[014/120] MIPS: R5900: Install final length of TLB refill handler rather than 256 bytes

Commit Message

Fredrik Noring Sept. 1, 2019, 3:41 p.m. UTC

The R5900 TLB refill handler is limited to 128 bytes, corresponding
to 32 instructions.

Installing a 256 byte TLB refill handler for the R5900 at address
0x80000000 overwrites the performance counter handler at address
0x80000080, according to the TX79 manual[1]:

        Table 5-2. Exception Vectors for Level 1 exceptions

             Exceptions      |      Vector Address
                             |   BEV = 0  |   BEV = 1
        ---------------------+------------+-----------
        TLB Refill (EXL = 0) | 0x80000000 | 0xBFC00200
        TLB Refill (EXL = 1) | 0x80000180 | 0xBFC00380
        Interrupt            | 0x80000200 | 0xBFC00400
        Others               | 0x80000180 | 0xBFC00380
        ---------------------+------------+-----------

        Table 5-3. Exception Vectors for Level 2 exceptions

             Exceptions      |      Vector Address
                             |   DEV = 0  |   DEV = 1
        ---------------------+------------+-----------
        Reset, NMI           | 0xBFC00000 | 0xBFC00000
        Performance Counter  | 0x80000080 | 0xBFC00280
        Debug, SIO           | 0x80000100 | 0xBFC00300
        ---------------------+------------+-----------

References:

[1] "TX System RISC TX79 Core Architecture" manual, revision 2.0,
    Toshiba Corporation, p. 5-7, https://wiki.qemu.org/File:C790.pdf

Signed-off-by: Fredrik Noring <[e-mail]>
---
 arch/mips/mm/tlbex.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

Patch

diff --git a/arch/mips/mm/tlbex.c b/arch/mips/mm/tlbex.c
index 1caa0214d57a..d356953509e6 100644
--- a/arch/mips/mm/tlbex.c
+++ b/arch/mips/mm/tlbex.c
@@ -1502,9 +1502,9 @@  static void build_r4000_tlb_refill_handler(void)
 	pr_debug("Wrote TLB refill handler (%u instructions).\n",
 		 final_len);
 
-	memcpy((void *)ebase, final_handler, 0x100);
-	local_flush_icache_range(ebase, ebase + 0x100);
-	dump_handler("r4000_tlb_refill", (u32 *)ebase, (u32 *)(ebase + 0x100));
+	memcpy((void *)ebase, final_handler, 4 * final_len);
+	local_flush_icache_range(ebase, ebase + 4 * final_len);
+	dump_handler("r4000_tlb_refill", (u32 *)ebase, (u32 *)(ebase + 4 * final_len));
 }
 
 static void setup_pw(void)