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Stash reent marker in upper bits of s1 on AMD GCN

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s[0:3] contain a descriptor used to set up the initial value of the
stack, but only the lower 48 bits of s[0:1] are currently used.
The reent marker is currently set in s3, but by stashing it in the
upper 16 bits of s[0:1] instead, s3 can be freed up for other purposes.
This commit is contained in:
Kwok Cheung Yeung
2019-11-07 14:46:41 -08:00
committed by Corinna Vinschen
parent 04d85dea57
commit d14714c690
1 changed files with 10 additions and 10 deletions
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20
newlib/libc/machine/amdgcn/getreent.c
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@@ -34,7 +34,7 @@ __getreent (void)
s11 contains the offset to the base of the stack. s11 contains the offset to the base of the stack.
s[4:5] contains the dispatch pointer. s[4:5] contains the dispatch pointer.
WARNING: this code will break if s[0:3] is ever used for anything! */ WARNING: this code will break if s[0:1] is ever used for anything! */
const register unsigned long buffer_descriptor asm("s0"); const register unsigned long buffer_descriptor asm("s0");
unsigned long private_segment = buffer_descriptor & 0x0000ffffffffffff; unsigned long private_segment = buffer_descriptor & 0x0000ffffffffffff;
const register unsigned int stack_offset asm("s11"); const register unsigned int stack_offset asm("s11");
@@ -54,20 +54,20 @@ __getreent (void)
if (sp >= addr) if (sp >= addr)
goto stackoverflow; goto stackoverflow;
/* Place a marker in s3 to indicate that the reent data is initialized. /* Stash a marker in the unused upper 16 bits of s[0:1] to indicate that
The register is known to hold part of an unused buffer descriptor the reent data is initialized. */
when the kernel is launched. This may not be unused forever, but const register unsigned int s1 asm("s1");
we already used s0 and s1 above, so this doesn't do extra harm. */ unsigned int marker = s1 >> 16;
register int s3 asm("s3"); if (marker != 12345)
if (s3 != 123456)
{ {
asm("s_mov_b32 s3, 123456"); asm("s_and_b32\ts1, s1, 0xffff");
data->marker = 123456; asm("s_or_b32\ts1, s1, (12345 << 16)");
data->marker = 12345;
__builtin_memset (&data->reent, 0, sizeof(struct _reent)); __builtin_memset (&data->reent, 0, sizeof(struct _reent));
_REENT_INIT_PTR_ZEROED (&data->reent); _REENT_INIT_PTR_ZEROED (&data->reent);
} }
else if (data->marker != 123456) else if (data->marker != 12345)
goto stackoverflow; goto stackoverflow;