From 464920104bf7adac12722035bfefb3d772eb04d8 Mon Sep 17 00:00:00 2001 From: Pratyush Anand Date: Mon, 27 Feb 2017 14:27:31 -0800 Subject: [PATCH] /proc/kcore: update physical address for kcore ram and text Currently all the p_paddr of PT_LOAD headers are assigned to 0, which is not true and could be misleading, since 0 is a valid physical address. User space tools like makedumpfile needs to know physical address for PT_LOAD segments of direct mapped regions. Therefore this patch updates paddr for such regions. It also sets an invalid paddr (-1) for other regions, so that user space tool can know whether a physical address provided in PT_LOAD is correct or not. I do not know why it was 0, which is a valid physical address. But certainly, it might break some user space tools, and those need to be fixed. For example, see following code from kexec-tools kexec/kexec-elf.c:build_mem_phdrs() if ((phdr->p_paddr + phdr->p_memsz) < phdr->p_paddr) { /* The memory address wraps */ if (probe_debug) { fprintf(stderr, "ELF address wrap around\n"); } return -1; } We do not need to perform above check for an invalid physical address. I think, kexec-tools and makedumpfile will need fixup. I already have those fixup which will be sent upstream once this patch makes through. Pro with this approach is that, it will help to calculate variable like page_offset, phys_base from PT_LOAD even when they are randomized and therefore will reduce many variable and version specific values in user space tools. Having an ASLR offset information can help to translate an identity mapped virtual address to a physical address. But that would be an additional field in PT_LOAD header structure and an arch dependent value. Moreover, sending a valid physical address like 0 does not seem right. So, IMHO it is better to fix that and send valid physical address when available (identity mapped). Link: http://lkml.kernel.org/r/f951340d2917cdd2a329fae9837a83f2059dc3b2.1485318868.git.panand@redhat.com Signed-off-by: Pratyush Anand Cc: Baoquan He Cc: Dave Young Cc: Dave Anderson Cc: Atsushi Kumagai Cc: Simon Horman Cc: Kees Cook Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/proc/kcore.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/fs/proc/kcore.c b/fs/proc/kcore.c index 0b80ad87b4d6..ea9f3d1ae830 100644 --- a/fs/proc/kcore.c +++ b/fs/proc/kcore.c @@ -373,7 +373,10 @@ static void elf_kcore_store_hdr(char *bufp, int nphdr, int dataoff) phdr->p_flags = PF_R|PF_W|PF_X; phdr->p_offset = kc_vaddr_to_offset(m->addr) + dataoff; phdr->p_vaddr = (size_t)m->addr; - phdr->p_paddr = 0; + if (m->type == KCORE_RAM || m->type == KCORE_TEXT) + phdr->p_paddr = __pa(m->addr); + else + phdr->p_paddr = (elf_addr_t)-1; phdr->p_filesz = phdr->p_memsz = m->size; phdr->p_align = PAGE_SIZE; } -- 2.13.6