch_get_unmapped_area_vmflags(struct file *filp, unsigned long addr, unsigned l if (flags & MAP_FIXED) return addr; - find_start_end(addr, flags, &begin, &end); + find_start_end(addr, len, flags, &begin, &end); if (len > end) return -ENOMEM; @@ -166,6 +170,7 @@ arch_get_unmapped_area_topdown_vmflags(struct file *filp, unsigned long addr0, struct mm_struct *mm = current->mm; unsigned long addr = addr0; struct vm_unmapped_area_info info = {}; + unsigned long task_size, mmap_base; /* requested length too big for entire address space */ if (len > TASK_SIZE) @@ -198,7 +203,8 @@ arch_get_unmapped_area_topdown_vmflags(struct file *filp, unsigned long addr0, else info.low_limit = PAGE_SIZE; - info.high_limit = get_mmap_base(0); + mmap_base = get_mmap_base(0); + info.high_limit = mmap_base; info.start_gap = stack_guard_placement(vm_flags); /* @@ -210,6 +216,19 @@ arch_get_unmapped_area_topdown_vmflags(struct file *filp, unsigned long addr0, */ if (addr > DEFAULT_MAP_WINDOW && !in_32bit_syscall()) info.high_limit += TASK_SIZE_MAX - DEFAULT_MAP_WINDOW; + if (flags & MAP_BELOW_HINT) { +#ifdef CONFIG_HAVE_ARCH_COMPAT_MMAP_BASES + task_size = task_size_32bit(); +#else + task_size = task_size_64bit(0); +#endif + /* + * mmap_base is defined by PAGE_ALIGN(task_size - gap - rnd) so + * subtract out the task_size to isolate the gap + rnd. + */ + info.high_limit = MIN(info.high_limit, + (addr + len) - (task_size - mmap_base)); + } info.align_offset = pgoff << PAGE_SHIFT; if (filp) {