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Kernel/LibC: Make memset implementations the same

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I dont know why we do a fast path in the Kernel, but not in Userspace

Also simplified the byte explosion in memset to "explode_byte"
it even seemed so, that we missed the highest byte when memseting something
This commit is contained in:
Hendiadyoin1 2021-04-07 15:11:13 +02:00 committed by Andreas Kling
parent 74de4795dc
commit e8ef10e2a6
Notes: sideshowbarker 2024-07-18 20:38:39 +09:00 
Author: https://github.com/Hendiadyoin1
Commit: https://github.com/SerenityOS/serenity/commit/e8ef10e2a63
Pull-request: https://github.com/SerenityOS/serenity/pull/6179
Reviewed-by: https://github.com/awesomekling
2 changed files with 18 additions and 7 deletions
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4
Kernel/StdLib.cpp
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@ -282,9 +282,7 @@ void* memset(void* dest_ptr, int c, size_t n)
// FIXME: Support starting at an unaligned address.
if (!(dest & 0x3) && n >= 12) {
size_t size_ts = n / sizeof(size_t);
size_t expanded_c = (u8)c;
expanded_c |= expanded_c << 8;
expanded_c |= expanded_c << 16;
size_t expanded_c = explode_byte((u8)c);
asm volatile(
"rep stosl\n"
: "=D"(dest)

21
Userland/Libraries/LibC/string.cpp
View file

@ -142,13 +142,26 @@ void* memcpy(void* dest_ptr, const void* src_ptr, size_t n)
void* memset(void* dest_ptr, int c, size_t n)
{
void* original_dest = dest_ptr;
size_t dest = (size_t)dest_ptr;
// FIXME: Support starting at an unaligned address.
if (!(dest & 0x3) && n >= 12) {
size_t size_ts = n / sizeof(size_t);
size_t expanded_c = explode_byte((u8)c);
asm volatile(
"rep stosl\n"
: "=D"(dest)
: "D"(dest), "c"(size_ts), "a"(expanded_c)
: "memory");
n -= size_ts * sizeof(size_t);
if (n == 0)
return dest_ptr;
}
asm volatile(
"rep stosb\n"
: "=D"(dest_ptr), "=c"(n)
: "0"(dest_ptr), "1"(n), "a"(c)
: "=D"(dest), "=c"(n)
: "0"(dest), "1"(n), "a"(c)
: "memory");
return original_dest;
return dest_ptr;
}
#else
void* memcpy(void* dest_ptr, const void* src_ptr, size_t n)