From FEDORA_PATCHES Mon Sep 17 00:00:00 2001

From: Tom de Vries <tdevries@suse.de>

Date: Mon, 6 Dec 2021 15:39:03 -0500

Subject: gdb-rhbz2019936-gdbserver-avx512-m32.patch

;; Backport "Fix avx512 -m32 support in gdbserver"

;; (Tom de Vries, RHBZ 2019936)

    PR27257 reports a problem that can be reproduced as follows:

    - use x86_64 machine with avx512 support

    - compile a hello world with -m32 to a.out

    - start a gdbserver session with a.out

    - use gdb to connect to the gdbserver session

    This makes us run into:

    ...

    Listening on port 2346

    Remote debugging from host ::1, port 34940

    src/gdbserver/regcache.cc:257: \

      A problem internal to GDBserver has been detected.

    Unknown register zmm16h requested

    ...

    The problem is that i387_xsave_to_cache in gdbserver/i387-fp.cc can't find a

    register zmm16h in the register cache.

    To understand how this happens, first some background.

    SSE has 16 128-bit wide xmm registers.

    AVX extends the SSE registers set as follows:

    - it extends the 16 existing 128-bit wide xmm registers to 256-bit wide ymm

      registers.

    AVX512 extends the AVX register set as follows:

    - it extends the 16 existing 256-bit wide ymm registers to 512-bit wide zmm

      registers.

    - it adds 16 additional 512-bit wide zmm registers (with corresponding ymm and

      xmm subregisters added as well)

    However, in 32-bit mode, there are only 8 xmm/ymm/zmm registers.

    The problem we're running into is that gdbserver/i387-fp.cc uses these

    constants to describe the size of the register file:

    ...

    static const int num_avx512_zmmh_low_registers = 16;

    static const int num_avx512_zmmh_high_registers = 16;

    static const int num_avx512_ymmh_registers = 16;

    static const int num_avx512_xmm_registers = 16;

    ...

    which are all incorrect for the 32-bit case.

    Fix this by replacing the constants with variables that have the appropriate

    values in 64-bit and 32-bit mode.

    Tested on x86_64-linux with native and unix/-m32.

diff --git a/gdbserver/i387-fp.cc b/gdbserver/i387-fp.cc

--- a/gdbserver/i387-fp.cc

+++ b/gdbserver/i387-fp.cc

@@ -23,10 +23,6 @@

 static const int num_mpx_bnd_registers = 4;

 static const int num_mpx_cfg_registers = 2;

 static const int num_avx512_k_registers = 8;

-static const int num_avx512_zmmh_low_registers = 16;

-static const int num_avx512_zmmh_high_registers = 16;

-static const int num_avx512_ymmh_registers = 16;

-static const int num_avx512_xmm_registers = 16;

 static const int num_pkeys_registers = 1;

 /* Note: These functions preserve the reserved bits in control registers.

@@ -256,14 +252,22 @@ void

 i387_cache_to_xsave (struct regcache *regcache, void *buf)

 {

   struct i387_xsave *fp = (struct i387_xsave *) buf;

+  bool amd64 = register_size (regcache->tdesc, 0) == 8;

   int i;

   unsigned long val, val2;

   unsigned long long xstate_bv = 0;

   unsigned long long clear_bv = 0;

   char raw[64];

   char *p;

+

   /* Amd64 has 16 xmm regs; I386 has 8 xmm regs.  */

-  int num_xmm_registers = register_size (regcache->tdesc, 0) == 8 ? 16 : 8;

+  int num_xmm_registers = amd64 ? 16 : 8;

+  /* AVX512 extends the existing xmm/ymm registers to a wider mode: zmm.  */

+  int num_avx512_zmmh_low_registers = num_xmm_registers;

+  /* AVX512 adds 16 extra regs in Amd64 mode, but none in I386 mode.*/

+  int num_avx512_zmmh_high_registers = amd64 ? 16 : 0;

+  int num_avx512_ymmh_registers = amd64 ? 16 : 0;

+  int num_avx512_xmm_registers = amd64 ? 16 : 0;

   /* The supported bits in `xstat_bv' are 8 bytes.  Clear part in

      vector registers if its bit in xstat_bv is zero.  */

@@ -452,7 +456,9 @@ i387_cache_to_xsave (struct regcache *regcache, void *buf)

   /* Check if any of ZMM16H-ZMM31H registers are changed.  */

   if ((x86_xcr0 & X86_XSTATE_ZMM))

     {

-      int zmm16h_regnum = find_regno (regcache->tdesc, "zmm16h");

+      int zmm16h_regnum = (num_avx512_zmmh_high_registers == 0

+			   ? -1

+			   : find_regno (regcache->tdesc, "zmm16h"));

       for (i = 0; i < num_avx512_zmmh_high_registers; i++)

 	{

@@ -469,7 +475,9 @@ i387_cache_to_xsave (struct regcache *regcache, void *buf)

   /* Check if any XMM_AVX512 registers are changed.  */

   if ((x86_xcr0 & X86_XSTATE_ZMM))

     {

-      int xmm_avx512_regnum = find_regno (regcache->tdesc, "xmm16");

+      int xmm_avx512_regnum = (num_avx512_xmm_registers == 0

+			       ? -1

+			       : find_regno (regcache->tdesc, "xmm16"));

       for (i = 0; i < num_avx512_xmm_registers; i++)

 	{

@@ -486,7 +494,9 @@ i387_cache_to_xsave (struct regcache *regcache, void *buf)

   /* Check if any YMMH_AVX512 registers are changed.  */

   if ((x86_xcr0 & X86_XSTATE_ZMM))

     {

-      int ymmh_avx512_regnum = find_regno (regcache->tdesc, "ymm16h");

+      int ymmh_avx512_regnum = (num_avx512_ymmh_registers == 0

+				? -1

+				: find_regno (regcache->tdesc, "ymm16h"));

       for (i = 0; i < num_avx512_ymmh_registers; i++)

 	{

@@ -710,12 +720,20 @@ i387_xsave_to_cache (struct regcache *regcache, const void *buf)

 {

   struct i387_xsave *fp = (struct i387_xsave *) buf;

   struct i387_fxsave *fxp = (struct i387_fxsave *) buf;

+  bool amd64 = register_size (regcache->tdesc, 0) == 8;

   int i, top;

   unsigned long val;

   unsigned long long clear_bv;

   gdb_byte *p;

-  /* Amd64 has 16 xmm regs; I386 has 8 xmm regs.  */

-  int num_xmm_registers = register_size (regcache->tdesc, 0) == 8 ? 16 : 8;

+

+   /* Amd64 has 16 xmm regs; I386 has 8 xmm regs.  */

+  int num_xmm_registers = amd64 ? 16 : 8;

+  /* AVX512 extends the existing xmm/ymm registers to a wider mode: zmm.  */

+  int num_avx512_zmmh_low_registers = num_xmm_registers;

+  /* AVX512 adds 16 extra regs in Amd64 mode, but none in I386 mode.*/

+  int num_avx512_zmmh_high_registers = amd64 ? 16 : 0;

+  int num_avx512_ymmh_registers = amd64 ? 16 : 0;

+  int num_avx512_xmm_registers = amd64 ? 16 : 0;

   /* The supported bits in `xstat_bv' are 8 bytes.  Clear part in

      vector registers if its bit in xstat_bv is zero.  */

@@ -845,9 +863,15 @@ i387_xsave_to_cache (struct regcache *regcache, const void *buf)

   if ((x86_xcr0 & X86_XSTATE_ZMM) != 0)

     {

-      int zmm16h_regnum = find_regno (regcache->tdesc, "zmm16h");

-      int ymm16h_regnum = find_regno (regcache->tdesc, "ymm16h");

-      int xmm16_regnum = find_regno (regcache->tdesc, "xmm16");

+      int zmm16h_regnum = (num_avx512_zmmh_high_registers == 0

+			   ? -1

+			   : find_regno (regcache->tdesc, "zmm16h"));

+      int ymm16h_regnum = (num_avx512_ymmh_registers == 0

+			   ? -1

+			   : find_regno (regcache->tdesc, "ymm16h"));

+      int xmm16_regnum = (num_avx512_xmm_registers == 0

+			  ? -1

+			  : find_regno (regcache->tdesc, "xmm16"));

       if ((clear_bv & X86_XSTATE_ZMM) != 0)

 	{