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tcg: Remove softmmu code_gen_buffer fixed address 

The commentary talks about "in concert with the addresses
assigned in the relevant linker script", except there is no
linker script for softmmu, nor has there been for some time.

(Do not confuse the user-only linker script editing that was
removed in the previous patch, because user-only does not
use this code_gen_buffer allocation method.)

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
This commit is contained in:
Richard Henderson 2019-12-17 13:31:13 -10:00
parent ee5195ee0f
commit 64547a3bb6
1 changed files with 5 additions and 32 deletions
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37
accel/tcg/translate-all.c
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@ -1043,47 +1043,20 @@ static inline void *alloc_code_gen_buffer(void)
{
int prot = PROT_WRITE | PROT_READ | PROT_EXEC;
int flags = MAP_PRIVATE | MAP_ANONYMOUS;
uintptr_t start = 0;
size_t size = tcg_ctx->code_gen_buffer_size;
void *buf;
/* Constrain the position of the buffer based on the host cpu.
Note that these addresses are chosen in concert with the
addresses assigned in the relevant linker script file. */
# if defined(__PIE__) || defined(__PIC__)
/* Don't bother setting a preferred location if we're building
a position-independent executable. We're more likely to get
an address near the main executable if we let the kernel
choose the address. */
# elif defined(__x86_64__) && defined(MAP_32BIT)
/* Force the memory down into low memory with the executable.
Leave the choice of exact location with the kernel. */
flags |= MAP_32BIT;
/* Cannot expect to map more than 800MB in low memory. */
if (size > 800u * 1024 * 1024) {
tcg_ctx->code_gen_buffer_size = size = 800u * 1024 * 1024;
}
# elif defined(__sparc__)
start = 0x40000000ul;
# elif defined(__s390x__)
start = 0x90000000ul;
# elif defined(__mips__)
# if _MIPS_SIM == _ABI64
start = 0x128000000ul;
# else
start = 0x08000000ul;
# endif
# endif
buf = mmap((void *)start, size, prot, flags, -1, 0);
buf = mmap(NULL, size, prot, flags, -1, 0);
if (buf == MAP_FAILED) {
return NULL;
}
#ifdef __mips__
if (cross_256mb(buf, size)) {
/* Try again, with the original still mapped, to avoid re-acquiring
that 256mb crossing. This time don't specify an address. */
/*
* Try again, with the original still mapped, to avoid re-acquiring
* the same 256mb crossing.
*/
size_t size2;
void *buf2 = mmap(NULL, size, prot, flags, -1, 0);
switch ((int)(buf2 != MAP_FAILED)) {