commit f74bd157c62f5c064418d038f9003c9c4b3dad0e
author Richard Henderson <richard.henderson@linaro.org> Fri Sep 17 19:10:25 2021 -0700
committer Richard Henderson <richard.henderson@linaro.org> Tue Nov 02 07:00:52 2021 -0400
tree e27f0cb209ae71fccc0cb8ef099d3ce4a6cce9ed
parent 860e0b965be0ac3b8e455c3d80d4ca6f5e30a97a

target/i386: Implement x86_cpu_record_sigsegv

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

diff --git a/target/i386/tcg/helper-tcg.h b/target/i386/tcg/helper-tcg.h
index 60ca09e..0a4401e 100644
--- a/target/i386/tcg/helper-tcg.h
+++ b/target/i386/tcg/helper-tcg.h
@@ -43,9 +43,15 @@
 #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);
 

target/i386/tcg/tcg-cpu.c

diff --git a/target/i386/tcg/tcg-cpu.c b/target/i386/tcg/tcg-cpu.c
index 3ecfae3..6fdfdf9 100644
--- a/target/i386/tcg/tcg-cpu.c
+++ b/target/i386/tcg/tcg-cpu.c
@@ -72,10 +72,11 @@
     .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,

target/i386/tcg/user/excp_helper.c

diff --git a/target/i386/tcg/user/excp_helper.c b/target/i386/tcg/user/excp_helper.c
index a89b522..cd507e2 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);
 }