[PATCH v3 27/41] target/i386: Implement x86_cpu_record_sigsegv

[Richard Henderson]

Record cr2, error_code, and exception_index.  That last means
that we must exit to cpu_loop ourselves, instead of letting
exception_index being overwritten.

Use the maperr parameter to properly set PG_ERROR_P_MASK.

Reviewed by: Warner Losh <imp@bsdimp.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 target/i386/tcg/helper-tcg.h       |  6 ++++++
 target/i386/tcg/tcg-cpu.c          |  3 ++-
 target/i386/tcg/user/excp_helper.c | 23 +++++++++++++++++------
 3 files changed, 25 insertions(+), 7 deletions(-)

diff --git a/target/i386/tcg/helper-tcg.h b/target/i386/tcg/helper-tcg.h
index 60ca09e95e..0a4401e917 100644
--- a/target/i386/tcg/helper-tcg.h
+++ b/target/i386/tcg/helper-tcg.h
@@ -43,9 +43,15 @@ bool x86_cpu_exec_interrupt(CPUState *cpu, int int_req);
 #endif
 
 /* helper.c */
+#ifdef CONFIG_USER_ONLY
+void x86_cpu_record_sigsegv(CPUState *cs, vaddr addr,
+                            MMUAccessType access_type,
+                            bool maperr, uintptr_t ra);
+#else
 bool x86_cpu_tlb_fill(CPUState *cs, vaddr address, int size,
                       MMUAccessType access_type, int mmu_idx,
                       bool probe, uintptr_t retaddr);
+#endif
 
 void breakpoint_handler(CPUState *cs);
 
diff --git a/target/i386/tcg/tcg-cpu.c b/target/i386/tcg/tcg-cpu.c
index 3ecfae34cb..6fdfdf9598 100644
--- a/target/i386/tcg/tcg-cpu.c
+++ b/target/i386/tcg/tcg-cpu.c
@@ -72,10 +72,11 @@ static const struct TCGCPUOps x86_tcg_ops = {
     .synchronize_from_tb = x86_cpu_synchronize_from_tb,
     .cpu_exec_enter = x86_cpu_exec_enter,
     .cpu_exec_exit = x86_cpu_exec_exit,
-    .tlb_fill = x86_cpu_tlb_fill,
 #ifdef CONFIG_USER_ONLY
     .fake_user_interrupt = x86_cpu_do_interrupt,
+    .record_sigsegv = x86_cpu_record_sigsegv,
 #else
+    .tlb_fill = x86_cpu_tlb_fill,
     .do_interrupt = x86_cpu_do_interrupt,
     .cpu_exec_interrupt = x86_cpu_exec_interrupt,
     .debug_excp_handler = breakpoint_handler,
diff --git a/target/i386/tcg/user/excp_helper.c 
b/target/i386/tcg/user/excp_helper.c
index a89b5228fd..cd507e2a1b 100644
--- a/target/i386/tcg/user/excp_helper.c
+++ b/target/i386/tcg/user/excp_helper.c
@@ -22,18 +22,29 @@
 #include "exec/exec-all.h"
 #include "tcg/helper-tcg.h"
 
-bool x86_cpu_tlb_fill(CPUState *cs, vaddr addr, int size,
-                      MMUAccessType access_type, int mmu_idx,
-                      bool probe, uintptr_t retaddr)
+void x86_cpu_record_sigsegv(CPUState *cs, vaddr addr,
+                            MMUAccessType access_type,
+                            bool maperr, uintptr_t ra)
 {
     X86CPU *cpu = X86_CPU(cs);
     CPUX86State *env = &cpu->env;
 
+    /*
+     * The error_code that hw reports as part of the exception frame
+     * is copied to linux sigcontext.err.  The exception_index is
+     * copied to linux sigcontext.trapno.  Short of inventing a new
+     * place to store the trapno, we cannot let our caller raise the
+     * signal and set exception_index to EXCP_INTERRUPT.
+     */
     env->cr[2] = addr;
-    env->error_code = (access_type == MMU_DATA_STORE) << PG_ERROR_W_BIT;
-    env->error_code |= PG_ERROR_U_MASK;
+    env->error_code = ((access_type == MMU_DATA_STORE) << PG_ERROR_W_BIT)
+                    | (maperr ? 0 : PG_ERROR_P_MASK)
+                    | PG_ERROR_U_MASK;
     cs->exception_index = EXCP0E_PAGE;
+
+    /* Disable do_interrupt_user. */
     env->exception_is_int = 0;
     env->exception_next_eip = -1;
-    cpu_loop_exit_restore(cs, retaddr);
+
+    cpu_loop_exit_restore(cs, ra);
 }
-- 
2.25.1