[PATCH STABLE for-4.8] x86emul/test: don't use *_len symbols

[Ian Jackson <ian.jackson@eu.citrix.com>]

From: Jan Beulich <JBeulich@suse.com>

... as they don't work as intended with -fPIC.

I did prefer them over *_end ones at the time because older gcc would
cause .L* symbols to be public, due to issuing .globl for all
referenced externals. And labels at the end of instructions collide
with the ones at the start of the next instruction, making disassembly
harder to grok. Luckily recent gcc no longer issues those .globl
directives, and hence .L* labels, staying local by default, no longer
get in the way.

Reported-by: Wei Liu <wei.liu2@citrix.com>
Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Wei Liu <wei.liu2@citrix.com>
Tested-by: Wei Liu <wei.liu2@citrix.com>

(cherry picked from commit 9315fa0ef736d1153c98ce42bff5853da5ec697f)

This backport had some conflicts.  Notably
   5ad98e3c7fa92f46d77a788e1109b7d282bd1256
   x86emul: support ADCX/ADOX
contains a change to the definition of set_insn.  This is not
mentioned in the commit message and therefore lacks any kind of
justification.

I strongly deprecate this; that change ought to have been split out
into its own commit, no matter that it's very small.  After
consultation I have decided to drop rather than backport that change
to the definition of set_insn.

CC: Jan Beulich <jbeulich@suse.com>
CC: Andrew Cooper <andrew.cooper3@citrix.com>
CC: Wei Liu <wei.liu2@citrix.com>
Signed-off-by: Ian Jackson <ian.jackson@eu.citrix.com>
---
 tools/tests/x86_emulator/test_x86_emulator.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/tools/tests/x86_emulator/test_x86_emulator.c b/tools/tests/x86_emulator/test_x86_emulator.c
index 7b467fe021..f902d0b99b 100644
--- a/tools/tests/x86_emulator/test_x86_emulator.c
+++ b/tools/tests/x86_emulator/test_x86_emulator.c
@@ -766,15 +766,15 @@ int main(int argc, char **argv)
         goto fail;
     printf("okay\n");
 
-#define decl_insn(which) extern const unsigned char which[], which##_len[]
+#define decl_insn(which) extern const unsigned char which[], \
+                         which##_end[] asm ( ".L" #which "_end" )
 #define put_insn(which, insn) ".pushsection .test, \"ax\", @progbits\n" \
                               #which ": " insn "\n"                     \
-                              ".equ " #which "_len, .-" #which "\n"     \
+                              ".L" #which "_end:\n"                     \
                               ".popsection"
 #define set_insn(which) (regs.eip = (unsigned long)memcpy(instr, which, \
-                                             (unsigned long)which##_len))
-#define check_eip(which) (regs.eip == (unsigned long)instr + \
-                                      (unsigned long)which##_len)
+                     (unsigned long)which##_end - (unsigned long)(which)))
+#define check_eip(which) (regs.eip == (unsigned long)which##_end)
 
     printf("%-40s", "Testing movq %mm3,(%ecx)...");
     if ( stack_exec && cpu_has_mmx )
-- 
2.11.0


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