diff options
author | Kwok Cheung Yeung <kcy@codesourcery.com> | 2019-11-08 01:46:41 +0300 |
---|---|---|
committer | Corinna Vinschen <corinna@vinschen.de> | 2019-11-08 12:34:28 +0300 |
commit | d14714c690c0b11b0aa7e6d09c930a321eeac7f9 (patch) | |
tree | fcfbeffbf5a2cd5c78cffb34fa41be05e5e26700 | |
parent | 04d85dea5746572ef4b45df9add7d7aaec9a0821 (diff) |
Stash reent marker in upper bits of s1 on AMD GCN
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.
-rw-r--r-- | newlib/libc/machine/amdgcn/getreent.c | 20 |
1 files changed, 10 insertions, 10 deletions
diff --git a/newlib/libc/machine/amdgcn/getreent.c b/newlib/libc/machine/amdgcn/getreent.c index bc50ca022..be7d2edc9 100644 --- a/newlib/libc/machine/amdgcn/getreent.c +++ b/newlib/libc/machine/amdgcn/getreent.c @@ -34,7 +34,7 @@ __getreent (void) s11 contains the offset to the base of the stack. 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"); unsigned long private_segment = buffer_descriptor & 0x0000ffffffffffff; const register unsigned int stack_offset asm("s11"); @@ -54,20 +54,20 @@ __getreent (void) if (sp >= addr) goto stackoverflow; - /* Place a marker in s3 to indicate that the reent data is initialized. - The register is known to hold part of an unused buffer descriptor - when the kernel is launched. This may not be unused forever, but - we already used s0 and s1 above, so this doesn't do extra harm. */ - register int s3 asm("s3"); - if (s3 != 123456) + /* Stash a marker in the unused upper 16 bits of s[0:1] to indicate that + the reent data is initialized. */ + const register unsigned int s1 asm("s1"); + unsigned int marker = s1 >> 16; + if (marker != 12345) { - asm("s_mov_b32 s3, 123456"); - data->marker = 123456; + asm("s_and_b32\ts1, s1, 0xffff"); + asm("s_or_b32\ts1, s1, (12345 << 16)"); + data->marker = 12345; __builtin_memset (&data->reent, 0, sizeof(struct _reent)); _REENT_INIT_PTR_ZEROED (&data->reent); } - else if (data->marker != 123456) + else if (data->marker != 12345) goto stackoverflow; |