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Message-Id: <20230609183632.48706-7-alexander.shishkin@linux.intel.com>
Date: Fri, 9 Jun 2023 21:36:26 +0300
From: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
To: linux-kernel@...r.kernel.org, x86@...nel.org,
Andy Lutomirski <luto@...nel.org>,
Dave Hansen <dave.hansen@...ux.intel.com>,
Ravi Shankar <ravi.v.shankar@...el.com>,
Tony Luck <tony.luck@...el.com>,
Sohil Mehta <sohil.mehta@...el.com>
Cc: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Subject: [PATCH v3 06/12] x86/vsyscall: Reorganize the #PF emulation code
From: Sohil Mehta <sohil.mehta@...el.com>
Separate out the actual vsyscall emulation from the page fault specific
handling in preparation for the upcoming #GP fault emulation.
Export is_vsyscall_vaddr() so that it can be reused later.
No functional change intended.
Signed-off-by: Sohil Mehta <sohil.mehta@...el.com>
Signed-off-by: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
---
arch/x86/entry/vsyscall/vsyscall_64.c | 51 +++++++++++++++++----------
arch/x86/include/asm/vsyscall.h | 10 +++---
arch/x86/mm/fault.c | 13 ++-----
3 files changed, 41 insertions(+), 33 deletions(-)
diff --git a/arch/x86/entry/vsyscall/vsyscall_64.c b/arch/x86/entry/vsyscall/vsyscall_64.c
index e0ca8120aea8..dd112e538992 100644
--- a/arch/x86/entry/vsyscall/vsyscall_64.c
+++ b/arch/x86/entry/vsyscall/vsyscall_64.c
@@ -82,6 +82,15 @@ static void warn_bad_vsyscall(const char *level, struct pt_regs *regs,
regs->sp, regs->ax, regs->si, regs->di);
}
+/*
+ * The (legacy) vsyscall page is the long page in the kernel portion
+ * of the address space that has user-accessible permissions.
+ */
+bool is_vsyscall_vaddr(unsigned long vaddr)
+{
+ return unlikely((vaddr & PAGE_MASK) == VSYSCALL_ADDR);
+}
+
static int addr_to_vsyscall_nr(unsigned long addr)
{
int nr;
@@ -117,8 +126,7 @@ static bool write_ok_or_segv(unsigned long ptr, size_t size)
}
}
-bool emulate_vsyscall(unsigned long error_code,
- struct pt_regs *regs, unsigned long address)
+static bool __emulate_vsyscall(struct pt_regs *regs, unsigned long address)
{
struct task_struct *tsk;
unsigned long caller;
@@ -127,22 +135,6 @@ bool emulate_vsyscall(unsigned long error_code,
long ret;
unsigned long orig_dx;
- /* Write faults or kernel-privilege faults never get fixed up. */
- if ((error_code & (X86_PF_WRITE | X86_PF_USER)) != X86_PF_USER)
- return false;
-
- if (!(error_code & X86_PF_INSTR)) {
- /* Failed vsyscall read */
- if (vsyscall_mode == EMULATE)
- return false;
-
- /*
- * User code tried and failed to read the vsyscall page.
- */
- warn_bad_vsyscall(KERN_INFO, regs, "vsyscall read attempt denied -- look up the vsyscall kernel parameter if you need a workaround");
- return false;
- }
-
/*
* No point in checking CS -- the only way to get here is a user mode
* trap to a high address, which means that we're in 64-bit user code.
@@ -294,6 +286,29 @@ bool emulate_vsyscall(unsigned long error_code,
return true;
}
+bool emulate_vsyscall_pf(unsigned long error_code, struct pt_regs *regs,
+ unsigned long address)
+{
+ /* Write faults or kernel-privilege faults never get fixed up. */
+ if ((error_code & (X86_PF_WRITE | X86_PF_USER)) != X86_PF_USER)
+ return false;
+
+ if (!(error_code & X86_PF_INSTR)) {
+ /* Failed vsyscall read */
+ if (vsyscall_mode == EMULATE)
+ return false;
+
+ /*
+ * User code tried and failed to read the vsyscall page.
+ */
+ warn_bad_vsyscall(KERN_INFO, regs,
+ "vsyscall read attempt denied -- look up the vsyscall kernel parameter if you need a workaround");
+ return false;
+ }
+
+ return __emulate_vsyscall(regs, address);
+}
+
/*
* A pseudo VMA to allow ptrace access for the vsyscall page. This only
* covers the 64bit vsyscall page now. 32bit has a real VMA now and does
diff --git a/arch/x86/include/asm/vsyscall.h b/arch/x86/include/asm/vsyscall.h
index ab60a71a8dcb..667b280afc1a 100644
--- a/arch/x86/include/asm/vsyscall.h
+++ b/arch/x86/include/asm/vsyscall.h
@@ -5,6 +5,8 @@
#include <linux/seqlock.h>
#include <uapi/asm/vsyscall.h>
+extern bool is_vsyscall_vaddr(unsigned long vaddr);
+
#ifdef CONFIG_X86_VSYSCALL_EMULATION
extern void map_vsyscall(void);
extern void set_vsyscall_pgtable_user_bits(pgd_t *root);
@@ -13,12 +15,12 @@ extern void set_vsyscall_pgtable_user_bits(pgd_t *root);
* Called on instruction fetch fault in vsyscall page.
* Returns true if handled.
*/
-extern bool emulate_vsyscall(unsigned long error_code,
- struct pt_regs *regs, unsigned long address);
+extern bool emulate_vsyscall_pf(unsigned long error_code,
+ struct pt_regs *regs, unsigned long address);
#else
static inline void map_vsyscall(void) {}
-static inline bool emulate_vsyscall(unsigned long error_code,
- struct pt_regs *regs, unsigned long address)
+static inline bool emulate_vsyscall_pf(unsigned long error_code,
+ struct pt_regs *regs, unsigned long address)
{
return false;
}
diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index e4399983c50c..645eb3323f34 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -730,7 +730,7 @@ kernelmode_fixup_or_oops(struct pt_regs *regs, unsigned long error_code,
* Per the above we're !in_interrupt(), aka. task context.
*
* In this case we need to make sure we're not recursively
- * faulting through the emulate_vsyscall() logic.
+ * faulting through the emulate_vsyscall_pf() logic.
*/
if (current->thread.sig_on_uaccess_err && signal) {
sanitize_error_code(address, &error_code);
@@ -798,15 +798,6 @@ show_signal_msg(struct pt_regs *regs, unsigned long error_code,
show_opcodes(regs, loglvl);
}
-/*
- * The (legacy) vsyscall page is the long page in the kernel portion
- * of the address space that has user-accessible permissions.
- */
-static bool is_vsyscall_vaddr(unsigned long vaddr)
-{
- return unlikely((vaddr & PAGE_MASK) == VSYSCALL_ADDR);
-}
-
static void
__bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code,
unsigned long address, u32 pkey, int si_code)
@@ -1329,7 +1320,7 @@ void do_user_addr_fault(struct pt_regs *regs,
* to consider the PF_PK bit.
*/
if (is_vsyscall_vaddr(address)) {
- if (emulate_vsyscall(error_code, regs, address))
+ if (emulate_vsyscall_pf(error_code, regs, address))
return;
}
#endif
--
2.39.2
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