linux-kernel - [PATCH v22 15/24] x86/sgx: ptrace() support for the SGX driver

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Message-Id: <20190903142655.21943-16-jarkko.sakkinen@linux.intel.com>
Date:   Tue,  3 Sep 2019 17:26:46 +0300
From:   Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
To:     linux-kernel@...r.kernel.org, x86@...nel.org,
        linux-sgx@...r.kernel.org
Cc:     akpm@...ux-foundation.org, dave.hansen@...el.com,
        sean.j.christopherson@...el.com, nhorman@...hat.com,
        npmccallum@...hat.com, serge.ayoun@...el.com,
        shay.katz-zamir@...el.com, haitao.huang@...el.com,
        andriy.shevchenko@...ux.intel.com, tglx@...utronix.de,
        kai.svahn@...el.com, bp@...en8.de, josh@...htriplett.org,
        luto@...nel.org, kai.huang@...el.com, rientjes@...gle.com,
        cedric.xing@...el.com,
        Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
Subject: [PATCH v22 15/24] x86/sgx: ptrace() support for the SGX driver

Add VMA callbacks for ptrace() that can be used with debug enclaves.
With debug enclaves data can be read and write the memory word at a time
by using ENCLS(EDBGRD) and ENCLS(EDBGWR) leaf instructions.

Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
---
 arch/x86/kernel/cpu/sgx/encl.c | 100 +++++++++++++++++++++++++++++++++
 1 file changed, 100 insertions(+)

diff --git a/arch/x86/kernel/cpu/sgx/encl.c b/arch/x86/kernel/cpu/sgx/encl.c
index 48306a868292..9bf49e30a568 100644
--- a/arch/x86/kernel/cpu/sgx/encl.c
+++ b/arch/x86/kernel/cpu/sgx/encl.c
@@ -343,6 +343,7 @@ int sgx_encl_may_map(struct sgx_encl *encl, unsigned long start,
 	return 0;
 }
 
+
 static int sgx_vma_mprotect(struct vm_area_struct *vma, unsigned long start,
 			    unsigned long end, unsigned long prot)
 {
@@ -350,10 +351,109 @@ static int sgx_vma_mprotect(struct vm_area_struct *vma, unsigned long start,
 				calc_vm_prot_bits(prot, 0));
 }
 
+static int sgx_edbgrd(struct sgx_encl *encl, struct sgx_encl_page *page,
+		      unsigned long addr, void *data)
+{
+	unsigned long offset;
+	int ret;
+
+	offset = addr & ~PAGE_MASK;
+
+	if ((page->desc & SGX_ENCL_PAGE_TCS) &&
+	    offset > offsetof(struct sgx_tcs, gs_limit))
+		return -ECANCELED;
+
+	ret = __edbgrd(sgx_epc_addr(page->epc_page) + offset, data);
+	if (ret)
+		return -EIO;
+
+	return 0;
+}
+
+static int sgx_edbgwr(struct sgx_encl *encl, struct sgx_encl_page *page,
+		      unsigned long addr, void *data)
+{
+	unsigned long offset;
+	int ret;
+
+	offset = addr & ~PAGE_MASK;
+
+	/* Writing anything else than flags will cause #GP */
+	if ((page->desc & SGX_ENCL_PAGE_TCS) &&
+	    offset != offsetof(struct sgx_tcs, flags))
+		return -ECANCELED;
+
+	ret = __edbgwr(sgx_epc_addr(page->epc_page) + offset, data);
+	if (ret)
+		return -EIO;
+
+	return 0;
+}
+
+static int sgx_vma_access(struct vm_area_struct *vma, unsigned long addr,
+			  void *buf, int len, int write)
+{
+	struct sgx_encl *encl = vma->vm_private_data;
+	struct sgx_encl_page *entry = NULL;
+	char data[sizeof(unsigned long)];
+	unsigned long align;
+	unsigned int flags;
+	int offset;
+	int cnt;
+	int ret = 0;
+	int i;
+
+	/* If process was forked, VMA is still there but vm_private_data is set
+	 * to NULL.
+	 */
+	if (!encl)
+		return -EFAULT;
+
+	flags = atomic_read(&encl->flags);
+
+	if (!(flags & SGX_ENCL_DEBUG) || !(flags & SGX_ENCL_INITIALIZED) ||
+	    (flags & SGX_ENCL_DEAD))
+		return -EFAULT;
+
+	for (i = 0; i < len; i += cnt) {
+		entry = sgx_encl_reserve_page(encl, (addr + i) & PAGE_MASK);
+		if (IS_ERR(entry)) {
+			ret = PTR_ERR(entry);
+			break;
+		}
+
+		align = ALIGN_DOWN(addr + i, sizeof(unsigned long));
+		offset = (addr + i) & (sizeof(unsigned long) - 1);
+		cnt = sizeof(unsigned long) - offset;
+		cnt = min(cnt, len - i);
+
+		ret = sgx_edbgrd(encl, entry, align, data);
+		if (ret)
+			goto out;
+
+		if (write) {
+			memcpy(data + offset, buf + i, cnt);
+			ret = sgx_edbgwr(encl, entry, align, data);
+			if (ret)
+				goto out;
+		} else
+			memcpy(buf + i, data + offset, cnt);
+
+out:
+		mutex_unlock(&encl->lock);
+
+		if (ret)
+			break;
+	}
+
+	return ret < 0 ? ret : i;
+}
+
 const struct vm_operations_struct sgx_vm_ops = {
 	.open = sgx_vma_open,
 	.fault = sgx_vma_fault,
 	.may_mprotect = sgx_vma_mprotect,
+	.access = sgx_vma_access,
 };
 
 /**
-- 
2.20.1